As you may know, Canada is absolutely full of impact craters. In fact, of the 10 largest craters on Earth, Canada contains 5 of them - but it just might contain 6. In Northwestern Ontario lies North Caribou Lake- another 20 km wide reminder that Canada once had glaciers. Yet from a satellite view it appears to occupy a vast egg-shaped formation made obvious by the Eyapamikama Lake to the north and an unnamed river to the south. Continuing to look around the area will reveal more features appearing to make a circular shape around 52.59706 N 90.824734 W. In total, the crater appears to measure at least 50 kilometers wide, making it the 15th largest possible crater on Earth (not including uncomfirmed craters)
Unfortunately the crater is in the middle of nowhere, the nearest town to it is Pickle Lake, with a population of only 425.
I could of course try to report it to the Earth Impact Database but they require evidence of an impact crater versus a geologic dome or volcanic crater - shatter cones, shocked quartz, impact breccia, etc etc. All of this would require a visit to the crater, yet I have neither the money or the time to do this any time soon. So I ask, by the off-chance anyone lives near the crater, consider taking a trip there and look for any of the above mentioned features.
In the mean time, I'll be saving up to go there myself.
Either way, happy New Year!
Wednesday, December 31, 2014
Monday, December 8, 2014
happy MJD 2457000.0!
Most of us know today as a rather unimportant day, as days go, with the rather unimportant number of December 8th. However if you're familiar with a timekeeping method used in many astronomy fields, then you'll know that from 12:00 today to 12:00 tomorrow is the julian date 2,457,000.
First, a brief history. The Julian date is a count of the days that have passed since January 1st, 4713 BC. It is used in timekeeping for astronomy to count individual days since that date, and in the case that I most often see, to provide epochs for minor planets' orbits. Today, exactly 2,457,000 days have passed since the count was started. 2456000 was March 14th, 2012 and 2458000 will be on September 4th, 2017.
So, happy JD 2457000!
First, a brief history. The Julian date is a count of the days that have passed since January 1st, 4713 BC. It is used in timekeeping for astronomy to count individual days since that date, and in the case that I most often see, to provide epochs for minor planets' orbits. Today, exactly 2,457,000 days have passed since the count was started. 2456000 was March 14th, 2012 and 2458000 will be on September 4th, 2017.
So, happy JD 2457000!
Wednesday, December 3, 2014
67P/Churyumov-Gerasimenko's double lobed shape
By far the most interesting and defining quality of comet 67P, when the Rosetta Probe visited it earlier this year, was its double-lobed shape. While not being completely new, this was the first example of such a process happening with a comet.
Contact binaries are assumed to have been two asteroids (or comets) that joined together through a collision slow enough that they wouldn't fly past each other, or destroy each other. A defining quality for these is the notable double-lobe nature of them when a telescope points itself at them. Naturally, based on the images, that's what I would have thought if I didn't know better. However I have a couple of reasons to believe otherwise.
First, long exposure images of the comet have found that both lobes of the comet are erupting. And, based on a JPL small-body database search, asteroids outnumber comets just a bit over 200:1. The chances of two comets merging together is less than 0.1%. To further this, every picture taken shows most of the outgassing coming from the center of the comet, along with the shape of the comet indicating that the area was dug away rather than gravitationally connected- a contact binary owuld have a distinct divider between each asteroid, with gravitational attraction flattening only the closest parts to one another, giving it more of a bowling pin look than an apple-core look.
Second, the density of the comet is 0.4 g/cm<sup>3</sup>, which is typical of a comet, but based on such a size and a density, a contact binary alone would not be sufficient to mold the two lobes of the comet together to such a high degree. Plus, you would expect the density to be higher had two asteroids collided with each other, pushing each other together and giving a density of at least a few more decimals than the found density.
Lastly, notice that, contrary to the rest of the comet, the 'bridge' is relatively smooth, without any craters. This shows that the surface is young in comparison, and that any craters that form are quickly wiped away as the dust that they are imprinted upon flies off the comet.
Based on the given evidence, I can conclude that 67P is a single comet, but through an unknown force, the center of it is being melted away quicker than the rest of the comet, and that we are perhaps observing live exactly how comets fragment. It may be quite a while before this one fragments, but I think the mechanism behind this quicker core sublimation would be a good target for more in-depth study, and that it will help us better understand exactly how comets work.
Contact binaries are assumed to have been two asteroids (or comets) that joined together through a collision slow enough that they wouldn't fly past each other, or destroy each other. A defining quality for these is the notable double-lobe nature of them when a telescope points itself at them. Naturally, based on the images, that's what I would have thought if I didn't know better. However I have a couple of reasons to believe otherwise.
First, long exposure images of the comet have found that both lobes of the comet are erupting. And, based on a JPL small-body database search, asteroids outnumber comets just a bit over 200:1. The chances of two comets merging together is less than 0.1%. To further this, every picture taken shows most of the outgassing coming from the center of the comet, along with the shape of the comet indicating that the area was dug away rather than gravitationally connected- a contact binary owuld have a distinct divider between each asteroid, with gravitational attraction flattening only the closest parts to one another, giving it more of a bowling pin look than an apple-core look.
Second, the density of the comet is 0.4 g/cm<sup>3</sup>, which is typical of a comet, but based on such a size and a density, a contact binary alone would not be sufficient to mold the two lobes of the comet together to such a high degree. Plus, you would expect the density to be higher had two asteroids collided with each other, pushing each other together and giving a density of at least a few more decimals than the found density.
Lastly, notice that, contrary to the rest of the comet, the 'bridge' is relatively smooth, without any craters. This shows that the surface is young in comparison, and that any craters that form are quickly wiped away as the dust that they are imprinted upon flies off the comet.
Based on the given evidence, I can conclude that 67P is a single comet, but through an unknown force, the center of it is being melted away quicker than the rest of the comet, and that we are perhaps observing live exactly how comets fragment. It may be quite a while before this one fragments, but I think the mechanism behind this quicker core sublimation would be a good target for more in-depth study, and that it will help us better understand exactly how comets work.
Thursday, November 27, 2014
Updates
again, sorry for the delay. I know the blog hasn't been very active, but I've never seen a blog that updates much more than once a week. Anyways, here's what happened since my last post.
I've finished my list of comets by type on wikipedia - https://en.wikipedia.org/wiki/List_of_comets_by_type
I also started another project to find transneptunian objects from SDSS data - so far I've found images of 10, two of which I found from before they were discovered, 2004 XR190 and 2011 GM27.
I recently found what should be precovery observations of the asteroid 2014 UM33, however it only has an observation arc of 2 days, and is currently magnitude ~20. If there's anyone who can observe it in the next few days, for me to get an observation from 2009-01-17, that would be quite helpful. The asteroid probably needs a 2-meter telescope or larger, or at least a telescope that can see to mag=20.
more updates in the next few months!
I've finished my list of comets by type on wikipedia - https://en.wikipedia.org/wiki/List_of_comets_by_type
I also started another project to find transneptunian objects from SDSS data - so far I've found images of 10, two of which I found from before they were discovered, 2004 XR190 and 2011 GM27.
I recently found what should be precovery observations of the asteroid 2014 UM33, however it only has an observation arc of 2 days, and is currently magnitude ~20. If there's anyone who can observe it in the next few days, for me to get an observation from 2009-01-17, that would be quite helpful. The asteroid probably needs a 2-meter telescope or larger, or at least a telescope that can see to mag=20.
more updates in the next few months!
Monday, September 8, 2014
Have we already made first contact?
It's something science fiction readers and writers love to talk about all the time. Making first contact with another civilization would of course revolutionize everything about the way we live. Of course the typical science fiction book will lead you to believe that first contact is in the form of direct contact with alien races, as in meeting them in person, but it's much more likely that our first form of contact will be through signals sent to one another, and chances are that's going to take a long time, which brings me to the topic this post is on.
While we've only sent out signals to distant worlds for the last decade or two. Just traveling at the speed of light, not taking into account the decrease in signal strength over distance, we've only reached a few hundred stars, most of which are red or brown dwarfs. However, we've unintentionally been sending out signals for much longer, going back into the early 20th century, however most early signals were only intended for short-distance communication and likely wouldn't get beyond the orbit of the Moon, much less interstellar space. However more intense radio signals have been used over time, to a point where our planet is essentially a beacon of radio waves in space. Of course any civilization within 50 light years, with sufficient signal sensitivity, would have already noticed us and possibly recognized us as a civilization. But how long would it be before we made contact?
Well assume we send out a signal in 2000 AD, and it reaches an alien civilization 50 light years away. By the time it reaches them, it's 2050. It would be 2100 before we receive any signal whatsoever from them, and much longer for them to reach us. Even if they traveled at 1/10th at the speed of light, or ~1,086 miles per second it would take them 500 years. In other words, if a civilization recognized we exist recently, we won't know for quite some time, and if decide not to send any signals before arriving, it could take until at least 2500 AD before we know.
Then its also possible we've already found alien signals long ago. On August 15, 1977, Jerry Ehman, working for SETI using the Big Ear radio telescope, detected a radio signal coming from the constellation Sagittarius. The location is fairly uncertain, and is limited to between two narrow bands in the area, neither of which contains any remarkable stars. Chances are that whatever the signal came from is very distant, leaving one to wonder how strong the signal sender would have to be. According to one source, it would have to be approximately 2,200,000 watts of power. For comparison the strongest signal transmitter on Earth is only 2,500 watts, roughly 1/1000th of the required amount. Whether or not it came from an intelligent civilization is likely something we won't know for quite a long time.
While we've only sent out signals to distant worlds for the last decade or two. Just traveling at the speed of light, not taking into account the decrease in signal strength over distance, we've only reached a few hundred stars, most of which are red or brown dwarfs. However, we've unintentionally been sending out signals for much longer, going back into the early 20th century, however most early signals were only intended for short-distance communication and likely wouldn't get beyond the orbit of the Moon, much less interstellar space. However more intense radio signals have been used over time, to a point where our planet is essentially a beacon of radio waves in space. Of course any civilization within 50 light years, with sufficient signal sensitivity, would have already noticed us and possibly recognized us as a civilization. But how long would it be before we made contact?
Well assume we send out a signal in 2000 AD, and it reaches an alien civilization 50 light years away. By the time it reaches them, it's 2050. It would be 2100 before we receive any signal whatsoever from them, and much longer for them to reach us. Even if they traveled at 1/10th at the speed of light, or ~1,086 miles per second it would take them 500 years. In other words, if a civilization recognized we exist recently, we won't know for quite some time, and if decide not to send any signals before arriving, it could take until at least 2500 AD before we know.
Then its also possible we've already found alien signals long ago. On August 15, 1977, Jerry Ehman, working for SETI using the Big Ear radio telescope, detected a radio signal coming from the constellation Sagittarius. The location is fairly uncertain, and is limited to between two narrow bands in the area, neither of which contains any remarkable stars. Chances are that whatever the signal came from is very distant, leaving one to wonder how strong the signal sender would have to be. According to one source, it would have to be approximately 2,200,000 watts of power. For comparison the strongest signal transmitter on Earth is only 2,500 watts, roughly 1/1000th of the required amount. Whether or not it came from an intelligent civilization is likely something we won't know for quite a long time.
Tuesday, July 22, 2014
An attempted explanation of Dark Matter and Dark Energy
My blog is listed as a Planetary Science blog, and that's what all the topics have been about so far. However the thing is that planetary science is an awfully small topic when considering all of astronomy, so with this post I widen the topic of this blog to all of astronomy, from planetary science to orbital mechanics to astrophysics. As a result, for this post I will be attempting to explain what dark matter and dark energy are. They're often explained and implied to be much more mysterious than they are, and my explanation will attempt to simplify what exactly they are and their effect on the universe.
Dark Matter was first hypothesized in the early-to-mid 1900s to explain the missing mass needed for galaxies to hold together at the speed they travel, as their visible mass alone could not account for that. Dark matter is essentially what the name suggests- just matter that does not in any way interact with light or directly with matter. Imagine it as a pane of glass; light travels through it, does not interact with it, and is not stopped by it. However while we can see the refraction caused by light's slight change in direction while traveling through glass, light simply does not interact with dark matter. However it interacts with gravity, which slightly bends light, letting us use gravitational lensing to view its effect on the universe. Imagining space like Einstein's famous flat, stretchable sheet analogy, photons traveling across the sheet would be bent in very slight, nearly unnoticeable ways that can be measured to see how much gravity is in a certain area. Scientists compare the lensing effect and the amount that the visible mass of an object could account for, and the difference is the amount of dark matter in the area.
Like normal matter, Dark Matter was created in the Big Bang ~13.8 billion years ago, and today it still makes up the majority of matter in the universe, but when it was first created it made up over 60% of all matter. Eventually, the clumps of Dark Matter formed in the Big Bang began to form into clusters and filaments, and formed the structures that galaxies and galaxy clusters now occupy, akin to plaster pouring into a mold.
But where did all of that dark matter go? In the 1990s, studies of the universe's speed of expansion showed that the universe is accelerating faster and faster, and at a loss to explain it any other way, physicists hypothesized that space itself has an energy in it that has a sort of negative gravitational effect, causing the universe to get larger, making more space to further enlarge the universe in a gigantic feedback loop.
Unlike the names suggest, dark matter and dark energy aren't actually at all related to one another except the fact that they don't interact with light. However the effects of them are very much at odds with one another, with dark matter pulling the universe in on itself, and dark energy pulling the universe outwards in a cosmic tug-of-war,a game that dark matter is destined to lose.
Dark Matter was first hypothesized in the early-to-mid 1900s to explain the missing mass needed for galaxies to hold together at the speed they travel, as their visible mass alone could not account for that. Dark matter is essentially what the name suggests- just matter that does not in any way interact with light or directly with matter. Imagine it as a pane of glass; light travels through it, does not interact with it, and is not stopped by it. However while we can see the refraction caused by light's slight change in direction while traveling through glass, light simply does not interact with dark matter. However it interacts with gravity, which slightly bends light, letting us use gravitational lensing to view its effect on the universe. Imagining space like Einstein's famous flat, stretchable sheet analogy, photons traveling across the sheet would be bent in very slight, nearly unnoticeable ways that can be measured to see how much gravity is in a certain area. Scientists compare the lensing effect and the amount that the visible mass of an object could account for, and the difference is the amount of dark matter in the area.
Like normal matter, Dark Matter was created in the Big Bang ~13.8 billion years ago, and today it still makes up the majority of matter in the universe, but when it was first created it made up over 60% of all matter. Eventually, the clumps of Dark Matter formed in the Big Bang began to form into clusters and filaments, and formed the structures that galaxies and galaxy clusters now occupy, akin to plaster pouring into a mold.
But where did all of that dark matter go? In the 1990s, studies of the universe's speed of expansion showed that the universe is accelerating faster and faster, and at a loss to explain it any other way, physicists hypothesized that space itself has an energy in it that has a sort of negative gravitational effect, causing the universe to get larger, making more space to further enlarge the universe in a gigantic feedback loop.
Unlike the names suggest, dark matter and dark energy aren't actually at all related to one another except the fact that they don't interact with light. However the effects of them are very much at odds with one another, with dark matter pulling the universe in on itself, and dark energy pulling the universe outwards in a cosmic tug-of-war,a game that dark matter is destined to lose.
Thursday, July 17, 2014
Expect long breaks, and no this blog is not dead.
I've had this blog for 6 months now, and it is certainly not at the height of its activity. I've taken several breaks, some much longer than others, but I will make no promise not to have these. I've been doing a lot of work recently and there's no indication of any of that changing, so expect several days to a month between new posts. However, on the bright side, previously I had been discussing topics, nearly copied word-for-word from Wikipedia. In future posts, I'll be trying to upload more 'original' content, and I plan to give this blog more activity in the coming weeks and months, starting with a special post next tuesday.
Friday, March 28, 2014
I need you! (click to help!)
Hello again. Previously, I've just been posting planetaryscience-related articles, but now I need you to help me with something!
For a while, I've noticed that there's no central, easily-navigable database on comets for people to browse, and if there is one, it's not seen very often. So, I've decided to start working on a 'list of comets by type' on Wikipedia. I've made good progress, getting up to C/1913 R1 as of now, but the progress is continuing slowly, and I'll need your help to help me compile the list!
Here's how you can help:
First, no Wikipedia account is required, but one would be required to receive recognition for it. Minimal HTML experience is required, along with being able to follow basic rules and guidelines:
First of all, I'm getting my work from the JPL Small-Body Database Browser, searching for comets using the search term "C/19*" to search for every non-periodic comet found in 1900. But how do you work?
Well, Here is my main workplace, full of unfinished projects that I should really get around to. Just go start editing the table there, and I'll give some guidelines if you still need help there. Thanks for the help!
I'll be posting about the final 'rings' post on the weekend, so stay tuned!
For a while, I've noticed that there's no central, easily-navigable database on comets for people to browse, and if there is one, it's not seen very often. So, I've decided to start working on a 'list of comets by type' on Wikipedia. I've made good progress, getting up to C/1913 R1 as of now, but the progress is continuing slowly, and I'll need your help to help me compile the list!
Here's how you can help:
First, no Wikipedia account is required, but one would be required to receive recognition for it. Minimal HTML experience is required, along with being able to follow basic rules and guidelines:
First of all, I'm getting my work from the JPL Small-Body Database Browser, searching for comets using the search term "C/19*" to search for every non-periodic comet found in 1900. But how do you work?
Well, Here is my main workplace, full of unfinished projects that I should really get around to. Just go start editing the table there, and I'll give some guidelines if you still need help there. Thanks for the help!
I'll be posting about the final 'rings' post on the weekend, so stay tuned!
Thursday, March 27, 2014
not so large now. The rings of Uranus
Continuing from my previous post of the rings of Saturn, we'll keep going out to the last 2 planets with rings: Uranus and Neptune.
First of all, I apologize for the delayed post; I came back late yesterday and didn't have much time, and spent the rest of the day messing around with imgur and writing this: Enjoy!
Uranus's rings, unlike the inner gas giants, are very thin and dim. The ε ring, the brightest of the rings, is only a fraction of Saturns' rings brightness. Despite these obvious differences, we'll list the rings as regular from closest to Uranus to furthest.
The ζ & 1986U2R rings
The rings begin pretty much as soon as Uranus ends. The ζcc ring, the closest of the rings, is one of a couple of extensions of the ζ (Zeta) ring orbiting, in full, between 26,840 and 41,350 kilometers from the center of Uranus (~1,300-15,800 km from the surface.) Aside from being the closest, however, it isn't exactly the brightest. The ring is around 100 times fainter than the brightest ring in the system usually, but is very bright if looked at the right way (no, not like those 3D paintings). Since nearby 1986U2R's discovery in 1986, though, the ring has moved in slightly. These rings are fairly dynamic, unlike Saturn's, changing over the course of mere months or years.
The numbered (4, 5, and 6) rings
Slightly further out from the ζ ring, we find a system of bright, narrow rings elevated slightly from Uranus's equatorial plane. These rings were designated the 6, 5, and 4 rings radiating out from the surface for lack of an appropriate Greek symbol. These rings, unlike the ζ ring, don't have much dust in them.
The α & β rings
These rings are the first of the Greek-lettered rings, but unfortunately not the last. These rings are the 2nd and 3rd brightest after the ε ring, but for some reason don't have any dust in them. They are each about half the mass of the brighter ε ring.
More Greek alphabetics: the η ring, ηc ring, and γ ring
The next few rings on our journey are all narrow and a bit dim, but that doesn't make them any less fun. The η ring is pretty dense, but the ηc ring is more broad and dim. The γ ring is much more eccentric than the other rings, and slightly wider than the η ring.
Done yet? the δc and δ rings, and why not add in the λ and ε, too?
These rings, comprising the outer parts of Uranus's thin section of the ring system, also mark the beginning of the moons. Circling just inside the λ ring is Cordelia, only about 40 km across. Despite its small size, it's still large enough to pack a bit of a punch on the ring, acting as its inner Shepard moon. Furthest out and brightest is the ε ring, also one of the largest in the system. The outer Shepard moon for this ring is Ophelia, larger than Cordelia by only 3 kilometers.
The ν ring
Not last, or least, comes the ν ring. This ring, much dimmer than the other rings, is one of two outer very dusty rings. The ring, discovered in 2003-5, is clearly bordered by the moons Portia and Rosalind (inside and outside respectively.) The ring is much larger and broader than all of the other rings closer to Uranus than it, and doesn't appear to be changing much.
Last, and least, the μ ring
The furthest of Uranus's rings, the μ ring, orbits the planet at more than twice the distance of the ε ring, and also has a few guides of its own: Puck, the largest of the inner moons, orbits on the inner part of the ring, and slightly smaller Mab orbits the ring near the center, where it's brightest. This ring, in unlike the red ν ring, is blue in color, probably made of water ice from minor collisions and/or geysers on Mab, and then slowly traveling inwards until it is picked up by Puck's gravity.
Well, that's it. Hope you enjoyed!
P.S. I made a diagram of the rings:
Enlarged (inner halo rings):
Enlarged (thin, central rings):
Enlarged (v ring and surrounding moons):
Enlarged (μ ring):
First of all, I apologize for the delayed post; I came back late yesterday and didn't have much time, and spent the rest of the day messing around with imgur and writing this: Enjoy!
Uranus's rings, unlike the inner gas giants, are very thin and dim. The ε ring, the brightest of the rings, is only a fraction of Saturns' rings brightness. Despite these obvious differences, we'll list the rings as regular from closest to Uranus to furthest.
The ζ & 1986U2R rings
The rings begin pretty much as soon as Uranus ends. The ζcc ring, the closest of the rings, is one of a couple of extensions of the ζ (Zeta) ring orbiting, in full, between 26,840 and 41,350 kilometers from the center of Uranus (~1,300-15,800 km from the surface.) Aside from being the closest, however, it isn't exactly the brightest. The ring is around 100 times fainter than the brightest ring in the system usually, but is very bright if looked at the right way (no, not like those 3D paintings). Since nearby 1986U2R's discovery in 1986, though, the ring has moved in slightly. These rings are fairly dynamic, unlike Saturn's, changing over the course of mere months or years.
 |
| An image of the 1986U2R ring showing its irregular ring arcs and ever- changing shape. Credit: NASA |
Slightly further out from the ζ ring, we find a system of bright, narrow rings elevated slightly from Uranus's equatorial plane. These rings were designated the 6, 5, and 4 rings radiating out from the surface for lack of an appropriate Greek symbol. These rings, unlike the ζ ring, don't have much dust in them.
The α & β rings
These rings are the first of the Greek-lettered rings, but unfortunately not the last. These rings are the 2nd and 3rd brightest after the ε ring, but for some reason don't have any dust in them. They are each about half the mass of the brighter ε ring.
More Greek alphabetics: the η ring, ηc ring, and γ ring
The next few rings on our journey are all narrow and a bit dim, but that doesn't make them any less fun. The η ring is pretty dense, but the ηc ring is more broad and dim. The γ ring is much more eccentric than the other rings, and slightly wider than the η ring.
Done yet? the δc and δ rings, and why not add in the λ and ε, too?
These rings, comprising the outer parts of Uranus's thin section of the ring system, also mark the beginning of the moons. Circling just inside the λ ring is Cordelia, only about 40 km across. Despite its small size, it's still large enough to pack a bit of a punch on the ring, acting as its inner Shepard moon. Furthest out and brightest is the ε ring, also one of the largest in the system. The outer Shepard moon for this ring is Ophelia, larger than Cordelia by only 3 kilometers.
The ν ring
Not last, or least, comes the ν ring. This ring, much dimmer than the other rings, is one of two outer very dusty rings. The ring, discovered in 2003-5, is clearly bordered by the moons Portia and Rosalind (inside and outside respectively.) The ring is much larger and broader than all of the other rings closer to Uranus than it, and doesn't appear to be changing much.
Last, and least, the μ ring
The furthest of Uranus's rings, the μ ring, orbits the planet at more than twice the distance of the ε ring, and also has a few guides of its own: Puck, the largest of the inner moons, orbits on the inner part of the ring, and slightly smaller Mab orbits the ring near the center, where it's brightest. This ring, in unlike the red ν ring, is blue in color, probably made of water ice from minor collisions and/or geysers on Mab, and then slowly traveling inwards until it is picked up by Puck's gravity.
Well, that's it. Hope you enjoyed!
P.S. I made a diagram of the rings:
 |
| A diagram of Uranus's rings. Credit: Me |
 |
| The inner rings of Uranus Credit: Me |
 |
| The bright, central rings of Uranus. Credit: Me |
 |
| Uranus's v ring and the numerous moons around it. Credit: Me |
 |
| The μ ring in all its boring glory. Credit: Me |
Friday, March 21, 2014
[3-5 days later]
Hey there, guys! I'll be going on vacation for the next few days, and when I get back, I'll be continuing with my dragged-out topic on rings with Uranus! Stay tuned till later, and thanks for still visiting the blog! :D
Tuesday, March 18, 2014
When an asteroid isn't an asteroid: the false alarms of fake asteroids.
Face it, You couldn't exactly call astronauts 'clean'.
Space missions, whether manned or unmanned, most always leave debris behind, whether if its when astronomers decide to let a telescope disintegrate in the atmosphere, or if STS-32's external tank had a few pieces break off before tumbling into the ocean.
To tell the truth, we've launched over 8,000 objects into space, and currently have about 1,000,000 pieces of debris in orbit of Earth. Most of these are small, only a few millimeters across, but occasionally some of these are a good 10 feet (3 meters) Across.
So, what does all of this have to do with asteroids? Well, to put it simply, we're sometimes just plain idiots.
On September 3rd, 2002, an amateur astronomer, Bill Yeung, found an asteroid that appeared to be in orbit around Earth. Of course, astronomers were surprised by this, because the only natural satellite in orbit of Earth was the Moon! (see previous post) Of course, they were right. After analyzing the object's orbital path and spectrum, they discovered it to have been S-4B stage of Apollo 12, which was intended to orbit the sun, but a small error in the rocket procedure left the stage in orbit for over 30 years! Soon, however, the rocket left Earth orbit to come near it 40 years later.
Of course, this is nothing new: In 2006, the Catalina Sky Survey discovered an asteroid orbiting outside the Moon's orbit around Earth, and was quickly found to have the spectra of the paint found on Saturn V rockets. This asteroid/satellite has the most stable orbit of any orbiting earth: it has been in a relatively stable orbit for 11 to 13 years!
If you thought all of this was crazy, you're in for a surprise:
Astronomers searching for near-earth asteroids (NEO's) found an 'asteroid' in 2007 that would make a very, very close encounter with Earth. At first they were worried- until they found out it was the Rosetta spacecraft, mistakenly designated 2007 VN84.
While numerous of these encounters have happened, I'm not going to mention them all, and just restate the main point:
We're sometimes just plain idiots.
I hope you found this article informative.
Space missions, whether manned or unmanned, most always leave debris behind, whether if its when astronomers decide to let a telescope disintegrate in the atmosphere, or if STS-32's external tank had a few pieces break off before tumbling into the ocean.
To tell the truth, we've launched over 8,000 objects into space, and currently have about 1,000,000 pieces of debris in orbit of Earth. Most of these are small, only a few millimeters across, but occasionally some of these are a good 10 feet (3 meters) Across.
So, what does all of this have to do with asteroids? Well, to put it simply, we're sometimes just plain idiots.
On September 3rd, 2002, an amateur astronomer, Bill Yeung, found an asteroid that appeared to be in orbit around Earth. Of course, astronomers were surprised by this, because the only natural satellite in orbit of Earth was the Moon! (see previous post) Of course, they were right. After analyzing the object's orbital path and spectrum, they discovered it to have been S-4B stage of Apollo 12, which was intended to orbit the sun, but a small error in the rocket procedure left the stage in orbit for over 30 years! Soon, however, the rocket left Earth orbit to come near it 40 years later.
Of course, this is nothing new: In 2006, the Catalina Sky Survey discovered an asteroid orbiting outside the Moon's orbit around Earth, and was quickly found to have the spectra of the paint found on Saturn V rockets. This asteroid/satellite has the most stable orbit of any orbiting earth: it has been in a relatively stable orbit for 11 to 13 years!
If you thought all of this was crazy, you're in for a surprise:
Astronomers searching for near-earth asteroids (NEO's) found an 'asteroid' in 2007 that would make a very, very close encounter with Earth. At first they were worried- until they found out it was the Rosetta spacecraft, mistakenly designated 2007 VN84.
While numerous of these encounters have happened, I'm not going to mention them all, and just restate the main point:
We're sometimes just plain idiots.
I hope you found this article informative.
Is the Moon alone?- the search for other satellites of Earth
For millenia, from the earliest of civilizations to now, people have looked up into the sky at night, and saw, along with the milky way's faint smudge, and the occasional meteor shower or comet, the only thing in the sky that lit up the night around them: the Moon.
Unlike the other planets, however, since the Moon was first studied in detail, it's been known to orbit the Earth (although not exactly found by the same methods, as in the Geocentric model.)
For a slightly shorter time, people have also looked up and wondered if the Moon was accompanied by anything else orbiting the Earth. Here are a few of the more notable discoveries:
The first, and most popular claim of another moon, was in 1846, when Frederic Petit made a 'not-so-tiny' claim of another moon in orbit of Earth. According to him, the moon orbited Earth about every 2 3/4 hours, and orbited only 11.4 kilometers (7.1 miles) off the Earth's surface, based on visual perturbations of the Moon's orbit. While his theory was grounded through research, however, we know this definitely not to be true: First of all, if the moon orbits only 7 miles off the surface of Earth, then here's what it would look like:
Not only this an unrealistic orbit, and not only are the crust deviations in Earth's surface enough to have this place hit Mt. Everest or something else in the Himalayas, but it's so close that not only would it orbit inside the atmosphere, but it orbits low enough that average commercial jets should have collided with it by now.
Even with all these inaccuracies, the asteroid still managed to get mentioned in Jules Verne's Around the Moon.
5 decades later, another astronomer proposed a slightly-more-believable, but also problem-ridden theory: He proposed not one, but a moon with moons orbiting it, orbiting Earth- at 1,030,000 kilometers (640,000 miles) away from Earth, and 700 kilometers (430 miles) wide, that orbits the Earth in 119 days.
Here's the a-bit-more-realistic orbital diagram:
His explanation for why it hadn't been seen before, however, was a bit of a stretch:
He claimed that the moon was very dim, except for an hour when it shines like the Sun. Wouldn't it have been noticed before, however?
Soon, after a prediction that it would become exceedingly bright in February 1898, unsurprisingly missed, the moon was found to be nonexistent.
As if that wasn't enough, he proposed another, slightly larger and closer moon in August 1898. Here's the same diagram with this other moon:
This moon was rejected so predictably and unsurprisingly that the fact that I had to say this fact was pretty much pointless because the moon's nonexistence was already assumed by the reader long before I even started on this long, drawn-out sentence.
While numerous other (fake) moons were proposed during the rest of the early to mid 20th century, let's just move on to ones with more scientific grounding:
Date: February 9th, 1913, 7:00 PM
All over eastern and North America, people are leaving their late-night jobs and returning home, having dinner, and going to bed, in various stages. Over most of the east coast, it's overcast, nothing out of the regular. In Canada and the northern USA, however, it's fairly clear.
Date: February 9th, 1913, 8:50 PM
Most of the Eastern United States and Canada is asleep, with only a few avid astronomers, insomniacs, and night-shift workers awake. The night is still continuing as usual, with nothing special appearing to happen.
Date: February 9th, 1913, about 9:15 PM
A few minutes after the clock hits 9:00, people begin to notice a series of bright fireballs traveling towards them from the northwest. As another minute ticks by, the observers count between 5 and 10 of these fireballs traveling slowly across the sky, taking about 40 seconds to pass by. As more of these go by, more keep coming, bringing the total from 10, to 20, to 30, to 50. By the end of 5 minutes, the observers across the Northeastern USA and southern Canada were nearly done witnessing the procession, but they were just about to be in for the most spectacular part:
Date: February 9th, 1913, about 9:20 PM
The trail is nearly finished, but at the back is a bright, white, huge fireball traveling slowly behind them. While the other fireballs slowed down and sped up, eventually disintegrating, this fireball kept burning brightly for nearly a minute, eventually passing over the horizon, bringing an end to that night 's chaos.
Date: February 10th, 1913, 2:20 AM
Observers jolted awake by the meteors who stayed awake all night to see if anything else would happen were not disappointed: 5 hours later, a dimmer meteor procession came over the area, although not nearly as bright as the original- possibly the debris coming a full revolution around. Based on this, the meteorites were traveling 8,020 kilometers (4,980 miles) per hour, or nearly 2 kilometers per second.
Date: February 10th, 1913, the following morning.
As newspapers and emergency phone lines are piled with reports of 'the end of the world', people struggle to find out what actually happened: Many reported a loud, thundering noise, and many more thought it to be unidentified flying objects.
Current analysis shows that the procession could have been the orbital decay of a temporary satellite captured by the Earth, or possibly even the last remnants of a temporary ring around Earth! However, we may never know exactly what did cause it.
Jump forward 93 1/2 years, and in Tuscon, Arizona, at the Catalina Sky Survey telescope, astronomers find a new asteroid, designated 2006 RH120, that is unlike any other asteroid found before:
It was a moon of Earth.
The asteroid, 3-6 meters across, typically orbited the Sun near Earth, but in September of 2006, made a very close approach to Earth and was captured into orbit of it.
By June 2007, however, perturbations by the Moon and Earth threw the asteroid back into orbit of the Sun, where it is now.
Here are a couple of other honerable mentions that don't really count as 'satellites' exactly:
In 2010, the WISE team found a Trojan asteroid- an asteroid that orbits near a planet's Lagrangian points, where they can have a stable orbit without gravitational pushes and pulls from another planet- designated 2010 TK7. These sort of bodies are common around Jupiter and Saturn- but this one was found near Earth. It is the first, and only asteroid to be a Trojan of Earth, although it doesn't exactly 'orbit' Earth, it shares an orbit with it around the Sun.
Then there's the slightly-more complicated type of minor planet, called a quasi-satellite. These asteroids orbit the Sun at the exact same amount of time as Earth, but don't share an orbit. Currently, there are 5 of these: 3753 Cruithne (see image below), 2002 AA29, (164207) 2004 GU9, (277810) 2006 FV35, and 2010 SO16. All of these asteroids will probably move out of this orbit soon, but for the moment technically 'orbit Earth'.
So, to summarize: Searches for other moons around earth have mostly turned out not to be very fruitful, and while some objects may get into temporary orbits of Earth, most never stay. While Mars may have two, Jupiter may have over 60, and many more orbiting other planets, Earth will always have a single, special satellite that we call the Moon.
Unlike the other planets, however, since the Moon was first studied in detail, it's been known to orbit the Earth (although not exactly found by the same methods, as in the Geocentric model.)
For a slightly shorter time, people have also looked up and wondered if the Moon was accompanied by anything else orbiting the Earth. Here are a few of the more notable discoveries:
The first, and most popular claim of another moon, was in 1846, when Frederic Petit made a 'not-so-tiny' claim of another moon in orbit of Earth. According to him, the moon orbited Earth about every 2 3/4 hours, and orbited only 11.4 kilometers (7.1 miles) off the Earth's surface, based on visual perturbations of the Moon's orbit. While his theory was grounded through research, however, we know this definitely not to be true: First of all, if the moon orbits only 7 miles off the surface of Earth, then here's what it would look like:
 |
| Badly/quickly-drawn picture of Earth showing the proposed orbit of the satellite to-scale (Top) [MS paint ftw] |
Even with all these inaccuracies, the asteroid still managed to get mentioned in Jules Verne's Around the Moon.
5 decades later, another astronomer proposed a slightly-more-believable, but also problem-ridden theory: He proposed not one, but a moon with moons orbiting it, orbiting Earth- at 1,030,000 kilometers (640,000 miles) away from Earth, and 700 kilometers (430 miles) wide, that orbits the Earth in 119 days.
Here's the a-bit-more-realistic orbital diagram:
 | ||
| Diagram showing the Earth, and the orbit of the Moon (to scale) and
the orbit of the 2nd proposed moon, twice as far away.
|
He claimed that the moon was very dim, except for an hour when it shines like the Sun. Wouldn't it have been noticed before, however?
Soon, after a prediction that it would become exceedingly bright in February 1898, unsurprisingly missed, the moon was found to be nonexistent.
As if that wasn't enough, he proposed another, slightly larger and closer moon in August 1898. Here's the same diagram with this other moon:
 |
| Diagram showing slightly-smaller orbit of the 3rd moon. |
While numerous other (fake) moons were proposed during the rest of the early to mid 20th century, let's just move on to ones with more scientific grounding:
Date: February 9th, 1913, 7:00 PM
All over eastern and North America, people are leaving their late-night jobs and returning home, having dinner, and going to bed, in various stages. Over most of the east coast, it's overcast, nothing out of the regular. In Canada and the northern USA, however, it's fairly clear.
Date: February 9th, 1913, 8:50 PM
Most of the Eastern United States and Canada is asleep, with only a few avid astronomers, insomniacs, and night-shift workers awake. The night is still continuing as usual, with nothing special appearing to happen.
Date: February 9th, 1913, about 9:15 PM
A few minutes after the clock hits 9:00, people begin to notice a series of bright fireballs traveling towards them from the northwest. As another minute ticks by, the observers count between 5 and 10 of these fireballs traveling slowly across the sky, taking about 40 seconds to pass by. As more of these go by, more keep coming, bringing the total from 10, to 20, to 30, to 50. By the end of 5 minutes, the observers across the Northeastern USA and southern Canada were nearly done witnessing the procession, but they were just about to be in for the most spectacular part:
Date: February 9th, 1913, about 9:20 PM
The trail is nearly finished, but at the back is a bright, white, huge fireball traveling slowly behind them. While the other fireballs slowed down and sped up, eventually disintegrating, this fireball kept burning brightly for nearly a minute, eventually passing over the horizon, bringing an end to that night 's chaos.
Date: February 10th, 1913, 2:20 AM
Observers jolted awake by the meteors who stayed awake all night to see if anything else would happen were not disappointed: 5 hours later, a dimmer meteor procession came over the area, although not nearly as bright as the original- possibly the debris coming a full revolution around. Based on this, the meteorites were traveling 8,020 kilometers (4,980 miles) per hour, or nearly 2 kilometers per second.
Date: February 10th, 1913, the following morning.
As newspapers and emergency phone lines are piled with reports of 'the end of the world', people struggle to find out what actually happened: Many reported a loud, thundering noise, and many more thought it to be unidentified flying objects.
Current analysis shows that the procession could have been the orbital decay of a temporary satellite captured by the Earth, or possibly even the last remnants of a temporary ring around Earth! However, we may never know exactly what did cause it.
Jump forward 93 1/2 years, and in Tuscon, Arizona, at the Catalina Sky Survey telescope, astronomers find a new asteroid, designated 2006 RH120, that is unlike any other asteroid found before:
It was a moon of Earth.
The asteroid, 3-6 meters across, typically orbited the Sun near Earth, but in September of 2006, made a very close approach to Earth and was captured into orbit of it.
By June 2007, however, perturbations by the Moon and Earth threw the asteroid back into orbit of the Sun, where it is now.
Here are a couple of other honerable mentions that don't really count as 'satellites' exactly:
In 2010, the WISE team found a Trojan asteroid- an asteroid that orbits near a planet's Lagrangian points, where they can have a stable orbit without gravitational pushes and pulls from another planet- designated 2010 TK7. These sort of bodies are common around Jupiter and Saturn- but this one was found near Earth. It is the first, and only asteroid to be a Trojan of Earth, although it doesn't exactly 'orbit' Earth, it shares an orbit with it around the Sun.
Then there's the slightly-more complicated type of minor planet, called a quasi-satellite. These asteroids orbit the Sun at the exact same amount of time as Earth, but don't share an orbit. Currently, there are 5 of these: 3753 Cruithne (see image below), 2002 AA29, (164207) 2004 GU9, (277810) 2006 FV35, and 2010 SO16. All of these asteroids will probably move out of this orbit soon, but for the moment technically 'orbit Earth'.
 | |
| Diagram showing the orbit of Cruithne coinciding with the orbit of Earth Credit: Various, including the Celestia program, GDFL, and Wikipedia user Jecowa. |
So, to summarize: Searches for other moons around earth have mostly turned out not to be very fruitful, and while some objects may get into temporary orbits of Earth, most never stay. While Mars may have two, Jupiter may have over 60, and many more orbiting other planets, Earth will always have a single, special satellite that we call the Moon.
Monday, March 17, 2014
Back from the dead
Hey guys, sorry for not posting on the blog for a while. After learning how many asteroids the IAU finds every single day (about 50!), I've been discouraged from posting them, so will continue the blog now without posting those, and, due to timing issues, I'll probably miss a scheduled post now and then (as I've demonstrated before) but at any rate, the blog is not going to die like this, with me to see it here. Don't worry guys, life will continue as usual here with another post late today or early tomorrow.
stay tuned for more updates from the blog that came back from the dead! ;)
stay tuned for more updates from the blog that came back from the dead! ;)
Friday, February 28, 2014
02-28-2014 Catchup: Asteroid discoveries
Sorry guys, turns out that I've missed a few* asteroids, but don't have enough time to give the orbital details of each one, but here they are:
etc. etc.
…
okay, i think that's the last of them!
*actually, a lot.
I'll try to keep track more!
The biggest of them all: Saturn's ring system (rings:part 2)
While Jupiter and the ice giants have small systems of rings around them, Saturn's is by far the largest. With over a thousand rings, it is also very elaborate. But only some of the rings are permanent. The main rings are designated with letters A through G, in the order discovered (not from the center of Saturn.) The rings are presented by distance from Saturn, with the main rings bolded.
The D ring:
Width: 7,600 km
Distance: 66,900-74,510 km
Thickness: unknown
Density: unknown
Eccentricity: unknown
Total mass: unknown
The D ring is the closest to Saturn of any of the known rings, and is fainter than any of the other main rings. This ring, unlike the others, has no distinct structure except for a series of faint, evenly-spaced ringlets. The brighter of the rings are designated D68, D72, and D73. In 1980, the rings orbited at 67,000, 72,000, and 73,000 kilometers respectively. However, later images by the Cassini space probe showed that D72 had moved 200 kilometers closer to Saturn and had grown dimmer. It's expected that the disruption was caused by a comet pushing the ring slightly out of its orbit, and it is currently reverting back into its original orbit.
The C ring:
Width: 17,342 km
Distance: 74,658-92,000 km
Thickness: 5 meters
Density: varies from 1.4 g/cm2 (inner edge) to 17 (titan ringlet)
Eccentricity: unknown
Total mass: 1.1 Pentillion kg.
The C ring is slightly brighter and larger than the D ring, and has more detail in it than the D ring. The main structures of it are the Colombo gap, a hole in the ring system, about 77,900 kilometers from Saturn, and, inside that gap, the Titan ringlet. These two structures are likely caused by an orbital resonance with Titan. The ringlet is slightly eccentric, with the end furthest from the Sun pointing towards Titan's location. Another, weirder gap in the rings is the Maxwell gap. This gap is about 87,500 kilometes out, and has a smaller ringlet within it. This ringlet is called the Maxwell ringlet for lack of a better name. While this ringlet has wave-like structures, implying a shepard moon orbiting near it, there has been no moon discovered to create the Maxwell gap and ringlet.
Width: 14,600 km
Distance: 122,170-136,775
Thickness: 10-30 meters
Density: 30-40 g/cm2
Eccentricity: unknown
Total mass: 6.2 pentillion kg
The A ring marks the end of the popular, bright group of Saturn's rings. The ring is also the largest of the main rings. While the ring is mostly devoid of structure in the form of bright and dark rings, it still contains a few gaps and ringlets. The most notable is the Encke gap. This gap, about 133,590 kilometers from Saturn, is the closest ring to Saturn that is caused by a moon in its orbit, which was discovered in 1990. This moon, named Pan, orbits the closest of any 'moon' of Saturn (not including the moonlet S/2009 S1.) Further out, near the outer boundary of the ring, is the Keeler gap. This gap is much smaller than the Encke gap, only about 1/6th the size. This gap is caused by the moon Daphnis which is about 1/4th the size of Pan. Both of these gaps appear to have small, disturbed ringlets within them probably caused by tidal interactions with the moons in them. Other than these two main moons, hundreds of moonlets have been discovered in the ring. These are only a few hundred meters large, and are only seen from their effects on the ring around them. The most-studied of these has the unofficial name "Bleriot".
The Roche Division:
Width: 2,600 km
Distance: 136,775-139,380 km
The Roche Division marks the 'end' to Saturn's main ring system, and is a gap of low-density material between the A and F rings. Around this distance, completely coincidentally, is the Roche Limit. This is the distance from a parent body (in this case Saturn) where a moon of a reasonable size is able to accrete from small particles. The reason the rings drop off significantly here is because most of the rings further out have accreted into small moons already. Anyways, this division is probably caused by the moon Atlas. This moon, about 40*35*19 kilometers across, orbits near the center of this division. It, along with sweeping material out of this area, also forms the F ring. Prometheus, a moon much larger than Atlas, also contributes to the Roche Division, but in an opposite way. This moon pulls material out of the F ring and into the Roche Division. This helps keep the division from being completely devoid of particles, but rather simply a low-density area. Other small moonlets also appear to contribute to it a bit, such as R/2004 S1 and R/2004 S2.
The F ring:
Width: 30-500 km
Distance: 140,180 km
Thickness: unknown
Density: unknown
Eccentricity: 0.0026
Total mass: unknown
Just out of the main ring system orbits a small, faint ring called the F ring. It officially marks the end of Saturn's visible rings and is formed by the shepard moons, Pandora and Prometheus. The ring, despite being small, is the most dynamic ring in the system. This ring is also very irregular because Prometheus passes through the orbit of it, leaving gravitational deviations in it. The main ring seems to consist of 3 ringlets: A large, outer one that is sometimes split apart by Prometheus's gravity, a dimmer, inner one that is often straighter, and a faint once near the center that appears to be a faint 'halo'.
Janus/Epimetheus ring:
Width: 5,000 km
Distance: 149,000-154,000 km
While the F ring marks the end to the visible rings, there are several faint rings orbiting out of the main system. The closest of these is the Janus/Epimetheus ring. This ring, named after the moons that orbit in it, is extremely faint and is about midway between the F and G ring. The ring is probably caused by ejecta from impacts on these two moons.
The G ring:
Width: 10,000-12,000 km
Distance: 168,000-175,000 km
Thickness: 100,000 meters (100 kilometers)
Density: unknown
Eccentricity: unknown
Total mass: unknown.
The G ring is the furthest out legitimately 'bright' ring, and orbits between the F and E ring. The outer edge of the ring is only 10-20,000 kilometers away from the moon Mimas, which likely formed it. Aegaeon, another moon orbiting within the ring itself, is likely formed by the ring, and not vice versa, accreting out of the ring's faint disk.
Methone Ring arc:
Width: unknown, probably small.
Distance: 194,230 kilometers
Caused by the moon Methone, the Methone Ring arc appears to be caused by collisions with the moon Methone, which explains why it's not very bright (see image below).
Anthe Ring arc:
Width: unknown
Distance: 197,665 kilometers
This ring, slightly larger than the Methone ring, was formed by impacts with the slightly-more impacted moon, Anthe. This ring, along with the moon, is in a 10:11 resonance with Mimas, leaving the ring confined to a fairly small space.
Pallene ring:
Width: 2,500 km
Distance: 211,000-213,500 km
This ring is the largest of the lunar rings of Saturn, and is formed by the moon Pallene, which is fairly small, but has many impacts on it, forming the large ring. The ring is about as bright as the Janus/Epimetheus ring.
The E ring:
Width: 302,000 km
Distamce: 181,000-483,000 km
Thickness: 10,000,000 meters (10,000 kilometers)
Density: very low
Eccentricity: unknown
Total mass: unknown
The 2nd outermost of the known rings, and the faintest of the lettered ones, the E ring is one of the dimmest and largest rings of Saturn. The ring begins near Mimas's orbit and ends at that of Rhea, making it span an enormous distance and encompassing everything further than the F ring. Most of the material of the ring seems to come from geysers on Enceladus, which later spreads out around Saturn and occasionally falls to form a blanket on other moons like Tethys, Telesto, Calypso, Helene, and Polydeuces.
The Phoebe Ring:
Width: 9,000,000 km
Distance: 4,000,000->13,000,000 km
Thickness: 2,300,000 km
In 2009, after the Cassini and Voyager probes had finished finding new rings, scientists searching through Spitzer data found a huge ring around the orbit of Phoebe that, if visible from Earth, would be the size of 2 moons. The ring is probably formed by impacts with Phoebe, which doesn't seem unlikely considering Phoebe's extremely cratered surface. The ring, while orbiting Saturn, orbits Saturn on an angle of 27 degrees. The ring likely migrates inwards over time, eventually falling onto Saturn's outer moons, like Iapetus.
The D ring:
Width: 7,600 km
Distance: 66,900-74,510 km
Thickness: unknown
Density: unknown
Eccentricity: unknown
Total mass: unknown
The D ring is the closest to Saturn of any of the known rings, and is fainter than any of the other main rings. This ring, unlike the others, has no distinct structure except for a series of faint, evenly-spaced ringlets. The brighter of the rings are designated D68, D72, and D73. In 1980, the rings orbited at 67,000, 72,000, and 73,000 kilometers respectively. However, later images by the Cassini space probe showed that D72 had moved 200 kilometers closer to Saturn and had grown dimmer. It's expected that the disruption was caused by a comet pushing the ring slightly out of its orbit, and it is currently reverting back into its original orbit.
 |
| The D ring, showing the evenly-spaced ringlets. Credit: NASA/JPL/Space Science Institute |
 | |
| The D ring in 1980 (bottom) and 2005 (top) showing the inward travel of the D72 ringlet (2nd from left) Credit: NASA/JPL/Space Science Institute |
Width: 17,342 km
Distance: 74,658-92,000 km
Thickness: 5 meters
Density: varies from 1.4 g/cm2 (inner edge) to 17 (titan ringlet)
Eccentricity: unknown
Total mass: 1.1 Pentillion kg.
The C ring is slightly brighter and larger than the D ring, and has more detail in it than the D ring. The main structures of it are the Colombo gap, a hole in the ring system, about 77,900 kilometers from Saturn, and, inside that gap, the Titan ringlet. These two structures are likely caused by an orbital resonance with Titan. The ringlet is slightly eccentric, with the end furthest from the Sun pointing towards Titan's location. Another, weirder gap in the rings is the Maxwell gap. This gap is about 87,500 kilometes out, and has a smaller ringlet within it. This ringlet is called the Maxwell ringlet for lack of a better name. While this ringlet has wave-like structures, implying a shepard moon orbiting near it, there has been no moon discovered to create the Maxwell gap and ringlet.
 |
| The C ring, showing the Titan gap (right) with the ringlet visible on the outer edge of it. The Maxwell gap is visisble at the upper right corner as a dim area outside the broad, fairly bright ring, and then a small, bright ringlet. |
The B ring:
Width: 25,500 km
Distance: 92,000-117,580 km
Thickness: 5-10 meters
Density: 20-100 g/cm2
Eccentricity: unknown
Total mass: 28 Pentillion kg
Of all of Saturn's rings, the B ring is definitely the brightest, largest, and most massive of any of them. It seems to have a wide range of ringlets and objects, but no apparent gaps. While most of the ring is flat, however, the outer edge of the ring also appears to be full of small moonlets up to 2.5 km across. Among other formations, the ring also appears to have small clouds of dust, called 'spokes, in it. This is confusing, because previously the rings had been believed to be created by gravity alone, but the regular appearance of the spokes doesn't seem to follow the theory. The current explanation for them is that small electric charges in them pushes them slightly away from the rest of the ring (similar to how 2 magnets will repel each other if faced the same direction against each other.) The rings also appear to be seasonal, appearing during Saturn's 'spring' and 'fall' equinoxes. While the ring doesn't appear to have any shepard moons, in 2009, while analyzing Cassini data, scientists found a moonlet about 400 meters in diameter. The moon was given the designation S/2009 S1.
The Cassini Division
Width: 4,700 km
Distance: 117,580-122,170 km
Thickness: 20 meters
Density: 18-20 g/cm2
Eccentricity: unknown
Total mass: unknown, probably around 0.05-0.3 pentillion kg
While Saturn's B ring is the most massive, on the contrary, the Cassini Division, which is right outside it, is the most noticeable gap in the system. It is named after Giovanni Domenico Cassini, who discovered it in 1675. With only a 90x magnification, it's possible to view the gap. However, at the time, the gap appeared to be completely devoid of matter, but today's telescopes show it to have some dust inside of it, including a couple of real 'gaps'. The more notable of these is the Huygens gap, at around 117,700 kilometers out. It marks the beginning of the Cassini division, and appears to be caused by a 2:1 resonance with Mimas (it orbits twice for every orbit of Mimas.) Inside of this gap is a small ringlet called (surprise surprise) the Huygens ringlet. The smaller of these gaps is located at about 121,000 kilometers from Saturn, and is called the Laplace gap. This gap doesn't appear to have any direct cause for its formation except that it is near the outer boundary of the ring. It, unlike most other gaps, doesn't have any known ringlet within it and has no moon causing it to be there, leaving astronomers puzzled.
The A ring:Total mass: 28 Pentillion kg
Of all of Saturn's rings, the B ring is definitely the brightest, largest, and most massive of any of them. It seems to have a wide range of ringlets and objects, but no apparent gaps. While most of the ring is flat, however, the outer edge of the ring also appears to be full of small moonlets up to 2.5 km across. Among other formations, the ring also appears to have small clouds of dust, called 'spokes, in it. This is confusing, because previously the rings had been believed to be created by gravity alone, but the regular appearance of the spokes doesn't seem to follow the theory. The current explanation for them is that small electric charges in them pushes them slightly away from the rest of the ring (similar to how 2 magnets will repel each other if faced the same direction against each other.) The rings also appear to be seasonal, appearing during Saturn's 'spring' and 'fall' equinoxes. While the ring doesn't appear to have any shepard moons, in 2009, while analyzing Cassini data, scientists found a moonlet about 400 meters in diameter. The moon was given the designation S/2009 S1.
 |
| The outer B ring, showing the small moonlets embedded in it. Credit: NASA/JPL/Space Science Institute |
 |
| S/2009 S1's discovery image. Note the long shadow despite the fairly small moon to cast it. Credit: NASA/JPL |
Width: 4,700 km
Distance: 117,580-122,170 km
Thickness: 20 meters
Density: 18-20 g/cm2
Eccentricity: unknown
Total mass: unknown, probably around 0.05-0.3 pentillion kg
While Saturn's B ring is the most massive, on the contrary, the Cassini Division, which is right outside it, is the most noticeable gap in the system. It is named after Giovanni Domenico Cassini, who discovered it in 1675. With only a 90x magnification, it's possible to view the gap. However, at the time, the gap appeared to be completely devoid of matter, but today's telescopes show it to have some dust inside of it, including a couple of real 'gaps'. The more notable of these is the Huygens gap, at around 117,700 kilometers out. It marks the beginning of the Cassini division, and appears to be caused by a 2:1 resonance with Mimas (it orbits twice for every orbit of Mimas.) Inside of this gap is a small ringlet called (surprise surprise) the Huygens ringlet. The smaller of these gaps is located at about 121,000 kilometers from Saturn, and is called the Laplace gap. This gap doesn't appear to have any direct cause for its formation except that it is near the outer boundary of the ring. It, unlike most other gaps, doesn't have any known ringlet within it and has no moon causing it to be there, leaving astronomers puzzled.
 | ||||||
| The Cassini Division is visible at the center of this image, with the Huygens gap visible to the right, and the ringlet on the outer edge of it. The Laplace gap is also visible near the outer edge of the division, showing the obvious lack of a ringlet within it. Credit: NASA/JPL/Space Science Institute |
Width: 14,600 km
Distance: 122,170-136,775
Thickness: 10-30 meters
Density: 30-40 g/cm2
Eccentricity: unknown
Total mass: 6.2 pentillion kg
The A ring marks the end of the popular, bright group of Saturn's rings. The ring is also the largest of the main rings. While the ring is mostly devoid of structure in the form of bright and dark rings, it still contains a few gaps and ringlets. The most notable is the Encke gap. This gap, about 133,590 kilometers from Saturn, is the closest ring to Saturn that is caused by a moon in its orbit, which was discovered in 1990. This moon, named Pan, orbits the closest of any 'moon' of Saturn (not including the moonlet S/2009 S1.) Further out, near the outer boundary of the ring, is the Keeler gap. This gap is much smaller than the Encke gap, only about 1/6th the size. This gap is caused by the moon Daphnis which is about 1/4th the size of Pan. Both of these gaps appear to have small, disturbed ringlets within them probably caused by tidal interactions with the moons in them. Other than these two main moons, hundreds of moonlets have been discovered in the ring. These are only a few hundred meters large, and are only seen from their effects on the ring around them. The most-studied of these has the unofficial name "Bleriot".
 | ||||
| The Encke Gap is visible, showing a small ringlet with 'knots' caused by previous gravitational interactions with Pan. Credit: NASA/JPL/Space Science Institute |
 | |
| The Keeler Gap with Daphnis in it, showing 'waves' caused by its interaction with the rings. The shadows give a general impression of height relative to the moon itself. Credit: NASA/JPL/Space Science Institute |
 |
| The Moonlet Bleriot is visible at center bottom in this image, causing small waves in the ring around it, and a partial ring around its orbit. Credit: NASA |
Width: 2,600 km
Distance: 136,775-139,380 km
The Roche Division marks the 'end' to Saturn's main ring system, and is a gap of low-density material between the A and F rings. Around this distance, completely coincidentally, is the Roche Limit. This is the distance from a parent body (in this case Saturn) where a moon of a reasonable size is able to accrete from small particles. The reason the rings drop off significantly here is because most of the rings further out have accreted into small moons already. Anyways, this division is probably caused by the moon Atlas. This moon, about 40*35*19 kilometers across, orbits near the center of this division. It, along with sweeping material out of this area, also forms the F ring. Prometheus, a moon much larger than Atlas, also contributes to the Roche Division, but in an opposite way. This moon pulls material out of the F ring and into the Roche Division. This helps keep the division from being completely devoid of particles, but rather simply a low-density area. Other small moonlets also appear to contribute to it a bit, such as R/2004 S1 and R/2004 S2.
 | ||||
| The Roche Division and Atlas are visible here, along with the F ring and the Encke and Keeler gaps. Credit: NASA |
Width: 30-500 km
Distance: 140,180 km
Thickness: unknown
Density: unknown
Eccentricity: 0.0026
Total mass: unknown
Just out of the main ring system orbits a small, faint ring called the F ring. It officially marks the end of Saturn's visible rings and is formed by the shepard moons, Pandora and Prometheus. The ring, despite being small, is the most dynamic ring in the system. This ring is also very irregular because Prometheus passes through the orbit of it, leaving gravitational deviations in it. The main ring seems to consist of 3 ringlets: A large, outer one that is sometimes split apart by Prometheus's gravity, a dimmer, inner one that is often straighter, and a faint once near the center that appears to be a faint 'halo'.
 | |||||
| A straightened-out composite of the F ring, showing the extreme tidal disturbances in it. Note that the inner ring appears to travel within the main ring about 2/3rd to the right of the image. Credit: NASA/JPL/Space Science Institute |
Width: 5,000 km
Distance: 149,000-154,000 km
While the F ring marks the end to the visible rings, there are several faint rings orbiting out of the main system. The closest of these is the Janus/Epimetheus ring. This ring, named after the moons that orbit in it, is extremely faint and is about midway between the F and G ring. The ring is probably caused by ejecta from impacts on these two moons.
 | |
| Saturn's outer ring system, showing the Janus & Epimetheus ring about midway between the F ring (bright, outer ring) and the G ring (shown) Credit: NASA/JPL/Space Science Institute |
Width: 10,000-12,000 km
Distance: 168,000-175,000 km
Thickness: 100,000 meters (100 kilometers)
Density: unknown
Eccentricity: unknown
Total mass: unknown.
The G ring is the furthest out legitimately 'bright' ring, and orbits between the F and E ring. The outer edge of the ring is only 10-20,000 kilometers away from the moon Mimas, which likely formed it. Aegaeon, another moon orbiting within the ring itself, is likely formed by the ring, and not vice versa, accreting out of the ring's faint disk.
.jpg/800px-Aegaeon_(2008_S1).jpg) | |
| The central G ring, with Aegaeon (bright dot) orbiting within the brightest segment. The image was taken over 10 minutes. Credit: NASA/JPL/Space Science Institute |
Width: unknown, probably small.
Distance: 194,230 kilometers
Caused by the moon Methone, the Methone Ring arc appears to be caused by collisions with the moon Methone, which explains why it's not very bright (see image below).
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| Image of Methone, showing blatant, obvious lack of impact craters. Credit: NASA/JPL-Caltech/Space Science Institute |
Width: unknown
Distance: 197,665 kilometers
 |
| The Anthe Ring arc is visible, with Anthe being the bright 'star' near the end of it. |
 | |
| The discovery of Anthe (red square). Note how Mimas appears significantly brighter than the rest of the moons. Credit: NASA/JPL/Space Science Institute |
Pallene ring:
Width: 2,500 km
Distance: 211,000-213,500 km
This ring is the largest of the lunar rings of Saturn, and is formed by the moon Pallene, which is fairly small, but has many impacts on it, forming the large ring. The ring is about as bright as the Janus/Epimetheus ring.
 |
| The moon Pallene. Credit: NASA/JPL/Space Science Institute |
Width: 302,000 km
Distamce: 181,000-483,000 km
Thickness: 10,000,000 meters (10,000 kilometers)
Density: very low
Eccentricity: unknown
Total mass: unknown
The 2nd outermost of the known rings, and the faintest of the lettered ones, the E ring is one of the dimmest and largest rings of Saturn. The ring begins near Mimas's orbit and ends at that of Rhea, making it span an enormous distance and encompassing everything further than the F ring. Most of the material of the ring seems to come from geysers on Enceladus, which later spreads out around Saturn and occasionally falls to form a blanket on other moons like Tethys, Telesto, Calypso, Helene, and Polydeuces.
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| The E ring, showing Enceladus's silhouette and its effects on the ring. The bright dot directly below it is a geyser erupting near its south pole. Credit: NASA/JPL/Space Science Institute |
Width: 9,000,000 km
Distance: 4,000,000->13,000,000 km
Thickness: 2,300,000 km
In 2009, after the Cassini and Voyager probes had finished finding new rings, scientists searching through Spitzer data found a huge ring around the orbit of Phoebe that, if visible from Earth, would be the size of 2 moons. The ring is probably formed by impacts with Phoebe, which doesn't seem unlikely considering Phoebe's extremely cratered surface. The ring, while orbiting Saturn, orbits Saturn on an angle of 27 degrees. The ring likely migrates inwards over time, eventually falling onto Saturn's outer moons, like Iapetus.
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| The Phoebe Ring in infrared, comparing the size of Saturn to its extent. Credit: NASA/ESA/STScl/AURA |
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| Image of Phoebe, showing heavily-cratered surface. Credit: NASA/JPL/Space Science Institute |
Wednesday, February 26, 2014
02-26-2014 Astronomy anniversaries and new asteroids
Asteroid discoveries:
None today
Comet discoveries:
None today
Today's astronomy anniversaries:
None today
Comet discoveries:
None today
Today's astronomy anniversaries:
- Discoveries:
- None
- Events:
- None
- Births:
- 1928 (86 years ago)- Anatoly Filipchenko, a Russian cosmonaut on Soyuz 7 and Soyuz 16, is born in Davydovka, Russia.
- 1958 (56 years ago)- Susan J. Helms, an American astronaut on STS-54, STS-64, STS-78, STS-101, STS-102, and STS-105, is born in Charlotte, North Carolina.
- Deaths:
- None
Coming up later today:
I'll be finishing up Saturn's Rings guys! I promise this time, later today!
Tuesday, February 25, 2014
02-25-2014 Astronomy anniversaries and new asteroids
Asteroid discoveries:
None today
Comet discoveries:
None today
Today's astronomy anniversaries:
None today
Comet discoveries:
None today
Today's astronomy anniversaries:
- Discoveries:
- None
- Events:
- None
- Births:
- None
- Deaths:
- None
Monday, February 24, 2014
02-24-2014 Astronomy anniversaries and new asteroids
Asteroid discoveries:
None today
Comet discoveries:
None today
Today's astronomy anniversaries:
I honestly don't know. Probably Saturn's rings, just keep waiting.
None today
Comet discoveries:
None today
Today's astronomy anniversaries:
- Discoveries:
- 1916 (98 years ago)- 25D/Neujmin is discovered by Grigory Neujmin.
- Events:
- 2011 (3 years ago)- Space Shuttle Discovery launches for the last time before being decommissioned on March 9th.
- Births:
- 1967 (47 years ago)- Brian Schmidt, an Australian astrophysicist who studied supernovae types, is born in Missoula, Montana.
- Deaths:
- None
I honestly don't know. Probably Saturn's rings, just keep waiting.
Sunday, February 23, 2014
02-23-2014 Astronomy anniversaries and new asteroids
Asteroid discoveries:
None today
Comet discoveries:
None today
Today's astronomy anniversaries:
None today
Comet discoveries:
None today
Today's astronomy anniversaries:
- Discoveries:
- None
- Events:
- 1987 (27 years ago)- Supernova 1987a, the closest supernova for over 400 years, explodes in the Large Magellanic Cloud, killing a few obscure alien civilizations.
- Births:
- 1583 (431 years ago)- Jean-Baptiste Morin, a French astronomer who attempted to solve the longitude problem by calculating the distance of the Moon, is born in Villefranche-sur-Saône, France.
- 1928 (86 years ago)- Vasily Lazarev, a Soviet cosmonaut who flew on Soyuz 12 and Soyuz 18a, is born in Poroshino, Russia.
- 1929 (85 years ago)- Jaan Einasto, an Estonian astrophysicist who helped discover the large-scale structure of the universe, is born in Tartu, Estonia.
- 1949 (65 years ago)- Marc Garneau, a Canadian astronaut who was on STS-41 G, STS 77, and STS-97, is born in Quebec City, Canada.
- 1959 (55 years ago)- Clayton Anderson, an American astronaut on STS-117 who participated in ISS expedition 15, is born in Omaha, Nebraska.
- Deaths:
- 1855 (159 years ago)- Carl Friedrich Gauss, a German astronomer who is responsible for a number of Astronomical contributions, including the prediction of Ceres' orbit after being recently discovered, dies in Göttingen, Germany.
Coming up later today:
It's the middle of the night! What did you expect me to make? Saturn's ring system will be a more extensive article than the usual, and is still under construction.
Saturday, February 22, 2014
02-22-2014 Astronomy anniversaries and new asteroids
Asteroid discoveries:
None today
Comet discoveries:
None today
Today's astronomy anniversaries:
Rings of the Solar System 2: Saturn's rings.
None today
Comet discoveries:
None today
Today's astronomy anniversaries:
- Discoveries:
- 1928 (86 years ago)- 30P/Reinmuth, a periodic comet with a period of 7.33 years, is discovered by Karl Reinmuth.
- Events:
- None
- Births:
- 1796 (218 years ago)- adolphe Quetelet, a Belgian astronomer who founded the Royal Observatory of Belgium, is born in Ghent, Belgium.
- 1824 (190 years ago)- Pierre Janssen, a French astronomer who discovered Helium on the Sun, is born at age 0.
- Deaths:
- None.
Rings of the Solar System 2: Saturn's rings.
Friday, February 21, 2014
If you like it so much, why not put a ring on it: the rings of the Solar System, from past to future part 1
In 1610, when Galileo turned his newly-invented telescope towards saturn, he observed what appeared to be 'ears' around it. After further observations of the planet, he concluded them to be 2 satellites orbiting the planet closely. Later, in 1616, he noticed the objects to have disappeared, making him confused. While it certainly was odd, he'd accidentally found an interesting formation- a ring system. Since his initial discovery of them in 1611, and their recognition as rings in 1655, rings have been found orbiting all of the other gas giants, including Jupiter. Recent visits by spacecraft have allowed us to learn more about these objects, how they formed, what they're made of, and what will happen to them. Here are the different planets' ring systems, including past and future ones.
The inner planets:
While none of the rocky planets have rings currently, it's likely that a couple of the planets had/will have rings at some point in their life.
Earth:
Earth (obviously) doesn't have any natural satellites or rings other than the Moon (as far as we can tell), and it's likely there weren't for a fairly long time. However, Earth's violent history says otherwise. Early in Earth's formation, a planetesimal the size of Mars collided on an angle with Earth, throwing debris from both planets' crust and mantle into orbit, leaving Earth slightly smaller today than it used to be. While this material eventually coalesced into the Moon, it stayed in orbit for a few million years, long enough for it to become a ring system. The total mass of the ring system was about 15% of Earth's. After a while, half of this mass left Earth's orbit or collided with it, and the other half became 2 moons. As the Moons' gravity affected one another, they slowly 'squished' into one another, with the smaller moon forming a thicker layer of crust on the far side of the current Moon. This was probably one of the slowest collisions in the history of the Solar System.
Mars:
While it's unlikely Mars originally had a ring system, it probably will in only 50 million years. This may seem like a long time, but, for comparison, the solar system is about 4,600 millions years old. Anyways, Mars's moon, Phobos, is the only moon that orbits faster than the planet itself. Because of this, Mars is slowing down Phobos's orbit, causing it to become closer to Mars by a centimeter per year. This means that by 3000 AD, it will be 10 meters closer. Eventually, as it spirals inward from its current distance of 9234-9517 Kilometers, it will eventually pass an imaginary location called the Roche limit. This area is the location relative to a body where any orbiting object will have such great a gravitational difference that the object will be pulled apart. For Phobos, it will pass the limit when it becomes closer than 5450 kilometers away, in about 50 million years. Once this happens, the satellite will be pulled apart into a ring around Mars. This just goes to show you that nothing in the Solar System is permanent.
The outer planets:
Right now, the planets with rings currently around them in our solar system are Jupiter, Saturn, Uranus, and Neptune. Saturn's are by far the most extensive, with Uranus having loose rings, Neptune having even looser ones, and Jupiter having only a few, but fairly dense, rings, around it.
Jupiter:
Until Voyager 1 passed by Jupiter in 1979, the only known planets with rings were Saturn and Uranus. The Voyager 1 images weren't very detailed, but later images by the Voyager 2 and Galileo probes showed the structure of the rings. These are the rings from closest to furthest from the planet:
Halo ring:
The halo ring orbits Jupiter the closest, at only about 100,000 kilometers. It's not very massive, and is the dimmest of the rings in the system, only visible in infrared. It's also the thickest, being nearly twice as thick as the second-most, the Thebe ring.
Main ring:
The brightest ring in the system, the Main ring has a mass of 100,000,000,000 to 10,000,000,000,000,000 Kilograms, making it the most massive ring, too. Despite its mass, it's also the thinnest of any of the rings, only 6,500 kilometers wide. The ring appears to have a shepard moon, Adrastea. A shepard moon is a moon who, through its gravitational pull, keeps a ring bounded to an area instead of spreading out further. The only visible detail in the ring is a notch near the orbit of Metis. Because of this apparent association, it has been named the Metis notch. Apart from this notch, the ring doesn't show much detail except a sharp decrease in brightness outside of it.
Amalthea gossamer ring:
While the Halo ring and the Main ring form the main rings of the system, the Amalthea gossamer ring and the Thebe gossamer ring are very faint rings outside of it that appear to be more like haloes of material than 'rings' in the strict sense. The Amalthea gossamer ring is named after the moon Amalthea, which appears to be the shepard moon for the outer part of the ring. The ring is 53,000 kilometers wide, and 2,000 kilometers thick. It doesn't have any visible features, and is only visible at 5-10x light sensitivity.
Thebe gossamer ring:
The faintest of the rings in the Jupiter system is the Thebe gossamer ring. Named after Thebe, it's fainter than all of the other rings, only visible at 20x light sensitivity. The ring is 97,000 kilometers wide and 8400 kilometers thick. Despite its name, however, Thebe isn't actually a shepard moon of it. The ring has been seen to continue past the moon. It's thought that the ring is formed by dust from impacts on Thebe, which are probably unusual, and therefore leaving the ring fairly not-dense.
Phewph! It seems that this ring article is taking longer than expected, so i'm going to split it into two or three parts. Tomorrow, I'll cover Saturn's ring system, and if I have time, Uranus and Neptunes. Stay tuned till then!
The inner planets:
While none of the rocky planets have rings currently, it's likely that a couple of the planets had/will have rings at some point in their life.
Earth:
Earth (obviously) doesn't have any natural satellites or rings other than the Moon (as far as we can tell), and it's likely there weren't for a fairly long time. However, Earth's violent history says otherwise. Early in Earth's formation, a planetesimal the size of Mars collided on an angle with Earth, throwing debris from both planets' crust and mantle into orbit, leaving Earth slightly smaller today than it used to be. While this material eventually coalesced into the Moon, it stayed in orbit for a few million years, long enough for it to become a ring system. The total mass of the ring system was about 15% of Earth's. After a while, half of this mass left Earth's orbit or collided with it, and the other half became 2 moons. As the Moons' gravity affected one another, they slowly 'squished' into one another, with the smaller moon forming a thicker layer of crust on the far side of the current Moon. This was probably one of the slowest collisions in the history of the Solar System.
Mars:
While it's unlikely Mars originally had a ring system, it probably will in only 50 million years. This may seem like a long time, but, for comparison, the solar system is about 4,600 millions years old. Anyways, Mars's moon, Phobos, is the only moon that orbits faster than the planet itself. Because of this, Mars is slowing down Phobos's orbit, causing it to become closer to Mars by a centimeter per year. This means that by 3000 AD, it will be 10 meters closer. Eventually, as it spirals inward from its current distance of 9234-9517 Kilometers, it will eventually pass an imaginary location called the Roche limit. This area is the location relative to a body where any orbiting object will have such great a gravitational difference that the object will be pulled apart. For Phobos, it will pass the limit when it becomes closer than 5450 kilometers away, in about 50 million years. Once this happens, the satellite will be pulled apart into a ring around Mars. This just goes to show you that nothing in the Solar System is permanent.
The outer planets:
Right now, the planets with rings currently around them in our solar system are Jupiter, Saturn, Uranus, and Neptune. Saturn's are by far the most extensive, with Uranus having loose rings, Neptune having even looser ones, and Jupiter having only a few, but fairly dense, rings, around it.
Jupiter:
Until Voyager 1 passed by Jupiter in 1979, the only known planets with rings were Saturn and Uranus. The Voyager 1 images weren't very detailed, but later images by the Voyager 2 and Galileo probes showed the structure of the rings. These are the rings from closest to furthest from the planet:
Halo ring:
The halo ring orbits Jupiter the closest, at only about 100,000 kilometers. It's not very massive, and is the dimmest of the rings in the system, only visible in infrared. It's also the thickest, being nearly twice as thick as the second-most, the Thebe ring.
 |
| The Halo ring in infrared- the bright yellow line is the Main Ring. Credit: NASA/JPL-Caltech |
The brightest ring in the system, the Main ring has a mass of 100,000,000,000 to 10,000,000,000,000,000 Kilograms, making it the most massive ring, too. Despite its mass, it's also the thinnest of any of the rings, only 6,500 kilometers wide. The ring appears to have a shepard moon, Adrastea. A shepard moon is a moon who, through its gravitational pull, keeps a ring bounded to an area instead of spreading out further. The only visible detail in the ring is a notch near the orbit of Metis. Because of this apparent association, it has been named the Metis notch. Apart from this notch, the ring doesn't show much detail except a sharp decrease in brightness outside of it.
 |
| The Main ring. The faint dust visible inside is the Halo ring, and the dim- mer part in the middle is the Metis notch. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute |
While the Halo ring and the Main ring form the main rings of the system, the Amalthea gossamer ring and the Thebe gossamer ring are very faint rings outside of it that appear to be more like haloes of material than 'rings' in the strict sense. The Amalthea gossamer ring is named after the moon Amalthea, which appears to be the shepard moon for the outer part of the ring. The ring is 53,000 kilometers wide, and 2,000 kilometers thick. It doesn't have any visible features, and is only visible at 5-10x light sensitivity.
 |
| The Gossamer rings, with the Amalthea ring's edge being visible as a slight decrease in brightness 2/3 to the left of the image. Credit: NASA/JPL-Caltech |
The faintest of the rings in the Jupiter system is the Thebe gossamer ring. Named after Thebe, it's fainter than all of the other rings, only visible at 20x light sensitivity. The ring is 97,000 kilometers wide and 8400 kilometers thick. Despite its name, however, Thebe isn't actually a shepard moon of it. The ring has been seen to continue past the moon. It's thought that the ring is formed by dust from impacts on Thebe, which are probably unusual, and therefore leaving the ring fairly not-dense.
 |
| An image of the rings of Jupiter, showing the gradual decrease in brightness further away from Jupiter. |
Phewph! It seems that this ring article is taking longer than expected, so i'm going to split it into two or three parts. Tomorrow, I'll cover Saturn's ring system, and if I have time, Uranus and Neptunes. Stay tuned till then!
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