Asteroids In Resonance With JupiterFebruary 19, 2011 11:17 AM   Subscribe

A video plotting the movement of Hilda and Trojan asteroids that are locked in a resonance with the orbit of Jupiter. Best watched in HD. Previously
posted by bonobothegreat (25 comments total) 18 users marked this as a favorite

?
posted by oddman at 11:55 AM on February 19, 2011

This needs a bit of explanation either here or on the video itself.
posted by sfts2 at 12:00 PM on February 19, 2011

I think I had that album in the early '70s.
posted by Curious Artificer at 12:04 PM on February 19, 2011

The video does have some explanation:

This video highlights 2 groups of asteroids that have orbits in resonance with Jupiter. To highlight the motion we rotate the view at the same speed as an idealized version of Jupiter, that is, we keep the rotation constant as if the planet was on a circular orbit.

The first group highlighted is in the 3:2 resonance, Objects in this group complete 3 orbits in the time that Jupiter takes to complete 2. The periodic interaction with Jupiter's gravity creates the 3 lobed pattern you see where they never come close to the giant planet. This makes their orbits more stable by protecting them from strong interactions with the planet.

The second group consists of those which have orbital periods identical to Jupiter, these are primarily found in 2 clusters around the Jovian Lagrange points. These points are 60 degrees ahead and behind Jupiter in its orbit.

There are many other mean-motion resonances that influence the dynamics of the asteroid belt, some are very unstable, for example there are almost no asteroids in the 3:1 resonance, also known as the Kirkwood gap. Asteroids which are in this resonance have their orbital eccentricities increase quickly until their orbits cross those of other planets and they suffer a close encounter.

Hilda asteroids
Jupiter Trojan asteroids
posted by lukemeister at 12:06 PM on February 19, 2011 [1 favorite]

This video highlights 2 groups of asteroids that have orbits in resonance with Jupiter. To highlight the motion we rotate the view at the same speed as an idealized version of Jupiter, that is, we keep the rotation constant as if the planet was on a circular orbit.

The first group highlighted is in the 3:2 resonance, Objects in this group complete 3 orbits in the time that Jupiter takes to complete 2. The periodic interaction with Jupiter's gravity creates the 3 lobed pattern you see where they never come close to the giant planet. This makes their orbits more stable by protecting them from strong interactions with the planet.

The second group consists of those which have orbital periods identical to Jupiter, these are primarily found in 2 clusters around the Jovian Lagrange points. These points are 60 degrees ahead and behind Jupiter in its orbit.

There are many other mean-motion resonances that influence the dynamics of the asteroid belt, some are very unstable, for example there are almost no asteroids in the 3:1 resonance, also known as the Kirkwood gap. Asteroids which are in this resonance have their orbital eccentricities increase quickly until their orbits cross those of other planets and they suffer a close encounter.

posted by troll on a pony at 12:06 PM on February 19, 2011 [1 favorite]

posted by troll on a pony at 12:08 PM on February 19, 2011 [2 favorites]

The video shows the relative movements of planets and clouds of asteroids. It's a top down view of the solar system. The two groups of asteroids have been organized into clumps by the gravitational field of Jupiter. If you watch Jupiter passing each clump, you can see asteroids cycling in and out of each clump in circular motions as Jupiter passes. It's interesting because it is a complex, emergent and unexpected phenomenon.
posted by carter at 12:09 PM on February 19, 2011 [1 favorite]

Just in case anybody isn't quite sure of what they're looking at, the 3 objects in the middle are Mercury, Venus, Earth and Mars. The green donut is the cloud of objects that make up the main asteroid belt. Jupiter is the slowest moving dot and the clouds of white dots are the asteroids locked in resonance with Jupiter.
posted by bonobothegreat at 12:26 PM on February 19, 2011

Gah,.. the four objects circling the Sun in the middle are Mercury, Venus, Earth and Mars
posted by bonobothegreat at 12:28 PM on February 19, 2011 [1 favorite]

But the Jupiter object doesn't seem to be moving, or am i missing something?
posted by OHenryPacey at 12:40 PM on February 19, 2011

But the Jupiter object doesn't seem to be moving, or am i missing something?

The whole thing is projected from the point of view of Jupiter, I think. So in the animation, the asteroids and other planets are moving past Jupiter. But relative motion is still relative motion.

Now that you have pointed this out, I think my explanation above is poorly phrased.
posted by carter at 12:53 PM on February 19, 2011

relative motion is still relative motion = relative motion is still motion ...
posted by carter at 12:53 PM on February 19, 2011

The camera's point of view is rotating at a rate that keeps Jupiter to the left. The rotation rate is constant, set to be equal to the time Jupiter takes to rotate around the sun. As Jupiter's orbit is not exactly circular, you see it moving a bit.
posted by cosmac at 12:56 PM on February 19, 2011 [1 favorite]

got it thanks
posted by OHenryPacey at 1:08 PM on February 19, 2011

In astronomy, the word trojan refers to a minor planet or natural satellite (moon) that shares an orbit with a larger planet or moon, but does not collide with it because it orbits around one of the two Lagrangian points of stability (Trojan points), L4 and L5, which lie 60° ahead of and behind the larger body.

How does that work? What does it mean that it orbits a point? What forces are keeping it there?
posted by popechunk at 1:39 PM on February 19, 2011

From the first video sidebar, here's a related video. There's 500,000 asteroids* plotted, with the Hilda asteroids in red. It shows a normal view, with Jupiter moving in orbit, and the planets labeled.

* Here's the video showing asteroid discoveries. From the video description:
As the video moves into the mid 1990's we see much higher discovery rates as automated sky scanning systems come online. Most of the surveys are imaging the sky directly opposite the sun and you'll see a region of high discovery rates aligned in this manner.
posted by jjj606 at 1:43 PM on February 19, 2011 [2 favorites]

Some of those asteroids have really eccentric orbits. I kept thinking "Hang in there little guy".
posted by dibblda at 2:00 PM on February 19, 2011 [3 favorites]

Ah that was awesome. For some reason, I am reminded of that old physics class trick where you put some iron filings on a card, then put a magnet under it, to see the magnetic lines of force.

And this is sort of like that, on a massive scale, and we're plotting little specks of matter flying around large gravitational forces. I didn't get that until I saw the group of two 1:1 asteroids swirling around two points, one ahead and one behind Jupiter. Then I read the explanation, those are the Jovian Lagrange points. Of course.
posted by charlie don't surf at 2:08 PM on February 19, 2011 [1 favorite]

How does that work? What does it mean that it orbits a point? What forces are keeping it there?

Lagrange point. Basically a point in space where the gravity of two separate objects (Like the sun and the earth) balances out.

Also, remember this is from the 'point of view' of Jupiter, so these objects are rotating around the sun as quickly as Jupiter does.
posted by delmoi at 2:10 PM on February 19, 2011 [1 favorite]

jjj606's discovery video is pretty awesome. As the technology improves you can see the "beam of discovery" facing away from the Sun sweeping up some of the structures in the OP video. BTW, does anybody know what the two "beams of discovery" are from in the last couple of frames, pointing fore and aft along the Earth's orbital trajectory instead of away from the Sun?
posted by localroger at 2:58 PM on February 19, 2011

What forces are keeping it there?

Gravity--specifically the Sun's gravity and Jupiter's gravity acting on the asteroids. posted by flug at 3:07 PM on February 19, 2011

BTW, does anybody know what the two "beams of discovery" are from in the last couple of frames, pointing fore and aft along the Earth's orbital trajectory instead of away from the Sun?

from the video description: At the beginning of 2010 a new discovery pattern becomes evident, with discovery zones in a line perpendicular to the Sun-Earth vector. These new observations are the result of the WISE (Widefield Infrared Survey Explorer) which is a space mission that's tasked with imaging the entire sky in infrared wavelengths.

posted by Max Power at 3:20 PM on February 19, 2011

Sadly, WISE was shut down last week. It ran out of coolant.
posted by dirigibleman at 5:38 PM on February 19, 2011

Orbital resonances are harder to grasp until you get a handle on what resonances are in daily experience. It's a really neat phenomenon ... wish someone would write a great book on the subject.

The WP article: "Resonance is the tendency of a system to oscillate with larger amplitude at some frequencies than at others. These are known as the system's resonant frequencies. At these frequencies, even small periodic driving forces can produce large amplitude oscillations, because the system stores vibrational energy."

Some examples from daily life:
• Soldiers have brought bridges down by marching across them in lockstep. The famous "Galloping Gertie" bridge was a victim of structural resonance, the wind blowing on it made it vibrate like a violin string.
• Speaking of which: different acoustical music instruments have pieces that resonate at different frequencies, which gives them their 'timbral' character (cellos don't sound like bassoons or tubas) ... distinguishing Strads from poorer violins
• Feedback in a sound system can happen when 'just the right frequency' entering the mike 'finds' a resonance and creates a 'feedback loop'.
• Much of electronics depends on "resonant" circuits ... a radio is 'tuned' to one station by changing the circuit so that it "resonates" at that frequency.
• If you've ever stood on a swing and 'pumped' it to go higher and higher with your body, you've done it by feeling the swing's resonant frequency.

Waves and resonances are everywhere in nature ... makes sense, most physical bodies (including yours) will respond to vibrations of one or more frequencies.
posted by Twang at 5:49 PM on February 19, 2011 [2 favorites]

I think I had that album in the early '70s.

Hawkwind.
posted by stargell at 10:37 PM on February 19, 2011

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