Study: Earth shares its orbit with tiny asteroid

Jul 27, 2011 By MALCOLM RITTER , AP Science Writer

(AP) -- Like a poodle on a leash, a tiny asteroid runs ahead of Earth on the planet's yearlong strolls around the sun, scientists report.

The discovery of this companion, which measures only about 300 yards across, makes Earth the fourth planet in the solar system that's known to share its orbit with an asteroid.

Imagine Earth and the asteroid traveling around a clock face, with the sun in the middle. Generally, the asteroid runs about two numbers ahead.

However, the asteroid sometimes ranges so far ahead that it's on the opposite side of the sun from Earth, said Martin Connors of Canada's Athabasca University in Alberta. He reports the work with colleagues in Thursday's issue of the .

Asteroids are giant space rocks that orbit the sun, and ones that share an orbit with a planet are called Trojans. Scientists had previously found a few for Mars and and nearly 5,000 for Jupiter. Spotting one in Earth's orbit is difficult from the ground because the potential locations are generally in the daytime sky.

The newfound object, called 2010 TK7, was discovered last year by NASA's WISE satellite. Connors and colleagues were able to focus a ground-based telescope in Hawaii on it in April, determining its with enough precision to show it was a Trojan.

Donald K. Yeomans, manager of NASA's Near-Earth Object Program Office, who didn't participate in the discovery, agreed that the is a Trojan. Most scientists suspected Earth had them, he said, and "I would guess there's others.

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User comments : 17

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DoubleD
3 / 5 (2) Jul 27, 2011
Any chance of the difference in orbit velocities resulting in a collision?
that_guy
2.3 / 5 (3) Jul 27, 2011
I expect that it is not stable in the long term, even if it is temporarily stable or resonant because of other gravitational forces.

It is my understanding that to be stable long term, it would have to be at one of the lagrange points. I could be wrong, and I certainly wouldn't mind someone with a little more knowledge on the matter to chime in.

Now, regarding the idea that we should land on an asteroid next (Then mars)...I think we found the perfect space rock to explore. Earth's little buddy.
emsquared
2.5 / 5 (2) Jul 27, 2011
Crazy. How have we not noticed until recently? I don't suppose we can have any idea how long it's been there? I realize 300 yds isn't big astronomically, but that's extremely dangerous size if it were to collide with earth... the Tsar Bomb was ~100 MT, that thing would be ~1600 MT...
SincerelyTwo
not rated yet Jul 27, 2011
I expect that it is not stable in the long term, even if it is temporarily stable or resonant because of other gravitational forces.

It is my understanding that to be stable long term, it would have to be at one of the lagrange points. I could be wrong, and I certainly wouldn't mind someone with a little more knowledge on the matter to chime in.

Now, regarding the idea that we should land on an asteroid next (Then mars)...I think we found the perfect space rock to explore. Earth's little buddy.


http://en.wikiped...nts2.svg

I'm no expert but based on their description of this objects location it sounds about right for the L4 lagrange point. Actually, it sounds like this thing is just barley within L4, so we might run out of 'luck' when something comes by and nudges this thing in the wrong way. : |
that_guy
not rated yet Jul 27, 2011
@sincerely two - on the clock comparison, the asteroid generally runs about two numbers ahead ~66 degrees, but it also ranges all the way to the opposite side of the sun, or 180 degrees.

That doesn't indicate that the orbit is in equilibrium...and it goes all the way from L3 to L4. Apparently when it crosses the lagrange points, it has too much speed to stay in them?

If it is relatively stable, I would assume it does not use the exact same orbit, but one that is similar.

@emsquared, have you tried to spot an asteroid that is in the glare of the sun? Based on the orbit, the only time you could catch a glimpse of the asteroid from earth is during the day or early night or morning, like venus - So there are challenges to finding it in addition to its extremely small relative size.
SincerelyTwo
not rated yet Jul 27, 2011
I don't understand how an object can change direction without something pulling back on it. Unless it's some crazy GR effects/maths that explain it I would intuitively expect an orbiting body to simply move in an elliptical path. So how exactly do you go from L4 to L3 and back? Wouldn't there have to be an additional body somewhat between L3 and L4 but also further out to pull it back as it approaches either point?

I feel a bit lost in trying to understand this back-and-forth kind of orbit, or am I misunderstanding?
that_guy
not rated yet Jul 27, 2011
Yeah, that's where I was confused too. But I think I figured it out because of your mention of the ellipse.

Lets say that the asteroid's orbit is more oval than the earth's. It would travel faster in one part of its orbit, and slower in another - it could move in relation to the earth, while still following a traditional ellipse.

so lets say that on the opposite side of the sun it is at aphelion (farthest from the sun), and going slower. The earth catches up. Then when at around 66 degrees off from the earth it is nearing perihelion and going faster, closer to the sun than the earth's orbit, and speeding ahead of the earth. This could put it at a resonance with the earth, in the same orbital area, but with a different shaped orbit?

Pyle
5 / 5 (4) Jul 27, 2011
My first guess was to go back toward the horseshoe orbit like this link:

http://www.physor...oid.html

But then I found this.

http://www.space....tk7.html

Pretty crazy little rock.
that_guy
not rated yet Jul 27, 2011
I thought the horseshoe at first too, but it didn't seem to jive with what they were saying.

Thanks for the link Pyle. Just trying to understand that orbit while looking at it makes my f---ing head hurt.

So the orbit is an oval that covers a quarter of the circumfrerence of earth's orbit, plus it shifts forward each orbit...I wouldn't have expected an orbit like that to be possible. They definitely need an orbital diagram or movie with this article.

Although it would be near impossible to verbally describe it, perhaps they should step away from calling it a trojan given our preconceptions of what a trojan would be.
SincerelyTwo
not rated yet Jul 27, 2011
Pyle, Ok, well, it at least now makes sense how it can move from L3 and L4 without the extra body, but how it manages to orbit offset like that ... it's got to be a very unstable orbit!

Pretty amazing, and very fascinating. I'm trying to develop an N-Body sim to recreate that right now lol.
SincerelyTwo
5 / 5 (4) Jul 28, 2011
I came across a much better image of this asteroid's orbit on this article of it;
http://www.pbs.or...rth.html

There's also a video/animation of its orbit if you scroll down on that article. :D
88HUX88
5 / 5 (1) Jul 28, 2011
Is it shaped like a teapot? http://en.wikiped...s_teapot
rawa1
1 / 5 (1) Jul 28, 2011
IMO it's regular moonlet... We have two Moons from now...
yyz
5 / 5 (3) Jul 28, 2011
Co-discoverer Paul Wiegert has a page devoted to 2010 TK7 with nice animations and mucho info: http://www.astro....0TK7.pdf
yyz
5 / 5 (3) Jul 28, 2011
A preprint of the Nature paper can be found here: http://www.astro....0TK7.pdf

(hope this posts correctly)
yyz
5 / 5 (1) Jul 28, 2011
Hmmm. Dunno what happened to my link to Wiegert's 2010 TK7 page above, was working earlier. In any case, try here: http://www.astro....2010TK7/

[This really is an informative page for this object]
LKD
not rated yet Jul 29, 2011
I notice the motion between how far the trojan departs from a close orbit of L4 matches up to the time it takes for Jupiter's synodic period. I assume there is a relationship here?

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