Astronomers Find a New Asteroid Sharing Earth's Orbit

Astronomers have discovered a captive asteroid shadowing Earth in its orbit. From a report: The asteroid, known as 2020 XL5, is only the second of its type ever seen, shepherded by Earth's gravity into an orbit that is locked in synchrony with our planet's. It has not shared our orbit for long -- a few centuries, probably. And it will not be there in the far future. Simulations indicate that 2020 XL5 will slip out of Earth's grasp within 4,000 years and head into the wider solar system. But its presence offers a tantalizing glimpse of what else might be out there in the local gravitational whirlpools. Some bits might date back to the beginning of the solar system -- shades of the building blocks that coalesced into our planet. "These objects are not as exotic as we think," said Toni Santana-Ros, a postdoctoral researcher at the University of Barcelona in Spain and an author of a paper describing the discovery, which was published on Tuesday in the journal Nature Communications.

Great

[fj3k]

Now the IAU is going to declare that the Earth hasn't cleared its orbit and demote it to dwarf-planet.

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[K. S. Kyosuke]

It's a Trojan. The existence of Trojans for a body is evidence of strong gravitational influence of that body, and hence of that body clearing its orbit.

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[jbengt]

The planet Pluto will clear it's orbit . . .

The dwarf planet Pluto will not clear Uranus.

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[kenwd0elq]

I was just about to write pretty much the same thing. According to IAU rules, Earth isn't a planet.

Can we just repeal the IAU convention that said that?

And Pluto IS SO a planet.

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[whitroth]

Ah, yes. The convention was mostly over, 90% of the astronomers had left, and that's when this idiocy passed. An astronomer I know told me most astronomers ignore it.

And *my* solar system has nine planets, and Pluto is most *certainly* one of them.

Can we mine it?

[fabioalcor]

Even if it's not made of rare or precious elements, if it contains simple things like iron or even water, it'd be pretty useful out there. Most of the cost of building things in space is transport them from here to there.

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[ceoyoyo]

Maybe. It's a loooong way away, but apparently in some cases the trojans might take less energy to reach than the moon.

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[RockDoctor]

Less energy than the Moon? Difficult. But if you went through the Earth-Moon L4 (or L5) point to get to Earth-Sun L4 (or L5) you might be able to get the energy requirements down that far.

Less energy to get to E-S L4 (or L5) than to get to co-orbiting with Mars ... now that would be a lot easier case to demonstrate.

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[ceoyoyo]

I'm not sure if that's compared to some lunar orbit, or the surface. There might well be some weird orbit like you mention that's lower energy, but I don't think it would be very significant. Either way, any reasonable transfer orbit would take ages.

They are playing catchup with me.

[Gravis Zero]

I don't mean to brag but I discovered this asteroid when I was a child. Yep, looked out at night and saw it with my eagle-eyed sight. I noticed a few other people online have noticed it as well and they have started calling it "the moon" which seems like a strange name IMHO. Though people have gone as far as to claim we've landed on it which just sounds nuts but OK guys, whatever.

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[znrt]

and you haven't even see the dark side ...

This sounds familiar

[DontBeAMoran]

https://en.wikipedia.org/wiki/... [wikipedia.org]

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[vbdasc]

In fact, it's this

https://en.wikipedia.org/wiki/... [wikipedia.org]

A Fireball crashes to Earth

[jtalle]

Holy Saturday Morning TV, it's Fireball XL-5!

Slip into space?

[bjwest]

If it slips out of Earths grasp, how will it move into space and not fall into the sun? Does it have engines that will accelerate it out of orbit, instead of fall out and spiral into the sun?

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[RockDoctor]

If it slips out of Earths grasp, how will it move into space and not fall into the sun?

I'm not quite sure what you think you mean in the first phrase, but the answer to the second is "inertially".

But it's a near certainty that this body will, at some point have a relatively close passage to either Venus or Mars, and that'll probably move it to an Earth-crossing orbit. As it is, the friendly paper (fig 1c specifically) points out that the body, on it's current orbit, spends about 10% of it's time moving aro

cool animations of trojan orbits

[602]

Among the many links in the "co-orbital asteroids" section of this Wikipedia page are several really cool orbit animations: https://en.wikipedia.org/wiki/... [wikipedia.org]