I A very small object following Earth in the same orbit

[Michaela SJ]

A bunch of years ago, I read about a very small object following Earth in the same orbit, but not in any danger of collision with Earth (at least in the next few billion years).

Anyone know about the object. I have done a search but cannot find any reference to what I think I read about?

 

[Bandersnatch]

Probably this one:
https://en.wikipedia.org/wiki/2010_TK7
Same orbit implies libration points, and that's the only object so far discovered there.

 

[Vanadium 50]

Or maybe this one? https://en.wikipedia.org/wiki/J002E3

 

[Michaela SJ]

Thanks to both of you. I am absolutely certain the article I am trying to find was not about a space vehicle remnant.

The description of 2010 TK7 meets my estimated time frame but my recollection is slightly different (and likely wrong ). I remember the object as being in the 'same' orbit. [Repeat] (and likely wrong )

 

[davenn]

The description of 2010 TK7 meets my estimated time frame but my recollection is slightly different (and likely wrong ). I remember the object as being in the 'same' orbit. [Repeat] (and likely wrong )

It is in the same orbit as the Earth ... what made you think it wasn't ?

 

[Ratman]

It is in the same orbit as the Earth

...from a certain point of view. I guess Michaela's recollection stems from a simplified press note about the first Earth Trojan. It is not that coorbital objects stay in any given point – more than 7000 known Jupiter Trojans couldn't fit into two Lagrange points on the planet's orbit. They appear to orbit these points instead, following tadpole and horseshoe-shaped trajectories, and some even circle the planets outside the Hill sphere, mimicking true moons. Check https://en.wikipedia.org/wiki/(469219)_2016_HO3 as an example of not-the-second-moon of Earth.

 

[davenn]

...from a certain point of view.

no, not at all

more than 7000 known Jupiter Trojans

we are not talking about 1000's of objects, just 1 object

 

[Bandersnatch]

@davenn @Ratman makes valid points. He highlights that objects never stay exactly at the libration points (hence their name). He gives Jupiter's Trojans as an example. Each one of them oscillates around the L4 and L5 points, forming a dynamic cloud. Still, they'd be normally referred to as 'being at the libration points', or 'sharing Jupiter's orbit' - even though neither is literally true. So it's quite likely the OP heard of 2010 TK7 as being in the same orbit. Whereas by looking at the animations on the Wiki page one can get the impression that this crazy-looking trajectory cannot mean that the orbits are the same.

 

[hmmm27]

3753 Cruithne

 

[Ratman]

Weird thing about L₄ and L₅ libration points is that they are stable equilibria, despite the fact they are the maxima of effective potential. So it is not that they attract any object like a gravity well. The stability (in a rotating frame) comes from the fact that while any perturbation displaces the test particle from the exact location of the libration point, the displacement also results in Coriolis force putting the particle into stable orbit around it.