What is the mysterious asteroid that has been tagging along with Earth?

[Neandethal00]

Today I see news articles everywhere on an asteroid that tagging along with the earth.
I was hoping there would be a thread on the subject here.

My questions are
1) What is it?
2) Why on Earth (excuse the pun) haven't we noticed it until now! Is it new in Earth's orbit? We are busy locating objects billions light years away, but an object on our orbit goes totally unnoticed?
3) Is there any danger to Earth from it? I have a feeling the answer is 'yes', even though many top astro-brains will assure us it is harmless.

 

[russ_watters]

Could you post a link to one of these stories please...

 

[D H]

The OP is referring to 2010 TK₇, the first Earth Trojan to be discovered. Here's one of many articles: http://www.scientificamerican.com/article.cfm?id=first-asteroid-companion.

Why haven't we noticed it? Because it is small and dark while space is big and dark.

 

[Drakkith]

Today I see news articles everywhere on an asteroid that tagging along with the earth.
I was hoping there would be a thread on the subject here.

My questions are
1) What is it?
2) Why on Earth (excuse the pun) haven't we noticed it until now! Is it new in Earth's orbit? We are busy locating objects billions light years away, but an object on our orbit goes totally unnoticed?
3) Is there any danger to Earth from it? I have a feeling the answer is 'yes', even though many top astro-brains will assure us it is harmless.

1. It is an asteroid that orbits along with the Earth and the moon around the sun at one of our lagrange points.

2. It is very small and hard to see.

3. Not currently. It all depends on whether its orbit stays stable or not. I don't know any details.

 

[D H]

1. It is an asteroid that orbits along with the Earth and the moon around the sun at one of our lagrange points.

It doesn't orbit at one of the Lagrange points. It is in a pseudo orbit about one of the Lagrange points. The L4 point, to be specific.

Minor quibble? Perhaps, perhaps not. 2010 TK₇'s pseudo orbit takes it very close to the L3 point (close to the point on the Earth's orbit about the Sun that is separated from the Earth by 180 degrees).

 

[Drakkith]

It doesn't orbit at one of the Lagrange points. It is in a pseudo orbit about one of the Lagrange points. The L4 point, to be specific.

Minor quibble? Perhaps, perhaps not. 2010 TK₇'s pseudo orbit takes it very close to the L3 point (close to the point on the Earth's orbit about the Sun that is separated from the Earth by 180 degrees).

Ah ok. I didn't realize its orbit varied so much.

 

[Neandethal00]

The OP is referring to 2010 TK₇, the first Earth Trojan to be discovered. Here's one of many articles: http://www.scientificamerican.com/article.cfm?id=first-asteroid-companion.

Why haven't we noticed it? Because it is small and dark while space is big and dark.

It is not small, it is a rock with a diameter of 3 football fields. With our telescopic power on ground and in space, this rock should put all astronomers to shame for not detecting sooner.
It is like a fly sitting on our nose and not knowing it.

Its orbit is very funny as shown by animation. It makes spiral orbit around 'earth's path around the sun'. How long has it been ahead of the earth? I think any answer to this question will be a 'guess'.

 

[Drakkith]

It is not small, it is a rock with a diameter of 3 football fields. With our telescopic power on ground and in space, this rock should put all astronomers to shame for not detecting sooner.
It is like a fly sitting on our nose and not knowing it.

Its orbit is very funny as shown by animation. It makes spiral orbit around 'earth's path around the sun'. How long has it been ahead of the earth? I think any answer to this question will be a 'guess'.

No, it's like a fly moving around 10,000 miles away from us. It is nowhere near our nose. And yes, it is small. Very very small compared to thousands upon thousands of objects in the solar system. Ever heard of the Wide-Field Infrared Survey Explorer (WISE) space telescope? It was launched on December 14 2009:

By May 27, 2010, WISE discovered 12,141 previously unknown asteroids, of which 64 were considered near-Earth, and 11 new comets.

It took an infrared telescope in space to detect these. Should we be ashamed that we didn't detect them sooner? Or does this instead tell us of the difficulty in detecting these objects?

 

[D H]

It is not small, it is a rock with a diameter of 3 football fields. With our telescopic power on ground and in space, this rock should put all astronomers to shame for not detecting sooner.
It is like a fly sitting on our nose and not knowing it.

No, it is like a small molecule sitting on our nose and not knowing it.
Or a virus sitting across the room and not knowing it.A rock with a diameter of 3 football fields that is 80 million kilometers from the Earth has an angular diameter of 0.8 milliarcseconds. That is incredibly small. Resolving that rock with a telescope is equivalent to spy satellite in low Earth orbit that can read the fine print on a legal contract. Hubble's best instruments have a resolution of 85 milliarcseconds. There is no way to see this rock with Hubble. WISE, the satellite telescope that did see it, saw it as a sub-pixel sized object that was radiating in the infrared.

 

[D H]

No, it's like a fly moving around 10,000 miles away from us.

No reason to exaggerate! It's like a fly moving around 2,000 miles away from us.

 

[Drakkith]

No reason to exaggerate! It's like a fly moving around 2,000 miles away from us.

I was referring to a horsefly!

 

[hubewa]

While we are on this topic, I'm just wondering, how are Trojan asteroids supported in their orbit around a certain planet?

 

[Nik_2213]

http://en.wikipedia.org/wiki/Trojan_(astronomy ) ( Doesn't explain theory )

http://en.wikipedia.org/wiki/Lagrangian_point ( Explains equipotential surfaces & zones)

You should also look through...
http://en.wikipedia.org/wiki/Interplanetary_Transport_Network
http://www.esm.vt.edu/~sdross/superhighway/description.html
... as these allow a space mission to frugally, but slowly 'hitch-hike' to a destination by riding the constantly changing relative positions of planets' Lagrange zones...

 

[Redbelly98]

EDIT: After thinking about this and reading other posts in the thread, I realize what I wrote here is wrong:

[STRIKE]Just to add to the difficulty of detection, ground-based telescopes can only see this asteroid during daylight hours. So it's like looking for a small, dimly lit object while somebody is shining a light into your eyes.[/STRIKE]

 

[~jet]

It is not small, it is a rock with a diameter of 3 football fields. With our telescopic power on ground and in space, this rock should put all astronomers to shame for not detecting sooner.
It is like a fly sitting on our nose and not knowing it.

Its orbit is very funny as shown by animation. It makes spiral orbit around 'earth's path around the sun'. How long has it been ahead of the earth? I think any answer to this question will be a 'guess'.

http://www.youtube.com/watch?v=S_d-gs0WoUw&feature=fvwrel" ... its not really any surprise that these are coming to light only in recent years. We're getting better at this

 

[Neandethal00]

While we are on this topic, I'm just wondering, how are Trojan asteroids supported in their orbit around a certain planet?

Now time for theoretical astronomers to get into action and explain the strange path of the asteroid resulting from gravity of earth, moon and sun.

Note the asteroid is not exactly in L4 or L5 lagrange points. These points, correct me if I miscalculated, are off Earth's orbit and far from the location of the asteroid.

The thing to watch is how does its orbit change over time and if there is any drift of the orbit towards earth.

If simulation of the orbit I have seen is correct, the asteroid should be visible from some parts of Earth at night, specially before morning.

 

[D H]

Now time for theoretical astronomers to get into action and explain the strange path of the asteroid resulting from gravity of earth, moon and sun.

They have already done that. Read the link in post #3. Remember, this is asteroid is called 2010 TK₇, not 2011 TK₇. That means it was discovered last year. They have enough data on hand to get a good estimate of the asteroid's orbit.

Another point of interest: Right now we have multiple spacecraft in pseudo orbits about the Sun-Earth L1 and Sun-Earth L2 points. The same concept (pseudo orbits about a Lagrange point) applies to the L4 and L5 points.

Note the asteroid is not exactly in L4 or L5 lagrange points. These points, correct me if I miscalculated, are off Earth's orbit and far from the location of the asteroid.

The L4 and L5 points are on the Earth's orbit but are separated from the Earth by an angle 60 degrees. As I mentioned before, the asteroid is in a pseudo orbit about the L4 point.

If simulation of the orbit I have seen is correct, the asteroid should be visible from some parts of Earth at night, specially before morning.

No. Even at its closest approach to Earth (20 million km), it will have an apparent magnitude of about 16.8. The dimmest object you can see with your naked eye has an apparent magnitude of 8. A pair of binoculars bring that up to 9.5. With a very, very expensive amateur telescope (think new automobile) you can see objects with an apparent magnitude of 14 or so.