Earth's First Trojan Asteroid 2010 TK7 Discovered

We are not alone – a small asteroid, 1,000 feet across, has finally been found and it’s orbital path shares Earth’s orbit.

2010 TK7 teases Earth by straying in the planet’s orbit but at the same time is about 50 million miles ahead of Earth. This is the first of the so-called Earth’s Trojan asteroids, a family of space rocks so called because they share the same orbit as the Earth but is always far away enough so as not to collide with the planet. 

2010 TK7 was discovered last year by the astronomers from Athabasca University, UCLA, and University of Western Ontario, who used NASA’s Wide-field Infrared Survey Explorer (WISE) satellite and ground-based telescopes but it was only recently that it was determined as a Trojan asteroid. Their work was published in Nature magazine on Wednesday.

Discovery of 2010 TK7 is significant because Trojan asteroids, scientists believe, may hold elements rare on Earth’s surface. Moreover, Martin Connors of Athabasca University said Trojan asteroids sometimes range so far ahead that they’re on the opposite side of the sun from Earth. Besides spotting one in Earth’s orbit becomes difficult from the ground because they are generally up in the daytime sky.

In an interview with The Vancouver Sun, Connors said he had been hunting for an Earthly Trojan for almost 20 years and was ecstatic when he finally discovered one.

However, despite the name ‘Trojan’, 2010 TK7 is harmless. “On timescales of hundreds of thousands of years, this particular object would not be a threat,” he said.

There are thousands of Trojan asteroids in our solar system – a few have been found for Mars and Neptune and nearly 5,000 for Jupiter.ibtimes.com

WISE finds the very first Earth Trojan asteroid

NASA’s Wide-field Infrared Survey Explorer (WISE) has found the very first asteroid that (more or less) shares an orbit with Earth! Called 2010 TK₇, this asteroid is about 300 meters (roughly 1000 feet) across, and is the first in an up-to-now theoretical class of objects called Earth Trojans.

Here’s a WISE image of the little bugger:

Doesn’t look like much, does it? Of course, from 80 million km (50 million miles) from Earth it’s amazing we can see it at all. Moreover, given its position in the sky, it’s only up during the day as seen from Earth; it was only discovered because WISE orbits the Earth, so the sky is always dark. Also, WISE sees in the infrared, so warmer objects are easier to spot. This rock is probably around the freezing point of water or so, which, to an astronomer, is pretty warm.

So what makes this asteroid special?

If you have a large body (like the Sun) orbited by a smaller body (like the Earth), then there exist some points in space where, if you place a much smaller object (like an asteroid) it will remain there. Normally, if you put this smaller body in some random spot, the gravity of the two objects will alter its path, making its orbit unstable. But these five special places, called Lagrangian points, are stable. Well, kinda. Two are stable, in that if you put an object there it’ll tend to stay there even if you poke it gently — think of it like a small dip in flat table. Put a marble there and it’ll stay put, even if you push it a little. It’ll fall back into place in the center of the dip. In the diagram here, those are the L4 and L5 points.

The other three points (L1, 2 and 3) are stable as long as nothing perturbs any objects located in them; if you do poke an object orbiting there, it’ll tend to keep moving. Think of each these points as a bump in the table, where you can just barely balance a marble. It’ll stay there until you push it, then it rolls away. That’s called an unstable equilibrium, if you want to impress people at parties.

Anyway, the first real-world (real-Universe?) example of this was found in 1906, when an asteroid was spotted in Jupiter’s L4 point, 60° ahead of it in its orbit. It was named Achilles, which started the tradition of naming them after characters involved with the Trojan War (the asteroids ahead of Jupiter are named after Greeks, and the ones behind at the L5 point after Trojans). Since then, Trojan asteroids have been found for Mars as well as Neptune.MORE