Help astronomers observe the first Earth 'Trojan' asteroid, 2010 TK7

Observations from the Faulkes Telescope Project have helped NASA confirm the discovery of the Earth's first Trojan asteroid.

On July 27, NASA announced the discovery of the first Trojan asteroid, which shares the Earth's orbit and we would like FT users to help astronomers observe this exciting new object!
Named 2010 TK7, this asteroid was initially spotted by the Wide-field Infrared Survey Explorer (WISE) mission on 2010 October 1 and was flagged on the Minor Planet Centre's NEO Confirmation Page shortly afterwards. Using the Faulkes Telescope South located at Siding Spring, Sergio Foglia (an FT user involved in the joint Faulkes-IASC education programme) observed the NEOCP object (as seen in the image here) and reported its position and movement to the Minor Planet Centre in Harvard, on October 6.  

However, since the final observing arc spanned a total of only 6 days, its special nature was not evident at that time.  Martin Connors of Athabasca University in Canada and colleagues, Paul Wiegert and Christian Veillet, used observations made in late April this year with the 3.6-m CFHT on Mauna Kea to identify 2010 TK7 as a Trojan object; one which currently circulates around the L4 Lagrangian point thereby leading the Earth in its orbit around the Sun.  A version of their paper published in the journal, Nature, can be found here.

What is a Trojan?

350px-Lagrange_very_massive.svg.pngAll planets, comets and asteroids in the Solar System travel around the Sun in well-defined orbits. Some of these asteroids (or minor planets as they are known) share an orbit with a larger planet or moon. Luckily for them, they are positioned at one of 2 very stable points in this orbit (known as Lagrangian points and shown as L4 and L5 on the image here - the Sun is the yellow circle, the Earth is shown as the blue dot), so they have no chance of colliding with their larger neighbour.  These types of asteroids are called trojans.

Such objects typically remain gravitationally trapped for relatively short periods (1,000-100,000 years) and eventually switch to one or other Lagrangian point or are even ejected altogether thereby losing their unusual Trojan status.  

Future landing sites?

Trojans are of particular interest in that they are potentially useful as a spacecraft destination in that they can be energetically less
costly to reach than our Moon - even as a possible site for a future space observatory.  It is likely that there are a number of natural objects which are loosely bound to each of the Earth's Lagrangian points.  However, astronomers have searched for Earth Trojans for some years now without success and so those that do exist are all likely to be less than 1 km in size.  By measuring how this asteroid reflects the sun's light, astronomers estimate 2010 TK7 to be 150-500 metres across.

However, although it orbits the Sun almost exactly once per year, the orbit is at present rather too inclined (I = 21 degrees) and has too large an eccentricity (e = 0.19) for it to be a convenient target for a visitation by a spacecraft in the near future.

Follow-up work

Follow-up observations are required to better define the exact shape of this Earth Trojan's orbit.  Following on from successful asteroid observing collaborations between the BAA, IASC and FT school users, we will be asking schools to take images of this exciting object as it becomes visible to the Faulkes Telescopes later in the year. So keep an eye out for observing requests for this object on our daily-updated 'Exciting Targets' page - you could soon be helping astronomers investigate this rarely-seen object in our Solar System!