A Trojan asteroid has been discovered coorbiting with the planet Neptune. Trojans and Greeks are the names given to asteroids that gather at gravitational null points called Lagrangian points. In every two body system – Neptune orbiting the Sun in this case – there are five of them. One each in front and behind the planet, one on the opposite side of the orbit to the planet’s position, one sixty degrees ahead of the planet in its orbit and one sixty degrees behind. It is these final two points where Trojans may be found. Jupiter has quite a collection, the lion’s share of the 200,000 known Trojans, Earth has a few, but because of the distance and the Lagrangian point’s present position in an area of bright stars, it has been difficult to examine Neptune’s potential cache.
Researchers using the Subaru telescope were able to filter out the starlight using interstellar dust. Then an image of the 100km large Trojan, the sixth to be found round the eighth planet, popped out. The researchers estimate there to be around 150 similar sized Trojans waiting to be discovered in the area.
Very well timed for Earth’s present display of space rubble – the Perseid Meteor shower, which can be enjoyed through the twitter meteorwatch until the weekend (and probably informally long afterward).