NASA Science
Trojan asteroid
Asteroids parked in the gravitational lay-bys 60° ahead of and behind a planet.
The Lagrange points 60 degrees ahead of and behind a planet in its orbit are stable enough to collect debris that then stays for billions of years. Jupiter has the largest collection — more than a million larger than a kilometre — and Neptune, Mars, Uranus and Earth all have some. Because they have sat undisturbed since the solar system formed, they are a sample of the original material, which is why the Lucy mission is spending twelve years touring eight of them.
Where it has come up lately
Related terms
Near-Earth object
An asteroid or comet whose orbit brings it inside 1.3 astronomical units of the Sun.
Asteroid and comet
Rock that stays rock, and ice that grows a tail when it gets warm.
Coma and tail
A comet's atmosphere, and the two separate tails the Sun pushes off it.
Oort cloud
A shell of icy bodies at the edge of the Sun's influence, inferred rather than observed.
Questions
What is Trojan asteroid?
Asteroids parked in the gravitational lay-bys 60° ahead of and behind a planet.
Why does it matter?
Jupiter has the largest collection — more than a million larger than a kilometre — and Neptune, Mars, Uranus and Earth all have some. Because they have sat undisturbed since the solar system formed, they are a sample of the original material, which is why the Lucy mission is spending twelve years touring eight of them.