WISE Discovers Earth’s First-Known Trojan Asteroid

NEOWISE discovered the first (and so far only) Trojan asteroid in Earth’s orbit, known as 2010 TK7. In this artist’s concept, Earth’s orbit around the Sun is indicated by blue dots, and the asteroid is shown in gray, with its orbit traced in green, as it oscillates above and below Earth’s orbit every 395 years. WISE was able to spot 2010 TK7 because of that eccentric orbit, which takes the asteroid as far as 90 degrees away from the glare of the Sun. Trojan asteroids share an orbit with a planet, orbiting the Sun ahead of or behind the planet – mostly Jupiter, but also around Mars and Neptune. The clock at upper left shows how the orbit of 2010 TK7 changes over time. Its orbit is well defined and, for at least the next 100 years, the asteroid will not come closer to Earth than 15 million miles (24 million kilometers). Objects shown are not to scale.