U.S. astronomers discover asteroid with shortest year

James Marshall
July 10, 2019

"You don't find kilometre-size asteroids very often these days", said Ye in the Caltech press release. The asteroid measures 1km (0.6miles) in diameter making it relatively big for an asteroid.

"Thirty years ago, people started organizing methodical asteroid searches, finding larger objects first, but now that a lot of them have been found, the bigger ones are rare birds", Ye said. Before 2019 LF6 came along, 2019 AQ3 had the shortest known year of any asteroid, orbiting the sun roughly every 165 days. The ZTF is responsible for scanning the skies for transient objects that can be anything from exploding stars to asteroids and, because it's capable of scanning the sky quite fast, it's flawless for finding the "Atira" asteroids, which usually only have 20 to 30-minute observation windows. The Near-Earth Object Camera would be capable of picking up the heat signatures of asteroids.

The orbit of asteroid 2019 LF6 (white), discovered by ZTF, falls entirely within the orbit of Earth (blue). Both of these asteroids orbit well outside of the plane of the solar system. Like the grooves on a vinyl record, most planets align along a flat disk.

At its most distant point from the Sun, 2019 LF6's orbit flings it beyond Venus' path and at its closest point, it's reeled back in within Mercury's orbit. The unique orbit of the asteroid is what allowed it to remain undiscovered for so long. "Like other asteroids, Atiras are leftovers from the formation of our solar system".

2019 LF6 was discovered via the Zwicky Transient Facility (ZTF), a state-of-the-art camera at the Palomar Observatory that scans the skies every night for transient objects, such as exploding and flashing stars and moving asteroids. Because ZTF scans the sky so rapidly, it is well-suited for finding Atira asteroids, which have short observing windows.

Ye said that the team could only search for them about 20 to 30 minutes before sunrise and after sunset. But ZTF is also good at finding asteroids in general.

"Both of the large Atira asteroids that were found by ZTF orbit well outside the plane of the solar system", Tom Prince, Ira S. Bowen Professor of Physics at CalTech said.

One proposed NASA mission named NEOCam (for Near-Earth Object Camera) would launch a spacecraft equipped to look specifically for Atira asteroids.

Most asteroids are found deeper in space, past the next planet along from Earth, Mars. "Therefore, we can improve our understanding of the inventory of near-Earth asteroids by studying the Atiras".

Other reports by Click Lancashire

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