An asteroid the size of one kilometer found rotates around the sun every 151 days

Astronomers have spotted an unusual asteroid with the shortest "year" known to all asteroids. The rocky body, named 2019 LF6, is about one kilometer long and goes around the sun every 151 days or so. In its orbit, the asteroid rocks beyond Venus and sometimes approaches Mercury, which surrounds the sun every 88 days. 2019 LF6 is one of the 20 known "Atira" asteroids, whose orbits belong entirely to the Earth.

"Nowadays, we do not often find as many as one kilometer-long asteroids," says Quanzhi Ye, a postdoctoral researcher at Caltech who discovered LF6 in 2019 and works with Tom Prince, physics professor Ira S. Bowen to Caltech and Principal Investigator. JPL and George Helou, executive director of IPAC, an astronomy center of Caltech.

"Thirty years ago, people began to organize methodical searches for asteroids, first looking for larger objects, but now that most of them have been found, the larger ones are rare birds, "he says. "The LF6 is very unusual both in orbit and size, and its unique orbit explains why such a large asteroid has escaped decades of careful research."

The 2019 LF6 was discovered via the Zwicky Transient Facility, or ZTF, a state-of-the-art camera from the Palomar Observatory, which scans the skies every night to search for passenger objects, such as exploding stars and asteroids in motion. Because ZTF scans the sky so quickly, it is well suited to search for Atira asteroids, which have short observation windows.

"We only have 20 to 30 minutes before sunrise or after sunset to find these asteroids," Ye said.

To find Atira asteroids, the ZTF team conducted a dedicated observation campaign, named Twilight according to the time of day most conducive to the discovery of objects. Twilight was developed by Ye and Wing-Huen Ip of the National Taiwan Central University. Until now, the program has discovered another Atira asteroid, named 2019 AQ3. Before 2019, the LF6 arrived, 2019 AQ3 had the shortest known year of all asteroids, circling the sun about every 165 days.

"The two big Asteroids discovered by ZTF are spinning well outside the solar system plan," says Prince. "This suggests that they have already been thrown into the past by the solar system because they have moved too close to Venus or Mercury," Prince said.

In addition to the two Atira objects, ZTF has so far found about 100 near-Earth asteroids and about 2,000 asteroids orbiting the main belt between Mars and Jupiter.

Ye hopes that the Twilight program will lead to more discoveries about Atira, and he looks forward to NASA's possible selection of NEOCam (Near-Earth Object Camera), a satellite project designed to search for asteroids closer to the sun than previously. surveys. NEOCam would detect infrared or thermal signatures of asteroids. (You work at IPAC, who would process and archive the data for the NEOCam mission, but is not part of this team.)

"As Atira asteroids are closer to the sun and warmer than other asteroids, they are brighter in the infrared," says Helou. "NEOCam has the double advantage of its position in space and its infrared ability to find these asteroids more easily than telescopes at visible wavelengths of the ground".