The unusual orbits of Atira asteroids makes them hard to find even if they're large. The ZTF is created to find asteroids that fall within Earth's orbit and have short observing windows, which are also known as Atiras.
Ye discovered the chunk of rock using Palomar Observatory's Zwicky Transient Facility (ZTF), a camera that rapidly scans the night sky searching for signals from exploding or flashing stars and moving asteroids.
A team of astronomers led by Quanzhi Ye from Caltech University in the US found 2019 LF6 using the Zwicky Transient Facility (ZTF) at the Palomar Observatory in California, as noted in a press release.
As reported by CNET, Quanzhi Ye of Caltech, who discovered the asteroid released a statement saying: "You don't find kilometre-size asteroids very often these days". "Thirty years ago, people started organizing methodical asteroid searchers, finding larger objects first, but now that majority have been found, the bigger ones are rare ones".More news: New Orleans Floods as Gulf Coast Braces for Torrential Rains
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"LF6 is very unusual both in orbit and in size-its unique orbit explains why such a large asteroid eluded several decades of careful searches", he said.
The newly discovered asteroid - now referred to as 2019 LF6, orbits the sun every 151 days, or about the last day of May. It was named Twilight after the time of day which is the most recommended time for looking for Atira asteroids. "This means that sometime prior to now, they have been flung out of the plane of the solar system as a result of they came too close to Venus or Mercury". The camera system surveys the sky extremely fast, making an ideal tool for finding asteroids. In other words, 2019 LF6's aphelion (farthest distance from the Sun) is still shorter than Earth's perihelion (closest distance to the Sun).
The ZTF also discovered around 100 near-Earth asteroids, as well as 2,000 asteroids that orbit the Asteroid Belt between Mars and Jupiter.
The discovery of 2019 LF6 was announced in the Minor Planet Electronic Circular (MPEC) newsletter issued by the IAU's Minor Planet Center on June 19, 2019.
It's hard to spot the asteroids because astronomers only have about 20 to 30 minutes before or after sunset to find them, Ye said.