Fastest-orbiting asteroid in solar system discovered

Artist's illustration of 2021 PH27, a newfound asteroid that orbits the sun once every 113 Earth-days. This is faster than any other known object in the solar system, except Mercury (see below and to left of 2021PH27).
A new asteroid speeds around the sun faster that any of its known kin.

It is also known as 2021 PH27. The discovery team determined that the space rock completes one orbit around our star every 113 Earth day. This is the shortest orbital time of any solar system object, except Mercury which takes only 88 days.

However, 2021 PH27 travels a more elliptical route than Mercury and is therefore closer to the sun at 12.4 million miles (20,000,000 kilometers) when it comes closest to it, compared with 29 million miles (47,000,000 km) for the innermost planet of the solar system.

Related: 7 Strangest Asteroids in the Solar System

The discovery team estimates that 2021 PH27's top temperature can reach 900 Fahrenheit (500 Celsius) during close solar passes. The asteroid also experiences the greatest general relativity effects, despite being deep in the sun's gravity. These effects are manifested in a slight wobble around the sun's elliptical orbit 2021 PH27, which has been observed by the team.

This orbit is, however, not stable over the long-term. Team members stated that 2021 PH27 is likely to collide with Venus, Mercury, and the sun in a few millions years if it doesn't get ejected by a gravitational interaction.

2021 PH27 was first spotted by astronomers using Dark Energy Camera (DEC) on Aug. 13. This powerful multipurpose instrument is mounted on the Vctor Blanco 4-meter Telescope at Cerro Tololo Inter-American Observatory, Chile.

Thanks to additional observations from the DEC and Magellan Telescopes at Las Campanas Observatory, Chile, and smaller scopes operated by the Las Cumbres Observatory, the team was able pinpoint the asteroid's orbit within the next few days.

Team members stated that although some observations with the instruments were delayed by the 2021 PH27 push, it was well worth it.

Scott Sheppard, an Astronomer at the Carnegie Institution for Science, Washington, D.C., stated in a statement that "Telescope time for astronomers can be very precious, but the international nature of the unknown makes astronomers very willing override their science and observations for new, interesting discoveries such as this."

Images of discovery images of the newfound asteroid 2021 PH27 taken on the night Aug. 13-2021 with the Dark Energy Camera. This camera is mounted on the Vctor M. Blanco 4-meter Telescope, Cerro Tololo Inter-American Observatory, Chile. (Image credit: CTIO/NOIRLab/NSF/DOE/DECam/AURA/S.S. Sheppard (Carnegie Institution of Science).

Sheppard and his coworkers estimate that 2021 PH27 measures approximately 0.6 miles (1km) in width. According to the researchers, the space rock could have been formed in the main asteroid belt, which is located between Jupiter and Mars, and then moved inward due to gravitational interactions with other planets.

But, 2021 PH27 is tilted 32 degrees in relation to the plane of our solar system. This suggests that it could be an extinct comet, which was first born in the outer solar system and then moved closer to Earth, Mars, or another rocky planet.

Additional observations may help to solve this mystery. However, Sheppard and other Astronomers will need to wait for a few more months before collecting additional data. The discovery team stated that 2021 PH27 is currently moving behind the sun and won't return to Earth until early 2022.