Asteroid 2021 PH27 takes just 113 Earth days to circle the Sun. The newly discovered asteroid orbits the sun faster than any of its known relatives.
The space rock, known as 2021 PH27, makes one circle around our star every 113 Earth days, according to its discoverers. This is the shortest orbital period of any known object in the solar system, with the exception of the planet Mercury, which takes only 88 days to circumnavigate the sun.
However, 2021 PH27 travels on a much more elliptical path than Mercury and is therefore significantly closer to the Sun - about 12.4 million miles (20 million kilometers) at closest approach, compared to 29 million miles (47 million kilometers) for the innermost planets of the solar system.
During such close passages of the Sun, the surface of 2021 PH27 becomes hot enough to melt lead - about 900 degrees Fahrenheit (500 degrees Celsius), the research team estimates. These deep dives into the sun's gravity well also mean that the asteroid is experiencing the greatest general relativity effects of any known object in the solar system. These effects show up as a slight wobble of the 2021 PH27 elliptical orbit around the Sun, as the team observed.
This orbit, by the way, is not stable in the long term. 2021 PH27 is likely to collide with the Sun, Mercury or Venus in a few million years, unless first thrown out of its current path by gravitational interaction, team members say.
2021 PH27 was first seen on August 13 by astronomers using the Dark Energy Camera (DEC), a powerful multipurpose instrument mounted on the 4-meter Víctor M. Blanco telescope at the Cerro Tololo Inter-American Observatory in Chile.
Over the next few days, the team was able to pinpoint the asteroid's orbit through further observations with DEC and Magellanic Telescopes at the Las Campanas Observatory in Chile, as well as small telescopes in Chile and South Africa operated by the Las Cumbres Observatory.
Sheppard and colleagues estimate the 2021 PH27's width to be about 0.6 miles (1 km). According to the researchers, the space rock may have originated in the main asteroid belt between Mars and Jupiter, and then was thrown into space as a result of gravitational interaction with one or more planets.
However, the orbital path of 2021 PH27 is tilted 32 degrees relative to the plane of the solar system. This steep tilt suggests it could be an extinct comet that was born far beyond the solar system and then moved to a closer orbit after passing by Mars, Earth, or another rocky planet.
Further observations may help solve this mystery, but Sheppard and other astronomers will have to wait several months to collect more data. 2021 PH27 is now moving behind the Sun from our point of view, and it won't reappear until early 2022, members of the research team say.