Astronomers have discovered the fastest asteroid ever orbiting the Sun – and sometimes it gets closer to the Sun than the planet Mercury.
Asteroid 2021 PH27 was discovered earlier this month and has the shortest orbital period of any known asteroid in the solar system. The asteroid’s orbit, about one kilometer in diameter, takes it 20 million kilometers (12 million miles, or 0.13 AU) from the Sun every 113 days.
This illustration shows the positions of the planets and the asteroid 2021 PH27 on the night of discovery of August 13, 2021 as they would be seen from a vantage point in the plane of the solar system. Credit: CTIO / NOIRLab / NSF / AURA / J. da Silva
But subsequent observations of this object indicate that it is in an unstable orbit that crosses the orbits of Mercury and Venus. That means, say astronomers, that within a few million years it will likely be destroyed or ejected from its current position in a collision with one of these planets or the sun.
One idea of the origin of this object is that it could be an extinct comet from the outer solar system that was captured in a short orbit while passing near one of the terrestrial planets. But there are other options too.
“Most likely, in 2021, PH27 was removed from the main asteroid belt between Jupiter and Mars and the gravity of the inner planets shaped its orbit into its current configuration,” said Scott S. Sheppard of the Carnegie Institution of Science, who made the discovery with Ian Dell ‘ Antonio and Shenming Fu from Brown University.
This artist’s rendering shows the asteroid (above) and the planet Mercury (below). Credit: CTIO / NOIRLab / NSF / AURA / J. da Silva
The asteroid is so close to the Sun’s massive gravitational field that it is experiencing the largest general relativistic effects of any known object in the solar system, the team said. At its closest point to the sun, the object should be almost 500 degrees C (900 degrees F). It’s hot enough to melt lead.
2021 PH27 has now passed behind the sun and will only be visible again in early 2022. Further observations are then planned to determine its exact orbit, which will allow it to be officially named.
Sheppard said the 2021 PH27 discovery was significant as it will help astronomers learn more about asteroids that might one day hit Earth.
“Understanding the asteroid population in orbit is important in completing the census of asteroids near Earth, including some of the most likely Earth impactors that could approach Earth in daylight and that cannot be easily detected in most nocturnal surveys. away from the sun, ”said Sheppard.
Press release from NOIRLab
Carnegie Science press release