Most of the asteroids in our solar system orbit around the sun in the main asteroid belt between Mars and Jupiter, or in a cluster in the same orbit as Jupiter called the Trojans. Plus, there are asteroids that come close to the orbit of Earth, called Near-Earth asteroids. But now, for the first time, an asteroid has been discovered orbiting entirely inside Venus.
Astronomers from Caltech’s Zwicky Transient Facility (ZTF) observed the asteroid, called 2020 AV2, as part of a small class of asteroids called Atira. These bodies orbit within Earth, but only 2020 AV2 orbits within Venus.
“This is a very exciting discovery,” Quanzhi Ye, a visiting assistant research scientist in the University of Maryland Department of Astronomy and ZTF co-investigator, said in a statement. “Astronomers have been systematically searching the skies for small bodies since the 1970s and ’80s, and there’s not much uncharted frontier left in the inner solar system. Asteroids with orbits interior to Venus’s orbit are challenging to observe, and I’m thrilled we finally found this one.”
The 2020 AV2 asteroid is the first asteroid found to have an orbit entirely inside the orbit of Venus. Discovered with the Zwicky Transient Facility at Palomar Observatory 2020, AV2 orbits the sun in approximately 151 days. NASA/JPL
2020 AV2 is between 1 and 3 kilometers (0.6 to 1.8 miles) wide, with a slightly tilted orbit relative to the rest of the solar system. It says inside Venus throughout its entire orbit, and even comes close to the orbit of Mercury at some points. It has one of the shortest years of any asteroid discovered so far, completing an orbit around the sun in approximately 151 days.
Astronomers believe the asteroid likely began further out in the solar system before migrating inward over time. “An encounter with a planet probably flung the asteroid into Venus’s orbit,” said Tom Prince, Professor of Physics at Caltech and a senior research scientist at NASA’s Jet Propulsion Laboratory. “It’s the opposite of what happens when a space mission swings by a planet for a gravity boost. Instead of gaining energy from a planet, it loses it.”
George Helou, executive director of the IPAC astronomy center at Caltech, concurred that it must have been a tough journey for the asteroid. “Getting past the orbit of Venus must have been challenging [for 2020 AV2],” he said.
And the future is not looking bright for the plucky little asteroid. “The only the way it will ever get out of its orbit is if it gets flung out via a gravitational encounter with Mercury or Venus,” Helou said, “but more likely it will end up crashing on one of those two planets.”