Astronomers discover an asteroid that's closer to the Sun than any other

Artist’s rendition of what an asteroid would look like flying past the SunNASA/JPL-Caltech
  • Asteroid 2020 AV2 has the smallest semi-major axis and smaller aphelion of any known asteroid.
  • Zwicky Transient Facility deems this to be a new class of asteroid.
  • Its orbit falls entirely within the Earth's but does not cross the orbit of any other planet in the Solar System.
Most asteroids that orbit the Sun can be found in the Asteroid Belt or along the outer edges of the Solar System, in the Kuiper Belt — home of the former planet Pluto. Some anomalies break free and cross the orbits of other planets as they swing around the Solar System's star.

However, astronomers At the Zwicky Transient Facility ( ZTF) have discovered a new asteroid that does neither of those things.

Instead of being located in the Asteroid belt, 2020 AV2 has an orbit that falls between Mercury and Venus. And, it doesn't cross either of their paths. Its orbit resides entirely between the two planets. According to ZTF, it's an entirely "new class of Solar System objects".


2020 AV2’s orbit around the Sun which resides entirely between Mercury and VenusNASA/JPL-Caltech

"Currently 2020 AV2 has both the smallest semi-major axis and smallest aphelion of any known asteroid," as per the International Asteroid Warning Network's ( IAWN) notification.

The semi-major axis is a useful way to measure how far an asteroid is from the Sun on average. If 2020 AV2 has the ‘smallest semi-major axis', this means — on average — its closer to the Sun than any other asteroid in the Solar System.

The aphelion is the point when the orbit of an asteroid is the furthest from the Sun. So if every asteroid known to man was put in a line-up of their distance from the Sun at aphelion, 2020 AV2 would be the closest to Earth's star.

It's not a threat to Earth

2020 AV2 has a diameter of between 1 to 3 kilometres — about half the height of Kilimanjaro — and it doesn't pose a threat to Earth. The Jet Propulsion Laboratory ( JPL) estimates that the 2020 AV2 will be at its closest point to the planet on 14 October 2020.

Mount Kilimanjaro, a dormant volcano in TanzaniaPixabay

Even then, it will be nearly 0.35 AU away from Earth. That's over 11 million kilometres more than how far Venus is from the planet at its closest point.

Icaruses of the Solar System

The discovery of 2020 AV2 doesn't mean that other asteroids don't come even closer to the Sun. They do — but only for a very small fraction of their entire orbit.

For instance, Icarus — the first asteroid to ever be observed by radar — comes closer to the Sun than even Mercury, every year 1 year and 1 month.


However, the asteroid named after the Greek myth of the boy who flew too close to the Sun also crosses the paths of Venus and Mercury in doing so.

Goldstone delay-Doppler image of Icarus obtained on 17 June 2015NASA

Since Icarus' discovery in 1968, astronomers have found other asteroids that fly even closer to the giant flaming ball of gas at the centre of our Solar System. The asteroid with smallest known perihelion — the point when the orbit of an asteroid is the closest to the Sun — is 2005 HC4.

2005 HC4 orbit around the Sun which stretches beyond the orbit of MarsNASA/JPL-Caltech


It flies within 0.071 AU of the Sun, that's 23% closer than Mercury, but also goes out as far that 3.562 AU away from the Sun — well beyond the orbit of Mars. It may not always be the closest to the Sun, but the large divergence between its perihelion and aphelion, makes it the fastest asteroid discovered so far travelling at 565,000 kilometres per hour (kph).

In doing so, its orbit crosses the orbits of Mercury, Venus and Mars.

Radar images of 163693 Atira taken at Arecibo Observatory on 20 January 2017NASA/Arecibo Observatory

Only 20 asteroids spotted so far have orbits that fall entirely within Earth's dubbed Atira asteroids. And, even they cross the paths of other planets.

2020 AV2 is the only asteroid so far that orbits the Sun within Earth's, and doesn't cross any other planet's orbit.

See also:
NASA's 'Lucy' is going to travel 4 billion miles to explore seven Trojan asteroids — and an asteroid Moon

The 10 biggest asteroids that pose a threat to Earth in 2020

Not an asteroid but massive volcanic eruptions in India might have set off mass extinction 66 million years ago