Other than the planet Mercury, this particular space rock, named 2020 AV2, has the smallest aphelion – distance from the sun – of any known natural object in the solar system.
It also has the shortest known orbital period, circling the sun in just 151 days.
Space.com said astronomers learned about 2020 AV2 last week after it was spotted in the night on 4 January by the 1.2 metre Samuel Oschin Schmidt telescope at the Zwicky Transient Facility in California.
This was conducted by the Virtual Telescope Project, an online observatory based in Italy that was looking for asteroids inside the Earth’s orbit.
Gianluca Masi, founder and director of the Virtual Telescope Project, explained the challenges of photographing new asteroids closer to the sun.
The image revealing 2020 AV2 was produced using the average of 14, 60-second exposures.
“Taking those images was hard, because the object was quite low (25 degrees or less) above the western horizon, at dusk. The sky background was bright, an almost full moon was up in the sky too and the target was lower and lower, minute after minute,” he wrote.
The Bad Astronomy blog said asteroids could be anywhere in the solar system, although the vast majority were in what was called the Main Belt, orbiting between Mars and Jupiter.
A smaller class of asteroids called Atiras orbited the sun inside the Earth’s orbit. These are hard to spot in the sun’s brightness and fewer than two dozen are known. 2020 AV2 has been classed as a Vatira, derived from Venus and Atira.
“It's hard to know just how big it is, because it's too small to resolve,” the blog said.
“But based on its distance and brightness (and assuming how reflective it is) it's likely to be a few kilometres across. It's possible bigger Vatiras might exist in orbits closer to the sun but their increased brightness would be offset by the increased sky brightness, making them harder to find.”
So, what does 2020 AV2 look like? It’s actually hard to tell as the astronomical images only show a small dot to a backdrop of the sky and distant stars.
Scientists have calculated that 2020 AV2 never gets closer than 12 million kilometres from Mercury and 10 million kilometres from Venus.
Bad Astronomy said this discovery cold be the start of many more. There’s an ongoing search for what are called vulcanoids, asteroids inside the orbit of Mercury. None have yet been spotted.
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