Astronomers have found the closest asteroid to the sun ever seen, a relatively large space rock that gets within 20 million kilometres of our star 鈥� about 13 per cent of the distance between the sun and Earth. They have also spotted two other strange asteroids as part of a hunt for the rare space rocks that orbit closer to the sun than Earth does.
These asteroids are hard to find because, in order to look for them, astronomers must point their telescopes towards the sun. That means there is a huge amount of glare to deal with, and the brightness of the sky makes it tough to spot any but the brightest objects. at the Carnegie Institution for Science in Washington DC and his team worked around this by observing only during the 10 minutes in the morning and evening when the sun is just below the horizon.
Using the Dark Energy Camera in Chile, they found two asteroids with orbits that are entirely within Earth鈥檚 orbit. One of them, called 2021 PH27, stays closer to the sun during its entire orbit than any other asteroid we have seen, and gets closer at its nearest point than any other object we know of.
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鈥淥n average, it鈥檚 the second-closest object [to the sun] in the solar system, but it approaches the sun much closer than Mercury,鈥� says Sheppard. The average distance is so different because, at its furthest point, 2021 PH27 gets much further from the sun than Mercury does. Its surface reaches temperatures of about 500掳C when it is at its nearest to the sun.
2021 PH27 will also get extremely close to Venus in the next thousand years or so, and may even collide with it within a few million years. But that isn鈥檛 the only planetary crash the researchers are predicting 鈥� another asteroid they found may someday smash into Earth.
That space rock, called 2022 AP7, is most likely more than 1.5 kilometres across, making it one of the larger potentially hazardous asteroids astronomers have spotted. It is much further from the sun than the other two objects, with its orbit stretching from inside Earth鈥檚 orbit to just beyond Jupiter鈥檚. For now, when it crosses Earth鈥檚 orbit, it is always on the other side of the sun from Earth, but that is slowly changing.
鈥淚t鈥檒l take thousands, if not tens of thousands, of years before it slowly works its way to where it鈥檒l be bright in the night sky, and then maybe [it will] get really close to Earth,鈥� says Sheppard. 鈥淚t won鈥檛 get near Earth anytime soon.鈥�
As we find more of these objects, we can test our predictions about how many of them there should be overall, and therefore increase our understanding of the near-Earth environment and the history of the solar system.
The Astronomical Journal
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