Once discovered and suddenly disappeared: Lost asteroids are a mystery in astronomy. And sometimes the celestial bodies become a threat to the Earth.
A thought experiment: You have misplaced your key and have an idea where it might be, but the search is still unsuccessful. And you suspect: They may never find your key again. Astronomers feel the same way about so-called lost asteroids. The difference: A lost key is annoying. But if an asteroid cannot be found again, it can be dangerous. Of the many thousands of celestial bodies that are considered lost, astronomers consider some to be threatening to the Earth – a threat that astronomers are determined to ward off. Researchers around the world are working together to find the missing asteroids.
But what exactly are lost asteroids? These are celestial bodies that were discovered and observed by astronomers at some point, but whose exact positions are no longer known. Particularly in early astronomy, when observation techniques were less precise than today’s methods, many celestial bodies disappeared from our field of vision.
A famous example is the dwarf planet Ceres, which is located in the asteroid belt between Mars and Jupiter. After its discovery in January 1801, researchers lost sight of the celestial body. It was only months later that Ceres was found again by the German astronomer Franz Xaver Freiherr von Zach – a stroke of luck in modern astronomy that is not always successful.
Because sometimes celestial bodies remain missing, like the asteroid 1979 XB, which was discovered in December 1979. 1979 XB is considered a Near Earth Object (NEO) and a potentially dangerous asteroid with a diameter of around 400 to 900 meters.
Physicist Richard Moissl, who heads the Planetary Defense Office of the European Space Agency (Esa), said in an interview with t-online: “There is a non-negligible probability that he [1979 XB, Anm. d. Red.] could collide with Earth within the next 100 years.” This makes the asteroid fascinating and worrying at the same time, said the scientist.
And actually: According to a risk list from Esa, an asteroid impact on Earth could occur on December 12, 2056 at 9:38 p.m. It is not known where it could hit. But one thing is certain: the impact of an impact near an inhabited region would be devastating. For comparison: the meteor that broke over the Russian city of Chelyabinsk in 2013 was only about 20 meters tall. At that time, more than 1,500 people were injured.
“The Chelyabinsk meteor was a special case,” says Moissl. The celestial body flew to us from the direction of the sun. Such small objects could hardly be seen at the moment.
But how can a 900 meter large chunk disappear? There are numerous reasons for this: In addition to the imprecise observation techniques already mentioned in the early days of astronomy, it may happen, for example, that researchers cannot observe newly discovered objects long enough to calculate their further orbits.
The astrophysicist Richard Moissl is head of the Planetary Defense Office at the European Space Agency (Esa). In his role, he is responsible for monitoring and researching Near-Earth Objects (NEOs) that could pose a potential threat to Earth. Moissl is working on identifying threats from asteroids and comets at an early stage and developing possible defense measures. His tasks include assessing the risk of collisions and researching strategies for deflecting asteroids.
Sometimes it can also happen that an asteroid that has been discovered is too small and faint to be observed further. Perhaps it is too far away from Earth and will be hidden from view by telescopes after a few days. Then researchers try to find the object again.
“It’s real detective work,” says Moissl. To find the lost asteroids, astronomers around the world are constantly developing new methods. “For example, we systematically analyze certain regions in the solar system where such objects could be hiding.”
Sometimes objects close to Earth can actually be found again – such as the celestial body 6344 PL. The asteroid was discovered by astronomers in 1960 and classified as potentially dangerous for Earth. Then he got lost. It was only in 2007 that 6344 PL was found again thanks to modern observation methods and now has the alternative name 2007 RR.