Long-term observations of the object 2016 HO3, a kind of "second moon" of the Earth, have shown that it really is a small asteroid, and not an accumulation of "space debris", said scientists speaking at the annual DPS planetary conference in Provo, USA.
“Despite the fact that HO3 is very close to the Earth, it is extremely difficult to study it due to the fact that it has a very small size, not exceeding, quite possibly, 30 meters. Our observations show that this celestial body makes one revolution on its axis in about 28 minutes and consists of typically asteroidal rocks,”said Vishnu Reddy of the University of Arizona in Tucson (USA).
Earth's closest and most stable quasi-moon, asteroid 2016 HO3, was discovered by renowned astronomer Paul Chodas of NASA's Jet Propulsion Laboratory and colleagues at the end of April last year. It is a small object with a diameter of 30-100 meters, which has been circling our planet for at least one century.
Astronomers know four more such celestial bodies that became temporary "moons": these are asteroids 2003 YN107, 2004 GU9, 2001 GO2 and 2002 AA29. All of them can regularly approach the Earth, but these objects, unlike 2016 HO3, spent moments in the Earth's company by astronomical standards - years and decades.
Initially, scientists believed that 2016 HO3 will spend several hundred more evens with the Earth, which is an unusually long time for quasi-satellites, but later it turned out that the “second moon” would travel with our planet for several million more years.
The unusual trajectory of the Earth's "second moon" and its small size, as Reddy recalls, made many planetary scientists, including himself, doubt that it really is an asteroid.
Many scientists have suggested that this celestial body could be a fragment of a booster block or some other large piece of "space debris" that fell into an unusually elongated orbit as a result of some complex processes in near-earth space.
Reddy and his colleagues tested this by observing 2016 HO3 with the LBT telescope in the Pinaleno Mountains in southern Arizona over several months. During these observations, scientists relied on one simple rule - the metal sheathing of spaceships and rockets reflects light waves in a completely different way than the matter of asteroids, which consists mainly of silicon rocks, does.
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As it turned out, the "second moon" of the Earth reflects light and thermal radiation poorly enough, which makes it possible to say with confidence that it is an asteroid, and not "space debris", and that it is one of the most common S-type asteroids, consisting of iron silicates and magnesium.
The same measurements indicated that the actual dimensions of 2016 HO3 are noticeably more modest than Chodas and his colleagues initially assumed - the diameter of this "moon" does not exceed 36 meters, which brings it closer in size to the Chelyabinsk meteorite.
All this, according to Reddy and his colleagues, makes the "second moon" of the Earth one of the most attractive objects for testing the instruments of future asteroid capture missions - it is only 12 million kilometers away from us, and it can be easily reached using robotic or manned spacecraft in the next decade.
