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A visitor from another star – it was the news a few days after October 19, 2017, when researchers discovered an enigmatic cigar-shaped object away from the solar system at 57,000 km / h (57,000 mph). The entity was moving too fast to come from our own system, traveling in a U-shaped hyperbolic orbit that drove it around the sun and sent it back into interstellar space.
Astronomers using the pan-survey telescope and the Rapid Response System (Pan-STARRS 1) in Hawaii discovered the strange object, which had first been designated as A / 2017 U1. But soon, that received the name & # 39; Oumuamua, which in Hawaiian means "scout" or "visitor from far coming first," according to the International Astronomical Union.[[[[& # 39; Oumuamua: the first interstellar visitor of the solar system explained in photos]
"It has long been theorized that such objects existed – asteroids or comets moving between the stars and sometimes crossing our solar system – but this is the first such detection," said Paul Chodas, head of the Center's 39, studies on objects close to the Earth. NASA's reaction propulsion laboratory in Pasadena, California, said in a report.
The researchers immediately trained as many telescopes as possible on "Oumuamua" to learn about the object before it became too dark for an instrument. They found that it measured between 400 meters (1,300 feet) and 800 meters (2,000 feet) long and quite thin – perhaps six times less than the length. The visitor was also tumbling from end to end and had a dark red color, similar to other small cold objects in the external solar system. Scientists have determined that this came from the direction of the Lyra constellation, although no one has yet figured it out precisely what system it is from.
So what is it?
& # 39; Oumuamua was classified as a comet during its first observation. But the fact that it does not produce a large swollen coma flowing behind like a tail, as comets normally do when heated by the sun, has led astronomers to suspect themselves. Some researchers have argued that it was a rocky asteroid or maybe even a new class of interstellar object.
Others have speculated that & # 39; Oumuamua is a planetesimal, or a piece of rock normally incorporated into a larger planet that was projected from its native system by the forces of gravitation. And it could even be a zombie comet or, more precisely, "a monstrous and extremely mellow aggregate of poorly bound dust grains", as a paper on the idea was left behind by a comet that disintegrated as the sun approached.
Generally speaking, the scientific community hears to say that "Oumuamua is a comet because it moves slightly faster than expected if it had just propelled itself under the effect of the force of gravity of the sun. The most likely explanation is that the object degazes like a comet, creating jets that push it. The observations suggest that it is 10 times more reflective than the local comets of our solar system, perhaps because Oumuamua's degassing blew up the dust from its surface, revealing a glossy ice beneath.
A visitor of space?
This jet-driven movement almost makes Oumuamua look like a spacecraft coming from another star, which quickly passed through our system, then sped at full speed. Even astronomers have been intrigued by this possibility, and researchers at Search for Extraterrestrial Intelligence (SETI) listened for potential technological signals fleeing from the object not once, but twice. Both campaigns have not heard anything.
With his co-author Shmuel Bialy, Avi Loeb of the Harvard-Smithsonian Astrophysical Center has published his own conjecture "Oumuamua was a very fine veil of light (a kind of propulsion using sun photons) resulting from an advanced technological civilization. His reasoning was based on the fact that degassing would have changed the visitor's rotation period – an effect that should have been easy to identify but was not observed.
Loeb suggested that Oumuamua could be a messy piece of space that would have accidentally landed in our system or potentially an exploratory ship sent to check our area. Few scientists have supported Loeb's assertions, but he argues that rejecting the possibility of foreigners at first eliminates useful assumptions that should be acceptable elements of a rational inquiry.
"Science should be open minded," he told Space.com at the first announcement of his idea.
After seeing Oumuamua, researchers are now eager to spot other similar objects. Greg Laughlin, an astronomer at Yale University, thought there might be billions on billions of Oumuamua-type entities drifting through the Milky Way. This gives credence to the idea that microbes could have hitched a ride on objects of the type 'Oumuamua in the past and prevalent in space – a theory known as panspermia.
Astronomers may not have to wait too long to find other interstellar objects. The large synoptic surveyed telescope (LSST) in Chile, which is expected to be online by the beginning of the next decade, will look at the night sky with unprecedented details and may discover one or two more "Oumuamua".
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