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When astronomers first saw a strange cigar-shaped object passing by the sun last October, they could say that it was coming from another stellar system . I do not know exactly what it was.
Now they know it. A study published Wednesday in the journal Nature indicates that the interstellar visitor, nicknamed Oumuamua, is neither an asteroid nor an extraterrestrial spaceship (as some wags had suggested), but a small interstellar comet
"This is the only object discovered so far." Marco Micheli, an astronomer from the European Space Agency and lead author of the new study, told NBC News MACH in an email [19659006] Image: Oumuamua “/>
Comets – icy and dusty objects that have been likened to dirty "snowballs" – usually form long tails when they approach the sun. Such a tail n & # 39; 39; was not visible in the earlier observations of Oumuamua (which means "scout" in Hawaiian), which has led other astronomers to conclude that it was a problem. an asteroid.
But an analysis of new observations made by ground telescopes and the Hubble Space Telescope produced a surprise: the trajectory of Oumuamua could not be explained solely by the gravitational forces exerted on it by the sun and the planets – as would be the case if it was an asteroid or a space rock. Unexpectedly, we found that Oumuamua did not slow down as fast as it did. It should have been under the sole force of gravity ", Micheli in a statement.
His team concluded that the unexpected movement of Oumuamua was to be caused by amounts of gaseous material from its surface. This "degassing" – commonly seen in comets – was too small to be visible but significant enough to affect Oumuamua's trajectory
But not everyone buys this explanation – at least not completely.
an astronomer from the University of Toronto at Scarborough, told MACH in an email that if Oumuamua is a comet, she must be the one who lost much of her ice before leaving her stellar system [19659004] "A comet that has lost ice is essentially the same as an asteroid," he said. "Oumuamua therefore seems to be in this ambiguous region between the two."
Jackson led Previous research on Oumuamua but was not involved in the new study.
Regardless of its precise identity, Oumuamua might be the first of many interstellar visitors we will encounter. "Jackson said new telescopes should help astronomers find "many more objects like Oumuamua and then we will be able to gather a more complete picture of what planets' building blocks look like in other systems planetary, which will also help us planets. "
Oumaumau is now directed to the outer solar system at a speed of about 70,000 miles per hour." Astronomers expect him to spend the orbit of Neptune in four years.
"The object is now too weak to be observed, so no new data will be acquired," said Micheli in the email. "But I think scientists will continue to work on their data for a while. some time. "
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