|Interstellar scout: artist’s impression of ‘’Oumuamua. (Courtesy: ESO/M Kornmesser)|
‘Oumuamua, a mysterious cigar-shaped object travelling through the solar system having arrived from interstellar space, is being propelled by outgassing as it is heated by the Sun. That is the conclusion of Marco Micheli of the European Space Agency and colleagues, who have looked at ground- and space-based observations of the motion of the object.
First spotted on 19 October 2017 by the Haleakala Observatory in Hawaii, ‘Oumuamua is 230 m long and is the first object to be identified as entering the solar system from interstellar space. ‘Oumuamua means “scout” in Hawaiian to reflect its long voyage from a distant planetary system.
The object’s extremely eccentric orbit and shiny surface initially led the International Astronomical Union (IAU) to classify ‘Oumuamua as a comet. However, that status was quickly changed to an asteroid when astronomers could not find a “coma” of gas and dust surrounding the object, something that is seen around comets. Then in November 2017, ‘Oumuamua was again reclassified by the IAU as the first ever “interstellar object” – a new classification created in light of the object’s discovery.
Interstellar object ‘Oumuamua is propelled by outgassing, say astronomers
Hamish Johnston, Physics World
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