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An artist's impression of the interstellar asteroid 'Oumuamua

Key suspect stars identified in origin mystery of asteroid space invader

Image credit: ESA/Hubble/NASA/ESO/M

Four stars have been identified as the possible birth place of an interstellar asteroid that last year invaded the Solar System containing planet Earth.

The approximately 800ft-long, 100ft-wide, dark-red, cigar-shaped object – given the Hawaiian name ’Oumuamua, a Hawaiian word meaning ‘a messenger from afar arriving first’ – was so mysterious that there were serious suggestions it could be alien in origin. After extensive observation, it was confirmed as an asteroid. It is believed that ’Oumuamua has a high metal content, lacks any significant amount of water or ice and displays no visible signs of dust.

’Oumuamua is the first known interstellar object detected passing through the Solar System. ’Oumuamua is tumbling, rather than smoothly rotating, and is moving so fast relative to the Sun that there is no chance that it originated in the Solar System.

Its high velocity also means that ’Oumuamua cannot be captured into any solar orbit, so it will eventually leave the Solar System and continue its journey through interstellar space.

Astronomers used the European Space Agency’s Gaia orbiting telescope to trace ’Oumuamua’s trajectory back along its path thus far.

From a starting total of seven million stars, the scientists whittled the list down to identify four dwarf stars that would have been in the right place to have ‘launched’ ’Oumuamua at some point between one and seven million years ago.

Scientists believe the object was cast out from its home star, eventually reaching our solar system after an epic journey through space.

However, despite the theoretical identification of these four stars, none of the identified stars is known either to harbour planets or be part of a binary star system.

A giant planet or companion star would have been the most likely cause of the object’s ejection.

Gaia project scientist Dr Timo Prusti said: “While it’s still early to pinpoint ’Oumuamua’s home star, the result illustrates the power of Gaia to delve into the history of our Milky Way galaxy.”

The research has been accepted for publication in Astronomical Journal.

Asteroids, which orbit the Sun but are much smaller than planets, are among the oldest objects in the Solar System. As such, they may help explain how Earth evolved, including the formation of oceans and the start of life. Scientists are accordingly very keen to study and explore passing asteroids whenever possible.

In June, a Japanese spacecraft arrived at an asteroid – named Ryugua, after an undersea palace in a Japanese folktale – to probe its insides. The Japan Aerospace Exploration Agency (JAXA) confirmed that a probe launched three-and-a-half-years ago had arrived at its intended destination.

Meanwhile, in the same month, the potential threat of a devastating asteroid collision with Earth prompted Nasa to call for a boost in improved asteroid detection, tracking and deflection in order to prevent damage from celestial impacts.

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