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We got a good look at the interstellar asteroid and it's weird

21 November 2017

The hunk rock of that whipped through the solar system in October looks like no other asteroid we've seen before, they say, long and thin like a javelin and colored red from millions of years of accumulated radiation exposure.

Recently, NASA scientists discovered A/2017 U1, an asteroid that's believed to be the first known object within our solar system to have originated from beyond the reach of our beloved home star. But based on its orbit, the astronomers realized that the object came from interstellar space. They had to be speedy, given that the object is now moving 95,000 kilometres per hour and heading away from the sun. The team is composed of Karen J. Meech (Institute for Astronomy, Honolulu, Hawaii, USA [IfA]) Robert Weryk (IfA), Marco Micheli (ESA SSA-NEO Coordination Centre, Frascati, Italy; INAF-Osservatorio Astronomico di Roma, Monte Porzio Catone, Italy), Jan T. Kleyna (IfA) Olivier Hainaut (ESO, Garching, Germany), Robert Jedicke (IfA) Richard J. Wainscoat (IfA) Kenneth C. Chambers (IfA) Jacqueline V. Keane (IfA), Andreea Petric (IfA), Larry Denneau (IfA), Eugene Magnier (IfA), Mark E. Huber (IfA), Heather Flewelling (IfA), Chris Waters (IfA), Eva Schunova-Lilly (IfA) and Serge Chastel (IfA).

According to NASA, the interstellar asteroid is a "rocky, cigar-shaped object with a somewhat reddish hue". Most objects astronomers observe in our solar system are roughly spherical, drawn into a ball by gravity. This cycle suggests that the asteroid is long and skinny and rotates every 7.34 hours. This complex and convoluted shape means the object varies incredibly in brightness. The predicted interstellar number density of icy interstellar objects of 2.4×10 au suggested that these should have been detected by surveys, yet hitherto none had been seen.

So what is it?

After observing the object on its outbound journey, scientists noted that 'Oumuamua didn't spawn a tail of gas or dust as it flew by the sun.

A closer study of the trajectory confirmed that 'Oumuamua was on an open-ended parabolic trajectory and was making its first and only visit to the Solar System.

But where did it come from?

That odd shape is unprecedented among the some 750,000 asteroids and comets observed in our solar system where they formed, said the researchers. So it would stand to reason that other planetary systems are sending the same remnants our way.

There are most likely between one and 10 of these types of "visitors" per year in our solar system - but they move so fast that we've never been able to see or study them. However, Vega wasn't near the asteroid's point of origin 300,000 years ago, around the time A/2017 U1 would have passed through this particular region of space.

The object from another star is now called 'Oumuamua - meaning "a messenger from afar arriving first" in Hawaiian, according to the National Aeronautics and Space Administration - as it was first picked up by telescopes at the University of Hawaii's Haleakalā Observatory.

"Certainly this is a new type of object". "This serendipitous discovery is bonus science enabled by NASA's efforts to find, track and characterize near-Earth objects that could potentially pose a threat to our planet". "It is 124 million miles from Earth - the distance between Mars and Jupiter - but its trajectory has taken the object past Mars" orbit, and it will pass Jupiter in May, go beyond Saturn's orbit in January 2019 and then leave our solar system, bound for the Pegasus constellation.

If planets form around other stars the same way they did in the Solar System, many objects the size of 'Oumuamua should get slung out into space.

We got a good look at the interstellar asteroid and it's weird