The First Interstellar Object to Visit Us Is More Incredible Than We Ever Expected

This asteroid is unlike anything we’ve seen before.

The first asteroid observed visiting our Solar System from elsewhere isn’t just unusual in its interstellar origin. It’s also unlike any other asteroid we’ve seen before. The object was discovered recently, and now we’re being rewarded with exciting new details thanks to the astronomers and their telescopes. This newly discovered asteroid was named ‘Oumuamua’. It’s up to 400 meters long and with a distinguishable cigar shape. It’s around 10 times longer than its width with a shape never seen before in an asteroid.

The asteroid was first spotted by the Pan-STARRS 1 telescope in Hawaii, late October. It didn’t take long for astrophysicists to figure out that its trajectory and velocity both indicated that it was an extrasolar stranger, perhaps flung out by a neighborhood star.

There was something very odd about this object from the very beginning. The observations at the beginning suggested that it was a comet, but it didn’t show any of the characteristics associated with comets. That’s why later it was categorized as an asteroid.

This was actually the first time a comet’s categorization has changed into an asteroid. This is not the only unusual thing though. Initial calculations of ‘Oumuamua’ showed that the direction this asteroid came from was from the star Vega, in the Lyra constellation.  But even if ‘Oumuamua’ was travelling with a speed of 95,000 kilometers per hour, it would have taken 300,000 years for the asteroid to reach our planet from Vega – and the star wasn’t in the same place all those years ago.

This information could mean that the newly discovered asteroid could have been traveling through space unattached to any particular star system for over hundreds of millions of years.

“Many years we’ve had a theory that these kinds of interstellar objects are out there, and now for the first time in history we have direct evidence they do. This discovery is opening a new window to study formation of solar systems beyond our own”, said NASA astrophysicist Thomas Zurbuchen.

When this new asteroid ‘Oumuamua’ was discovered, scientists set up telescopes all over the world in order to make observations.

Gemini, the ESO’s Very Large Telescope in Chile, the Canada France Hawaii Telescope, the United Kingdom Infrared Telescope, and many other observatories kept their eyes on the asteroid for a long time. After the observations they combined images from the various telescopes.  An international team found out that the asteroid varies in brightness by a factor of about 10 every 7.3 hours, matching its spin about its axis. This was not the case with other comets or asteroids in the Solar System.

“This unusually big variation in brightness means that the asteroid is highly elongated. We also found out that it had a red color, similar to objects in the outer Solar System, and confirmed that it is completely inert, without dust around it” , said Karen Meech from the Institute for Astronomy in Hawaii.

The discoveries imply that the asteroid is made of dense material, probably rock and possibly metal. The scientists also discovered that there is no ice or water on its surface. The color of the surface was probably caused by cosmic irradiation from travelling the Milky Way galaxy for over a hundred million years.

‘Oumuamua’ passed around the Sun on September 9th with a speed of 315,000 kilometers per hour. The asteroid is now travelling out of the Solar System. It is due to pass Jupiter’s orbit in May 2018, and Saturn’s in January 2019. Scientists will continue taking observations until ‘Oumuamua is out of reach.



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