Our First Interstellar Visitor is More Spectacular than We Could Have Ever Imagined

From the moment it was first picked up by the Pan-STARRS 1 telescope in Hawaii on October 19th, the object has been giving scientists one surprise after another. At first, astrophysicists believed that ‘Oumuamua had been a comet, but further investigation revealed that it did not exhibit characteristics of a comet, and it was recategorized as an asteroid, the first time this type of categorizing change has occurred in the history of science.

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Another unusual point about ‘Oumuamua: the star of Vega, part of the constellation of Lyra, was determined as the asteroid’s place of origin, based on the first set of calculations. However, given the speed it is moving—an incredible 95,000 kilometers per hour—300,000 years is the time it would have taken to reach us. All this adds up, until the scientists noted that Vega was not in the same location 300,000 years ago. This sets up another completely different scenario: ‘Oumuamua travelled hundred of millions of years to make contact with our Solar System!

"For decades we've theorised that such interstellar objects are out there, and now—for the first time—we have direct evidence they exist," NASA astrophysicist Thomas Zurbuchen said, adding about the impact of the interstellar visit, “This history-making discovery is opening a new window to study formation of solar systems beyond our own."

A few more facts about the asteroid based on observations so far: the object has a length of roughly 400 meters, and a distinct cigar shape. In addition, the brightness variation factor for ‘Oumuamua is 10 for each 7.3 hours, a factor that has never been observed in any asteroid, or even comet, in the Solar System. 

These two factors together create a fascinating picture for scientists:

"This unusually big variation in brightness means that the object is highly elongated: about ten times as long as it is wide, with a complex, convoluted shape,” shared Karen Meech from the Institute for Astronomy in Hawaii, adding, "We also found that it had a reddish color, similar to objects in the outer Solar System, and confirmed that it is completely inert, without the faintest hint of dust around it."

With an estimated time of passing Jupiter’s orbit and Saturn’s orbit in May 2018 and January 2019, respectively, the good news is there is plenty of time left to spot ‘Oumuamua.

The title of an article with the findings of the research, which were published in this week’s Nature journal, perfectly captures the atmosphere of excitement that ‘Oumuamua’s visit has created: “A brief visit from a red and extremely elongated interstellar asteroid”.