Its outbound path is about 20 degrees above the plane of planets that orbit the Sun. Two of NASA’s space telescopes ( Hubble and Spitzer ) tracked the object traveling about 85,700 miles per hour (38.3 kilometers per second) relative to the Sun. These properties suggest that ‘Oumuamua is dense, composed of rock and possibly metals, has no water or ice, and that its surface was reddened due to the effects of irradiation from cosmic rays over hundreds of millions of years.Ī few large ground-based telescopes continued to track the fading object as it receded from our planet. “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.”

“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,” said Meech.

The most elongated objects we have seen to date are no more than three times longer than they are wide. No known asteroid or comet from our solar system varies so widely in brightness, with such a large ratio between length and width. Urgency for viewing from ground-based telescopes was vital to get the best data.Ĭombining the images from the FORS instrument on the ESO telescope using four different filters with those of other large telescopes, a team of astronomers led by Karen Meech of the Institute for Astronomy in Hawaii found that ‘Oumuamua varies in brightness by a factor of 10 as it spins on its axis every 7.3 hours. Immediately after its discovery, telescopes around the world, including ESO’s Very Large Telescope in Chile, were called into action to measure the object’s orbit, brightness and color. “For decades we’ve theorized that such interstellar objects are out there, and now― for the first time― we have direct evidence they exist,” said Thomas Zurbuchen, associate administrator for NASA’s Science Mission Directorate in Washington, in November 2017. The observations suggest this unusual object had been wandering through the Milky Way, unattached to any star system, for hundreds of millions of years before its chance encounter with our star system. While its elongated shape is quite surprising, and unlike objects seen in our solar system, it may provide new clues into how other solar systems formed. That aspect ratio is greater than that of any asteroid or comet observed in our solar system to date. The object, named ‘Oumuamua by its discoverers, is up to one-quarter mile (400 meters) long and highly-elongated-perhaps 10 times as long as it is wide. The first confirmed object from another star to visit our solar system, this interstellar interloper appears to be a rocky, cigar-shaped object with a somewhat reddish hue. Image Credit: European Southern Observatory / M. The aspect ratio of up to 10:1 is unlike that of any object seen in our own solar system. Artist's concept of interstellar object1I/2017 U1 ('Oumuamua) as it passed through the solar system after its discovery in October 2017.

Quaqua asteroid