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By Brooks Hays, UPI
Scientists have placed a new upper limit on the size of the interstellar object known as 'Oumuamua.
Newly analyzed data also suggests the alien visitor is 10 times more reflective than asteroids and comets found within the solar system.
Researchers published an updated portrait of 'Oumuamua this week in the Astronomical Journal.
Shortly after 'Oumuamua was spotted, astronomers around the world pointed telescopes in the direction of the interstellar traveler. Spitzer Telescope was one of several that tried to observe the icy migrant. But just two months after making its closet approach to Earth, 'Oumuamua proved too faint to register.
"'Oumuamua has been full of surprises from day one, so we were eager to see what Spitzer might show," David Trilling, professor of astronomy at Northern Arizona University, said in a news release. "The fact that 'Oumuamua was too small for Spitzer to detect is actually a very valuable result."
Spitzer's inability to see 'Oumuamua allowed scientists to put a more accurate upper limit on the object's size. Their analysis suggests the object is smaller than originally estimated.
Depending on the object's composition, 'Oumuamua's spherical diameter could be as small as 320 feet or as large as 1,440 feet.
The revelation confirms the hypothesis of an earlier study of outgassing forces exacted on the 'Oumuamua. The research showed the forces created by the sublimation of frozen gases could explain slight shifts in the object's trajectory, but the theory required 'Oumuamua to be relatively small.
In addition to being smaller, 'Oumuamua is also more reflective than most comets in the solar system.
By studying 'Oumuamua in infrared, scientists can gauge its temperature. Because an object's reflectivity, or albedo, affects its temperature, scientists can use infrared observations to estimate how much light the object's surface reflects. 'Oumuamua's estimated low temperature suggests it reflects much of the sunlight that hits its surface.
In addition to being smaller, 'Oumuamua is also more reflective than most comets in the solar system.
By studying 'Oumuamua in infrared, scientists can gauge its temperature. Because an object's reflectivity, or albedo, affects its temperature, scientists can use infrared observations to estimate how much light the object's surface reflects. 'Oumuamua's estimated low temperature suggests it reflects much of the sunlight that hits its surface.
Researchers think 'Oumuamua's trip around the sun melted significant amounts of ice, revealing more reflective interior layers.
Earlier studies predicted 'Oumuamua's icy composition, while followup research suggested the object originated from a faraway binary star system. Scientists think the object has been tumbling around the universe for billions of years.
The updated portrait of 'Oumuamua may offer the last word on the interstellar object. It's currently on its way out of the solar system.
"Usually, if we get a measurement from a comet that's kind of weird, we go back and measure it again until we understand what we're seeing," said Davide Farnocchia, astronomer at the the Center for Near Earth Object Studies at NASA's Jet Propulsion Laboratory. "But this one is gone forever; we probably know as much about it as we're ever going to know."
