Their analysis suggests the object is smaller than originally estimated.
Shortly after 'Oumuamua was spotted, astronomers around the world pointed telescopes in the direction of the interstellar traveler.
Scientists have learned more about 'Oumuamua, the hunk of matter that is the first known interstellar object to ever be detected by scientists within the boundary of the solar system.
The updated portrait of 'Oumuamua may offer the last word on the interstellar object. Observations of 'Oumuamua indicate that it must be very elongated because of its dramatic variations in brightness as it tumbled through space. Recently, a team of Harvard scientists have revealed that Oumuamua could actually be an alien probe looking for signs of life in the universe, and they claimed that the unexpected boost in speed it attained intermittently might be an indication of its artificial origin. Sure, they'd have loved to see more of the unusual visitor, but not being able to see it meant that the object, at its current distance, was too small to see, adding yet another valuable data point.
"In addition to sweeping away dust and dirt, some of the released gas may have covered the surface of 'Oumuamua with a reflective coat of ice and snow - a phenomenon that's also been observed in comets in our solar system".
"'Oumuamua has been full of surprises from day one, so we were eager to see what Spitzer might show", lead author David Trilling, an astronomy professor at Northern Arizona University, said in the NASA statement.
Unlike traditional telescopes, the Spitzer detects a heat signature, rather than looking for reflected light.
For example, 'Oumuamua's "spherical diameter" - how big it would be if it were a spherical object, which it nearly certainly is not - is likely between 320 feet and 1,440 feet (100 to 440 meters), the researchers determined.
These figures are consistent with other estimates, which generally hold that 'Oumuamua is less than 2,600 feet (800 m) in its longest dimension.
As NASA's Jet Propulsion Laboratory notes in a new blog post, the Spitzer telescope's inability to detect Oumuamua using its infrared hardware puts a size limit on the object.
"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", according to paper co-author Davide Farnocchia, of the Center for Near Earth Object Studies (CNEOS) at JPL.
The new study was published online Wednesday (Nov. 14) in The Astronomical Journal. "But this one is gone forever; we probably know as much about it as we're ever going to know".