NASA Study Reveals New Details About Interstellar Visitor ‘Oumuamua

The research is based on Spitzer observations and offers new clues on 'Oumuamua size and albedo.

A new NASA study uncovered that our interstellar visitor 'Oumuamua is small and very reflective.
ESO / M. Kornmesser / Wikimedia Commons / Cropped and Resized (CC BY 4.0)

The research is based on Spitzer observations and offers new clues on 'Oumuamua size and albedo.

Fresh details have emerged regarding the features of our first interstellar visitor — the puzzling object that we have dubbed ‘Oumuamua, which translates as “messenger from afar arriving first” in Hawaiian.

According to a NASA study just published in the Astronomical Journal, this weird object that came cruising through our solar system is actually smaller than we thought — and a lot more reflective.

“‘Oumuamua has been full of surprises from day one,” said study lead author David Trilling, a professor of astronomy at Northern Arizona University.

Discovered in October 2017 by the Pan-STARRS-1 telescope at the Haleakala Observatory in Hawaii, the object was initially classified as an asteroid, the Inquisitr reported at the time. The first observations of ‘Oumuamua revealed that the object had a peculiar shape and was extremely elongated — originally estimated to be around a quarter-mile wide.

Earlier this year, another investigation unveiled the true identity of ‘Oumuamua, showing substantial evidence that the object is actually a comet, the Inquisitr previously reported. Among the chief reasons that triggered this reclassification was a strange speed boost uncovered in the object’s trajectory — which was put down to an “outgassing” phenomenon.

This is what usually happens to comets when they wander too close to a star. These icy bodies made of dust, rock, and frozen gases get heated up by the star’s rays, which melt the ice on the comet’s surface and cause gas to start leaking out.

Artist's impression of 'Oumuamua, showing cometary outgassing produced by the proximity to the sun.
Artist’s impression of ‘Oumuamua, showing cometary outgassing produced by the proximity to the sun. ESA/Hubble, NASA, ESO, M. Kornmesser / Wikimedia Commons/Resized (CC BY 4.0)

In the case of ‘Oumuamua, this outgassing phenomenon — believed to have occurred when the interstellar comet had its close brush with our sun in September 2017 — expelled gases that “acted like a small thruster, gently pushing the object” and giving it extra speed, reports NASA.

This revelation meant that ‘Oumuamua was smaller than the average comet — a finding corroborated by the new study.

The team pointed NASA’s Spitzer Space Telescope at ‘Oumuamua last November, a couple of months after the comet’s close approach to the sun and to Earth — on September 9, 2017, the object came within 60 lunar distances from our planet, per a previous Inquisitr report.

The problem was, they couldn’t spot it — at all. This was because the object was too small to be picked up by Spitzer, an infrared telescope that detects heat signatures coming from asteroids and comets.

Nevertheless, their effort was not in vain, Trilling points out.

“The fact that ‘Oumuamua was too small for Spitzer to detect is actually a very valuable result.”

Although Spitzer was unable to see ‘Oumuamua, the “non-detection” revealed something unexpected about the comet, putting “a new limit on how large the strange object can be,” explains NASA.

While the telescope couldn’t infer anything on the object’s shape, it did, however, provide an estimate on its “spherical diameter” — indicating the maximum width that ‘Oumuamua would have if it were spherical.

“Using three separate models that make slightly different assumptions about the object’s composition, Spitzer’s non-detection limited ‘Oumuamua’s ‘spherical diameter’ to 1,440 feet (440 meters), 460 feet (140 meters) or perhaps as little as 320 feet (100 meters),” detailed the space agency.

Another important thing to come out of the Spitzer study was a new discovery about ‘Oumuamua’s albedo — the reflectivity of the object’s surface. The findings suggest that the outgassing phenomenon experienced by the interstellar comet in September 2017 brushed off the dust and dirt from its surface, leaving behind a very reflective coat of ice.

“We suggest that ‘Oumuamua may have experienced low-level post-perihelion volatile emission that produced a fresh, bright, icy mantle,” the authors write in their paper.

In light of the recent event (pun intended), ‘Oumuamua is now thought to be up to 10 times more reflective than the comets in our 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 study co-author Davide Farnocchia of the Center for Near Earth Object Studies (CNEOS) 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.”