NASA’s Spitzer Space Telescope has searched for the mysterious interstellar object known as ‘Oumuamua (“visitor from afar arriving first”), and couldn’t find it.

NASA says that doesn’t mean the object is, in fact, an alien space probe, it just means that the object is too small for Spitzer to see, which confirms scientific theories the object is just a weird space rock.

“Oumuamua was too faint for Spitzer to detect when it looked more than two months after the object’s closest approach to Earth in early September. However, the “non-detection” puts a new limit on how large the strange object can be,” explains NASA in a statement published on November 15.

The new scientific study is published in a paper in the Astronomical Journal and co-authored by scientists at NASA’s Jet Propulsion Laboratory in Pasadena, California.

And when Spitzer looked for ‘Oumuamua and didn’t find it, it doesn’t mean that the object mysterious vanished from sight, it’s still there but ‘Oumuamua was too faint for Spitzer to detect, which tells us a lot about the size of the object.

“‘Oumuamua has been full of surprises from day one, so we were eager to see what Spitzer might show,” said David Trilling, lead author on the new study and a professor of astronomy at Northern Arizona University.

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

Scientists have therefore proposed a new size limit and suggest that the object’s strange acceleration was caused—not by alien light sails attached to it—but due to outgassing.

NASA explains that outgassing is responsible for the slight changes in ‘Oumuamua’s speed and direction as it was tracked last year. Experts say that expelled gas coming from the space rock helped propel the object across the solar system acting as small thrusters that gently pushed the object, altering its trajectory and speed.

‘Oumuamua has given us a lot to talk about ever since it was spotted for the first time by the University of Hawaii’s Pan-STARRS 1 telescope on Haleakala, Hawaii.

A recent theory set forth by experts from Harvard suggests that ‘Oumuamua’s anomalous acceleration and change of trajectory were due to ‘solar sails’ attached to the object.

In their paper, Harvard scientists Shmuel Bialy, Ph.D., and Professor Abraham Loeb, Ph.D. argues that solar radiation pressure, where photons from the sun may have impacted and pushed Oumuamua along may be responsible for the object’s acceleration.

However, they also suggest a more exotic scenario where ‘Oumuamua may be a fully operational probe sent intentionally to Earth vicinity by an alien civilization.