Tuesday, September 28News That Matters

Oumuamua: It Came From Another Solar System

Of course, that’s not the end of the story.

In an email Dr. Loeb complained, among other things, that if Oumuamua was made of nitrogen it should also contain carbon (which was not detected by the Spitzer Space Telescope), because both nitrogen and carbon are produced together by a thermonuclear carbon-nitrogen-oxygen cycle in stars.

Dr. Desch responded in an email: “Spoken like a cosmologist!” He went on to note that planets have ways of sifting and separating the elements they were born with. Otherwise Earth’s atmosphere, which is 79 percent nitrogen, should be several percent carbon instead of one-tenth of 1 percent carbon. Or, as another astronomer pointed out, the Great Lakes would all be full of sparkling water.

Dr. Desch noted, moreover, that the reddish color of Oumuamua is an exact match to the redness of the ice on Pluto, which is 0.1 percent carbon, in the form of methane.

Another issue is statistics. How is it that these cosmic icebergs are so common — more than 50 trillion per cubic light-year of space, according to a calculation by Dr. Laughlin — that the Pan-STARRS project would have discovered one after just five years of searching?

“That puts a lot of pressure on the galaxy to manufacture exo-Plutos,” Dr. Laughlin said.

If so, Oumuamua was just the tip of an unsuspected iceberg, so to speak, which is exactly what Dr. Desch and Dr. Jackson contend.

A lot of things get ejected from planetary systems, Dr. Desch pointed out; older papers assumed that these would be as big as comets, and so predicted them in much lower numbers. But if they are smaller, Dr. Desch added, there would be many more fragments flying out, so something like Oumuamua would not necessarily be an anomaly.

“So far we’ve seen one N2 ice fragment and one comet among the interstellar objects,” he wrote in an email. “Small-number statistics doesn’t get much smaller than that.” Those numbers were about what is expected, according to their calculations, he said: “Maybe we got a little lucky to see one so quickly, but it’s not a fluke or anything. This is a common object to be entering our solar system.”