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

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

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

Dr. Desch also noted that the reddish color of Oumuamua exactly matches the reddening of the ice on Pluto, which contains 0.1 percent carbon in the form of methane.

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

“This is putting a lot of pressure on the galaxy to make exoplutos,” said Dr. Laughlin.

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

Many things are ejected from planetary systems, emphasized Dr. Desch; older papers assumed these would be the size of comets and therefore predicted them in much fewer numbers. But if they were smaller, Dr. Desch added, a lot more fragments would fly out, so something like Oumuamua wouldn’t necessarily be an anomaly.

“So far we have seen an N2 ice fragment and a comet among the interstellar objects,” he wrote in an email. “Statistics with small numbers don’t get much smaller.” Those numbers were as expected and he said, “We may have been a little lucky to see one so quickly, but it’s not a coincidence or anything. This is a common target to invade our solar system. “