Cipher the nature of 'Oumuamua – it's probably a comet, but …

Shortly before Halloween, the chairman of the Harvard Astronomy Department openly declared that an interstellar object pbading through our solar system might well be part of an extraterrestrial craft. And then … crickets

Three days later, the astrophysics blog Centauri Dreams told the story to cognoscenti. He presented an informed study of the academic paper that evoked this bold opportunity, reinforced by quotes and comments from the co-author of the paper (and chair of the department), Avi Loeb. It was already late in November, before newspapers such as CNN, Time, and The Washington Post resumed history, filled with the inevitable sarcastic quotation marks and sneaky titles. The object, named Oumuamua had a number of strange and seemingly contradictory properties; it may be that these properties appear so because our observations were not very good. There are also other possibilities.

I read Loeb's paper, which was quickly accepted for publication by the respected Astrophysical Journal . A few days later, Loeb and I sat for the longest and, after what Loeb says, the most serious and thorough interview that he gave to this topic. The built-in audio player that follows the two dots at the end of this very phrase presents an hour-long edition, which includes all the highlights:

If you don? are not in the spoken word audio, we 're I have a transcript available in plain text and in PDF (which is probably a bit easier to read).

"I'm not saying they're aliens, but …"

Avi Loeb is clearly poking around. one of the most extraordinary claims of astronomy. This, of course, requires extraordinary evidence – a requirement to which Loeb's fancy job title yields no exception. But we should also avoid the reflex reaction of the inverted-knee elbow, which looks like this: "This is not because the president of Harvard astronomy says that could be d & # 39; To be an alien as is ; and in fact, that means is not because irony! Oh, and girlfriend too. "

My Interview with Loeb should not settle this debate in favor of extraterrestrials for you, me, or anyone else (Loeb himself needs more evidence to consider the case as resolved). But the story of Oumuamua is intrinsically fascinating. By digging in, non-astronomers can not help but learn about the workings of the Universe. If you follow this path, keep in mind that extraterrestrial technology has been taken into account and finally abandoned as an explanation for many astronomical phenomena. Oumuamua will probably join this list definitely someday. But we learn a lot by tracking down the tracks – both by the field of astronomy and by curious strangers who follow the process.

If you listen to our interview (or read our transcript, probably-OK-ish), you'll understand. this debate at a more subtle level than most people who talk about it. And the really cool thing? For the reasons we discuss near the end of our conversation, the big questions here could be resolutely resolved as early as 2022, when a major new telescope will be put online.

For those in a hurry, I will now provide a summary of our interview, punctuated with timestamps to help you find the parts that interest you the most

There is something about & # Oumuamua

Our story begins on October 19 of last year (at the timestamp 07:55 of the interview audio above, if you wish listen for more details than those contained in this brief description). It was then that the object that was to be called Oumuamua was spotted for the first time by the pan-STARRS system of Hawaii, which tracks and detects nearby objects of the earth.

Astronomers quickly established that & # 39; Oumuamua was traveling too fast to be bound by our Sun. which meant that it originated in a distant star system. This makes it the first interstellar object definitively identified in our solar system. Rightly intrigued, the astronomical community has pointed a lot of material towards the blip in decline. Mbades of observational data were obtained before Oumuamua disappeared from sight in January.

& # 39; Oumuamua was bizarre on multiple fronts from the beginning. What is interesting is that he travels to the "local rest standard" (time stamp 15:36 ) among our local star group. For the reasons given by Loeb, it is a fascinating attribute – and improbable (although not impossible) for a natural object.

In June (timestamp 23:22 Nature published a rigorous badysis of the trajectory of "Oumuamua." Its authors determined – with 30 standard deviations of confidence – that the object was gaining momentum as it retreated from the Sun.This was interpreted as evidence that it was a comet rather than an asteroid (l & rsquo; Another probable candidate.) Comets generally accelerate in this manner, propelled by gases released by the heat of the Sun, which create their characteristic tail.

However, several observations go against this idea For example, no tail has ever been observed on "Oumuamua." The coma either (the fuzzy head of a comet). There was no sign of water on it, and comets usually carry water and the surface reflectivity of muamua is well beyond the limits badociated with comets.

These quirks and others can be explained or justified by themselves. But for Loeb, the last drop was a September article by Roman Rafikov of the University of Cambridge (time stamp 28:39 ). He argues that "Oumuamua's rotational speed (which was pretty fast – another quirk) remained constant throughout the duration of the observations, while degbading should have significantly disrupted the spin.

Loeb concluded that degbading would not have caused the acceleration of Oumuamua. He envisioned alternative forces and opted for a force that astronomers understand quite well: the pressure of radiation emitted by the sun. But it is a much weaker force than degbading. S & # 39; he was responsible, "Oumuamua should be much smaller than the number of rock astronomers of a quarter of a kilometer and more envisioned. Specifically, Loeb identified it as not exceeding 20 meters in diameter. And, here is the pin, less than a millimeter thick.

Close encounters, in one form or another

No known natural process can produce anything so distant in space. But it looks a lot like a solar sail. And Loeb spent long hours modeling solar sails physics by participating in Yuri Milner's Breakthrough Starshot project (timestamp 18:55 .) Yes, the cliché that hammer owners who take nails for nails immediately come to mind, and Loeb recognizes it ( 30:07 ) But it is also known that hammers identify nails accurately.

The most exotic possibility evoked in Loeb's paper ( 33:55 ) is that 'Oumuamua was on a reconnaissance mission targeted (without necessarily selecting the Earth – but perhaps generally cruising in the habitable areas of the star systems This is based on legacy calculations concerning the relative abundance of interstellar objects and other factors.

Loeb and I then discuss online archives where he and his co-author, Bo Shmuel Bialy, postdoctoral ursier, initially placed their article ( 36:58 ) and the unusual speed with which Astrophysical Journal accepted and published it at the same time ( 40: 19459022. I then present to Loeb the critics of some of his critics, whom he answers ( 44:51 ). This leads to a discussion of Loeb's philosophy on the roles and responsibilities of academics.

/ The unusual approach to the object suggests that it comes from outside our solar system.