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Nailing properties & # 39; Oumuamua – maybe it's a comet, but …



Image of a space shuttle from the film Close Encounters of the Third Kind.
Enlarge / I mean, maybe, right? Maybe? Probably not. Almost certainly not.

Shortly before Halloween, the chairman of the Harvard astronomy department publicly stated that interstellar objects that shot through our Solar System might only be part of a spacecraft. And then … crickets.

The astrophysics blog Centauri Dreams breaks the story to cognoscenti three days later. It presents a survey of information from academic papers that raise the possibility of this insolence, supported by quotes and comments from co-authors (and the famous chairman of the department), Avi Loeb. That's good until November before outlets like CNN, Time, and The Washington Post took the story, filled with inevitable sarcastic quotes and snarky news titles. Object, named & # 39; Oumuamua, has a number of strange and seemingly contradictory traits; it could be that these qualities appear as they do because our observations are not very good. There are also other possibilities.

I read Loeb's paper – which at that time was quickly accepted for publication by respected people Astrophysical Journal. A few days later, Loeb and I sat the longest and – by Loeb himself – the most serious and deep interview he gave about this. The embedded audio player follows the colon at the end this very sentence One hour edit feature from it, including all highlights:

If you don't like audio words, we have transcripts available both as plain text and as PDF (which might be a little more readable).

"I'm not saying it's an alien, but …"

Avi Loeb clearly found one of the most extraordinary astronomical claims. This of course requires extraordinary evidence – the requirements of Loeb's fancy job title make him no exception. But we must also avoid the inverse spontaneous response, which goes something like, "Just because the Harvard astronomy chief said that can being alien is meaningless I s one; and actually, that means not one, because of the irony! Oh, and arrogant too. "

My interview with Loeb should not have completed this debate for the sake of strangers to you, me, or anyone (Loeb himself needs more evidence to approach considering the case was resolved). But the story & # 39; Oumuamua is inherently enchanting. Digging into it, non-astronomers cannot help learning one or three things about how the universe works. If you walk down this road, you must remember that alien technology has been considered, and finally dropped as an explanation for many astronomical phenomena. & # 39; Oumuamua might join this list with certainty someday. But much is learned by pursuing direction – both by astronomy and by curious outsiders who follow the process.

If you listen to our interviews (or read our probably-OK-ish transcripts), you will understand this debate at a lower level than most people who rant about it. And what's really cool? For the reasons we discussed near the end of our conversation, the big questions here can be resolved dramatically as early as 2022, when important new telescopes start online.

For those who are in a hurry, I will now provide a synopsis of our interview, interspersed with a time stamp to help you zip into the parts that are most interesting to you.

There is something about Oumuamua

Our story begins on October 19 last year (at the timestamp 7:55 from the audio interview above, if you want to hear more details than those listed in this brief report). That's when the object that will be named 'Oumuamua was first discovered by the Pan-STARRS Hawaii system, which tracks and detects near-Earth objects.

Astronomers immediately determined that Oumuamua was traveling too fast to be bound by our Sun, which meant it was from a distant star system. This makes it the object between the first stars that are definitively identified in our Solar System. Really curious, the astronomical community shows a lot of hardware in the direction of the blip receding. The mass of observation data is thus obtained before & # 39; Oumuamua disappears from view in January.

An artist's impression of a strange interstellar asteroid & O39amua. "Src =" https://cdn.arstechnica.net/wp-content/uploads/2017/11/1I_eso_artistimpression-640x400.jpg "width =" 640 "height =" 400 "srcset =" https: //cdn.arstechnica .net / wp-content / uploads / 2017/11 / 1I_eso_artistimpression-1280x800.jpg 2x
Enlarge / An artist's impression of a strange interstellar asteroid & O39amua.

O Oumuamua is strange in various fields from the beginning. What's interesting is the journey with "local standards of rest" (time stamp) 15:36) Among our local star packages. For reasons explained by Loeb, this is an interesting attribute – and that is impossible (though not impossible) for natural objects to have.

In June (time stamp) 23:22), Natural released a rigorous analysis of the Oumuamua track. The authors determine – with 30 standard deviations of belief – that the object gets faster when it moves away from the Sun. This is interpreted as evidence that it is a comet, rather than an asteroid (other possible candidates). Comets usually accelerate in this way, driven by gas released by the sun's heat, which creates their signature.

However, some observations contradict this. (time stamp 25:44) For example, no tail has ever been observed in & # 39; Oumuamua. There is no comma (fuzzy comet head). There are no signs of water on it, and comets usually carry water. And itas Oumuamua's surface reflectivity lies far outside the boundary associated with comets.

This and each other's habits can be explained or justified by themselves. But for Loeb, the final straw was a September paper by Roman University Roman Rafikov (timestamp 28:39) It argues that the Oumuamua spin rate (which is quite zippy – another oddity), remains constant throughout the observation range, while outgassing should interfere with spin significantly.

Loeb concluded that outgassing would not have caused Oumuamua's acceleration. He considered alternative forces and settled in one that astronomers understood well: radiation pressure radiated out of the sun. But this is a power that is far weaker than outgassing. If you are responsible, & Oumuamua must be much smaller than a quarter of a mile-plus the chunks of rock astronomers imagined. In particular, Loeb pegged it as 20 meters in diameter. And – this is what determines – less than one millimeter thick.

Close such or other meetings

There is no known natural process that can produce anything thin in space. But this sounds very much like a sun screen. And Loeb has spent a lot of time modeling solar screen physics, in helping lead the Starshot Breakthrough project Yuri Milner (timestamp 18:55) Yes, the cliche about hammer owners who misunderstand nails for nails immediately jumps to mind, and Loeb acknowledges this (30:07) But hammerers are also known to accurately identify nails.

The most exotic possibilities entertained on Loeb paper (33:55) is that & # 39; s Oumuamua is on a targeted reconnaissance mission (it doesn't have to alienate Earth – but may generally explore habitable star system zones). This is based on inheritance calculations about the relative abundance of interstellar objects, and other factors.

Loeb and I then discussed the online archive where he and his co-author, postdoctoral colleague Shmuel Bialy, initially placed their paper (36:58) and speed that is rare Astrophysical Journal both received and published (40:35) I then presented Loeb with jabs from some of his criticisms, which he responded to (44:51) This leads to a discussion of Loeb's philosophy of the roles and responsibilities of academics.

The unusual approach of this object shows that it originated from outside our Solar System. "Src =" https://cdn.arstechnica.net/wp-content/uploads/2018/06/Screen-Shot-2018-06-28-at-1.51 .22-PM-640x379.png "width =" 640 "height =" 379 "srcset =" https://cdn.arstechnica.net/wp-content/uploads/2018/06/Screen-Shot-2018-06- 28-at-1.51.22-PM.png 2x
Enlarge / The unusual approach of this object shows that it originated from outside our Solar System.

We are closing in on the interesting prospects that a large telescope debuting in 2022 might quickly answer questions that avoid today's hardware (56:56) This goes back to the many interstellar objects such as & # 39; Oumuamua. If they are as scarce as the previous calculations, new, more powerful equipment will find only a small number of new ones. But if they are common enough to make Oumuamua's discovery not surprising, new telescopes must quickly find thousands of them.

This argument is too involved to be fully explored here (I am a podcaster, not a journalist). So I encourage you to listen to this section. That was all but gave Loeb's controversial explanation of the sale-by-date date, and that date was only a few years.

Personally, I can't wait to follow the event closely as they approach. Listen to this section, and you will know the underlying problem like me. However thin, at least there is little chance that 2022 will bring intriguing evidence that Oumuamua is an artificial relic. And whatever the results, wouldn't it be cool to follow that story when it was revealed?

This interview is the latest episode of my podcast After On. If you enjoy it, my full episode archive can be found on my site or through your favorite podcast application by searching under the word "After On." A broader series is built around in-depth interviews with world-class thinkers, founders and scientists, and tends to be heavy technology and science.


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