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Interstellar Interloper (A/2017 U1)

Nikolai

By Nikolai
in Science & Spaceflight

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Green Baron

Green Baron

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And the solar system sits between two spiral arms and outside of the galactic plane most of the time ... facts that have actually been described as fortunes for the evolution of life because less radiation and quieter surroundings most of the time.

All in all, i don't give much for a guess about the appearance of specific objects without any factual basis. We don't even have profound guesses about asteroid encounters !

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kerbiloid

kerbiloid

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8 minutes ago, FreeThinker said:

Well it is really confusing what number to use

What is even more funny, according to the table the density varies between 10-4 and 106 particles/cm3, i.e. 1010 times.

As we can see, the difference between the densiest metals and the air is just 104/10-3 = 107 times.

I.e. flying through the interstellar medium is like flying through the air full of flying rocks, but 1000 times even more contrast.
(Like doing this at 60 km altitude)

Like in Star Wars s1e5 "The Empire Strikes Back", when the Millenium Falcon flies through the asteroid cloud.

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FreeThinker

FreeThinker

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11 minutes ago, kerbiloid said:

What is even more funny, according to the table the density varies between 10-4 and 106 particles/cm3, i.e. 1010 times.

As we can see, the difference between the densiest metals and the air is just 104/10-3 = 107 times.

I.e. flying through the interstellar medium is like flying through the air full of flying rocks, but 1000 times even more contrast.
(Like doing this at 60 km altitude)

Ok, so the term average density is really misleading, as it isn't representative at all. What I find confusing as well as that notion is that we are supposed to travel though a local interstellar cloud while at te same time beeing in a local bubble .W.T.F is it?

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kerbiloid

kerbiloid

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8 minutes ago, FreeThinker said:

What I find confusing as well as that notion is that we are supposed to travel though a local interstellar cloud while at te same time beeing in a local bubble .What what is it?

Probably, I don't understand the question.

I've mentioned "1000 cm-3" value as a response to a question "could an asteroid form far from the stars", not necessary in/out of the Local Bubble, and 1000 looks like even better conditions that in the L.B.
I think, such concentration would require AU-sized volume to be compressed by self-gravity to form something, so unlikely any asteroid can be unrelated to a homestar.

If speak about "travel through", I mean that drawing interstellar navigation maps for starships one should depict the molecular clouds as huge rocks on the way.

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Scotius

Scotius

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16 minutes ago, FreeThinker said:

Ok, so the term average density is really misleading, as it isn't representative at all. What I find confusing as well as that notion is that we are supposed to travel though a local interstellar cloud while at te same time beeing in a local bubble .W.T.F is it?

It means that Solar System is currently traversing an empty area of space called Local Bubble (it's about 300 light years across). But even in this empty (compared to statistical average for Milky Way) area there are regions with higher density - like clouds of dust and gas. Those "clouds" are just a bit denser than the rest of the Bubble - and our system is currently inside one of those clouds.

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PakledHostage

PakledHostage

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55 minutes ago, Green Baron said:

Without offending anybody, but really, how relevant are such guesses ? Do we have standard-density-parsecs now :-) ? It is, to say it clear, not serious to deduct any rule from a single observation. Those guys can't have much knowledge of how statistics work.

Don't shoot me. I am just the messenger.

And, I might add, their paper supports your own assertion that Oumuamua is not that much of an anomaly. Sorry if I am ruffling feathers by asking (we all seem to get along quite well here on this forum), but how is your guess better or more valid than theirs?

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Green Baron

Green Baron

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I don't shoot noone ! Just stating my opinion :-)

I don't give numbers and i don't overstrain statistics, i hope. I only recited in a general way what others used as an introduction into their work, that is the first observation and there may/will be more in the future.

If that doesn't make my guess better then my guess probably isn't better at all :-)

@PakledHostage: which paper do you mean ? I thought it was in that scifi channel video ?

Forget it, i decided to watch the video, they basically conclude with the same as i did, so we are all in the main stream. Here is the (yet unpublished) paper for those like me who didn't get it: https://export.arxiv.org/pdf/1711.03558

about sola lapis. It is interesting, but based on assumptions. And a single specimen.

 

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PakledHostage

PakledHostage

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59 minutes ago, Green Baron said:

@PakledHostage:

paper do you mean ? I thought it was in that scifi channel video ?

I mean the one in the PBS SpaceTime video that @DAL59 linked to, above. (Here: https://forum.kerbalspaceprogram.com/index.php?/topic/166919-interstellar-interloper-a2017-u1/&do=findComment&comment=3243636)

I think what the authors of the paper that they are citing are saying is that, in order for this observation not to be crazily anomalous, the density of such debris in interstellar space has to be on the order of the value that they quoted. We only caught this one because it basically flew past our telescopes at the relatively close distance of ~0.3 AU and waved at us. It isn't unreasonable to assume that there must be many more of these objects that pass through our system unnoticed. Most are probably either too small, come from directions that make them hard to detect, or are too far away from us during their transit to be seen.

 

 

 

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Green Baron

Green Baron

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16 minutes ago, PakledHostage said:

I mean the one in the PBS SpaceTime video that @DAL59 linked to, above. PBS SpaceTime is a YouTube series on various astrophysics topics; there is nothing "sci-fi" about it. 

I think what the authors of the paper that they are citing are saying is that, in order for this observation not to be crazily anomalous, the density of such debris in interstellar space has to be on the order of the value that they quoted. We only caught this one because it basically flew past our telescopes at the relatively close distance of ~0.3 AU and waved at us. It isn't unreasonable to assume that there must be many more of these objects that pass through our system unnoticed. Most are probably either too small, come from directions that make them hard to detect, or are too far away from us during their transit to be seen.

I found the paper and read it. It is not published yet but it seems to be accepted for review by MNRAS. Lt. Wharf has a short appearance in the video with the remark that "Its never aliens !". The last name in the author list is probably just a funny coincidence.

I completely agree with every word you say. It is basically a reprise of the same theme. Btw., the LSST is mentioned in the video as well.

To the paper's conclusion: i find it too hasty to conclude the galaxy is rich in sola lapis. Though i share that opinion, without proof or at least more samples it is only an opinion. The model calculations throughout the paper are based on assumptions, which can reflect reality, part of it, or be wrong.

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PakledHostage

PakledHostage

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1 hour ago, Green Baron said:

To the paper's conclusion: i find it too hasty to conclude the galaxy is rich in sola lapis. Though i share that opinion, without proof or at least more samples it is only an opinion. The model calculations throughout the paper are based on assumptions, which can reflect reality, part of it, or be wrong.

And that is just it: So far we only have a sample of one, but after less than a decade of searching. We can merely guess what that means; you can't extrapolate from a single data point. You can try to bound the range of possible explanations, however, and that is what I understand the authors are attempting to do. Hopefully the discovery of this object and the public interest in astronomy that it  has generated will help justify funding for further research.

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  • 2 weeks later...
kerbiloid

kerbiloid

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I'd just leave this here.

https://en.wikipedia.org/wiki/ʻOumuamua

Quote

 estimated to be about 230 by 35 meters (800 ft × 100 ft) in size.

 

https://en.wikipedia.org/wiki/General_Products#GP_#3_hull

Quote

A #3 GP is a cylinder with rounded ends and a flattened belly. It is opined in Ringworld that a #3 hull makes a good multi-crewed passenger ship. Before acquiring the Lying stand-up guy, the Ringworld expeditionaries transfer from the Long Shot to the Puppeteer homeworld in a ship based on a #3 hull. The Hot Needle of Inquiry which carried Chmeee, Louis Wu, and the Hindmost from Known Space to the Ringworld in The Ringworld Engineers also had a #3 hull. The Hot Needle of Inquiry is described as being 110 feet (34 m) across in Ringworld's Children.


A cylinder 35 m in diameter you say?...

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Green Baron

Green Baron

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As a relief from the monotonous starship talk :sticktongue: a few serious thoughts on Ummagamma:

https://www.nature.com/articles/s41550-017-0361-4

tl:dr: billions of years of exposure to cosmic radiation might have covered it in an insulating shell, which can be the reason why there is apparently no surface activity.

Edited by Green Baron
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monophonic

monophonic

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19 hours ago, DAL59 said:

You haven't seen the last jedi?

I haven't seen the last jedi! ;.;

Although I do instantly recognize Mon Calamari esthetics even if it hits me in the head, from behind, with full broadside. And I am sensitive enough in hollywood economics force to know said esthetics would feature in said motion picture. Nothing actually spoilt for me then.

The tears were just because I haven't seen the movie.

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