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Oumuamua: Alien lightsail probe?

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#1 InterStellarGuy

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Posted 02 November 2018 - 02:07 PM

Interesting read:

 

https://www.universe...ial-solar-sail/

 


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#2 Dynan

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Posted 02 November 2018 - 02:22 PM

It was doing all it could to get back to its father...

 

https://www.youtube....h?v=EQrQjNNZCAo


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#3 555aaa

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Posted 02 November 2018 - 03:57 PM

There is no mass to area known for Oumuamua. Don't know where they got that from. There is an interesting excess velocity term but that might not all be light pressure, because the lack of a detected coma could have other explanations (like it's too faint). 

 

FYI there has been some debate about an object (ZU8D586 which is a temporary designator) on the PCCP page of the minor planet center being another interloper. Right now it is listed at e=0.87

 

 https://www.minorpla...cp_tabular.html

 

Another maybe interstellar comet from the past. Points out the importance of good astrometry for long period comets.

 

 https://arxiv.org/pdf/1810.12766.pdf



#4 lavudyar

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Posted 02 November 2018 - 04:05 PM

Interesting timing, as I am currently in the middle of The Mote in God's Eye (for about the 20th time).



#5 Astroman007

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Posted 02 November 2018 - 04:07 PM

A fascinating and not unreasonable possibility...although Oumuamua much more closely resembles a massive, heavily battered, and long-dead cigar-shaped interstellar mother ship than a solar sail.



#6 555aaa

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Posted 02 November 2018 - 05:50 PM

A fascinating and not unreasonable possibility...although Oumuamua much more closely resembles a massive, heavily battered, and long-dead cigar-shaped interstellar mother ship than a solar sail.

The artist's conception made it look more like the old planet killer thing from the original star trek series. 

 

I do think it might be something thin and flakey. My personal theories are either alien space junk or it is some sort of refractory material which is generated in the atmosphere of cool stars, or it is some sort of organic sludge or dusty clump. There is a lot of dust and crap out in space. Why wouldn't you expect there to be cosmic dust bunnies?



#7 goodricke1

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Posted 02 November 2018 - 06:15 PM

The fact the author has connections with the Breakthrough lightsail project might lead to some conflict of interest suggestions... doesn't change the fact that 'Oumuamua is a truly compelling object.



#8 Astroman007

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Posted 02 November 2018 - 06:19 PM

I do think it might be something thin and flakey. My personal theories are either alien space junk or it is some sort of refractory material which is generated in the atmosphere of cool stars, or it is some sort of organic sludge or dusty clump. There is a lot of dust and crap out in space. Why wouldn't you expect there to be cosmic dust bunnies?

Regardless of what the true nature of this object is determined to be or not to be, Oumuamua remains a fascinating object, and a marked oddity when compared to the asteroids of our own solar system that we are familiar with. There is a distinct possibility that it may not even be a natural body, for a number of reasons, some of them predating the pass of this object through our region of space.

BTW, when I hear the words "cosmic dust bunnies," the images that most readily come to mind are those of the dark nebulae (in either our own galaxy or others), for some reason.



#9 rockethead26

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Posted 02 November 2018 - 06:33 PM

Interesting timing, as I am currently in the middle of The Mote in God's Eye (for about the 20th time).

Hey, me too!


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#10 philipdehazya

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Posted 06 November 2018 - 09:20 AM

The book sounds fascinating (per Wikipedia) and I just requested it from our local library.


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#11 InterStellarGuy

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Posted 06 November 2018 - 10:44 AM

Regardless of what the true nature of this object is determined to be or not to be, Oumuamua remains a fascinating object, and a marked oddity when compared to the asteroids of our own solar system that we are familiar with. There is a distinct possibility that it may not even be a natural body, for a number of reasons, some of them predating the pass of this object through our region of space.

BTW, when I hear the words "cosmic dust bunnies," the images that most readily come to mind are those of the dark nebulae (in either our own galaxy or others), for some reason.

The shape of the object..being much longer than it is wide, in the ratios given and represented in the various artists renderings, as well as its path into the solar system, where it went, and where it's going, just give you that "what if.." feeling in the back of your mind...


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#12 lavudyar

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Posted 06 November 2018 - 12:24 PM

The book sounds fascinating (per Wikipedia) and I just requested it from our local library.

Quite possibly the greatest scifi book ever written. Niven and Pournelle were at the absolute top of their game for this one.


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#13 555aaa

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Posted 06 November 2018 - 04:01 PM

There has been a lot more discussion of this topic in the minor planet community it seems. One issue that seems to be cropping up is that when the minor planet center generates the proposed ephemeris for follow-up observations on newly discovered objects, their code is biased towards fitting a normal elliptic orbit and sometimes a parabola, but not a hyperbola. The MPEC format doesn't even handle parabolic orbits, and when a presumptive orbit is generated, there can be solutions for both hyperbolic and ellipsoidal that are both reasonable, but without letting observers know that there is a hyperbolic fit, there is no extra incentive to follow up with astrometry. Right now the system is highly biased towards NEOs that are potentially hazardous, so they get most follow-up attention. The bulk of the time, the elliptical fit is going to be correct, or it's an artificial satellite, orbiting the earth, but having some sort of flag on candidate hyperbolic orbits looks really attractive. So now people are looking at long period comet orbit solutions from the past, looking up the old astrometry, and seeing how many of those also have a hyperbolic solution as well as the published and often not very accurate solution. There's a big need to go find archival images that might contain those comets and which are good enough for astrometry, even if they are on glass plates. There was already one paper on an object flagged in the past as a comet which might actually be another interstellar interloper. It's a difficult problem because these objects, like the small NEOs, may only be visible for a few days. 


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#14 goodricke1

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Posted 06 November 2018 - 06:20 PM

....

Maybe some interstellar comets have slipped through the net, but that doesn't change the fact that this one went within 0.25 AU of the Sun and no outgassing was detected.



#15 BillP

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Posted 06 November 2018 - 09:01 PM

There is no mass to area known for Oumuamua. Don't know where they got that from.

 

Per their paper, they got it from a reference - Jewitt, D., Luu, J., Rajagopal, J., et al. 2017, The Astrophysical Journal Letters, 850, L36.



#16 BillP

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Posted 06 November 2018 - 09:03 PM

Interesting timing, as I am currently in the middle of The Mote in God's Eye (for about the 20th time).

 

After you are finished with that, read Rendezvous with Rama!



#17 epee

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Posted 07 November 2018 - 08:11 AM

I know that the shape was proposed due to the rather extreme changes in illumination the object exhibited within a regular cyclic period. However, how sure are the researchers about that shape versus a surface of widely differing albedo?

 

Granted, it would be hard to explain why an object, rotating for, presumably, millions if not billions of years should have a multicolored surface...



#18 llanitedave

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Posted 07 November 2018 - 10:08 AM

I know that the shape was proposed due to the rather extreme changes in illumination the object exhibited within a regular cyclic period. However, how sure are the researchers about that shape versus a surface of widely differing albedo?

 

Granted, it would be hard to explain why an object, rotating for, presumably, millions if not billions of years should have a multicolored surface...

Strobe lights?


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#19 epee

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Posted 07 November 2018 - 11:43 AM

Maybe it was a turn indicator grin.gif


Edited by epee, 07 November 2018 - 11:44 AM.

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#20 B l a k S t a r

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Posted 07 November 2018 - 06:24 PM

Maybe it has a salt lick like Ceres...

 

Maybe the asteroid went close enough to Sol to cause a localized expansion that did not erupt until far enough away to cool and 'pop', a vector changing event with no gas expulsion.

 

Maybe they want to keep low profile ...



#21 BillP

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Posted 08 November 2018 - 09:31 AM

There is no mass to area known for Oumuamua.

 

There is in this research letter because they calculated it based on the data and information from reference Jewitt, D., Luu, J., Rajagopal, J., et al. 2017, The Astrophysical Journal Letters, 850, L36.  It's on page 2 of their paper.



#22 Gvs

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Posted 09 November 2018 - 08:09 AM

Oumuamua is an interesting object indeed and deserves to be studied.

 

The pre print article can be found here.

 

The scientific method is not based on beliefs,  its based on providing evidence for or against a theory,  improving understanding of the subject of study. 

 

This method is what allowed humanity to develop current technology.  Quantumn physics,  the basis of most current electronics,  is proof of that, even though it's counterintuitive to our understanding of physics.

 

We all have opinions,  though they don't change our understanding of a subject,  just our perception of it.

 

All current scientist an amateurs, based their conclusion on the basis that our math and physics are universal.   Unfortunately humanity's interpretation of physics is based on our best sensory capacity we have  eyesight and sound, which leads us to develop instruments to detect wavelengths and understand the universe from that perspective.

 

If dogs ruled the world, they would most likely (assumption here) based their technology on chemicals and sounds which is how they perceive their surrounding.   Ants would use pheromones and chemicals. Their interpretation of physics would be based on these attributes,  and their communication devices as well.  So their technology would be significantly different than what we have now.

 

Considering that if aliens exist elsewhere,  (another assumption here)  their environment would be different,  their perception of time if they had one, would be based on the way they perceive their surrounding.  Which in any case be significantly different than humanity. Which would lead to a completely different type of technology than what humanity has.

 

So to assume they use solar sails is interesting , because, if true, it would mean they have somewhat similar understanding of physics as we do.  That is a big assumption.   Though by the same token, to assume they use electromagnetic devices for communication or to control their probes,  like humanity does,   is assuming a lot as well.


Edited by Gvs, 09 November 2018 - 05:51 PM.

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#23 epee

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Posted 09 November 2018 - 10:29 AM

Other creatures do have "primary" senses that differ from our own. However, I see these as "limiters" to the degree to which they can develop science and technology. Scent and hearing do not work well or at all in a rarefied medium or at long range; "long" being relative.


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#24 555aaa

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Posted 09 November 2018 - 01:07 PM

Per their paper, they got it from a reference - Jewitt, D., Luu, J., Rajagopal, J., et al. 2017, The Astrophysical Journal Letters, 850, L36.

There are two papers here and so maybe I am confused - there is the recent Bialy and Loeb paper which is all about mass to area ratio by assuming a light pressure based acceleration, and then the paper you mention is one of the summaries of observations.

 

The pre-release of the latter paper on Arixiv is here:

 https://arxiv.org/pdf/1711.05687.pdf

 

They know from the orbit solution the distance to the object and the apparent brightness, and then they guess that it is 10% reflective, so they assign a size to it using an empirical formula that covers the phase angle at which the observations were made (which is known geometrically). The depth of the light curve implies the shape factor as being highly elongated assuming constant albedo. They then guess a density about the same as water to get a mass. They also use the elongation factor and postulated rotation rate to calculate the strengthless density and get 6 g/cm^3 which is high but typical for solid metals, but such a small object isn't strengthless and some small asteroids spin above their cohesive limit.

 

The paper also points out that there is aliasing in the light curve data and there may be more than one solution which is pretty typical; often they are 50% or more different from each other.

 

The Bialy and Loeb paper's 0.1g/cm^3 number fits nicely with my dust bunny hypothesis. 


Edited by 555aaa, 09 November 2018 - 01:31 PM.


#25 llanitedave

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Posted 09 November 2018 - 11:25 PM

Other creatures do have "primary" senses that differ from our own. However, I see these as "limiters" to the degree to which they can develop science and technology. Scent and hearing do not work well or at all in a rarefied medium or at long range; "long" being relative.

Exactly.  Doesn't matter too much in the long run what a particular species' biological sensory apparatus consists of, there's really just one physics.




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