Author Topic: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)  (Read 58357 times)

Offline nacnud

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Re: Hyperbolic Hyperbole or Interstellar Interloper?
« Reply #20 on: 10/27/2017 09:25 PM »
I guess it's a Vulcan survey ship then, come to check out our progress with EM drives.

Online whitelancer64

Re: Hyperbolic Hyperbole or Interstellar Interloper?
« Reply #21 on: 10/27/2017 10:11 PM »
Makes me wonder, what would a rocky/metallic object, ~1/4 mile in diameter, entering Earth's atmosphere at 56,000+ mph look like?

6 km diameter crater, extensive local devastation and widespread regional damage.

http://www.purdue.edu/impactearth/
"One bit of advice: it is important to view knowledge as sort of a semantic tree -- make sure you understand the fundamental principles, ie the trunk and big branches, before you get into the leaves/details or there is nothing for them to hang on to." - Elon Musk
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Offline Bob Shaw

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Re: Hyperbolic Hyperbole or Interstellar Interloper?
« Reply #22 on: 10/27/2017 10:36 PM »
Rama!

Offline hop

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Re: Hyperbolic Hyperbole or Interstellar Interloper?
« Reply #23 on: 10/27/2017 10:40 PM »
Makes me wonder, what would a rocky/metallic object, ~1/4 mile in diameter, entering Earth's atmosphere at 56,000+ mph look like?

6 km diameter crater, extensive local devastation and widespread regional damage.

http://www.purdue.edu/impactearth/
FWIW per JPL the objects speed relative to Earth at closest approach was ~60 km/s (~134,000 mph) . Definitely gonna leave a mark ;)

The 25 km/s mentioned elsewhere is the speed relative to the Sun before entering / after leaving the solar system.

Offline Bob Shaw

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Re: Hyperbolic Hyperbole or Interstellar Interloper?
« Reply #24 on: 10/27/2017 10:40 PM »
On a more serious note, could this object be chased and surveyed in any reasonable timescale/technology?

Online QuantumG

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Re: Hyperbolic Hyperbole or Interstellar Interloper?
« Reply #25 on: 10/27/2017 10:44 PM »
I guess it's a Vulcan survey ship then, come to check out our progress with EM drives.

Or it's Karellen.


:(

Jeff Bezos has billions to spend on rockets and can go at whatever pace he likes! Wow! What pace is he going at? Well... have you heard of Zeno's paradox?

Offline hop

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Re: Hyperbolic Hyperbole or Interstellar Interloper?
« Reply #26 on: 10/27/2017 11:00 PM »
On a more serious note, could this object be chased and surveyed in any reasonable timescale/technology?
No realistically. We only spotted it after it passed Earth on the way out, and it's significantly faster than anything we've launched (Vinf ~25 km/s vs Voyager 1 at around ~16 km/s  ). Even if we built something faster, the time required to build it would give the asteroid a huge head start.

However, the fact Pan-STARRS found this one suggests that LSST will have a decent chance of finding more. Catching one on the inbound leg would allow a lot more study, perhaps even a flyby mission for a larger cometary object.

Offline notsorandom

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Re: Hyperbolic Hyperbole or Interstellar Interloper?
« Reply #27 on: 10/28/2017 12:04 AM »
Phil Plait does make an interesting point that if you were an alien race this is exactly where you would aim something to check out our solar system without alarming any local species. Isnít there an idea that one way of exploring other star systems is to embed technology into things like asteroids?
Any alien that might have sent this thing is either extremely long lived or long gone. It's moving fast but still took a long time to get here. That or it really slowed down right before it got here.

Offline Bob Shaw

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Re: Hyperbolic Hyperbole or Interstellar Interloper?
« Reply #28 on: 10/28/2017 12:41 AM »
On a more serious note, could this object be chased and surveyed in any reasonable timescale/technology?
No realistically. We only spotted it after it passed Earth on the way out, and it's significantly faster than anything we've launched (Vinf ~25 km/s vs Voyager 1 at around ~16 km/s  ). Even if we built something faster, the time required to build it would give the asteroid a huge head start.

However, the fact Pan-STARRS found this one suggests that LSST will have a decent chance of finding more. Catching one on the inbound leg would allow a lot more study, perhaps even a flyby mission for a larger cometary object.

Imagine seeing a part of another star system!

Offline sanman

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Re: Hyperbolic Hyperbole or Interstellar Interloper?
« Reply #29 on: 10/28/2017 01:08 AM »
It's Zor's battlefortress, and it's just missed us

« Last Edit: 10/28/2017 02:23 AM by sanman »

Offline hop

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Re: Hyperbolic Hyperbole or Interstellar Interloper?
« Reply #30 on: 10/28/2017 02:20 AM »
Any alien that might have sent this thing is either extremely long lived or long gone. It's moving fast but still took a long time to get here. That or it really slowed down right before it got here.
Agreed. It's moving fairly fast by our standards, but it's really slow for interstellar missions. Interestingly 25 km/s is also right in the middle of range the Engelhardt paper I linked earlier predicted for natural objects.

Of course one can imagine scenarios where an artificial object could be that slow, but IMO it makes arguments that the trajectory is "what a spaceship would do" a lot less compelling.


Offline the_other_Doug

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Re: Hyperbolic Hyperbole or Interstellar Interloper?
« Reply #31 on: 10/28/2017 03:22 AM »
My first thought, when I heard about this, was "Wow -- that would make one heck of a flash if it impacted even a small Solar System body -- and the extrasolar body was made of anti-matter."

I know it's extremely unlikely.  But boy, what a flash that would make, eh?  It would also prove without a shadow of a doubt that the body was extra-solar... :)
-Doug  (With my shield, not yet upon it)

Offline plutogno

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Re: Hyperbolic Hyperbole or Interstellar Interloper?
« Reply #32 on: 10/28/2017 05:20 AM »
and the extrasolar body was made of anti-matter."

if the object was made of anti-matter it would have followed the other branch of the hyperbola, the one without the Sun at its focus

Offline Star One

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Re: Hyperbolic Hyperbole or Interstellar Interloper?
« Reply #33 on: 10/28/2017 08:39 AM »
Phil Plait does make an interesting point that if you were an alien race this is exactly where you would aim something to check out our solar system without alarming any local species. Isnít there an idea that one way of exploring other star systems is to embed technology into things like asteroids?
Any alien that might have sent this thing is either extremely long lived or long gone. It's moving fast but still took a long time to get here. That or it really slowed down right before it got here.

Not sure that all applies if it was machine intelligence.

Offline ChrisWilson68

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Re: Hyperbolic Hyperbole or Interstellar Interloper?
« Reply #34 on: 10/28/2017 08:58 AM »
and the extrasolar body was made of anti-matter."

if the object was made of anti-matter it would have followed the other branch of the hyperbola, the one without the Sun at its focus

That's not how anti-matter works.  Anti-matter has positive mass just like regular matter.  You can't tell matter from anti-matter based on gravitational interactions of any sort.

However, if this object were somehow anti-matter, the charged particles of the solar wind hitting it would annihilate themselves and the anti-matter they hit, releasing enormous amounts of energy.  So there's no chance we would miss the fact that it was anti-matter.

Offline ChrisWilson68

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Re: Hyperbolic Hyperbole or Interstellar Interloper?
« Reply #35 on: 10/28/2017 09:01 AM »
Phil Plait does make an interesting point that if you were an alien race this is exactly where you would aim something to check out our solar system without alarming any local species. Isnít there an idea that one way of exploring other star systems is to embed technology into things like asteroids?
Any alien that might have sent this thing is either extremely long lived or long gone. It's moving fast but still took a long time to get here. That or it really slowed down right before it got here.

Not sure that all applies if it was machine intelligence.

Why not?  It seems to me the point is valid whether it's machine intelligence or not.  If machine intelligence sent this probe, that machine intelligence is either extremely long lived or long gone, unless the object slowed down right before it got here.

Offline Star One

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Re: Hyperbolic Hyperbole or Interstellar Interloper?
« Reply #36 on: 10/28/2017 09:21 AM »
Phil Plait does make an interesting point that if you were an alien race this is exactly where you would aim something to check out our solar system without alarming any local species. Isnít there an idea that one way of exploring other star systems is to embed technology into things like asteroids?
Any alien that might have sent this thing is either extremely long lived or long gone. It's moving fast but still took a long time to get here. That or it really slowed down right before it got here.

Not sure that all applies if it was machine intelligence.

Why not?  It seems to me the point is valid whether it's machine intelligence or not.  If machine intelligence sent this probe, that machine intelligence is either extremely long lived or long gone, unless the object slowed down right before it got here.

That was my point that machine intelligence is more likely to exist on long time scales compared to biological life.

Offline KelvinZero

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Re: Hyperbolic Hyperbole or Interstellar Interloper?
« Reply #37 on: 10/28/2017 10:22 AM »
How rare is this object really? Is it a 1 in a century sort of thing or have plenty of others probably passed by and we just didn't spot them?

Online LouScheffer

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Re: Hyperbolic Hyperbole or Interstellar Interloper?
« Reply #38 on: 10/28/2017 02:58 PM »
and the extrasolar body was made of anti-matter."

if the object was made of anti-matter it would have followed the other branch of the hyperbola, the one without the Sun at its focus
However, if this object were somehow anti-matter, the charged particles of the solar wind hitting it would annihilate themselves and the anti-matter they hit, releasing enormous amounts of energy.  So there's no chance we would miss the fact that it was anti-matter.

This is not clear - space is pretty sparse.  According to Wikipedia, interplanetary space has about 5-10 protons per cubic cm.  That's 10^7 protons per cubic meter.  According to JPL, the speed relative to the sun is about 60 km/sec, so each m^2 of surface sweeps up 10^7 x 6x10^4 = 6x10^11 protons.  Divide by Avagadro's number (6x10^23) to get 10^-12 grams/sec or 10^-15 kg/sec/m^2.  Now you need to multiply by 2*c^2 to get energy.  That's about 2*10^17, so it's releasing about 200 w/m^2, in assorted charged particles and gamma rays.  About 1/2 will head away from the object, and half into it and get absorbed.  So it's getting about 100 w/m^2 of extra heating.   But it's already absorbing most of the sunlight that hits it (estimated 92%) from 1300 w/m^2.  So it adds only a few percent to the heating.

Could we see the gamma rays?   We have at most 100W of gamma rays, so about 100/(1.6 x 10^-19 J/ev * 0.6 Mev) = 10^15 gamma rays per second.   If we are 10^10 meters away (much less than one AU) these are spread over an area of 4 x pi x 10^20 or about 10^21 m^2.  So at most 10^-6 gamma rays per square meter per second.  A gamma ray detecting satellite of 10 m^2 would see one per day.  No way we could see that either.

So it could be made of antimatter, without obvious consequences.


Offline Mark K

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Re: Hyperbolic Hyperbole or Interstellar Interloper?
« Reply #39 on: 10/28/2017 03:30 PM »

So it could be made of antimatter, without obvious consequences.

You skipped dust. Dust flux in inner solar system would conservativly mean 100s of partcles of mass around 10^-16 kgs or more hitting per second (flux would be much higher for nanodust many orders of magnitude more.) I think we oould detect the sparkling.

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