
Alien star system buzzed the Sun - dreamweapon
http://www.bbc.com/news/science-environment-31519875
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andyjohnson0
The article links to a paywalled source for the paper "The Closest Known Flyby
of a Star to the Solar System" by Mamajek et al. Full text is freely available
on arXiv at [1].

[1] [http://arxiv.org/abs/1502.04655](http://arxiv.org/abs/1502.04655)

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jessriedel
For reference, 0.8 light years is about 50,000 AU. (AU = the distance from the
Earth to the Sun.) Pluto is about 49 AU away.

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IndianAstronaut
It will take a few thousand years for the Voyager, the fastest spacecraft we
have ever built, to reach that distance.

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pdonis
Nearly 14,000 years (Voyager 1 is moving at 3.6 AU per year).

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will_work4tears
Wow, that's quite some perspective, thanks!

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1971genocide
Weren't humans alive back 70,000 years ?

I wonder if one of our ancestor then gazed at the sky and saw something or
not. Guess we will never know :(

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lkbm
Yes, I believe modern humans came about around 200 000 years ago, and around
70 000 years ago were heading out of Africa.

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ddeck
Not sure why you're being down voted without comment since you directly
answered the parents question with broadly accurate information:

 _Anatomically modern humans first appear in the fossil record in Africa about
195,000 years ago (see Omo remains), and studies of molecular biology give
evidence that the approximate time of divergence from the common ancestor of
all modern human populations was 200,000 years_ [1]

Migration out of Africa is estimated at around 125000 years ago for _modern_
humans. [2]

[1]
[http://en.m.wikipedia.org/wiki/Homo_sapiens](http://en.m.wikipedia.org/wiki/Homo_sapiens)

[2]
[http://en.m.wikipedia.org/wiki/Early_human_migrations](http://en.m.wikipedia.org/wiki/Early_human_migrations)

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S4M
I am wondering if we could predict those events, and then launch a space probe
similar to Voyager I and II that would be hooked in the alien star's gravity
and orbiting around it while it travels in the Milky Way, which would be a
some free speed for the space probe to explore space further.

Now, since stars rarely get that closed, I guess it's a bit pointless but I am
still curious about it.

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bdamm
I wonder if another civilization had this same idea, and dropped a probe off
some 70,000 years ago. Or perhaps the probe has yet to arrive, since elsewhere
in this thread I see that comets dislodged by the perturbations of the passing
stars are yet to arrive at Earth.

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hasenj
I'm starting to wonder if a somewhat similar event could have occurred ~66
million years ago and triggered a series of events leading to the extinction
of dinosaurs.

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Sanddancer
That's the basis of the Nemesis hypothesis [1]; that supposedly there's a star
that roughly orbits the sun and causes havoc every few miillion years.
However, it's been pretty much debunked at this point

[1][http://en.wikipedia.org/wiki/Nemesis_%28hypothetical_star%29](http://en.wikipedia.org/wiki/Nemesis_%28hypothetical_star%29)

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tomphoolery
Was gonna come in here to ask...will this explain Nemesis as not a recurring
event but rather a one-time event caused by that trailing brown dwarf (or the
star itself) flinging comets all over the place. It would also explain a lot
of other crater-rich surfaces dating back to that time...

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iwwr
If that's true it'd be hard to identify the responsible star since in a few
million years it would be thousands of light years away and difficult to
measure precise kinematics of it.

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jarin
Not only is this super amazing, it has probably the best sub-header I’ve ever
read in a science article: “Grand theft Oort-o?”

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ufmace
This reminds me of the story "A Pail of Air" [0] where a "dark star" passes
through the inner solar system, and its gravity causes the Earth to be ejected
from the Sun's orbit. The story features a family who can only survive by
maintaining a fire and constantly fetching pails of frozen Oxygen to heat up
to breathe and pressurize their living area.

I thought of it as one of those things that's extremely unlikely to happen,
but we'd be screwed if it did.

A little surprising that other start passing through the outer Oort cloud
might actually happen semi-regularly, on galactic timescales. Makes the idea
sound a little less unlikely, though the inner Solar System seems to have been
around for ~5 billion years, and hasn't been disrupted by any star-mass
galactic bodies yet.

[0]
[http://www.baenebooks.com/chapters/0743498747/0743498747___6...](http://www.baenebooks.com/chapters/0743498747/0743498747___6.htm)

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yongjik
Note that a distant star's ability to "perturb" the inner solar system is
basically tidal force: it's the _difference_ in how much the star attracts the
Earth vs. the Sun, because if they are pulled by exactly the same acceleration
then nothing is changed from the Earth and Sun's viewpoint.

So, the effect is proportional to 1/(distance)^3. I guess anything that zips
around at ~10,000 AU would basically have zero effect on the inner solar
system. And if we reduce the expected distance, the "target area" gets
incredibly small.

I think we're safe for the time being. :)

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lfnoise
20 light years per 70000 years in miles per hour = 191604.751 miles per hour,
according to google

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joshvm
It's travelling at around 80km/s radially according to the paper so that
sounds about right. Almost all the velocity is radial, only 3km/s is observed
tangential to us.

In perspective, it's only around 4-5 times faster than Voyager 1 or New
Horizons.

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eyko
It's also _speeding_ away (no info on how many km/s per year faster it is?).
It could've been much slower 70.000 years ago.

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mangeletti
Since it is moving away from a large body of mass, namely, the day star, it's
likely that it has been decelerating over the past 70k years, meaning it would
have been moving more quickly when it passed by.

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Zelphyr
I'm curious about what, if any, gravitational effects this would've had on the
earth? Seems like its a relatively small star and it was so far away that I'm
guessing any pull would've been negligible.

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jontas
It is explained in the article:

    
    
        > The effect of a passing star on the Oort Cloud is a function of the star's mass, speed and proximity. The worst case scenario for stirring up comets would be a slow-moving, massive star that came close to the Sun.
    
        > Scholz's star came relatively close, but the binary system (the red dwarf and its brown dwarf companion) has a low mass and it was speeding by. These factors conspired to make its effect on the Oort Cloud very small.

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NoMoreNicksLeft
How visible would this have been in the night sky?

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mangeletti
As a starting point, the sun's absolute brightness is much higher than this
star's, and this star supposedly came within .8 light years of us. That's
50,591 further than Earth is from the sun, which means it would be no brighter
than most of the stars you see in the sky... unfortunate, huh :(

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mangeletti
I meant "50,591 times further".

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oofabz
Someone should run an n-body simulation of the solar system and this star
backwards in time to see if it had any perturbative effects on us. What if
this star was responsible for ripping Pluto away from a planet or sending
Phobos down into the inner solar system to be captured by Mars?

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mkempe
How long would it take for Oort objects that are nudged out of their orbit to
become comets buzzing or hitting Earth?

Also, if that star system has its own Oort cloud, could some of the objects
there have jumped system and become long-term comets?

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kryptiskt
The Nature News article says: "Because Scholz’s star is puny and sped by
quickly, it would have had a negligible impact on the Oort cloud, Mamajek
notes. And any comets that the star might have sent hurtling towards the inner
Solar System will not arrive for another few hundred thousand years, says
Tremaine."

[http://www.nature.com/news/star-buzzed-solar-system-
during-h...](http://www.nature.com/news/star-buzzed-solar-system-during-human-
prehistory-1.16958?WT.mc_id=TWT_NatureNews)

~~~
mkempe
So the claim that the passage of the star had _negligible_ impact on the Oort
cloud (for life on Earth) is an untestable hypothesis.

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legohead
Dealing with asteroids feels plausible.. but how to deal with a star? scary
stuff

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arethuza
People have given a surprising amount of thought into how you could move a
star:

[http://en.wikipedia.org/wiki/Stellar_engine](http://en.wikipedia.org/wiki/Stellar_engine)

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legohead
Very cool, thanks for this!

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unreal37
Possibly the farthest away two things have ever been from each other where the
word "buzzed" was used to describe their proximity.

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smeyer
I'd wager the word's been used on galactic scales before.

