
The possible disappearance of a massive star in the galaxy PHL 293B - karxxm
https://academic.oup.com/mnras/article/496/2/1902/5863970
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antognini
To provide a little bit of context for this work, one of the open questions in
astronomy is how core collapse supernovae work. Computational scientists have
struggled for a long time to get simulations of core collapse to explode.
Typically to get an explosion they have to artificially insert a "piston"
somewhere in the system that kicks the system outwards during the collapse and
triggers the shock wave.

Over maybe the last decade or so there's been some thought that if our
simulations have trouble getting supernovae to explode, then perhaps nature
has trouble getting supernovae to explode, too. Maybe a lot of massive stars
just collapse directly into a black hole with no supernova. If this were the
case then it would explain a discrepancy between the observed supernova rate
and the total number of black holes; there seems to be about twice as many
black holes as there are supernovae.

When I was in grad school one of the ongoing projects in my department was the
so-called "Survey about Nothing" in which they took deep images of nearby
galaxies and waited to see if any bright stars just... disappeared. (They did
find one candidate:
[https://arxiv.org/abs/1411.1761](https://arxiv.org/abs/1411.1761))

The authors in this paper find another star that just disappeared. The trouble
with all this is that if a star disappears it's unclear what exactly happened.
Maybe it collapsed into a black hole, or maybe it just temporarily shrouded
itself in dust and will be back in a few decades. The new thing about this
star is that they have detailed spectra of the star prior to its
disappearance, which helps tremendously with modeling the star. The hope is
that with more detailed measurements they might be able to place limits on
what is currently there and thereby figure out if a direct collapse happened
or not.

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ctchocula
IANAP and this could be a bit of a stretch, but could the disappearance of the
star been caused by the completion of a Dyson sphere around it?

~~~
gnur
If you are into these kinds of mysteries, I highly recommend reading Pandora's
Star by Peter F Hamilton. (even more so if you want to spend a few days
reading this epic space opera)

~~~
throwaway_pdp09
Warning: he writes huge tomes. They're far too long. The first I read was fun,
the second a slog. There won't be a third.

~~~
ImaCake
He has a whole follow-up trilogy from Pandora's Star. They are every bit as
massive and pondorous. I personally liked them just enough to finish them, but
I won't re-read them.

However, I absolutely love the Night's Dawn Trilogy and re-read it once every
few years. I think I read it at an impressionable age and it really stuck.

One could also consider reading Charles Stross' "Accelerando" which has plenty
of stuff about dyson swarms.

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andyjohnson0
So today I learned that we have the ability to notice when a single star
(possibly) disappears from a galaxy 75 million light years away. A small
thing, but also a rather wonderful example of what we're capable of.

~~~
eru
It was a particularly massive and bright star, though.

Still a great achievement!

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codeulike
This sounds like the plot of Pandoras Star by Peter F Hamilton

 _At the farthest edge of the Commonwealth, astronomer Dudley Bose observes
the impossible: Over one thousand light-years away, a star... vanishes. It
does not go supernova. It does not collapse into a black hole. It simply
disappears._

Lets hope its not the [[SPOILER]]

~~~
mkl
Or Vernor Vinge's A Deepness in The Sky, which is also excellent.

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dmix
LBV = Luminous blue variable
[https://en.wikipedia.org/wiki/Luminous_blue_variable](https://en.wikipedia.org/wiki/Luminous_blue_variable)

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luspr
Sounds like "Pandora's Star" by Peter F. Hamilton.

~~~
SigmundA
Maybe we should check into the financial records of those funding the
observation.

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sheerun
So they hypothesize it either collapsed to a black hole without supernova or
stopped fusion. They don't mention it might just might have been swallowed by
black hole.

~~~
xorfish
Wouldn't that be a slow process?

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Jolter
That is my impression also. Stars/objects being swallowed by black holes tend
to emit a large amount of radiation as it happens, over longer periods.
Someone correct me if I'm wrong.

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saiya-jin
Maybe stupid question - what would happen to the star, if it actually
'collided' with black hole - ie black hole flew right through its core, not
just casually going nearby, trapping each other and black hole slowly sucking
it dry?

I would expect the thing to be over rather swiftly, albeit probably with some
accretion disc still generating some radiation.

~~~
kijin
A head-on collision with a black hole will likely produce a very noticeable
explosion.

Black holes don't just vacuum up all the matter around them silently. Any
matter falling into a black hole, not just the accretion disk, emits
radiation. This radiation causes surrounding matter to expand outward,
counteracting the gravity of the black hole. A black hole trying to eat an
entire star at once will quickly exceed its Eddington limit [1] and most of
the remaining matter will be blown away.

[1]
[https://en.wikipedia.org/wiki/Eddington_luminosity](https://en.wikipedia.org/wiki/Eddington_luminosity)

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TouchyJoe
Starjacking?

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sylens
More validation of the dark forest theory?

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AnimalMuppet
Probably not. If it got sniped by some other civilization, it would probably
produce a burst of radiation on many wavelengths.

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raxxorrax
Sometimes astrologists make me smile:

> important sources of ionizing photons

Nothing better than a morning with cereal, milk and ionized photons.

Wikipedia says that LVB often form clouds around them from their violent
outbursts that are sometimes miss-classified as supernovae. We will probably
have to wait if it pops up again.

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mellosouls
_Sometimes astrologists make me smile_

Nothing makes astronomers smile more than being called astrologists.

~~~
stargazer-3
We smile on the outside yet cry on the inside.

