
'Black neutron star' discovery changes astronomy - wglb
https://www.bbc.com/news/science-environment-53151106
======
gorgoiler
If you haven’t read RL Forward’s _Dragon’s Egg_ then take the weekend off and
treat yourself.

A 1980s hard sci-fi novel depicting the saga of a species called _cheela_ :
creatures who have evolved to live on the surface of a neutron star, where the
forces of nature are so powerful that daily life is 1,000,000x faster than
that of human beings.

 _...with hilarious consequences!!_

~~~
leejoramo
One of the best hard SF books I have ever read. I agree with your description,
but for those unfamiliar this is not a Terry Pratchett comedic story. Forward
was a physicist who specialized in gravity.

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goodcanadian
I was slightly frustrated when reading the article a couple of days ago, and
now, when reading these comments. Most likely, there is nothing exotic here.
Most likely, it is a black hole as everything heavier than a neutron star is
most likely a black hole. Lower mass black holes should exist, and perhaps, we
have finally found one.

The next most likely possibility is that it is a neutron star which would
suggest that our understanding of the mass limit of neutron stars is out. This
is entirely possible as the physics of neutron stars is pretty extreme, but it
seems a lot less likely to me.

Now, I'm happy to keep an open mind as we don't know for sure and we haven't
previously found anything in this mass range, but calling it a "black neutron
star" implies something new and exotic when it probably isn't.

~~~
incompatible
I think the article can be summarized as "A gravitational wave detector has
found an object of 2.6 solar masses. Astronomers don't know whether it's an
exotic type of neutron star or a light black hole".

It doesn't seem especially surprising that objects of 2.6 solar masses could
exist. It would be more surprising to me if they could not.

~~~
PopeDotNinja
I like the idea that a neutron star can be right at the limit of becoming a
black hole, but still be a star. Then a space pigeon flies down to the surface
for a quick rest, and shhhhhllurrrrrp... black hole.

~~~
Retric
The mass limit depends on how fast it’s rotating, so they can simply slow down
slightly and slurp, black hole.

~~~
PopeDotNinja
It blows my mind to think that shining a light on a black hole makes it grow.

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not2b
Maybe there's a zone between neutron stars and black holes where the object
consists at least partly of quark-gluon plasma because the neutrons have been
forced together until they break, but it's a hair too small to form a black
hole.

~~~
pdonis
There is no such thing as "too small to form a black hole". There is no
minimum mass for a black hole.

There is a _maximum_ mass for white dwarfs and neutron stars; for white
dwarfs, it's about 1.4 solar masses, and for neutron stars, it's somewhere
between about 1.5 and 3 solar masses. We can't pin it down for neutron stars
any closer because we have a poor understanding of the equation of state of
matter in the relevant density and pressure regime.

I don't know if quark-gluon plasma is even stable in the relevant density and
pressure regime, but if it is, I suppose there could be a maximum mass for a
quark-gluon plasma "star" that was somewhat larger than the maximum mass for a
neutron star, so there would be a range of masses where gravitational collapse
could stop at a quark-gluon plasma star instead of a neutron star, and would
not go on to form a black hole.

~~~
philipov
There is in fact a minimum mass for a black hole. That's called the Plank
Mass, which is the amount of mass that forms a Black Hole with a size of 1
plank length. This is also the maximum mass of an elementary point particle.

~~~
wnoise
There is no reason beyond numerology to believe that any of the Planck units
actually mean anything.

~~~
dogma1138
Plank Units represent physical constants, they are there to make equations and
more importantly hypotheses/predictions continue to work in a world where
measurements can be constantly refined. Hence they their actual SI values have
quite a bit over the years.

This is also why Plank units aren’t used much outside of theoretical physics
and cosmology which are fields where using absolute value based on current
measurements won’t mean that much.

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the8472
Is the title something the BBC came up with? The paper itself certainly
doesn't mention anything about neutron stars that are cool.

[https://iopscience.iop.org/article/10.3847/2041-8213/ab960f](https://iopscience.iop.org/article/10.3847/2041-8213/ab960f)

~~~
viscanti
The title comes from interviewing one of the authors of the paper. It's a term
one of the authors of the paper used to explain this. Presumably the way they
communicate with journalists (and the broader public) is different than how
they communicate with other experts in their field through their paper. There
are lots of things to criticize the media for, but this doesn't seem like one
of them.

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xvilka
Do they speak about strange stars[1] (quark stars with strange quarks)?

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

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empath75
Couldn’t it just be a normal, non-collapsed star? I’m sure they thought of
that, just curious how they ruled it out.

~~~
dandare
It would be probably ripped apart into an accretion disc thus no gravitational
waves. But i like your question and I hate it when articles omit the to
mention and explain layman's explanations.

~~~
dmurray
Yeah, the article really seems to be missing an important point. It's written
something like

\- we never observe any super dense thing between 2 solar masses and 5 solar
masses

\- 2 solar masses is the maximum for a neutron star, because otherwise it
would collapse and become a black hole

\- 5 solar masses is the minimum for a black hole, because...?

~~~
ISL
It is the minimum thought to be possible for a black hole produced by standard
stellar evolution.

GR has no limit, large or small, on the size of a black hole. Such black holes
could be formed by another mechanism -- in the big bang ("primordial" black
holes) or from the merger of neutron stars.

What has everyone atwitter about this is that, given the standard plan for
things, these objects should be very rare. To have seen even one example this
early in the history of gravitational-wave observation is a surprise.

Either there are more primordial black holes than people think, supernovae
don't work like we expect (historically a pretty good bet), neutron stars find
each other and merge more often than people think, or there's another process
for making mass-gap objects that people don't know about.

~~~
gliese1337
I would think neutron stars accumulating material from a binary companion
ought to be reasonably common. Unlike white dwarfs, they won't be able to blow
themselves apart in supernovae, so they should just keep accumulating mass
until they collapse into very small black holes.

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phyzome
So... merger of two neutron stars, resulting in a black hole? If we see black
hole mergers all the time, why not neutron star mergers?

~~~
netcraft
As the other person responded, they have seen a neutron star merger, and I
believe that is the one they were able to observe with EM radiation as well.
Also this event they suspect the larger mass was a black hole, they aren't
sure of the smaller one.

~~~
phyzome
So that means this object could well have been the result of such a merger,
right?

I guess I'm not sure what all the fuss is about. "Oh neat, we found something
in this mass gap" seems reasonable, but the "changes astronomy" headline seems
completely unsupported.

~~~
netcraft
No - neutron stars can merge to form a black hole or a larger neutron star,
but it was thought that this mass-gap is beyond a threshold that was too small
to form a black hole, but too large to still be a neutron star. The fuss is
that this mass-gap has been something that was theorized but also backed up by
a (lack of) astronomical observations. This result means that it is possible
to have _something_ in this range, and the fact that it was detected so
"early" in gravitational wave observations suggests that they are more common
than we otherwise would have thought, again from theory and previous
observations. Hence, there's something we don't understand about these
objects.

~~~
phyzome
« This result means that it is possible to have _something_ in this range »

What would it even mean for it not to be possible? Two neutron stars of
appropriate size collide -- you end up with _something_. I'm sure the physics
are interesting in this range, but I have a hard time understanding how it
could just not be possible. (Rare, yes.)

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matco11
I believe this is the original source paper:
[https://iopscience.iop.org/article/10.3847/2041-8213/ab960f](https://iopscience.iop.org/article/10.3847/2041-8213/ab960f)

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cogman10
Question? Could something like this explain "dark matter"? Like, is it
possible that space is more full of matter than we think? Or is my
understanding of dark matter just way off.

~~~
variaga
"Something like this" is one of the competing theories for what dark matter
is, although I think the current consensus is that it cannot explain _all_ the
dark matter effects, so there must be something else too.

see:
[https://en.wikipedia.org/wiki/Massive_compact_halo_object](https://en.wikipedia.org/wiki/Massive_compact_halo_object)

~~~
ddrt
Now I’ve got Macho man stuck in my head. Thanks.

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hindsightbias
What happens when the neutron star is a pulsar?

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lifeisstillgood
There was a thread earlier today on how VC forms did or did not invent tech.
Invention is the wrong word - this stuff here, science, does the invention.
the rest of us do the "evenly distributed" part later on.

And can I make a suggestion to us all as we barrel towards elections and post
lockdown changes - write to your representatives, show them this and say "more
funds, more"

Let's double the science budget in every western democracy.

~~~
garmaine
Discovery is not invention. These are fundamentally different things.
Scientists don’t think like engineers.

~~~
yummypaint
As a professional scientist, i think most of what i do day to day is
engineering. There is no product or customer, but you are absolutely working
within a set of design constraints to make a tool to perform a task. It makes
a tremendous difference whether your engineering budget is being paid by basic
research grants or venture capitalists. Funding science is a proven method of
producing new tech which may subsequently be of interest to the for-profit
people. The kinds of innovation that come out of big government funded science
projects can never be produced exclusively by organizations whose purpose is
to demonstrate growth to shareholders quarter over quarter.

~~~
mturmon
The GP comment did over-reach...I agree that many scientists do indeed do
engineering.

I work at a lab that builds expensive, highly-specialized scientific
instruments, and the scientists who lead that kind of work are right at the
edge of what's possible in _engineering_ an instrument that can make a
scientific measurement. They get super-excited about stuff like new CCDs,
exotic semiconductor doping, high-precision clocks, and detector cooling
technologies.

But there are also other scientists who aren't engineering-focused in that
same way. They mostly want someone else to make the measurement, and to scoop
up the data later and analyze it.

Although come to think of it, many of those scientists do have a focus on the
_technologies_ for analysis - say, machine learning or large-scale cloud
computations.

One way I used to conceptualize whatever science/engineering divide there is,
is in terms of the Myers-Briggs [* ] J/P distinction. Namely, J = judging =
engineering, P = perceiving = science. I.e., "build a gizmo to figure this
out" vs. "think abstractly about the consequences of theory."

[* ] Subject to the usual caveats.

