
The Largest Black Hole in the Known Universe - GlennCSmith
https://medium.com/@startswithabang/the-largest-black-hole-in-the-known-universe-67b792a1d856
======
antognini
It's interesting that this has made it to HN! My research is on the dynamics
of few body systems so I know OJ 287 well! One of the projects I've been
wanting to work on but haven't gotten around to is about this system. As the
article mentions, OJ 287 is strange because it is a blazar (which is very
rare, since the outflow has to be pointed directly at us) and is in a binary
(which is also rare), yet it also happens to be the largest black hole known
in the universe! So one could say that there's a low prior for such a system
to exist.

The reason that OJ 287 has to be so massive in this model is because the orbit
of the secondary black hole precesses so rapidly. For GR to give you that
precession rate, you need a very, very massive black hole.

An alternative model I would like to explore is a three-body model for OJ 287.
If this black hole binary is orbited by a tertiary black hole, the tertiary
can also induce precession in the inner binary, so OJ 287 would not need to be
so massive, which would make the triple model more plausible. It's unclear yet
whether the triple dynamics can reproduce the observed lightcurve of OJ 287,
though, so this is just an idea that's been on my to-do list for a year now.
Let me know if you have any questions!

~~~
z3phyr
Its good to see more Astrophysicists using HN. I am very much interested in
studying the workings of the cosmos, but I am not a professional degree holder
in space science. I do freelance software development, but want to catch up
with astrophysics too. Is it possible?

~~~
antognini
It is possible! But how you go about doing it would depend on your goals, how
much time you would have for it, and how much physics and math you know.

The thing about astronomy is that it changes quickly, but not _that_ quickly.
The timescale for major changes in our knowledge of astronomy is perhaps ~10
years or so (that's usually how long it takes a big problem to be solved), so
it's not as though it's something you need to keep on top of every day or
every week. (Unless you're a professional astronomer and want to be aware of
all the new papers coming out.) As a consequence of this, textbooks are a good
place to start for background. There are tons, but Carroll & Ostlie is a good
general introduction to all aspects of modern astrophysics. Each chapter also
has general and technical references so you know where to go to learn more
about any subjects that you find interesting.

For discussions of current problems in astronomy, the journal Annual Reviews
in Astronomy & Astrophysics is a good place to start. Current articles are
paywalled, but most of them appear on arxiv.org, so you can search for them
there. They contain summaries of all the recent research on a particular
problem. If you're interested in learned more about that particular problem,
they're a good place to start because they'll point you to all the important
papers on the subject.

Another good resource is ADS. You can search for papers here:
[http://adsabs.harvard.edu/default_service.html](http://adsabs.harvard.edu/default_service.html)
You can search for specific papers, or just search for papers with a
particular keyword in the abstract or title. There's a handy feature that lets
you sort by citations so that you can easily find the most influential papers.

Finally, you can find the newest papers here: [http://arxiv.org/list/astro-
ph/new](http://arxiv.org/list/astro-ph/new) About ~50 new papers appear here
every weekday. It's a lot to keep up with even if you're a professional, but
it can be useful to skim the titles every now and again and see what looks
interesting. The introduction to astronomy papers usually acts as a sort of
mini-review article. It'll review the problem that the paper is examining and
will reference other papers that have looked at this problem. So from reading
introductions you can get some background on the problem and the ways that
astronomers have been trying to solve it -- and it's a lot shorter than a full
review article!

Some of the problems may seem somewhat opaque if you don't have the necessary
physics background, but not all of them are, so don't get discouraged! Or if
that inspires you to learn more physics, so much the better!

~~~
z3phyr
Thank you very much!!! :)

------
ggreer
> While the ellipse that Mercury’s orbit makes around the Sun precesses at a
> rate of 43"-per-century due to relativistic effects (where 1° is 3600"),
> this smaller black hole should precess at 39°-per-orbit, and should inspiral
> in to the larger one in a timeframe of just a few thousand years!

In case anyone's curious: The double-quote is an arc-second. When measuring
angles, a single quote is an arc-minute, which is 1/60th of a degree. An arc-
second is, of course, 1/60th of an arc-minute. Rifle accuracy is measured in
minutes of arc, with 1' being about an inch diameter circle at 100 meters.
Proxima Centauri has a parallax of about 0.8".

To give you an idea of how far away Proxima Centauri is, we can scale
everything down. A light-year is about 63,240 AU. A mile is 63,360 inches. So
if Terra was an inch from Sol, Proxima Centauri would be about 4 miles away.
The parallax from Proxima Centauri is the same as if you looked at an object 4
miles away, then moved your head 2 inches laterally. That's 0.8 arc-seconds.
That's the second-closest star to us.

~~~
throwaway_yy2Di
(Incidentally that's what defines a "parsec" \-- a unit of distance of about 3
light years. If you see a parallax of one arcsecond ("par-sec"), from opposite
sides of the earth's orbit around the sun (2 AU apart), that something is 1
parsec away. If it's 10 parsecs away, the parallax will be 0.1 arcsec -- the
more distant the object, the less it appears to shift. This works to about
0.001 arcsec of precision (distance limit of ~1,000 parsecs), and soon down to
20 microarcseconds (~50,000 parsecs).

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

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

[https://en.wikipedia.org/wiki/Gaia_%28spacecraft%29](https://en.wikipedia.org/wiki/Gaia_%28spacecraft%29)

This is the lowest rung of the "cosmic distance ladder":

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

[https://terrytao.wordpress.com/2010/10/10/the-cosmic-
distanc...](https://terrytao.wordpress.com/2010/10/10/the-cosmic-distance-
ladder-ver-4-1/)

------
alixaxel
It not the complete list:
[http://en.wikipedia.org/wiki/List_of_most_massive_black_hole...](http://en.wikipedia.org/wiki/List_of_most_massive_black_holes#List)

On a related note, I never understood how a black hole (or frozen stars like
the Russians call them) could potentially orbit or be swallowed by another
black hole. If they "infinitely" deform space-time, shouldn't they be unable
to move at all? If time stands still past the event horizon as they say and
they also rip the space-time fabric so much, they shouldn't be able to "get
out of the hole". This is just too mind-bogging for me I guess.

~~~
wyager
I believe black holes can be treated as normal astronomical objects outside
their event horizon. The weird singularity behavior only applies within the
event horizons.

~~~
carljoseph
This is pretty much true. You could replace our sun with a black hole of the
same mass, and nothing would change in terms of planet's orbits.

The image of a black hole "sucking" things in like a vacuum cleaner is hugely
incorrect. I think this perception comes about from the funnel image we often
see representing black holes.

~~~
alixaxel
A black hole with the same mass as the sun wouldn't be a black hole at all,
would it?

------
Pxtl
The animation blew my mind. Especially S0-16. What the heck was that thing's
velocity at perihelion? A _whole star_ moving that much, that fast,
accelerating like that in only 16 years. An entire star, tossed about in space
like a ragdoll.

~~~
throwaway_yy2Di
I looked it up!

    
    
        "Given a recent estimate of 4.3 million solar masses for the
        mass of Sagittarius A* and S2's close approach, this makes
        S2 the fastest known ballistic orbit, reaching speeds
        exceeding 5000 km/s (11,000,000 mph) or 1.67~% of the speed
        of light and acceleration of about 1.5 m/s2 or almost
        one-sixth of Earth's surface gravity.[7]"
    

[https://en.wikipedia.org/wiki/S2_%28star%29](https://en.wikipedia.org/wiki/S2_%28star%29)

Edit: wait that's not it, that's S0-2, but you're talking about S14/S0-16:

[https://en.wikipedia.org/wiki/Sagittarius_A*#Central_black_h...](https://en.wikipedia.org/wiki/Sagittarius_A*#Central_black_hole)

From those parameters, its perihelion speed would be about 8,200 km/s (2.7%
c), using the classical approximation.

[https://en.wikipedia.org/wiki/Perihelion#Mathematical_formul...](https://en.wikipedia.org/wiki/Perihelion#Mathematical_formulae)

~~~
throwaway_yy2Di
Interesting tangent: when there's a _binary_ star system that gets very close
to this black hole, the three can interact in a way that one of the two stars
falls in, while the other steals its gravitational potential and is ejected at
extreme speed. There's a few "hypervelocity" rogue stars in the Milky Way,
which were probably accelerated by the black hole. They're on escape
trajectories leaving the galaxy.

[https://en.wikipedia.org/wiki/Stellar_kinematics#Hyperveloci...](https://en.wikipedia.org/wiki/Stellar_kinematics#Hypervelocity_stars)

[https://en.wikipedia.org/wiki/HE_0437-5439](https://en.wikipedia.org/wiki/HE_0437-5439)

~~~
valarauca1
Wow thank you for the second link. That was really interesting read.

------
thatthatis
Made me think if this:
[http://m.youtube.com/watch?v=JWVshkVF0SY&feature=kp](http://m.youtube.com/watch?v=JWVshkVF0SY&feature=kp)

Also, helps to remind me of how cosmically tiny the problems of building my
SaaS product really are.

~~~
sharkweek
Even this picture makes me think the same thing:

[http://www.nasa.gov/images/content/136063main_bm4_high.jpg](http://www.nasa.gov/images/content/136063main_bm4_high.jpg)

Then to get an astronomically bigger picture of just how small we all are, I
start getting dizzy at even the thought.

------
m_mueller
That blazar picture - it would be nice if articles would always credit it as
'artist's conception'. It almost looked like a feasible real light image with
the pixellation, so I was rather intrigued.

------
hyperliner
Here is the one thing that really keeps me awake at night: what if our science
was the equivalent of a bunch of ants in a typical ant hill in anyone of our
backyards, defining a mechanism or "method" through which they have explained
for themselves the nature of the solar system?

That's the one thing. And I can't shake it off.

~~~
autokad
dont let leorocky get you down.

if the universe keeps expanding, eventually it will expand at the speed of
light and everything that is not gravitationally locked with us (wich only
includes the milky way and about 5 or so other galaixies) will be moving
faster than the speed of light and will be impossible to observe in any way.

in a sense, it means leo is actually wrong. if an intelligent race comes into
being after said event, it could be true that no amount of science will ever
be able to show that the rest of the universe existed. that also means some
other phenomenon may have occurred that will make us as just as useless at
understanding what happened as ants are at knowing/exploring the stars.

that is, if certain theories about the expansion of the galaxy is true.

~~~
leorocky
This doesn't make me wrong about science, it's just that by then it will be
will not have the data to figure out what happened. You can't see the other
galaxies anymore. That's not a problem with science, that's a problem of
insufficient data. It may be the case an intelligent could figure things out
by looking at the evidence available to them within their finite, expanded
universe. Space will still be expanding, there will still be red shift, there
will still be gravity. And science will be the tool to use to figure this
stuff out.

------
mathattack
It's articles like this (and videos by Mr. Degrasse Tyson) that make me wish I
majored in Physics.

------
e40
_this smaller black hole should precess at 39°-per-orbit, and should inspiral
in to the larger one in a timeframe of just a few thousand years!_

So we are just incredible lucky to be here at this moment to have observed it?
Fascinating.

------
kghose
Wow. In my memory, it was the pressure from the hot gases that kept a star
from collapsing on itself. I did not know it was light pressure! Is this a
typo in the article, or is it really light pressure holding up stars?

~~~
avar
More specifically radiation pressure, not all of it is visible light. Some
quick searching turns up
[http://en.wikipedia.org/wiki/Radiation_pressure#Stellar_inte...](http://en.wikipedia.org/wiki/Radiation_pressure#Stellar_interiors)
and
[http://www.astro.caltech.edu/~george/ay20/Ay20-Lec7x.pdf](http://www.astro.caltech.edu/~george/ay20/Ay20-Lec7x.pdf)

~~~
kghose
And, from the wikipedia article:

"In the Sun, radiation pressure is still quite small when compared to the gas
pressure. In the heaviest non-degenerate stars, radiation pressure is the
dominant pressure component"

------
dnautics
what superenergetic catastrophe happens when those two black holes collapse
onto each other?

Is this black hole pair likely to be two galactic cores that collided, and
captured each other due to some sort of inelastic interaction (maybe ejecting
stars out?) and their surrounding galactic matter got eaten up due to
basically the three-body problem?

------
imaginenore
This was very easy to read, interesting subject, good photos. Thanks!

------
kabdib
Nice article, but overuse of italics made me cut and paste into Emacs to read
it.

~~~
gbog
Same here, except that in the end I didn't like the article. Medium is very
fit for startup chatter and discussions on the relative merits of ios 8 and
android 2.2. But writing about science in Medium, using this style and
narrative? Not for me.

~~~
bronson
What style and narrative would you prefer?

I think StartsWithABang is an excellent read: entertaining iand informative.
One of the few blog-type-things I follow anymore.

------
Pxtl
Well, I'm having a nice big existentialist crisis right now having being
reminded of our place in the universe. I'm going to go pour myself a whiskey
and hug my kids. G'night everybody.

~~~
ckuehne
Maybe a quote by David Deutsch will ease the pain:

"Some people get depressed when they find out how huge the universe is. They
feel tiny and insignificant and think that nothing matters in this world.

That makes no more sense than getting depressed when you find out that cows
are bigger than you. What is the big deal about bigness? A cow is much bigger
than you, but it is a ridiculous animal and you are a valuable person. You
know it’s a cow. It doesn’t know anything. it just stands there eating grass
(grass!) and mooing. And if it were bigger, that would only make it more
ridiculous."

~~~
swombat
A cow is still well within the realm of dimensions that a human mind can
comprehend. You won't feel insignificant when looking at a cow because while
bigger, it's not that much bigger. Apart from poisoning you when you eat it,
or kicking you by mistake, it has relatively little influence or impact on
you, your life, your fate, or indeed, the fate of the human race.

Now, if you had a cow the size of the earth, that just sits there and eats
cosmic grass, and could blow up earth and wipe out the human race with one of
its farts, then suddenly the cow is rather more significant than it was before
- if only because of its possible influence on you.

Finally, if the said cow is in fact not just an object but the very substrate
that you exist in, and its so big that you can't even begin to imagine how big
it is, and it is filled with inhuman processes that could wipe humanity out at
any moment from now to infinity, then a solid sense of insignificance seems
perfectly warranted.

~~~
cscurmudgeon
For me, it is the opposite. If the world was small, I would be sad to be a
part of a small un-awesome world. Looking at how big the world is makes me
happy and excited.

The difference I guess comes from whether you see yourself as a part of the
universe or as an observer separate from the rest of the world.

~~~
swombat
I didn't say it made me sad. I just said it made me (and you) fairly
insignificant in the greater scheme of things.

Insignificance is awesome. Significance seems highly overrated, more to do
with assuaging one's ego than with enjoying life.

~~~
cscurmudgeon
The key is to have no ego. That makes any question of significance
insignificant :)

