The Largest Black Hole in the Known Universe | Hacker News Reader

The Largest Black Hole in the Known Universe

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225 pointsGlennCSmith60 comments

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!

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?

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 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 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!

Thank you very much!!! :)

I'm also curious about this

>> So one could say that there's a low prior for such a system to exist.

I have no other knowledge, but just from the information in your comment, can we test the low prior assumption?

Would this bh still have been identifiable as the most massive known, if it did not have both of the following characteristics?

- blazar, pointed directly at us (makes it noticeable)

- binary, (makes it measurable at such a massive scale)

> 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.

(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/Hipparcos

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://terrytao.wordpress.com/2010/10/10/the-cosmic-distanc...

I've thought about scaled-down solar system models before but never encountered the coincidence between AUs in a lightyear and inches in a mile. That's effin' beautiful! Thank you!

It not the complete list: http://en.wikipedia.org/wiki/List_of_most_massive_black_hole...

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.

Also, according to that list, the central black hole of NGC 1277 is only 1/3 as large as claimed in the article, taking it out of contention entirely.

What I would like to know is what happens when the two black holes collide.

i believe stephen hawking stated that matter does/or could escape black holes, but this subject matter is beyond my expertise so i suggest you ask him.

with that being said, it would seem to me that yes, black holes can move, our milky way is not stationary, and black holes have been known to have very fast rotation speeds.

I wondered the same thing! This article seems to do a fine job on talking about black hole collisions: http://www.universetoday.com/13002/what-happens-when-superma...

TL;DR: blackhole mergers are really rare, because one often kicks the other out.

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.

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.

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

I'm Russian, and I've never heard "frozen star". In Russian, black hole is literally "black hole".

But I greet the new legend about Russians that just born here!

Not just born here. I've heard it before, at least 20 years ago. The version of the legend I heard is that "black hole" in Russian is (or suggests) an obscenity, so for a long time Russian physicists didn't want to use that term.

The term "frozen star" has certainly been used for black holes. If you Google both terms you'll find an article from 1971 called "Introducing the black hole", by Ruffini and Wheeler, which mentions that term. (It doesn't say anything about Russian obscenities, though.)

"Black hole" is not really an obscenity in Russian as much as it isn't in English.

But the paper you quoted does seem to explain the logic for this term's existence:

"The resulting system has been variously termed “continuing collapse,” a “frozen star,” and a “black hole.” Each name emphasizes a different aspect of the collapsing system. The collapse is continuing because even after an infinite time, as measured by a distant observer, the collapse is still not complete. Rather, the departure from a static configuration of Schwarzschild radius r=2m as seen by a distant observer diminishes exponentially in time, with a characteristic time of the order of 2m, or about 10 microseconds for an object of one solar mass. The box explains the purely geometrical system of units employed in general relativity. In this sense, the system is a “frozen star.”

In another sense, the system is not frozen at all. On the contrary, the dimensions shrink to indefinitely small values in a finite and very short proper time for an observer moving with the collapsing matter (see figure 3). Moreover, a spherical system appears black from outside; no light can escape. Light shot at it falls in. A particle shot at it falls in.

A “meter stick” would be let down in vain to measure the dimensions of the object. The stick is pulled to pieces by tidal forces, and the broken-off pieces fall in without a trace. In these senses, the system is a black hole"

So this seems to be an international term, and indeed both the Russian wikipedia http://ru.wikipedia.org/wiki/%D0%A7%D1%91%D1%80%D0%BD%D0%B0%... and English-language one mention it.

Couple of other hits in search do mention that the term was used in 1960s - which probably explains the reason why it does sound a bit strange :-)

Anyway, it was fun to do this little investigation, thanks!

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.

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

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...

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...

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/HE_0437-5439

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

Made me think if this: 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.

Even this picture makes me think the same thing:

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.

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.

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.

http://en.wikipedia.org/wiki/Epistemology

Useful. Thanks!

Science answers questions with evidence. None of this armchair conjecturing about what ifs. You don't increase smartphone screen resolutions and put rovers on mars with what ifs. Tangible benefits are the fruit of science. Objective results. None of this subjective shit you get from quackery. There's no room for interpretation when a SpaceX Dragon docks at the space station, that happened. Unless you are into solipsism.

There is nothing to shake off when it comes to science. If good science led us to wrong answers it is because of insufficient data, bad process, and human error. Science is the best tool we have ever created. Just look at your smartphone. The transistors in that thing are not individually visible with the human eye but you can post your selfies to snapchat just fine right? Right. Those transistors are measured in nanometers.

What makes you think ants are so stupid? They farm, own slaves and have organized raids.

Of course, the ones in your backyard typically don't do that. Those are like boring human villages.

I think they are very smart. They just don't really understand the solar system. And i think it is difficult for them to do.

"They just don't really understand the solar system. And i think it is difficult for them to do."

You could say that about many humans too right now, and certainly all humans up until the last however many years.

Exactly my original point, but referencing those ants who think they know the solar system.

How can you tell? If ants were able to understand the solar system, would you expect them to behave differently?

They would know I exist, and that I would massacre them every time they set foot on my yard, with my advanced chemical weapons of mass ant destruction. But they keep coming, and dying. They don't seem to be aware of me, let alone the solar system.

An ant as an individual is smart enough to recognize food and bring it back, do basic social behaviors. However, the real intelligence of ants is emergent from the entire colony.

http://www.fountainmagazine.com/Issue/detail/Collective-Inte...

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.

thank you autokad.

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.

Newton's law of gravity? Worked great for, what, 300+ years? Still, for a wide range of situations, it's darned accurate. Is it 'correct'? Nope: Einstein's law of gravity is more accurate, especially in what in our solar system neighborhood would have to be regarded as extreme situations.

Are we sure that Einstein's law of gravity is the really 'correct' one or the 'last' one we will discover? Nope. Indeed, that doubt is part of why the article got so excited about using one black hole orbiting another one to "test" Einstein's law of gravity. We keep testing that law because we will learn something, either (1) something doesn't fit and we have to ditch the law or (2) the law fits and we gain more 'confidence' in the law.

You can look at it this way: The stuff we 'accept' now is what we have dreamed up and that has passed some apparently 'significant' (don't mean statistics here) tests and so far never really failed a test. Net, stuff 'accepted' at present is what appears to work so far.

But, in physics and cosmology, we have some issues that, at least intuitively, appear to be potential biggies: (1) What happened before the big bang? Can we get some clues from the data we have on what might have happened before the big bang -- some physicists have tried to look. (2) What's with this stuff about dark energy and dark matter? (3) Why does it appear that there is much more matter than anti-matter? (4) What's with neutrinos and how they 'change'? (5) What can we dig out of 'spooky action at a distance', that is, Einstein–Podolsky–Rosen (EPR) paradox?

So, maybe more progress understanding one of these biggies will cause us to ditch some of our currently 'accepted' results, look for, and maybe find some new results.

Could everything we have seen so far be just some light show put on just for our amusement? We can't say. So far, it appears that somehow mathematics works shockingly well; why? We don't know.

That there is a law of gravity that works as well as even Newton's might be seen as surprising. That is, why doesn't the 'law of gravity' change each 10 minutes? Well, some things do change 'randomly', and for them the only laws we have are probabilistic. Newton's law is not probabilistic because so far it appears to work the same yesterday, today, and tomorrow, that is, doesn't change. Or our science is what we have found that in some important sense doesn't change, e.g., we can 'reproduce' results. Why are such results possible? Not at all clear.

Even if what we are seeing is just some light show for our amusement, still we get some utility, e.g., via applications to engineering, etc. So, the Internet works because Maxwell's equations of electro-magnetism continue to work as they have for 100+ years now.

> And I can't shake it off.

Relax and enjoy the light show or whatever the heck it is. There's a lot to be amazed about, curious about, etc. And we really do make progress, astounding progress. E.g., we've made a lot of progress since I studied physics i college. The math I studied has been more stable!

Well, for one thing we haven't found any other anthills and that's very weird. Other than that, just

      Stay Calm
         and
  Keep Doing Science

until you've scienced everything. The analogy with ants is weird, in that ants don't seem to be sentient and don't appear to have ant scientists that are trying to understand the mysteries of the universe. That makes it a bit hard to answer you on the level of the analogy, as such an answer would need to start with "assuming ants were sentient and had physicists, ...", from which point on the rest would be pure anthropocentric conjecture. We humans are a bit unique in that there are individuals who go "well I'm bored, guess I'll go observe the sun, moon and other bright discs in the night sky for decades and record their movements as precisely as I can, so that some other person, most probably of a race I've never seen from a place far beyond any horizon I've viewed, can read them centuries later and use them to come up with a heliocentric model of the solar system and from there on other mad toffs with nothing better to do could come up with the theory of gravity or something".

There is no reason to believe we will never ever find out some fundamental properties of the world, given enough time. If something exists, it can be interacted with and if it can be interacted with, it can be studied. If we can't interact with it ourselves, we'll make machines to interact with it. If we cannot make machines to interact with it, we'll study the results of other things interacting with it that we can observe. If it cannot be interacted with in any way via any method, its existence is largely a philosophical question.

It can be argued that we don't (and won't) have the absolute most simple, exact and perfect formulations for the rules of nature, but arguing whether those rules have a one true form and if there aren't equivalent ways to state them is again a largely philosophical question.

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

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.

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?

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... and http://www.astro.caltech.edu/~george/ay20/Ay20-Lec7x.pdf

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"

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?

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

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

There did seem to be some random emphasis going on in that article (not just with italics but with bold text too). It was a little distracting in places (maybe just because I'm dyslexic?) but the article was fascinating enough to keep me reading.

I was a little disappointed that the article ended with speculation though. Given the title, I was expecting something more concrete. But I guess I should be grateful that the author didn't feel the need to sensationalise the truth for the sake of narrative (like so many reporters do these days).

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.

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.

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.

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."

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.

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.

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.

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

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