[HN Gopher] Astronomers discover Milky Way's biggest stellar bla...
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Astronomers discover Milky Way's biggest stellar black hole
Author : c-flow
Score : 91 points
Date : 2024-04-16 07:50 UTC (15 hours ago)
(HTM) web link (www.theguardian.com)
(TXT) w3m dump (www.theguardian.com)
| qrios wrote:
| ,,Size" is misleading. 33 solar masses is in fact small for a
| black hole. Sigatarius A is still the biggest in the Milky Way.
| Natsu wrote:
| They don't seem too clear on the science they're reporting, but
| if I'm understanding it right, this is supposed to be the
| largest _stellar origin_ black hole. The fact that Sagittarius
| A* is just a bit under 4.3 million solar masses, which is a bit
| over 33, was my first thought, too.
| skywhopper wrote:
| The relevant definitions are explained in the article.
| aurareturn wrote:
| "Stellar" means star.
| tokai wrote:
| Sigatarius A is not a stellar black hole now is it?
| devoutsalsa wrote:
| We don't know how supermassive blackholes form. It's a bit of
| a mystery.
| tokai wrote:
| That doesn't matter, you are toying with semantics. If
| astronomers say stellar black hole, they don't mean
| supermassive black holes at galactic centers. Even if
| Sagittarius A* was initially a stellar black hole, its more
| now.
| Aachen wrote:
| I hadn't heard of the distinction stellar or non-stellar
| black hole before. It rather sounds like semantics to me
| to say this is one type of black hole and not another
| when it's physically the same thing and we don't know how
| it formed to begin with
|
| The headline confused me as well: 33 solar masses (not
| sizes) seems tiny to me, I was sure we knew of bigger
| ones
| tokai wrote:
| Its not semantics. Its precise terminology. Ignoring this
| and redefining the precis terms because one lacks
| knowledge about the subject and arguing from faulty
| assumptions is a waste of everyone's time.
| Sharlin wrote:
| The distinction is clear and relevant because the mass
| distribution is strongly bimodal. A stellar black hole is
| the result of the gravitational collapse of a single star
| (well, or two at most). And maybe some of them have since
| then merged with a companion body. There are zillions of
| these in any given galaxy. Whereas there are maybe one or
| two supermassive black holes per galaxy, sitting in the
| center, with mass of millions or billions of suns, and we
| don't quite know how they first formed and how they have
| accumulated so much mass. If the difference between "one"
| and "billion" doesn't matter to you, well, ok then.
|
| The difference is even more clear-cut because so-called
| intermediate mass black holes are something of a question
| mark. For a long time it wasn't clear whether they even
| exist in any significant numbers, and even now the
| evidence is not especially rock-solid, especially with
| regard to candidate objects in the Milky Way.
| BobbyTables2 wrote:
| It's quite easy to describe the origin of a supermassive
| black hole.
|
| It was just a stellar black hole that optimized logistics
| and utilized its gravitational pull to offer free
| shipping and one click accretion.
| hermitdev wrote:
| To add to a sibling comment, the distinction is
| important, because observed mass of black holes falls
| largely into super massive (millions to billions solar
| masses) to stellar (dozens of solar masses). There is
| very, very, astonishingly few observed black holes with
| an intermediate mass. So, how super massive black holes
| form is a mystery, and finding large stellar mass black
| holes starts filling in (possibly) that evolutionary gap
| in black holes. Not a physicist, just read/watch a lot of
| pop astronomy/cosmology.
| devoutsalsa wrote:
| Also, super massive blackholes can only "swallow" so much
| matter at a time. Given what we know about how fast a
| black hole can grow, super massive black holes seem to be
| bigger than should be possible.
| empath-nirvana wrote:
| > I hadn't heard of the distinction stellar or non-
| stellar black hole before.
|
| While it's possible that supermassive black holes were
| formed from stellar collapse, there are models where they
| didn't, while they _know_ that this one was formed from
| stellar collapse.
| scotty79 wrote:
| My bet is that they are older than 14 bln years.
| exe34 wrote:
| They're probably not formed by the merger of stellar
| blackholes.
| denton-scratch wrote:
| Yeah, that's what I thought. TFA says (unconditionally)
| that SagA was formed by direct collapse of gas clouds.
| andy_ppp wrote:
| AI making too many paperclips again...
| Prunkton wrote:
| >black hole - 33 times size of sun
|
| >black hole 33 times more massive than the sun
|
| What a confusing article. Its 33 times the mass of the sun
| codethief wrote:
| It's actually correct. The radius/diameter of a black hole is
| proportional to its mass.
| s1artibartfast wrote:
| Yes, but the size is not proportional to the suns mass, hence
| the error. size=/=mass
| pxeger1 wrote:
| Also "33 times more massive than the sun" means 34 times
| the mass of the sun.
| Etheryte wrote:
| Oh boy, this sent me down a memory lane. I remember
| arguing long and hard with my math teacher in elementary
| school that "two times as massive" and "two times more
| massive than" are not the same thing, but she did not
| agree. That's the point where I learned that the grownup
| world is weird and sometimes it's easier to just smile
| and nod.
| macintux wrote:
| For me, it was the science teacher in middle school who
| insisted that rivers couldn't flow north, because on a
| globe, north was up.
|
| Even pointing out the Nile didn't change her mind; I
| imagine there's a denial joke to be made there.
| xpe wrote:
| "That's the point where I learned that the grownup world
| is weird"
|
| That's a generous thing of you to say.
|
| How many people really want to be proven wrong? I'd like
| to think I am. Maybe I should make a t-shirt:
| Happy to proven wrong * * But only by people
| who reciprocate
| konstantinua00 wrote:
| would you say the same for "33 times longer"? that ut
| means "34 times the length"?
|
| for me "more X" and "Xer" are the same thing, so I don't
| get your system
| Etheryte wrote:
| Considering fractions might help you understand where
| he's coming from. If you say something is "0.5 times as
| long as a one meter thing" you would expect it to be 0.5
| meters, but if it's "0.5 times longer than a one meter
| thing", you would expect it to be 1.5 meters. The same
| logic applies when you ditch fractions and use integers.
| ChrisArchitect wrote:
| For a related visualization about size/mass of suns and black
| holes:
|
| _I Put 4M Suns in a Black Hole over New York [video]_
|
| https://www.youtube.com/watch?v=pDUUT2Y_9qk
|
| (https://news.ycombinator.com/item?id=39735510)
| swozey wrote:
| I totally forgot about this video, the amount of work is wild.
| tristramb wrote:
| Preprint:
| https://www.aanda.org/articles/aa/pdf/forth/aa49763-24.pdf
| raattgift wrote:
| Thanks, that's always useful.
|
| SS3 Discussion: "The estimated mass is also too large for one
| neutron stars or two neutron stars in a close orbit, so we are
| left with the possibility of: 1) a single BH; 2) an inner
| binary containing two BHs; or 3) a BH and another compact
| object. Although the single BH is the simplest explanation, the
| hypothesis of an inner binary of two BHs cannot be excluded
| [...] radial-velocity [...] perturbations are too small to be
| detected in the Gaia RVS [radial-velocity] data[.] For the
| purposes of the subsequent discussion we have adopted the
| single BH hypothesis as the most likely explanation."
|
| Someone with more patience (or more troll-energy) than I have
| right now might try to introduce this into the handful of
| threads here containing various complaints that (clearly
| assuming a single BH), "size" is being punned as mass in the
| newspaper article linked at the top. If, for example, the ~33
| M_sun ("mass of the sun") mass is evenly divided between two
| central BHs with the giant branch star companion orbiting them
| (cf. Alpha Centauri AB + wide companion Alpha Centauri C and
| similar triples), what's the most reasonable understanding of
| "size"? Or what if the dark component has a mass-ratio of ~
| 30:2 split between a BH and a satellite NS? Total mass remains
| ~33 M_sun, how has "size" changed?
|
| (Answer: "it hasn't". Generally I agree with the comments that
| read "size" as meaning mass and disagree that it should mean
| the Schwarzschild radius, and not just because the dark
| component might not be very Schwarzschild-like at all. Perhaps
| someone might do an ELI5 of dimensional analysis g = T^-2 L ->
| M = T^-2 L^3 or Gauss's law for gravity. (Serious ambition
| would be ELI12 of the argument around the "scale separation"
| towards the end of the excellent <https://physicscourses.colora
| do.edu/phys2210/phys2210_fa20/l...>, where we'd distinguish the
| scale of a possible inner-binary from the scale of the giant
| star's orbit around it.))
| martinpw wrote:
| That is a fairly epic author list. Presumably everyone involved
| in the larger overall project.
| vorticalbox wrote:
| I was always under the impression there was only 1 black-hole in
| our galaxy, at it's centre.
| tomrod wrote:
| There are many, many more, probably ranging in size to tinier
| than a period (.) to the 33 Sol mass (so far).
|
| The one at the center of the galaxy is along for the ride! A
| good video: https://www.youtube.com/watch?v=e-P5IFTqB98
| The_Colonel wrote:
| > probably ranging in size to tinier than a period (.)
|
| "Probably" is a strong word, these are very hypothetical, the
| lightest observed black hole has a mass of 3 Suns.
| robin_reala wrote:
| A three solar mass black hole is still only ~13km across.
| Not full-stop-sized, but closer to that than the diameter
| of the sun.
| volkadav wrote:
| I'm guessing the 13km diameter refers to the event
| horizon rather than the singularity itself, which I
| gather could be considered as zero-sized, or maybe one
| Planck length in size because we can't definitively
| measure anything smaller, or ...
|
| Admittedly, it gets a bit philosophical. The sphere of no
| return isn't the thing, but it might as well be for any
| outside observer, but it isn't, but it could be viewed as
| such, but... :) Suffice to say I'm glad the closest thing
| to black holes I have to contend with in my daily life is
| a 2+ million line php codebase dating from the late
| Clinton administration.
| floxy wrote:
| "Do Black Holes have Singularities?" by Roy Kerr (Yes,
| that Roy Kerr)
|
| https://arxiv.org/abs/2312.00841
|
| https://www.pbs.org/video/what-if-singularities-do-not-
| exist...
| Sharlin wrote:
| Well, your impression was wrong then.
| papichulo2023 wrote:
| There is even a theory about a mini black hole in our solar
| system pulling Uranus.
| xpe wrote:
| See e.g.
|
| "What If Planet 9 Is a Primordial Black Hole?" by Jakub
| Scholtz and James Unwin [1]
|
| [1] Phys. Rev. Lett. 125, 051103 - Published 29 July 2020 htt
| ps://journals.aps.org/prl/abstract/10.1103/PhysRevLett.12...
| klabb3 wrote:
| So far, I assume.
| habibur wrote:
| Largest "stellar" black hole in Milky Way. Not the "largest black
| hole" as some media are reporting it in their title.
|
| The largest black hole in Milky Way is million times more massive
| than our sun. Falls in super massive category.
| codeulike wrote:
| So they found the biggest one that isn't really big
| robin_reala wrote:
| They didn't find the biggest one, they found the biggest one
| they've found so far. Which in all probability is pretty
| small.
| DiogenesKynikos wrote:
| Code to fit the star's orbital parameters and make some of the
| plots in the paper: https://github.com/esa/gaia-
| bhthree/blob/main/Gaia_BH3_fit_a...
| codeulike wrote:
| Article triggers critical mass of pedantry on HN, thread
| collapses in on itself
| sega_sai wrote:
| Yes. It is kinda amazing to observe (as a professional
| astrophysicist) how people manage to find small (mostly
| irrelevant) things to nitpick instead of discussing a really
| interesting discovery.
| blueflow wrote:
| I postulated in another thread yesterday that the use of
| exxagerations / superlatives might be triggering contra. If
| we had the same article, but with the title "Black hole with
| 33 times the mass of the sun discovered" we could measure if
| the reactions are less severe.
| Ar-Curunir wrote:
| it unfortunately happens in every field, including more
| theoretical parts of computer science. the commenters usually
| don't understand the science, so choose to nitpick on the
| aesthetics.
| xpe wrote:
| People's contributions rise to the level of their expertise.
| m3kw9 wrote:
| Does every galaxy have a super massive black hole at the Center?
| kstrauser wrote:
| Nearly every. That's the current thinking.
| pfdietz wrote:
| Astronomers have not discovered the Milky Way's biggest stellar
| black hole. They have found the largest stellar black hole of all
| the galactic stellar black holes they've found so far. Since the
| Milky Way likely has 100 million stellar black holes, finding the
| largest is going to be quite a task.
|
| Bart: this is the biggest stellar black hole.
|
| Homer: this is the biggest stellar black hole _so far_.
| exegete wrote:
| I thought the "so far" was implied by science - this is what we
| know about the universe (so far).
| pfdietz wrote:
| Not a valid excuse here.
| TheDudeMan wrote:
| "Sagittarius A has the combined mass of several million suns. It
| lurks at the heart of the galaxy and formed not from an exploding
| star but the collapse of vast clouds of dust and gas."
|
| How is that known? Isn't "dust and gas" also how stars form?
| alje wrote:
| Every galaxy we know of contains a massive black hole in the
| center. Until recently, the widely held belief was that massive
| black holes are formed via the process of mearging smaller
| black holes in large timeframes. However, once the JWST came
| online, astrophysicists discovered early massive black holes
| close to big bang that could not be explained by that
| cumulative process. There just was no time for the cumulative
| creation to a such large black holes.
|
| So the current working hypothesis for massive black holes in
| galaxies is that they formed directly from the gravitational
| collapse of "vast clouds of gas and dust" with such high
| gravitational pressure that the core couldn't keep up, and the
| entire mass of gas and dust collapsed into a massive black
| hole. There is no supernova involvement; merely a direct
| transition into a black hole.
|
| Of course, take my laic simplification into account.
| xpe wrote:
| Somewhat of an aside: I've grown tired of Roman mythology being
| foisted upon our planet names. But I'm even more tired of hearing
| NASA spokespeople talk about e.g. "exploring the heavens". At
| least they don't say "firmament" or refer to the Earth's mantle
| as being infernal.
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