Comments on: Star eaten by a black hole: still blasting away

By: martin

martin — Thu, 03 May 2012 17:17:36 +0000

15 million is small for a black hole

YES it is 15 million becuase generally to have anything smaller requires a theoretical micro black hole etc

you cant have a star thats much smaller than 1.8 or so solar masses so the smallest would be about 1.3million or so

anything like 15 km would eat its way up in minutes if it fell into a star. munching its way through in a nice cylyndrical path

By: SurDin

SurDin — Tue, 06 Sep 2011 08:44:55 +0000

@1-7, Phil.

I found what’s the typo. The SS-Radius is 15 million *Miles* ~=24 Million KM.

By: Jeremy P

Jeremy P — Sat, 03 Sep 2011 15:51:25 +0000

@Dennis

so nothing can escape a black hole, but a black hole can, theoretically, evaporate. ha ha, I love science!

By: Frank Sellers

Frank Sellers — Fri, 02 Sep 2011 03:11:40 +0000

Why is this story in the “Bad Astronomy” section? Is it because the black hole was acting ‘bad’ly? I thought this section was for faulty science.

And yes, 15 million km doesn’t seems “small” to me, either.

By: Svlad Cjelli

Svlad Cjelli — Tue, 30 Aug 2011 12:09:27 +0000

You, apparently.
The referent is the same, and you still aren’t saying that the signifier doesn’t refer it, so I don’t see the point of contention here. If I ever implied that the Intergalactic Council of Pastry has baptised the star Urkel and burned the Steve-heretics, that wasn’t my intention.

By: VinceRN

VinceRN — Sun, 28 Aug 2011 23:28:12 +0000

@ Dirk #53 – Here is what contridicts it: Phil is named Phil officially, he likely has a piece of paper assinging him that name from the official organization that names young hairless apes of his particular lineage (his parents), and that paper likely bears a sealed of approve from the relevant government agency. You could call him Bob, and if enough people did he would come to be recognized as Bob, but he would still be Phil. The Sun is officially called the Sun by the only organization that officially names such things. You can call it ‘Sol’ and I can call it ‘Yellow’s and most will know what we are talking about. However, it will still be the Sun. Sol is not the name of any physical object in any official way, it is not used in Science or Academia anywhere as far as I can tell. The fact that science fiction writers like to refer to it that way is meaningless. Also a ‘sol’ as a shortened form of ‘solar day’ in reference to Mars really is a measure of time, and is in fact used in Academia and Science.

Ain’t it fun to be pedantic over something so totally meaningless as this? Call it Sol, the Sun, Helios, or that big yellow thing that peaks through the clouds and causes traffic problems hare in the Pacific Northwest. Who really cares?

By: Mike

Mike — Sun, 28 Aug 2011 19:10:18 +0000

So a bunch of folks here have been implying that the accretion disk and the rotational axis of the black hole itself line up. Is this actually the case? If a star came shooting in on a polar orbit to the black hole, would the accretion disk form that way, or would the black hole somehow drag the gunk around to be in line with the black hole’s equator?

By: Svlad Cjelli

Svlad Cjelli — Sun, 28 Aug 2011 13:38:44 +0000

48. VinceRN – Nothing you said contradicts that a solar mass is solar because it is the mass of a Sol.
Nothing you said contradicts that Sol is a physical object.
Nothing you said contradicts that the object is called “Sol”, anymore than it does that a Bad Astronomer is a Phil.
Nothing you said contradicts that 8 million specimen of the object would have 8 million times as much mass as a single specimen of the object has.

By: Juan

Juan — Sun, 28 Aug 2011 03:17:47 +0000

@48 VinceRN:
“Dirk Gently”, great catch!
See, I’d completely forgotten what his real name was.
Kudos, sir.

By: icemith

icemith — Sun, 28 Aug 2011 00:16:46 +0000

So, which is the “sunny side up”, Sonny?

Ivan.

By: John

John — Sat, 27 Aug 2011 23:22:55 +0000

Mmmmm star matter. I wonder what it tastes like.

By: Phil Plait

Phil Plait — Sat, 27 Aug 2011 19:27:22 +0000

Mark (50): Yup, thanks!

By: Mark

Mark — Sat, 27 Aug 2011 19:14:18 +0000

@Phil – This article says 2010, but the original article says 2011 and was written in 2011. I think you’ve got a typo.

By: Bill

Bill — Sat, 27 Aug 2011 17:27:49 +0000

As others have said, it would be nice to know how long this takes on a human time scale.

By: VinceRN

VinceRN — Sat, 27 Aug 2011 15:50:35 +0000

@ 47 Dirk Gently – “Sol” is simply Latin for “Sun”, it is not the name of the the Sun. We also use Helios in talking about the Sun, being the Greek word, but that’s not the name of the Sun either. Solar is used as the adjectival form probably because Sun, being a Germanic would would become Suner or some such as an adjective and just not sound right.

Time on mars is measured in solar days, and those days are sometimes referred to as sols, but I think that is colloquial, not really official. I could easily be wrong about that though.

My source is the IAU, who are the official namers of stuff in the sky. They refer to it as the Sun, capitalized, from which I conclude they are using Sun as a proper noun, and that makes it’s official name the Sun. Personally, I’d prefer it be officially called Helios, but I don’t get invited to those meetings.

By: Svlad Cjelli

Svlad Cjelli — Sat, 27 Aug 2011 08:48:35 +0000

“Don’t you mean 8 million solar masses?”

A “solar” mass is a “solar” mass because it is the mass of a “Sol”. “Sol” is not a measurement, but a named physical object.

By: srinivasvr

srinivasvr — Sat, 27 Aug 2011 07:51:01 +0000

ego here i go…

By: Messier Tidy Upper

Messier Tidy Upper — Sat, 27 Aug 2011 07:35:14 +0000

Great animation. Eerily silent, graphically beautful and very thought provoking.

Great write up too. Thanks BA.

@29. Keith Bowden :

So… in real time, how quickly was the sun actually consumed? Hours? Days? Years? Millennia? I’m so used to cosmological events happening slowly (by human reckoning), but this sounds like it was a faster process.

It does, but I’m not sure myself. I second the question & agree a timescale for the animation would be great too. Going by the description :

“Normally, things like this fade pretty quickly, but in this case, amazingly, it’s still pouring out energy and will probably be detectable even into 2012.”

It sounds like it just takes months to years but this really isn’t clear at least not to me.

@ 41. Arik Rice & others asking about /calculating the Black Hole’s size :

My understanding is that a stellar mass black hole is tiny – smaller than a city – but a supermassive black hole can be as large as our solar system. This one’s a supermassive galactic core variety of BH so it could be reasonably large. Sadly, I’m hopeless at maths so I’m not going to attempt to calculate it myself and that range hardly narrows it down much but still.

@20. Naked Bunny with a Whip : “For an object containing the mass of 8 million Sols, it is.”

[Nit-picking pedant.] But a Sol means a martian day and even 8 million Sols would therefore not have any mass – only time!

Don’t you mean 8 million solar masses? [/Nit-picking pedant.]

By: Wzrd1

Wzrd1 — Sat, 27 Aug 2011 06:13:11 +0000

@VinceRN, I remember that day! It was horrible!
The beer was hot, the women were cold. It was HORRIBLE!
I could get by on the hot beer, but…

Hey, in the morning, these days, it FEELS like I’m that old.

By: VinceRN

VinceRN — Sat, 27 Aug 2011 03:35:58 +0000

In late march of 3,999,997,989 BCE (or so)…

By: Wzrd1

Wzrd1 — Sat, 27 Aug 2011 00:55:38 +0000

@30 Chris, you are correct. Anything entering the event horizon isn’t returning intact. However, one interesting side effect of the math is, once through the event horizon, one would take an infinite amount of time, relative to the rest of the universe, to reach the singularity. In essence, the matter just beneath the event horizon is essentially forever at that point. Hence, the virtual particles should be radiating past the event horizon and lost to the singularity.
Of course, the amount is still miniscule compared to the amount absorbed by the black hole in the first place, so large mass singularities are in no real danger of evaporating during the life of this universe.
Only small singularities, typically sub stellar mass ones would evaporate quickly. IF it’s possible to generate one, which is dubious under most normal circumstances in the universe.

By: Arik Rice

Arik Rice — Fri, 26 Aug 2011 22:59:06 +0000

My math concurs with Chris’ math. I calculate that an 8-million-solar mass black hole would be 47 million km across, which is close enough for a rough estimation.

By: Thameron

Thameron — Fri, 26 Aug 2011 21:16:49 +0000

@31. mike burkhart

If the mass that falls into a black hole were exiting somewhere else then it stands to reason that the black holes would be getting less massive and I don’t think they are. I don’t think that mass is going anywhere.

To my knowledge there has been no actual proof of the existence of Hawking radiation. I’ll wait for that before giving it credence.

By: DrFlimmer

DrFlimmer — Fri, 26 Aug 2011 21:03:17 +0000

@ 37 Mephane

Well, if the jet is not pointed at out direction we could potentially still see it. Radio observations would definitely reveal it. However, since radio observatories do not make for good alerts, we need high energetic radiation to be detected by our flying observatories (mainly x- and gamma-rays).
What could that be? Ah, the accretion disk. The matter will get fairly hot, shining brightly in UV and probably also in X-rays. This could alert us to such an event, even without the jet pointing towards us.

By: Regner Trampedach

Regner Trampedach — Fri, 26 Aug 2011 20:57:15 +0000

Wzrd1 @ 27: I think you mean ionized and not excited. The charge of an ion only depends on how ionized (how many electrons it has lost) – not on the energies (excitation level) of its remaining electrons. The charge is what makes the plasma get accelerated along magnetic field lines, – and is what makes those magnetic fields in the first place.
mike burkhart @ 31: The problem with “…dump[-ing] nucler waste into the Sun.” is not pollution of the Sun – I mean, that is silly to the power of 30! (and I believe Phil would agree). The problem is cost and risk (rocket failure => explosion scattering highly radioactive waste). I have seen launch costs of US$10-25,000 per kg. According to Reuter’s “factbox-Key facts on radioactive waste”(Google it): “There are about 270,000 tonnes of spent fuel in storage worldwide”. That gives us a lower range of cost of US$2.7 trillion. That little expenditure definitely makes nuclear energy cheaper than wind, solar, geothermal and biogas…
@ various: The star is getting tidally disrupted well outside the black hole – both in reality and in the animation. The inside of a black hole normally refers to inside the event horizon (at 1 Schwarzschild radius, R_S). The singularity is a singular point at the center of the black hole, and hence shielded from our spying eyes by the event horizon. Hawking radiation is the only thing that (effectively) escapes the clutches of the event horizon (see Chris @ 30) – Only black holes less massive than about 0.6 lunar masses, will be net emitters – heavier ones will be overwhelmed by incoming cosmic background radiation (at 2.725K). The accretion disk ends about 6*R_S from the singularity where orbits become unstable and plasma plunges directly into the black hole. The jets are launched from the accretion disk and aligned along the rotation axis (not emitted from the poles!), but the details of the mechanism are not quite worked out yet (magnetic fields are most likely involved). The actual tidal disruption of the star forms the very outskirts of the accretion disk. So all of this happens fairly far away from the event horizon (although far too close for comfort!!!).
Chris @ 21: and general relativistic magnetohydronamics at that!
Cheers, Regner