APOD: At the Heart of Orion (2017 Mar 12)

[Ann]

A typical stellar-mass black hole in the Trapezium would be interesting. An intermediate black hole, containing more than 100 times the mass of the Sun, would be spectacular.

According to Wikipedia, the generally accepted stellar-mass black hole candidates in the Milky Way probably all contain less than 20 solar masses. Again according to Wikipedia, only one intermediate-mass black hole candidate has been discovered in the entire Milky Way, three light-years from Sagittarius A*, and this claim has been disputed by a group of astronomers making a dynamical study of the stars in the cluster where the intermediate black hole is supposed to reside. So for all we know, no good intermediate-mass black hole has been discovered in the entire Milky Way. Until some people took a good look at the Trapezium in the Orion Nebula, the most nearby high-mass star forming region in the galaxy?

If there is an intermediate-mass black hole in the Trapezium, only 1500 ly away (or a little more, but still incredibly nearby), isn't that amazing? Shouldn't a lot of people be studying it? Shouldn't we aim a lot of our best telescopes at the Trapezium to try to find out if an intermediate-mass black hole is really lurking there?

I find myself being critical of the claim of the presence of an intermediate-mass black hole in the Trapezium. Of course, arguing about whether it is there is not going to make it disappear if it is there, or appear if it isn't there. But I have to wonder why there has apparently been no real effort to find out if the remarkable claim of an intermediate-mass black hole in the Trapezium is true or not.

Ann

[Guest]

What would you expect the neighborhood to look like if a black hole was there? And what are the "Milky Way's Arches"?

They are more suggestive of magnetic fields than supernova bubbles, so at the scale of observation would you say they are unique to the galaxy's center?
Concentric sequential supernova bubbles? I can't go with that possibility

Well, I doubt there is any relation to magnetic fields. Interstellar magnetic fields, where they have been measured, are very weak and don't contribute to structure. We have many examples of supernova remnants that look like this, however.

I would say if a black hole was present there'd be evidence of gas flow being affected by it, stars with anomalous orbital behavior, an X-ray point source that would have visible components associated with it ..

Obviously there is no active black hole in Orion. So we're left with detecting it indirectly, which is difficult. However, the referenced work demonstrates that the production of a large black hole is feasible (or even necessary) given some assumptions about initial conditions, and that the motion of the Trapezium stars provides evidence for the existence of such a black hole. But more observation is required to detect one based on stellar motions.

Their model, I think, is based on predictions of 40 OB stars [?] and having only found 10. And the brightest Trapezium stars' proper motions did have ranges, were not all the same, so that implies their description involved some averaging.

The reason the Milky Way's hole is able to hide amidst all that dust and matter is the orbital motion. But Orion does not have that motion amidst its dust and matter. Chandra has even been used on the Trapezium itself.
"The Chandra X-ray Observatory identified X-ray emission from individual stars in the Trapezium for the first time and found that almost all of their upper atmospheres, or coronas, are much hotter than expected."
http://chandra.harvard.edu/photo/2000/o ... _hand.html
" .. nearly all the stars we see appear at rather extreme temperatures in X-rays, independent of their type"
http://space.mit.edu/~nss/orion/orion.html

( here we go .. )
"If it exists, the black hole would reside somewhere between the four bright stars which mark the center of the Orion Nebula. These stars are known as the Trapezium."
"The Orion Nebula Cluster has long been known as peculiar. Its stars move at a rapid speed, as if the whole cluster were flying apart. If the cluster contained more high-mass stars, the speed of these stars would be easier to understand. But it doesn’t, and so astronomers have wondered why these stars move so rapidly."
"The model showed that, as the gas was being driven outwards, the cluster began to expand. That explained why most stars in the Orion Nebula Cluster move so rapidly. Many of the heavy stars were sling-shot out of the cluster, while some were driven into the center of the cluster and collided with the most massive star there. At some point, this massive star became unstable and imploded into a black hole, with a mass about 200 times larger than the sun."
"Now, as you gaze at the Orion Nebula, you can imagine a black hole at its heart." And presumably imagine a scenario for Chandra being blind to its presence while scanning the region closely?
"Having such a massive black hole at our doorstep would be a dramatic chance for intense studies of these enigmatic objects." Yes. Intense studies of models could also be in order.
http://earthsky.org/space/a-black-hole- ... ion-nebula

" .. thorough observations of the cluster’s innermost 0.2 light-year are still needed to reveal whether the black hole exists, the authors conclude."
http://www.skyandtelescope.com/astronom ... -in-orion/
I suspect if there were a hole of that size there, so close to Earth at the highest resolution obtained by Chandra, that even the cluster stars' stellar winds would be fed upon by the hole and be observable. That would be one of those tensions between imagining "perfect" conditions of objects or models and real world "messiness".
Let the authors show orbital motion or let them expound upon their model's conditions.

[douglas]

A typical stellar-mass black hole in the Trapezium would be interesting. An intermediate black hole, containing more than 100 times the mass of the Sun, would be spectacular.

According to Wikipedia, the generally accepted stellar-mass black hole candidates in the Milky Way probably all contain less than 20 solar masses. Again according to Wikipedia, only one intermediate-mass black hole candidate has been discovered in the entire Milky Way, three light-years from Sagittarius A*, and this claim has been disputed by a group of astronomers making a dynamical study of the stars in the cluster where the intermediate black hole is supposed to reside. So for all we know, no good intermediate-mass black hole has been discovered in the entire Milky Way. Until some people took a good look at the Trapezium in the Orion Nebula, the most nearby high-mass star forming region in the galaxy?

If there is an intermediate-mass black hole in the Trapezium, only 1500 ly away (or a little more, but still incredibly nearby), isn't that amazing? Shouldn't a lot of people be studying it? Shouldn't we aim a lot of our best telescopes at the Trapezium to try to find out if an intermediate-mass black hole is really lurking there?

I find myself being critical of the claim of the presence of an intermediate-mass black hole in the Trapezium. Of course, arguing about whether it is there is not going to make it disappear if it is there, or appear if it isn't there. But I have to wonder why there has apparently been no real effort to find out if the remarkable claim of an intermediate-mass black hole in the Trapezium is true or not.

Ann

This would be a good start: find those 30 missing O or B stars by composition.

"Typically, star formation results in the formation of an "open cluster,” a group of young stars that have formed from the same gas cloud. The detailed chemical abundances of this gas cloud, as measured by traces of elements heavier than helium, are preserved within the young stars.

Open clusters only last for a few hundred millions years, their stars spreading out throughout the galaxy over time.

.. Fortunately, astronomers don’t need a home address to identify solar siblings. By measuring the motions of stars through space, astronomers can "reverse" their motions and see which stars were near the Sun when it formed."
If this has been done for stars far older than the Trapeziums ..

http://www.skyandtelescope.com/astronom ... ing-found/

"The authors suggest that the measured properties of the ONC, a benchmark of star-formation regions, will have to be revised. Once the ONC catalog is “cleaned” of false members, Lada says, adjustments may have to be made to the details of star-formation theories. Other results, such as the recent simulation that grew a massive black hole at the center of the nebula, are only marginally affected by the contamination."
http://www.skyandtelescope.com/astronom ... embership/

"Not only do Mu Col and AE Aur share the same 230,000 mph (100 km/sec) space velocity, they're racing away from one another in almost exactly opposite directions.
.. Today, they're 1,600 light-years apart."
So there's the authors' task: massive O or B stars with matching compositions moving at that speed would be the handles.
http://www.skyandtelescope.com/observin ... s12062105/

[Chris Peterson]

The reason the Milky Way's hole is able to hide amidst all that dust and matter is the orbital motion.

What do you mean by that? The orbital motion of what? The reason we don't see the Milky Way's central black hole directly is because it isn't active. The reason it isn't active is because the region contains little gas or dust. There are occasional interactions between the black hole and gas, which results in x-ray bursts. But there's nowhere near enough material to feed an accretion disk, so events are transient. We quite easily detect the black hole by looking at the orbits of surrounding stars, however. In a dust poor region like the Orion Nebula we need to use the same method, but it's much more difficult, because the stars are farther apart and the hypothesized black hole is 100,000 times less massive.

"If it exists, the black hole would reside somewhere between the four bright stars which mark the center of the Orion Nebula. These stars are known as the Trapezium."

If so, we're still talking about low orbital speeds. Higher than expected, yes, but still much lower than the stars that circle our galaxy's black hole. So that makes it difficult to measure (although something like Gaia might help, assuming the stars aren't too bright for it).

[douglas]

The reason the Milky Way's hole is able to hide amidst all that dust and matter is the orbital motion.

What do you mean by that? The orbital motion of what? The reason we don't see the Milky Way's central black hole directly is because it isn't active. The reason it isn't active is because the region contains little gas or dust. There are occasional interactions between the black hole and gas, which results in x-ray bursts. But there's nowhere near enough material to feed an accretion disk, so events are transient. We quite easily detect the black hole by looking at the orbits of surrounding stars, however. In a dust poor region like the Orion Nebula we need to use the same method, but it's much more difficult, because the stars are farther apart and the hypothesized black hole is 100,000 times less massive.

"If it exists, the black hole would reside somewhere between the four bright stars which mark the center of the Orion Nebula. These stars are known as the Trapezium."

If so, we're still talking about low orbital speeds. Higher than expected, yes, but still much lower than the stars that circle our galaxy's black hole. So that makes it difficult to measure (although something like Gaia might help, assuming the stars aren't too bright for it).

The Event Horizon Telescope will be coming on line this year, any month now.

Studies of the Milky Way's black hole show it feeds almost constantly producing a chatter of events. The bursts you refer to are the transient events. Both may be due to an accretion disk, like you essentially said.

I do find it inherently absurd for authors to claim they need to gain resolution in the .2 light-year space in the very midst of the 4 Trapezium stars to confirm or rule out the model's prediction.
We're to suppose a 100-200 solar mass black hole could be near the Earth, for instance, and we'd yet to have detected any sign of its presence??
" .. thorough observations of the cluster’s innermost 0.2 light-year are still needed to reveal whether the black hole exists .. "
http://www.skyandtelescope.com/astronom ... -in-orion/

But here, I'll play the game : the animations of the stars tightly orbiting our galaxy's central object don't show any true disturbance to their respective orbits even when their compatriots are at their periapses. This, therefore, indicates black holes in far less congested environs will similarly not affect their surroundings in detectable ways because they are "inactive".
https://io9.gizmodo.com/the-video-that- ... 1114918644
Notoriously "messy eaters", presumably non-spinning (after runaway collision events), no frame dragging, just .. "inactive"?
http://www.skyandtelescope.com/astronom ... al-vortex/

[sarc] Methinks the model proponents doth promoteth too-much. [/sarc]

EHT says SBH not as quiescent as thought
http://www.skyandtelescope.com/astronom ... 312201523/

HANSEN & MILOSAVLJEVI´C's Conclusion for the limits of what is known:
THE NEED FOR A SECOND BLACK HOLE AT THE GALACTIC CENTER
https://arxiv.org/pdf/astro-ph/0306074.pdf
"GCIRS 13E is racing around the galactic center at 626,300 miles per hour (280 kilometers per second)."
http://www.solstation.com/x-objects/s2.htm

[Chris Peterson]

"If it exists, the black hole would reside somewhere between the four bright stars which mark the center of the Orion Nebula. These stars are known as the Trapezium."

If so, we're still talking about low orbital speeds. Higher than expected, yes, but still much lower than the stars that circle our galaxy's black hole. So that makes it difficult to measure (although something like Gaia might help, assuming the stars aren't too bright for it).

The Event Horizon Telescope will be coming on line this year, any month now.

That's a radio telescope array. Not ideal for analyzing the motion of stars, nor capable of detecting an inactive black hole outside of some very specific conditions.

I do find it inherently absurd for authors to claim they need to gain resolution in the .2 light-year space in the very midst of the 4 Trapezium stars to confirm or rule out the model's prediction.
We're to suppose a 100-200 solar mass black hole could be near the Earth, for instance, and we'd yet to have detected any sign of its presence??

We would detect it because of its effect on planetary orbits (in fact, we probably would not be here because of that, but we can ignore that for the moment). We might detect it by its effect on nearby stars, but we might not. That's quite different from trying to detect the effect on a group of stars 1000 ly away, which are themselves around a half light-year from the hypothesized black hole. The need for very high resolution seems quite reasonable.

[douglas]

If so, we're still talking about low orbital speeds. Higher than expected, yes, but still much lower than the stars that circle our galaxy's black hole. So that makes it difficult to measure (although something like Gaia might help, assuming the stars aren't too bright for it).

The Event Horizon Telescope will be coming on line this year, any month now.

That's a radio telescope array. Not ideal for analyzing the motion of stars, nor capable of detecting an inactive black hole outside of some very specific conditions.

I do find it inherently absurd for authors to claim they need to gain resolution in the .2 light-year space in the very midst of the 4 Trapezium stars to confirm or rule out the model's prediction.
We're to suppose a 100-200 solar mass black hole could be near the Earth, for instance, and we'd yet to have detected any sign of its presence??

We would detect it because of its effect on planetary orbits (in fact, we probably would not be here because of that, but we can ignore that for the moment). We might detect it by its effect on nearby stars, but we might not. That's quite different from trying to detect the effect on a group of stars 1000 ly away, which are themselves around a half light-year from the hypothesized black hole. The need for very high resolution seems quite reasonable.

No microlensing from an object that massive?

You'll note I am refuting a description of "inactive" in such an unobscured environment.

[Chris Peterson]

No microlensing from an object that massive?

150 solar masses is not a large mass. The galaxy is full of ordinary stars with that mass. There is no difference at all in the gravitational effect of a 150 solar mass black hole and a 150 solar mass star until you're very close to the surface of the black hole. Any microlensing will only be apparent closed to the surface, as well, which means resolving something a few tens of kilometers across at a few tenths of a light year. That is extremely difficult.

You'll note I am refuting a description of "inactive" in such an unobscured environment.

That the hypothesized black hole is inactive is a given, since an active black hole would be readily detected by its UV and x-ray emissions. It is inactive because there simply isn't enough material nearby to feed it. The activity of the surrounding bright stars have cleared the area of gas and dust.

[douglas]

No microlensing from an object that massive?

150 solar masses is not a large mass. The galaxy is full of ordinary stars with that mass. There is no difference at all in the gravitational effect of a 150 solar mass black hole and a 150 solar mass star until you're very close to the surface of the black hole. Any microlensing will only be apparent closed to the surface, as well, which means resolving something a few tens of kilometers across at a few tenths of a light year. That is extremely difficult.

You'll note I am refuting a description of "inactive" in such an unobscured environment.

That the hypothesized black hole is inactive is a given, since an active black hole would be readily detected by its UV and x-ray emissions. It is inactive because there simply isn't enough material nearby to feed it. The activity of the surrounding bright stars have cleared the area of gas and dust.

If we can get some grad students to track down the 30 missing massive stars that precipitated this intermediate and do some occultation work to find this quantum monster, we could lay this issue to rest.

Several things to be cleared up first: the reason we don't image the central black hole is because of intervening dust clouds. Sagittarius A remains hidden, despite some mechanism having cleared the area around the hole itself.
Hansen's paper describes several other methods for the clearing. Care to comment on the "inactive" solar mass holes he says could be in the hole's vicinity, possibly many?
https://arxiv.org/pdf/astro-ph/0306074.pdf

I'd turn you loose on using inactive black holes to explain away dark matter, because they can't be proven they're not there, but I still have to ask first what the special conditions are for the EHT to detect black holes.
The EHT detects radio emission from ionized gas in twisted magnetic fields so should be able to image any black hole. With a magnetic field.

[Ann]

150 solar masses is not a large mass. The galaxy is full of ordinary stars with that mass.

That is not true. To the best of our knowledge, our galaxy may host one such star, HD 15558 A, whose mass according to Wikipedia is >152 ± 51 solar masses. But because I've taken a great interest in hot massive blue stars, I'm doubtful that HD 15558 A is that massive. Its spectral class is O5, not O3 or O2 as I would expect from a extremely young and tremendously massive star. Also HD 15558 A doesn't stand out that much among the other stars of Melotte 15, as I expect it would if it was much more massive than the other stars in the cluster. Compare with Tau CMa, which is only spectral class O9Ib, but which is very much brighter than the other stars of cluster NGC 2362.

Also Melotte 15 isn't a very compact cluster. Compare with NGC 3603. I expect the very compact and rich clusters to be more likely than others to contain very massive stars, although that isn't always true.

Wikipedia points out that HD 15558 A may itself be a double star and therefore not as incredibly massive as its binary orbit suggests.

So all in all, our galaxy may be completely devoid of individual stars as massive as 150 solar masses, which is a far cry from your claim that our galaxy is full of them.

But as for the main point of your argument, that it would be hard to spot an 150 solar mass black hole half a light-year from the Trapezium, I don't know enough to have an opinion.

Ann

[Chris Peterson]

150 solar masses is not a large mass. The galaxy is full of ordinary stars with that mass.

That is not true. To the best of our knowledge, our galaxy may host one such star.

Okay, "full of" may be a bit of an overstatement. But there are many more than one. Most of our galaxy is not visible to us. If we can detect one, there are quite a few more. None of which have any extreme gravitational effects, of course. We infer very massive stars because of their activity, but there are likely to be quite a few more which are "ordinary", and which we therefore don't even recognize as being very massive.

[Chris Peterson]

Several things to be cleared up first: the reason we don't image the central black hole is because of intervening dust clouds. Sagittarius A remains hidden, despite some mechanism having cleared the area around the hole itself.

No. It is "hidden" because all black holes that are not accreting material are hidden. As you noted, there are times when material does fall into it, and we see that radiation. The black hole is not obscured by dust. We readily see the stars orbiting it very closely- less than a parsec- simply by looking in the infrared where the dust is fairly transparent.

Hansen's paper describes several other methods for the clearing. Care to comment on the "inactive" solar mass holes he says could be in the hole's vicinity, possibly many?

I have no opinion. What has cleared the area isn't relevant to the discussion. What matters is that the area has little dust and gas.

I'd turn you loose on using inactive black holes to explain away dark matter, because they can't be proven they're not there, but I still have to ask first what the special conditions are for the EHT to detect black holes.

There needs to be a bright enough background to be detected as it is bent around the event horizon. That's what they plan to look at. The event horizon itself is, and will remain, invisible.

The EHT detects radio emission from ionized gas in twisted magnetic fields so should be able to image any black hole. With a magnetic field.

Yes. A supermassive black hole that has at least some material falling into it. Probably not a 150 solar mass black hole in a completely cleared area.

[douglas]

"The five brightest stars are on the order of 15-30 solar masses in size. They are within a diameter of 1.5 light-years of each other .. "
https://en.wikipedia.org/wiki/Trapezium_Cluster

Seeing as the analysis I quoted earlier determined the hole would be in the very center of the 5 brightest, and Chris says their "proper motions" don't indicate orbital conditions or even observable effects, we can hereby whittle down the must-be distance to 1/2 that diameter of 1.5 light years.

So here we have the scenario where the hole, caged in by 5 massive, big-blowing stars ... has nothing to feed on despite no orbital motion denying it food .. and is "inactive"!
And because the EHT is designed to detect ionized gas emitting in twisting magnetic fields, we're to theorize it doesn't have magnetic fields (non-spinning or w/e?) because the EHT requires "special conditions" which we're told won't be present with this IBH.

Looks like what will nail down this black hole is a lot of correlative work.

And a lot of these very massive stars turn out to be double or triples, generally the ones physics says are not possible at those sizes.

[douglas]

Several things to be cleared up first: the reason we don't image the central black hole is because of intervening dust clouds. Sagittarius A remains hidden, despite some mechanism having cleared the area around the hole itself.

No. It is "hidden" because all black holes that are not accreting material are hidden. As you noted, there are times when material does fall into it, and we see that radiation. The black hole is not obscured by dust. We readily see the stars orbiting it very closely- less than a parsec- simply by looking in the infrared where the dust is fairly transparent.

Hansen's paper describes several other methods for the clearing. Care to comment on the "inactive" solar mass holes he says could be in the hole's vicinity, possibly many?

I have no opinion. What has cleared the area isn't relevant to the discussion. What matters is that the area has little dust and gas.

I'd turn you loose on using inactive black holes to explain away dark matter, because they can't be proven they're not there, but I still have to ask first what the special conditions are for the EHT to detect black holes.

There needs to be a bright enough background to be detected as it is bent around the event horizon. That's what they plan to look at. The event horizon itself is, and will remain, invisible.

The EHT detects radio emission from ionized gas in twisted magnetic fields so should be able to image any black hole. With a magnetic field.

Yes. A supermassive black hole that has at least some material falling into it. Probably not a 150 solar mass black hole in a completely cleared area.

They can have the event horizon. If background object radiations are affected by the hole's gravity, those are the artifacts that will give its location. Quite simply, if there are no artifacts there is no black hole. It is not of the spooky quantum dimension.

If Chandra or Newton detect nothing it is not there. It has wind-supplied gas to feed on. It will not refuse it. lol

[Ann]

150 solar masses is not a large mass. The galaxy is full of ordinary stars with that mass.

That is not true. To the best of our knowledge, our galaxy may host one such star.

Okay, "full of" may be a bit of an overstatement. But there are many more than one. Most of our galaxy is not visible to us. If we can detect one, there are quite a few more. None of which have any extreme gravitational effects, of course. We infer very massive stars because of their activity, but there are likely to be quite a few more which are "ordinary", and which we therefore don't even recognize as being very massive.

As I said, there may not even be one.

Wikipedia wrote:
HD 15558 A is a spectroscopic binary system containing at least two massive luminous class O stars. The primary is an O4.5 giant star with a surface temperature over 46,800 K. It has a mass of 152 M☉ and a luminosity of 660,000 L☉. The star loses 1.5×10−5 M☉ per year.[7] The secondary is an O7V star. It has a mass of 46 M☉. The primary may itself be a double star, suggested by the improbably large mass found from the binary orbit when compared to the other stellar parameters.[4]

And as for the claim that we can't see most of our galaxy, that is true, but not entirely. Infrared observations of our galaxy have revealed a lot that was hidden at visual wavelengths.

In any case, we have reasons to believe that the Milky Way is not all that rich in star formation. According to Wikipedia, the Milky Way belongs to a galaxy where star formation is very clearly winding down:

Noticed in this diagram are three main features: the red sequence, the green valley, and the blue cloud. The red sequence includes most red galaxies which are generally elliptical galaxies. The blue cloud includes most blue galaxies which are generally spirals. In between the two distributions is an underpopulated space known as the green valley which includes a number of red spirals.
...
The Milky Way and the Andromeda Galaxy are assumed to lie in the green valley because their star formation is slowing down due to running out of gas.

My point is that we may very well already have discovered all the really high-mass regions of star formation in the Milky Way, and also all the really big bright star clusters. Any truly massive star in the Milky Way can be assumed to be located in or very near a massive bright cluster or a region of high-mass star formation. I think that we mostly know where to look for additional massive stars in our galaxy, even though we don't yet possess the means of determining the mass of the most massive individual stars in them.

But let's compare the Milky Way with the Large Magellanic Cloud. It is quite clear that the LMC is very rich in star formation and can be expected to contain many high-mass stars. The LMC is also nearby, and we can see it well. Wikipedia's list of the most massive stars known to us is dominated by stars in the LMC, which is to be expected. Yet even that list contains only nine LMC stars whose mass is ≥150 solar.

I don't think we have any reason to believe that the Milky Way contains as many high-mass stars as the LMC. So if we have found only ten or so ≥150 solar mass stars in the LMC, we should expect fewer in the Milky Way. Perhaps none.

Ann

[Chris Peterson]

They can have the event horizon. If background object radiations are affected by the hole's gravity, those are the artifacts that will give its location. Quite simply, if there are no artifacts there is no black hole. It is not of the spooky quantum dimension.

A black hole influences its environment. That isn't the same thing as us having the capability to detect the ways it influences it.

If Chandra or Newton detect nothing it is not there. It has wind-supplied gas to feed on. It will not refuse it. lol

Where your analysis fails is the assumption that there is enough material available to fall into the black hole that a detectable amount of radiation will be produced. That claim is not substantiated, and is contradicted by the work of the researchers. Almost certainly, the vast majority of black holes in the Universe are not detectable by any technology we currently possess.

[Ann]

There is one more thing. According to Wikipedia, the mass of Theta-1 C, the most massive star in the Trapezium, is 33 ± 5 M_☉. To create a black hole of 150 M_☉, we would need at least four and probably five stars similar to Theta-1 C colliding or merging with each other. Shouldn't such a titanic collision create a shock wave that might still be detectable?

Ann

[Guest]

They can have the event horizon. If background object radiations are affected by the hole's gravity, those are the artifacts that will give its location. Quite simply, if there are no artifacts there is no black hole. It is not of the spooky quantum dimension.

A black hole influences its environment. That isn't the same thing as us having the capability to detect the ways it influences it.

If Chandra or Newton detect nothing it is not there. It has wind-supplied gas to feed on. It will not refuse it. lol

Where your analysis fails is the assumption that there is enough material available to fall into the black hole that a detectable amount of radiation will be produced. That claim is not substantiated, and is contradicted by the work of the researchers. Almost certainly, the vast majority of black holes in the Universe are not detectable by any technology we currently possess.

I understand what you're saying about enough material captured to be detectable. Perhaps Ann can give an estimate of the mass deliverable by solar winds.
I do not know but it is likely Chandra has detected corresponding amounts being acted upon at far greater distances.
It's this request to imagine this IBH has such special conditions while so close that does not sit well.

Ann said in her latest post: "Shouldn't such a titanic collision create a shock wave that might still be detectable?"
That's one of my points, the nebula appears a relatively tranquil place where stellar winds are the predominantly observed forces.

[Ann]

Perhaps Ann can give an estimate of the mass deliverable by solar winds.

I can't, but the massive stars of the Trapezium are very young, but fully formed. They have definitely reached the main sequence, but not progressed very far along it. Such stars are not expected to have large outflows of matter.

Click to view full size image

Cygnus X-1, artist's impression.
Credit: NASA, ESA, Martin Kornmesser (ESA/Hubble)

On those occasions when we do see outbursts from a black hole, there is usually a stream of gas and dust being directly fed into the black hole, as is the case of the black hole of Cygnus X-1. The star feeding matter into the black hole of Cygnus X1, HD 226868, is an evolved and therefore somewhat "swollen" star orbiting very close to its black hole companion.

So, no, I don't think that the current stellar outflows from the stars of the Trapezium would be enough to stir appreciable reactions from a black hole half a light-year away from them.

(An aside here: The Wikipedia entry for Theta-1 C Orionis, the brightest and most massive star of the Trapezium Cluster, says that the age of this star is around two and a half million years, or 2.5 ± 0.5 Myr. That is much older than I would have thought. But the Wikipedia entry for the Trapezium Cluster says that the age of this cluster is 3 × 10⁵ years, only 300,000 years! If that is true, then Theta-1 C can't be expected to be much older than 300,000 years, either - and that is the age I would have expected for that star.)

Assuming the age of the Trapezium Cluster is about 300,000 years, then the formation of an 150 M_☉ black hole - if there is one - might have taken place fairly soon after the formation of the cluster. Let's say it happened some 200,000 years ago. The merger would have caused a titanic explosion. Would the remnant of it still be detectable?

Click to view full size image

Simeis 147 supernova remnant.
Photo: Rogelio Bernal Andreo.

That is touch and go, I think. At left is a supernova remnant, Simeis 147, which I think is one of the oldest known. Its age according to Wikipedia is about 40,000 years, much younger than the Trapezium Cluster. Then again, Simeis 147 does not contain any sort of black hole at all, and we can be sure that the supernova explosion that formed it was puny compared with the explosion that must have accompanied the formation of an 150 M_☉ black hole.

So I think it is possible that we should still see some remnants of the explosion that formed a putative 150 M_☉ black hole some 2-3 10⁵ years ago.

Ann

[Chris Peterson]

There is one more thing. According to Wikipedia, the mass of Theta-1 C, the most massive star in the Trapezium, is 33 ± 5 M_☉. To create a black hole of 150 M_☉, we would need at least four and probably five stars similar to Theta-1 C colliding or merging with each other. Shouldn't such a titanic collision create a shock wave that might still be detectable?

It isn't clear that a stellar collision would have much impact on its surrounds. Not saying it couldn't, but I don't think the nature of such collisions is well understood. The two stars may simply merge into one quite gently.

[Ann]

There is one more thing. According to Wikipedia, the mass of Theta-1 C, the most massive star in the Trapezium, is 33 ± 5 M_☉. To create a black hole of 150 M_☉, we would need at least four and probably five stars similar to Theta-1 C colliding or merging with each other. Shouldn't such a titanic collision create a shock wave that might still be detectable?

It isn't clear that a stellar collision would have much impact on its surrounds. Not saying it couldn't, but I don't think the nature of such collisions is well understood. The two stars may simply merge into one quite gently.

I agree that two stars could conceivably merge into a more massive star quite gently, but surely they couldn't merge into an 150 M_☉ black hole quite gently?

Ann

[Chris Peterson]

There is one more thing. According to Wikipedia, the mass of Theta-1 C, the most massive star in the Trapezium, is 33 ± 5 M_☉. To create a black hole of 150 M_☉, we would need at least four and probably five stars similar to Theta-1 C colliding or merging with each other. Shouldn't such a titanic collision create a shock wave that might still be detectable?

It isn't clear that a stellar collision would have much impact on its surrounds. Not saying it couldn't, but I don't think the nature of such collisions is well understood. The two stars may simply merge into one quite gently.

I agree that two stars could conceivably merge into a more massive star quite gently, but surely they couldn't merge into an 150 M_☉ black hole quite gently?

I'm not sure. We're looking at a two-part process here, right? First, some initial stellar collisions until the mass is high enough to form a black hole. Then, a series of star-black hole collisions to increase the total mass. I'm not sure how wide spread the effects are of a black hole swallowing a star, either. There's going to be a lot of optical energy released, but that might not result in much shock wave production in gases a few light years away.

I'm not sure the degree to which things like this have been modeled.

[Ann]

It isn't clear that a stellar collision would have much impact on its surrounds. Not saying it couldn't, but I don't think the nature of such collisions is well understood. The two stars may simply merge into one quite gently.

I agree that two stars could conceivably merge into a more massive star quite gently, but surely they couldn't merge into an 150 M_☉ black hole quite gently?

I'm not sure. We're looking at a two-part process here, right? First, some initial stellar collisions until the mass is high enough to form a black hole. Then, a series of star-black hole collisions to increase the total mass. I'm not sure how wide spread the effects are of a black hole swallowing a star, either. There's going to be a lot of optical energy released, but that might not result in much shock wave production in gases a few light years away.

I'm not sure the degree to which things like this have been modeled.

Okay. Fair enough. I get what you are saying. We don't know enough of the formation of this kind of black holes to be sure what impact their formation would have on their surroundings.

I would like to point out, nevertheless, that intermediate mass black holes (IMBHs) like the one that might possibly exist in Orion are extremely rare. Just an hour ago or so, bystander made a post about the first definite discovery of an IMBH in the Milky Way, namely in globular cluster 47 Tucanae.

Please consider what the conditions are like in 47 Tuc. This globular is the second brightest one of the Milky Way globulars, but 47 Tuc is also extremely concentrated in its central regions.

Consider how massive it is. According to Wikipedia, the mass of 47 Tuc is 7.0 x 10⁵ M_☉, or 700,000 times solar. That's a lot. Compare the mass of 47 Tuc with the mass of R136, the extremely bright and massive cluster that ionizes the Tarantula Nebula in the Large Magellanic Cloud. According to Wikipedia, the mass of R136 is "only" 90,000 times solar, one eighth of the mass of 47 Tuc! But then we must also remember that clusters always lose mass over time, and since 47 Tuc is about 13 billion years old while R136 is practically newborn - well, it might be about one and a half million years - it is clear that 47 Tuc must have been even more massive when it was young! 47 Tuc is a whopper, and a whopper with an incredible central density at that. So if we are looking for an intermediate mass black hole, 47 Tuc should be the perfect place to go sleuthing.

Now compare 47 Tuc with the Trapezium. Wikipedia does not make a mass estimate for the entire cluster, but says that the five brightest stars are on the order of 15-30 solar masses in size. Let's say that their combined mass is 120 M_☉. Add a black hole of 150 M_☉ and large numbers of small stars whose combined mass might be, oh, 2,000 M_☉? Or is it possible that the entire mass of everything that is a part of the Trapezium Cluster might be as much as 10,000 M_☉? I don't believe it is that massive, but let's assume it is. That would still make the Trapezium Cluster 70 times less massive than 47 Tuc, and nine times less massive than R136. And yet, there seems to be no sign of an IMBH in R136.

(And by the way, it seems certain that the Trapezium just can't hold as much as one ninth of the mass of R136.)

What I'm saying is that intermediate mass black holes are rare, that it takes very special circumstances to form them, and that the Trapezium Cluster is a quite ordinary region of high-mass star formation. While it is possible that not a single 150 solar mass star exists in the Milky Way, we can be sure that dozens and possibly hundreds of star forming regions comparable to or more fertile than the Trapezium can be found in our galaxy.

What I'm saying is that the Trapezium Cluster is nothing special. Not really. It is, course, very interesting to us, in view of the fact that we live in a galaxy where star formation is winding down and the Trapezium is the nearest region of high-mass star formation. But the Trapezium is modest, nevertheless.

So my question is, why should we assume that an ordinary, indeed quite modest, region of high-mass star formation like the Trapezium would give rise to such an utterly rare beast as an intermediate mass black hole, which, we may assume, is most easily formed in extremely massive and crowded conditions?

So I recommend skepticism. But I also recommend that the astronomical community intensify their efforts to settle this question. And if they do find that an intermediate mass black hole is indeed the most likely explanation for the stellar motions in the Trapezium, then we should reconsider our ideas about intermediate mass black holes in the first place. If there is one in the Trapezium, there should be many more elsewhere. Indeed, if there is one in the Trapezium there should be thousands or ten of thousands of them in the Milky Way, orbiting silently and unnoticed in the vast expanses of our galaxy.

Ann

[douglas]

First, I'd like to point out I was surprised someone would insist on the researchers' model which almost certainly is doing N-body simulations/Monte Carlo models. These Monte's have been for, what is it now? several decades?, been controversial because their results are highly dependent on initial conditions, or at the very least consistently yield black holes as causative, or binary system interactions.

Studies I found today have found .. 3 of the 4 Trapezium central stars are .. binaries, or greater.

My interpretation of the desire to ok the black hole explanation has something to do with, shall we say, "salesmanship" of black holes, kind of like paleobiology's dinosaurs being another hot topic people are interested in. I'm going to hunt down the referenced Charles U. study. But I'm going to put this reference up now because it by itself should clear all doubt, and note it comes Nowhere near utilization of black holes as cause of data. And the authors pulled the data in: Hubble, Spitzer, VLA, etc.

Here it is, note the date, and Ann, you should especially like it: do read the link

On the dynamical evolution of the Orion Trapezium
Christine. Allen,⋆ Rafael Costero, Alex Ruelas-Mayorga, L. J. Sanchez,
https://arxiv.org/pdf/1701.03440.pdf

some notable quotes from above:

13 January 2017

"Neither [of the 2 studies] attempted to use actual observed values of positions, velocities and masses of the Orion Trapezium components as initial conditions, due to the unavailability of such data. (While admitting I haven't read the Charles U. study, it does call into question their reasoning. Have they solely used modeling inputs, no observations? and then came up with another controversial result without binaries input?)

It is clear that the region near the Orion Trapezium has been very active dynamically. Studies of the radio sources embedded in the BN-KL region (Rodr´ıguez et al. 2005, G´omez et al. 2008) showed that three of these radio sources move away from a common point where they converged about 500 years ago. Costero et al. (2008), observing only the radial velocity, found that Component E of the Orion Trapezium is escaping from it, probably as a result of dynamical interactions within the system.

Component B is really a mini-cluster, composed by at least 5 stars in close proximity (Close et al. 2013).

Allen et al. (2015) conducted a numerical exploration of the dynamical evolution of this mini-cluster, arriving at the conclusion that its age is probably less than 30,000 years."

A "strong, non-thermal radio source first detected by Churchwell et al. (1987)."

From its IR photometric properties and assuming it belongs to the Trapezium Cluster, the mass
of this third component was estimated to be about 4 M⊙ by Weigelt et al (1999), Shertl (2003), Grellmann et al. (2013).

For the numerical N-body integrations we used the well-tested code by Mikkola & Aarseth (1993)."

"At 100 crossing times (about 1 million years) the dynamical evolution is practically over."

"We can conclude that Star E probably was bound to the Orion Trapezium in the recent past, and that it escaped only about 2,000 years ago."

" .. it is highly unlikely for systems resembling the Orion Trapezium as a whole to be able to generate runaway stars, as has sometimes been claimed."

"An interesting question is whether the widely accepted notion that the Orion Trapezium is a bound system is valid, especially in view of the rather short lifetimes we find, and of the escaping Component E. At least two arguments support its being a bound system. First, the probability of finding four bright stars within a radius of 10 arcseconds is very low.

Second, the relative motions of the main components in the plane of the sky are very small, also implying a bound system. However, if a better knowledge of the radial velocities should show widely discrepant values, the question would have to be re-examined."


This is other material which suggests more of the dynamic nature of the Trapezium area in the past:

"We study the dynamical interaction in which the two single runaway stars AE Aurigae and mu Columbae and the binary iota Orionis acquired their unusually high space velocity. The two single runaways move in almost opposite directions with a velocity greater than 100 km/s away from the Trapezium cluster. The star iota Ori is an eccentric (e=0.8) binary moving with a velocity of about 10 km/s at almost right angles with respect to the two single stars. The kinematic properties of the system suggest that a strong dynamical encounter occurred in the Trapezium cluster about 2.5 Myr ago. Curiously enough, the two binary components have similar spectral type but very different masses, indicating that their ages must be quite different. This observation leads to the hypothesis that an exchange interaction occurred in which an older star was swapped into the original iota Orionis binary. .. "

N-body simulations of stars escaping from the Orion nebula
https://arxiv.org/abs/astro-ph/0401451

"HD 37023: of the four Trapezium cluster stars this is the only one without a binary companion (Preibisch et al. 1999)."
http://www.aanda.org/articles/aa/full/2 ... 66-05.html

A "food source" for our sneaky black hole?
Theta1 Orionis C1 .. emits a powerful stellar wind that is a hundred thousand times stronger than the Sun's, and the outpouring gas moves at 1,000 km/s."
https://en.wikipedia.org/wiki/Theta1_Orionis_C

[douglas]

Dr. Ladislav Subr of Charles University in Prague

November 1, 2012 in the Astrophysical Journal

.. We further show that the putative massive black hole is likely to be a member of a binary system with ≈70% probability. [heh, really? ] In such a case, it could be detected either due to short periods of enhanced accretion of stellar winds from the secondary star during pericentre passages, or through a measurement of the motion of the secondary whose velocity would exceed 10 km s–1 along the whole orbit.

... In other words, the underabundance of the high-mass stars in the ONC not only indicates a period of prominent two-body relaxation in the past, but also the merging formation of a massive object that may represent an important footprint of the cluster's history.

.. Despite of its high mass, in several realizations the merging object has been ejected out of the cluster with velocity exceeding 10 km s−1.

Gas expulsion that starts at Tex = 0.5 Myr removes all gas from the cluster within a few hundred thousand years.

http://iopscience.iop.org/article/10.10 ... 0-40-1-105