Black holes - Are they real?

Black holes - Are they real? That is the question!

I'm especially interested in the opinion of amateur astronomers who would consider themselves to have a good knowledge of astronomy and physics. In other words, if you follow astronomy and science stuff, and you have a reasonable understanding of astrophysics, please do comment. I believe the view point of the amateur astronomer is just as valid as the scientist with the billion dollar telescope.

The question about black holes relates to an article in the Washington post called - Scientists witness the apparent birth of a black hole -
Article - www.washingtonpost.com/wp-dyn/content/ar...AR2010111504192.html
Same article black hole image gallery - www.washingtonpost.com/wp-dyn/content/ga...?sid=ST2010111504282

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Now the question i am really asking here is do you simply "believe" the evidence presented by todays science that black holes exist?

Does anyone here question the evidence for the existence of black holes?

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I think the evidence is highly questionable, regardless of what Einstein said. Einstein's equations predict the existence of black holes. Then modern astronomy "claims" they have proof of their existence from the pictures we see from giant telescopes.

Lets just take that article in the Washington post as an example. Like all news stories and TV stuff about black holes, they talk about "electromagnetic radiation emissions" that tell us where the black hole is!. But Einstein's equations specifically tell us NOTHING can escape from a black hole.

The emissions we do see, science currently tells us this is material "falling into" the black hole, just on the edge of the event horizon. Then other science tells us about giant gamma ray bursts of light or beams shooting out of the black hole, over long periods of time!!

Could modern astronomy be wrong? Maybe no material ever makes it across the event horizon! Maybe all of the material falling toward the event horizon is converted to electromagnetic energy and ejected, hence it never crosses the event horizon? The closer mass gets to the event horizon, the heavier it gets coz gravity will be crushing it. The more gravity compresses the mass, the more mass that undergoes nuclear fusion, releasing energy. So by the time any mass makes it to the event horizon, it will be converted to energy. ---- Thats my personal view.

John.

John

Media reports concerning black holes can often be misleading due to oversimplification and also language. High-energy beams do not, for example, get emitted directly by black holes - they get emitted from the accretion disc that many black holes have around them.

A more compelling argument for the existence of black holes - which avoids (to a very large extent) funny physics - is the work by two teams of astronomers (UCLA using the Keck telescope in Hawaii and the Max-Planck-Institut using ESO's NTT and later the VLT - both in Chile). This is basically to watch (i.e. observe and measure) how stars orbit the super-massive black hole candidate at the centre of our galaxy with the view to show that nothing else can explain these motions other than a black hole. It can be debated whether they have strictly achieved this but it's got to the point where its very hard to presume that there isn't a black hole at the centre of our galaxy.

Both teams have generally focused on studying the central one-arcsec square of our galaxy - in infra-red. The achieved resolution astounds me - that area would get lost in the Airy disc of one star for my set-up. The technique by both teams uses adaptive optics and lucky imaging (take lots of short exposures and choose the best).

Prior to 2002 the Max-Planck team were using the 3.58m New Technology Telescope (the NTT). This is the telescope that pioneered adaptive optics technology (according to the ESO website). Post 2002 the Max-Planck team were using the four 8.2m telescopes that comprise the VLT.

The work by UCLA is on a 10m Telescope.

The ESO started their observations in 1992 and the UCLA started 1995. There's now about 17 years observational data. These are independent studies which reconcile well. This region of space is about 50 light-days (note days) across - considering that our closest neighbouring star is approx 4 light-years away - that's a very small region. The measured orbits are of more than 20 stars (about the point coincident with energetic radio source Sgr A*) with orbital radii up to about 30 light days (that is up to the distance of 173 Neptune orbital radii).

So we have an excess of twenty stars orbiting something – at distances less than 173 Neptune orbit radii and that something that is at the foci of the orbits has to have a mass of 4 million suns (rounded to nearest integer) and using Newtonian mechanics – i.e. no funny physics required. When calculated using General Theory of Relativity – and rounding to nearest integer we have 5 million solar masses (both these mass estimates are calculated by members of the observing teams). Its hard to come up with an explanation other than a black hole.

Of particular interest - one star (designated S2 in the literature) has been recorded in time sequence through one complete orbit about Sgr A*. S2 orbits in 15.9 years.
www.mpe.mpg.de/ir/GC/res_dance.php?lang=en
The white star about half way across the frame and about 1/5 the way down is S2 - you get to see it whip around the black hole – I believe these are plots of astrometric measurements and not the source images themselves. it should be noted that the common foci of the orbits, while possibly having a small steady proper motion, is otherwise not moving.

There is a TED talk (a bit lacking in substance - it is to an audience of wide backgrounds - its not bad) by Andrea Ghez of the UCLA team



A lot of this information I got from one paper preprint on arXiv, “The Orbit of the Star S2 around SGR A* From VLT and Keck Data” S. Gillessen et al. Plus a little poking around and some calculator work.

Mark C.

Mark,
Thank you for replying to this thread.

Mark your very well read on this topic and you display an above average understanding of the physics. Forgive me for not writing out full explanations for the points i made. I done that to save typing everything out.

But let me cut to the crunch here. The image you linked to on this page; www.mpe.mpg.de/ir/GC/res_dance.php?lang=en - That is the very best data we have from 15 years of research. And Mark i don't disagree with you, looking at that incredible GIF image of Sgr A*, it looks like there MUST be something with an absolutely colossal mass in the middle that we can't see! Yes, the evidence is very convincing!

Now as you well know, everything is astrophysics does not fully add up with todays mathematics. We have the dark matter/dark energy problem, lets not go down that line. Black holes are now almost fully accepted and almost taken for grant-it by science.

But Mark, this is my theory, its just my personal view here.

All the stars in the Sgr A* image are moving at incredible speed around something, something with incredible mass. Is there any way this could happen without the need for a very heavy black hole we can't see? Well i think yes, it can happen another way Mark!

If we don't call it a black hole, but instead we chose to call it a fulcrum, or pivot point, just like the simple law of the lever. Lets pretend for one second that the fulcrum point itself has zero mass. What would happen? Would all the other stars fly off into space? No, they would not! The gravitational attraction of each star would pull on every other star and the galaxy would stay rotating the way we see it, give or take a bit.

So, when we look at the Sgr A* movie image, maybe we could be looking at just a simple fulcrum or pivot point. In the law of the lever, weights hang from a lever at different points to balance the lever. But i think maybe in a galaxy, the objects we are calling black holes could just be gravitational focal points, or the theoretical focal point where stars orbit around.

Although the evidence for the existence of black holes is good when you see that movie image of Sgr A*, what i am suggesting is not impossible either. What do you think?

John.

Mark,
Adding to my last post;

The measured mass of the Milkyway black hole is about 4 million solar masses.

With my theory, ALL matter gets ejected before it crosses the event horizon. Its ejected either as the star is crushed and the matter is ejected, or it undergoes nuclear fusion and is ejected as electromagnetic radiation.

Question; Could these new "Bubbles" have 4 million solar masses? - www.csmonitor.com/Science/2010/1110/Milk...hing-for-dark-matter Think of water swirling around the kitchen sink like a galaxy. The water swirls around until eventually it gets ejected, down the plug hole of the sink. In a galaxy, out one side or the other of the focal point.

My theory would concur with the observation that some Galaxy's seem to have a black hole, but others don't, or just a small one. The mass of the observed black hole would depend on how recently the black hole swallowed its last star and how many. If the material was ejected recently( a few million years), we might measure this as the black holes mass.

John.

John
First - thanks for the vote of confidence - but I should emphasise that I'm not qualified in physics and should not be regarded as an authority. Also, I'd encourage anyone who feels that I'm in error anywhere to point out their suspicions etc.

In my previous post I indicated that each measured stellar orbit has one focus of the orbit coincident on Sgr A* - and apart from maybe a small proper motion - it does not move. There's two pieces of crucial of evidence in that statement.

The meaning of this is that the measured stars are gravitationally bound to some dominant mass near that point. As a consequence each stellar orbit will - to a large degree - repeat and re-trace it's path.

The second inference is that if the mass at or near this point is sufficiently large it will not move appreciably when there are multiple bodies orbiting it. As we consider smaller and smaller masses it will wiggle as the barycentre (mean position of the centre of the combined masses) is displaced - but the stellar orbits will still be predictable and repeat.

If these stars were not gravitationally bound to this point then the paths of the stars would be very different. Sometimes one star, while passing another, will be drawn into a partial orbit of a third star, etc. The could be quite chaotic and difficult to model. But it would more than likely be quite a complex dance.

In particular, S2 is seen to whip around Sgr A* - that would be very difficult to explain if it there were no gravitational interaction with that point.

Now you may be tempted to believe that the centre of mass of the whole galaxy can be regarded to reside at that point and and assume that all stars orbit that (maybe your notion of pivot point or fulcrum).

This could be tempting because if we were to to model, say Andromeda's trajectory with respect to our own galaxy we would regard both as point masses (with total mass of each galaxy at a point at the centre of each galaxy). The latter treatment is valid - but is invalid for what we are considering. This is because the gravitational forces of the central stars are more influenced by each other than stars further out from the centre. That's because - to a large degree - the central stars reside in a gravitational shell (forces from more distant stars will tend to cancel out as we have lots of them pretty evenly distributed in a shell around our stars of interest). In the case of the spiral arms - well they're further out and have less influence and are still broadly symmetrical in a plane - I reckon they can be disregarded.

hyperphysics.phy-astr.gsu.edu/hbase/mechanics/sphshell2.html

I hope that helps.

Mark C.

With regards to the Christian Science Monitor article - I'm reluctant to pursue.

There maybe something there - there may not be. There's no references to secular sources and I'm reluctant to make comment. All links lead to other Christian Science articles.

I sincerely hope that doesn't offend.

Mark C.