K-Tec

Black holes - Are they real?

  • John37309
  • John37309's Avatar Topic Author
  • Offline
  • Proto Star
  • Proto Star
  • Posts: 50
  • Thank you received: 0

Black holes - Are they real? was created by John37309

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


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?



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.
12 years 2 months ago #87300

Please Log in or Create an account to join the conversation.

  • Posts: 470
  • Thank you received: 20

Replied by mjc on topic Re:Black holes - Are they real?

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.
12 years 2 months ago #87330

Please Log in or Create an account to join the conversation.

  • John37309
  • John37309's Avatar Topic Author
  • Offline
  • Proto Star
  • Proto Star
  • Posts: 50
  • Thank you received: 0

Replied by John37309 on topic Re:Black holes - Are they real?

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.
12 years 2 months ago #87332

Please Log in or Create an account to join the conversation.

  • John37309
  • John37309's Avatar Topic Author
  • Offline
  • Proto Star
  • Proto Star
  • Posts: 50
  • Thank you received: 0

Replied by John37309 on topic Re:Black holes - Are they real?

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.
12 years 2 months ago #87333

Please Log in or Create an account to join the conversation.

  • Posts: 470
  • Thank you received: 20

Replied by mjc on topic Re:Black holes - Are they real?

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.
12 years 2 months ago #87339

Please Log in or Create an account to join the conversation.

  • Posts: 470
  • Thank you received: 20

Replied by mjc on topic Re:Black holes - Are they real?

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.
12 years 2 months ago #87340

Please Log in or Create an account to join the conversation.

  • John37309
  • John37309's Avatar Topic Author
  • Offline
  • Proto Star
  • Proto Star
  • Posts: 50
  • Thank you received: 0

Replied by John37309 on topic Re:Black holes - Are they real?

With regard to the Christian Science Monitor website, its not a religious website if that's what you think. Its just another science news website. The same article appears on all the science news websites; blogs.discovermagazine.com/80beats/2010/...heart-of-the-galaxy/

Anyway, You make some excellent points and they are hard to argue with Mark!

One last example that explains my point;

Watch this 30 second Youtube video;
Radial Velocity Method For Finding Exoplanets -




Now everyone looking for exoplanets is now familiar with that very simple animation that shows how the star wobbles a small bit as a planet orbits it. In the animation there are only 2 objects, the star and the planet, both gravitationally bound to each other.

Now, just like that Sgr A* GIF image you posted, imagine we zoom in on that Youtube animation, what would we see? We would only see the star in the middle, the planet would be outside the picture. And what would it look like? Well we would see one very heavy star orbiting "SOMETHING"!!!! What would that single star be orbiting? In the zoomed in animation, you would see the star orbiting around an empty black area of space.

WHAT!!!!! Dam..... That sounds just like a black hole!! The star would be orbiting a black hole that, if we calculate it out, the mass would be equal to the mass of the planet that's currently outside our zoomed in animation image.

Do you get the point i'm making? With only two simple objects, i was able to make a black hole, and i was even able to calculate its mass. You have got to admit Mark, you can't completely rule out what i'm suggesting. Maybe the S2 star in the Sgr A* image is orbiting a focal point and not a black hole that has forever swallowed vast numbers of stars.

Now play the Youtube animation video again, and try ignore the orbiting planet. Imagine you have zoomed in and you can only see the star...... orbiting an empty black area of space that does appear to have a small mass.

Then multiply the animation image by about 200 billion and you have the Milkyway, and a possible focal point with stars orbiting very fast around it.

John.
Last edit: 12 years 2 months ago by John37309.
12 years 2 months ago #87341

Please Log in or Create an account to join the conversation.

  • Posts: 470
  • Thank you received: 20

Replied by mjc on topic Re:Black holes - Are they real?

John - I can see where you are coming from. However, the following thought experiment might help.

Think of a constellation of twelve equal-mass stars evenly distributed as a circle - rather like the configuration on the EU flag. Now place a suitable mass at the centre and consider the ring of stars to rotate about this mass such that each star is in orbit. This is like a constellation of GPS satellites encircling the Earth and I can imagine the twelve stars to continue in this fashion without any difficulty.

Now imagine the same constellation without a real central mass. Again we consider the ring of stars to be initially, at some instant, having a motion that can be considered as rotating about their centre of mass. Can you visualise this being stable and to continue to rotate with the same configuration - I cannot.

We can do a bit of analysis of this and see what we can tweak out. The barycentre - or centre of mass for this system (which has no real central mass) - is bang on centre. We can consider that point as a point-mass of 12 stellar masses when considering another point mass some distance away so we can predict its trajectory with respect to our constellation.

However, if we consider one star of the constellation we cannot compute the gravitational force between that and the centre of mass of the whole. This force is proportional to the product of the two masses under mutual attraction and, in this case, one twelfth of the centre of mass really belongs to the star under investigation. We've accounted for this mass twice and we can't have a star being attracted to itself somewhere else.

Okay - now lets try and get out of this problem by considering the gravitational force between the same star - and the centre of mass of the other 11 stars. Well, that centre of mass is at a different location to the centre of mass of the twelve. The same will be true when we consider each star in turn and each would be orbiting a different point - and therefore can not orbit as a ring of stars. Further, the bigger we make the ring - the bigger the problem. We have - what should be a stable orbital configuration but it cannot be supported with your model.

Does that help?

BTW - I did follow up on the Fermi - bubbles - very interesting - but for another day.

Mark C.
12 years 2 months ago #87343

Please Log in or Create an account to join the conversation.

  • John37309
  • John37309's Avatar Topic Author
  • Offline
  • Proto Star
  • Proto Star
  • Posts: 50
  • Thank you received: 0

Replied by John37309 on topic Re:Black holes - Are they real?

The EU flag stars scenario. I can visualise in a much simpler way.

Put your 12 stars floating in the kitchen sink with the water flowing down the drain in the middle. With the large mass in the middle, the "cone" shape of the sink is very deep and stars fall down the drain quicker. With no large mass in the centre, the "cone" shape of the sink would just be flatter and the stars would just take longer to go down the plug hole.

Either way, i think i made my point here. I think i have clarified in my own mind that my assumption could well be true. I just wanted to see if anyone else agreed and could see the point i was making.

As much as we think we have solved many of the problems in physics today, i think we are only at the tip of the iceberg.

Thanks Mark,
John.
Last edit: 12 years 2 months ago by John37309.
12 years 2 months ago #87344

Please Log in or Create an account to join the conversation.

Time to create page: 0.051 seconds
Powered by Kunena Forum