APOD: Too Close to a Black Hole (2014 Oct 26)

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APOD: Too Close to a Black Hole (2014 Oct 26)

Post by APOD Robot » Sun Oct 26, 2014 4:06 am

Image Too Close to a Black Hole

Explanation: What would you see if you went right up to a black hole? Featured is a computer generated image highlighting how strange things would look. The black hole has such strong gravity that light is noticeably bent towards it - causing some very unusual visual distortions. Every star in the normal frame has at least two bright images - one on each side of the black hole. Near the black hole, you can see the whole sky - light from every direction is bent around and comes back to you. The original background map was taken from the 2MASS infrared sky survey, with stars from the Henry Draper catalog superposed. Black holes are thought to be the densest state of matter, and there is indirect evidence for their presence in stellar binary systems and the centers of globular clusters, galaxies, and quasars.

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Re: APOD: Too Close to a Black Hole (2014 Oct 26)

Post by userloser » Sun Oct 26, 2014 6:03 am


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Re: APOD: Too Close to a Black Hole (2014 Oct 26)

Post by MarkBour » Sun Oct 26, 2014 6:13 am

Very nice. I wonder how detailed is the computer simulation of the light sources and paths here. It may have taken some serious work to generate this. One thing I'm wondering about. There should be light that is almost trapped but barely escapes, sometimes after multiple trips around the sphere. I would expect all the light as you approach the visual boundary to be more and more red-shifted. And in fact, the region should give off some infrared and microwave as a result. So, I would think that near the darkness, there is a "fade" to it.

Also, I wonder what actual radius was used for the simulated black hole, and how close the imagined observer is to it to get that visual size as shown. I am a bit suspicious (without yet thinking of how to work it out in any detail), that by the time one is able to "resolve" the disk of a black hole, one may already be in serious danger.
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Re: APOD: Too Close to a Black Hole (2014 Oct 26)

Post by Guest » Sun Oct 26, 2014 1:04 pm

MarkBour wrote:There should be light that is almost trapped but barely escapes, sometimes after multiple trips around the sphere. I would expect all the light as you approach the visual boundary to be more and more red-shifted. And in fact, the region should give off some infrared and microwave as a result. So, I would think that near the darkness, there is a "fade" to it.
Agreed... With proximity to the horizon, the 'point sources of light' should become 'streaks of light' with a brighter point source at the end of the 'streak' but fading to black at the other end. As it is a computer simulation, I would assume that this aspect was overlooked in the coding of the program, and would have added greatly to the generated image. Still an impressive effort in any case, and I look forward to the next iteration of the team responsible for it.

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Re: APOD: Too Close to a Black Hole (2014 Oct 26)

Post by emanueldewitt » Sun Oct 26, 2014 2:38 pm

Not one star between the Black Hole and the Observer?
If the star in between is close to the BH, would the BH attract ALL light from the star?
Don't see why, and don't believe that.
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Re: APOD: Too Close to a Black Hole (2014 Oct 26)

Post by Chris Peterson » Sun Oct 26, 2014 3:02 pm

emanueldewitt wrote:Not one star between the Black Hole and the Observer?
If the star in between is close to the BH, would the BH attract ALL light from the star?
Don't see why, and don't believe that.
We're far too close to this black hole for there to be a star between it and the observer. Are you wondering why there's no star, or why there's no image of a star deflected from some other part of the sky?
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Re: APOD: Too Close to a Black Hole (2014 Oct 26)

Post by ta152h0 » Sun Oct 26, 2014 9:19 pm

re black holes still considered a singularity ? And has the star movement been deciphered at the center of our own galaxy ?
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Re: APOD: Too Close to a Black Hole (2014 Oct 26)

Post by MikeS » Sun Oct 26, 2014 9:41 pm

We're far too close to this black hole for there to be a star between it and the observer.
Maybe that was the intent, but it looks extremely artificial. The perfectly rounded circle looks fake as well.

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Re: APOD: Too Close to a Black Hole (2014 Oct 26)

Post by Chris Peterson » Sun Oct 26, 2014 9:48 pm

MikeS wrote:
We're far too close to this black hole for there to be a star between it and the observer.
Maybe that was the intent, but it looks extremely artificial. The perfectly rounded circle looks fake as well.
Well, we're looking at the darkest, roundest thing in nature, something with no edge to scatter light. I don't know what else it would look like.
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Re: APOD: Too Close to a Black Hole (2014 Oct 26)

Post by Boomer12k » Sun Oct 26, 2014 11:06 pm

A primary building block of galaxies, then.....

I'm feeling a bit "BENT" myself. My own mass affecting Spacetime.
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Re: APOD: Too Close to a Black Hole (2014 Oct 26)

Post by Boomer12k » Sun Oct 26, 2014 11:17 pm

userloser wrote:In case someone missed it.

http://www.wired.com/2014/10/astrophysi ... lack-hole/

IF...a Black Hole looked like that....we would be able to SEE ALL OF THEM.....no doubt....and then they would not be called "Black Holes"...but AWESOME HOLES..... :D

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Re: APOD: Too Close to a Black Hole (2014 Oct 26)

Post by LocalColor » Sun Oct 26, 2014 11:36 pm

Boomer12k wrote:A primary building block of galaxies, then.....

I'm feeling a bit "BENT" myself. My own mass affecting Spacetime.
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:lol2:

You reminded me of our "gravity" cat. He seems to have more mass when you want the chair he is sitting in.

The image today really draws me in....

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Re: APOD: Too Close to a Black Hole (2014 Oct 26)

Post by alter-ego » Mon Oct 27, 2014 12:39 am

Boomer12k wrote:
userloser wrote:In case someone missed it.

http://www.wired.com/2014/10/astrophysi ... lack-hole/

IF...a Black Hole looked like that....we would be able to SEE ALL OF THEM.....no doubt....and then they would not be called "Black Holes"...but AWESOME HOLES..... :D

:---[===] *
It's likely that most do look something like that, at least if the simulations are reasonably accurate and if you're looking a the accretion disk nearly edge on.

The APOD shows the simplest BH condition: Non-rotating and no accretion disk. This case is probably not the norm. Today, the primary point of interest is the visible field distortion around a black hole using an actual star field in the simulation. The more general BH cases have frame dragging (spatial distortion due to rotation) and a messy accretion disk (that you probably can't see through anyway).

The video below show a nice simulation of viewing black hole with accretion disk (fixed view angle) and key feature descriptions. The link at the bottom takes you to a simulation showing an accretion disk ad different inclination angles (as well as intensity line-profiles at different angles). Userloser's wired.com image shows something close to what you find in that link.
Click to play embedded YouTube video.
http://jila.colorado.edu/~pja/black_hole.html
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Re: APOD: Too Close to a Black Hole (2014 Oct 26)

Post by Guest » Mon Oct 27, 2014 2:17 am

Chris Peterson wrote:
MikeS wrote:
We're far too close to this black hole for there to be a star between it and the observer.
Maybe that was the intent, but it looks extremely artificial. The perfectly rounded circle looks fake as well.
Well, we're looking at the darkest, roundest thing in nature, something with no edge to scatter light. I don't know what else it would look like.
Well, possibly the gravity well of a black hole is able to partially capture light from 360/360 degree directions that is able to spiral out of the gravity well because it was just not close enough to be caught. Logically, a 'black hole' (or the 'surface' just just outside the event horizon) seen from close up may appear fairly bright, if not brilliant, from the distance shown. And appearances of such a gravity well may appear non-circular given the variety of light sources perceived from source. Really, we must consider all possibilities, not just assume an 'all round knowledge' of all things that require imagination and insight of other possible explanations.

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Re: APOD: Too Close to a Black Hole (2014 Oct 26)

Post by alter-ego » Mon Oct 27, 2014 3:52 am

Guest wrote: ...
Well, possibly the gravity well of a black hole is able to partially capture light from 360/360 degree directions that is able to spiral out of the gravity well because it was just not close enough to be caught. Logically, a 'black hole' (or the 'surface' just just outside the event horizon) seen from close up may appear fairly bright, if not brilliant, from the distance shown. And appearances of such a gravity well may appear non-circular given the variety of light sources perceived from source. Really, we must consider all possibilities, not just assume an 'all round knowledge' of all things that require imagination and insight of other possible explanations.
Given the simplest Schwarzschild black hole, the mathematics describing all the observed phenomena (in the APOD) is on solid ground within the framework of general relativity, including non-circular Einstein Rings. I'm not sure what you meant about "may appear non-circular given the variety of light sources perceived from source". Extended, non-circular light sources behind the black hole are distorted in a very predictable way, and in fact visible in the image. Assuming no accretion process, as is the case for this APOD, no photons can escape so that they appear from within the black region. (But how fuzzy are the edges?)

Although future observations and data approaching 1.5 Schwarzschild Radii (we currently have none) may reveal new phenomena that require revisiting GR, there is no data today to suggest anything "out of the ordinary" :D The current GR theory is holding strong and not cracking yet. I'm anxiously awaiting the start of upcoming VLBI observations of the Sag A* (Milky Way's BH) event horizon (or at least to the Innermost Stable Circular Orbit). The telescope consortium is the Event Horizon Telescope a good S&T article about it can be found here.
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Re: APOD: Too Close to a Black Hole (2014 Oct 26)

Post by geckzilla » Mon Oct 27, 2014 4:04 am

Guest wrote:Well, possibly the gravity well of a black hole is able to partially capture light from 360/360 degree directions that is able to spiral out of the gravity well because it was just not close enough to be caught. Logically, a 'black hole' (or the 'surface' just just outside the event horizon) seen from close up may appear fairly bright, if not brilliant, from the distance shown. And appearances of such a gravity well may appear non-circular given the variety of light sources perceived from source. Really, we must consider all possibilities, not just assume an 'all round knowledge' of all things that require imagination and insight of other possible explanations.
This picture is already made using known theory, logic, and not assumptions. Adding imagination or guessing would only make it less accurate. It might be possible to make it more "realistic" with an improved simulated environment but that's a fault of the simulated environment and not the simulated physics of the black hole itself.
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Re: APOD: Too Close to a Black Hole (2014 Oct 26)

Post by Roland » Mon Oct 27, 2014 1:32 pm

If you are too close to the black hole for there to be a star between, then why is there no gravitational lensing in the background stars. you can't have it both ways.
Nice image.

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Re: APOD: Too Close to a Black Hole (2014 Oct 26)

Post by Chris Peterson » Mon Oct 27, 2014 2:13 pm

Roland wrote:If you are too close to the black hole for there to be a star between, then why is there no gravitational lensing in the background stars. you can't have it both ways.
Nice image.
Let's see. Do I go with a rigorous mathematical simulation by people who are experts in general relativity and tensor calculus, or do I go with your gut feeling?
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Re: APOD: Too Close to a Black Hole (2014 Oct 26)

Post by Ron-Astro Pharmacist » Mon Oct 27, 2014 3:42 pm

In "Black Holes Explained" , Alex Filippenko describes a simulation Robert Nemiroff developed to show a black holes effect on space time. I was happy to see it referred to again under the link "visual distortions." I also noticed, while looking for it myself, Dr. Nemiroff's efforts to further astronomy education and research had been recognized by Michigan Tech's Research Magazine back in 2013.

http://www.mtu.edu/research/archives/ma ... rch-award/

"Quote from above link" - The passion for education and outreach evident in the Astronomy Picture of the Day manifests itself throughout Nemiroff’s working life. “He really cares about teaching,” said Jay Norris of Boise State University. “Bob’s quest to understand Nature—and transfer that understanding to others—is unflagging.”

It's great to see that his influence has reached our neck of the woods. Many cudos!!
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Re: APOD: Too Close to a Black Hole (2014 Oct 26)

Post by morr » Mon Oct 27, 2014 4:57 pm

Boomer12k wrote:
userloser wrote:In case someone missed it.

http://www.wired.com/2014/10/astrophysi ... lack-hole/

IF...a Black Hole looked like that....we would be able to SEE ALL OF THEM.....no doubt....and then they would not be called "Black Holes"...but AWESOME HOLES..... :D

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They're too small to see at any distance. Even the SMBH at the center of the galaxy has an event horizon smaller than our solar system. Stellar mass black holes would be tinier (planet sized). Get close enough to one, and it may look something like that.

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Re: APOD: Too Close to a Black Hole (2014 Oct 26)

Post by Ron-Astro Pharmacist » Mon Oct 27, 2014 6:38 pm

It's odd that Leonard Susskind used this exact same illustration of a black hole in his lecture "The World As Hologram."

https://www.youtube.com/watch?feature=p ... DIl3Hfh9tY


I've never understood why they depict material falling into a black hole as going down. Is that just a random direction because we perceive gravity as pulling something downhill? It seems to me that it's just as rational to have it go up or sideways or all directions simultaneously. :?:
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Re: APOD: Too Close to a Black Hole (2014 Oct 26)

Post by geckzilla » Mon Oct 27, 2014 6:49 pm

Ron-Astro Pharmacist wrote:I've never understood why they depict material falling into a black hole as going down. Is that just a random direction because we perceive gravity as pulling something downhill? It seems to me that it's just as rational to have it go up or sideways or all directions simultaneously. :?:
I'm not sure what you mean. Falling into any gravity well, even a black hole, is still falling. The same thing happens on Earth, even if the scale is so large we don't think that someone falling in Australia is moving "up" relative to someone in Canada.
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Re: APOD: Too Close to a Black Hole (2014 Oct 26)

Post by ta152h0 » Mon Oct 27, 2014 8:00 pm

Wolf Kotenberg

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Re: APOD: Too Close to a Black Hole (2014 Oct 26)

Post by Ron-Astro Pharmacist » Mon Oct 27, 2014 8:13 pm

geckzilla wrote:
Ron-Astro Pharmacist wrote:I've never understood why they depict material falling into a black hole as going down. Is that just a random direction because we perceive gravity as pulling something downhill? It seems to me that it's just as rational to have it go up or sideways or all directions simultaneously. :?:
I'm not sure what you mean. Falling into any gravity well, even a black hole, is still falling. The same thing happens on Earth, even if the scale is so large we don't think that someone falling in Australia is moving "up" relative to someone in Canada.
When trying to simulate a black hole's or any gravity, one way to depict the thought is to use as picture such as:
gravity.jpg

I was asking wouldn't the "falling in" really be occurring in all directions; not just down as in the picture? I know the above is just an attempt to visualise the concept but when used over and over I wonder if we, perhaps, misrepresent the spacetime distortion in our minds to be uni-directional.
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Re: APOD: Too Close to a Black Hole (2014 Oct 26)

Post by geckzilla » Mon Oct 27, 2014 8:20 pm

I have no doubt that my brain's attempt at conceptualizing spacetime fails utterly but I'm still not understanding what you mean. Instead of thinking about it spatially, think of it in terms of potential energy.
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