Hubble directly observes the disc around a black hole

Nov 04, 2011
This picture shows a quasar that has been gravitationally lensed by a galaxy in the foreground, which can be seen as a faint shape around the two bright images of the quasar. Observations of one of the images show variations in color over time. This is caused by stars within the lens galaxy passing through the path of the light from the quasar, magnifying the light from different parts of the quasar's accretion disc as they move. This has allowed a team of scientists to reconstruct the color and temperature profile of the accretion disc with unprecedented precision. The level of detail involved is equivalent to being able to study individual grains of sand on the surface of the Moon while standing on Earth. Credit: NASA, ESA and J.A. Muñoz (University of Valencia)

(PhysOrg.com) -- Scientists have used the NASA/ESA Hubble Space Telescope to observe a quasar accretion disc -- a glowing disc of matter that is slowly being sucked into its galaxy's central black hole. Their study makes use of a novel technique that uses gravitational lensing to give an immense boost to the power of the telescope. The precision of the method has allowed astronomers to directly measure the disc's size and temperature across different parts of the disc.

An international team of astronomers has used a new technique to study the bright disc of matter surrounding a faraway black hole. Using the /ESA , combined with the effect of stars in a , the team measured the disc's size and studied the colours (and hence the temperatures) of different parts of the disc. These observations show a level of precision equivalent to spotting individual grains of sand on the surface of the Moon.

While black holes themselves are invisible, the forces they unleash cause some of the brightest phenomena in the . Quasars — short for quasi-stellar objects — are glowing discs of matter that orbit supermassive , heating up and emitting extremely bright radiation as they do so.

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The accretion discs around supermassive black holes are too distant and too small to observe using conventional methods. However, by combining gravitational macrolensing by an intermediate galaxy, and gravitational microlensing by stars within that galaxy, astronomers are able to probe the structure of these discs. This video explains the method used. The video begins by showing a simulation of the view from Hubble, with the lens galaxy and bright lensed images of the quasar. It then rotates round to a view from the side, showing the relative positions of the objects and the path of the light beams as they are lensed by the galaxy. This is gravitational macrolensing. Note that the distances are shortened. The video then zooms into three different points: The accretion disc at the heart of the quasar, the point at which the quasar’s light passes through the lens galaxy, and the view from Earth’s orbit showing Hubble’s location. The beams of light coming from the accretion disc are bluer when they come from the centre of the disc, and redder when they come from the edges. This is because the centre of the disc, the part closest to the black hole, is much hotter than the edge. As a star passes through the path of the light, beams of light from different parts of the disc get deflected towards the telescope at different times: note how the cross-hairs scanning across the disc of the quasar matches the colour that is deflected towards the telescope at any given time. This is gravitational microlensing. This method can be used to observe the colour profile of the disc with unprecedented precision, comparable to being able to distinguish individual grains of sand on the surface of the Moon. Credit: NASA, ESA, L. Calçada

"A quasar accretion disc has a typical size of a few light-days, or around 100 billion kilometres across, but they lie billions of light-years away. This means their apparent size when viewed from Earth is so small that we will probably never have a telescope powerful enough to see their structure directly," explains Jose Muñoz, the lead scientist in this study.

Until now, the minute apparent size of quasars has meant that most of our knowledge of their inner structure has been based on theoretical extrapolations, rather than direct observations.

The team therefore used an innovative method to study the quasar: using the stars in an intervening galaxy as a scanning microscope to probe features in the quasar's disc that would otherwise be far too small to see. As these stars move across the light from the quasar, gravitational effects amplify the light from different parts of the quasar, giving detailed colour information for a line that crosses through the accretion disc.

The team observed a group of distant quasars that are gravitationally lensed by the chance alignment of other galaxies in the foreground, producing several images of the quasar.

They spotted subtle differences in colour between the images, and changes in colour over the time the observations were carried out. Part of these colour differences are caused by the properties of dust in the intervening galaxies: the light coming from each one of the lensed images has followed a different path through the galaxy, so that the various colours encapsulate information about the material within the galaxy. Measuring the way and extent to which the dust within the galaxies blocks light (known to astronomers as the extinction law) at such distances is itself an important result in the study.

For one of the quasars they studied, though, there were clear signs that stars in the intervening galaxy were passing through the path of the light from the quasar. Just as the gravitational effect due to the whole intervening galaxy can bend and amplify the quasar's light, so can that of the stars within the intervening galaxy subtly bend and amplify the light from different parts of the accretion disc as they pass through the path of the quasar's light.

By recording the variation in colour, the team were able to reconstruct the colour profile across the accretion disc. This is important because the of an accretion disc increases the closer it is to the black hole, and the colours emitted by the hot matter get bluer the hotter they are. This allowed the team to measure the diameter of the disc of hot matter, and plot how hot it is at different distances from the centre.

They found that the disc is between four and eleven light-days across (approximately 100 to 300 billion kilometres). While this measurement shows large uncertainties, it is still a remarkably accurate measurement for a small object at such a great distance, and the method holds great potential for increased accuracy in the future.

"This result is very relevant because it implies we are now able to obtain observational data on the structure of these systems, rather than relying on theory alone," says Muñoz. "Quasars' physical properties are not yet well understood. This new ability to obtain observational measurements is therefore opening a new window to help understand the nature of these objects."

Explore further: 'Eye of Sauron': Using supermassive black holes to measure cosmic distances

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User comments : 18

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hemitite
5 / 5 (4) Nov 04, 2011
I did a quick calculation using the grain-of-sand-on-the-moon comparison from the article and came up with a resolution for this method of about 1/1000 of an arc second. Wow!
Temple
not rated yet Nov 04, 2011
Kinda nice when you've got a galactic scale lens on your 'telescope'!
rah
1 / 5 (2) Nov 04, 2011
Did I miss the estimated distance of the quasar? Why would they not include that? It just said that it was "far away" and "distant". I jumped ahead of them and assumed that.
Simonsez
2 / 5 (1) Nov 04, 2011
@ rah
You did miss the estimated distance. From the article:
"A quasar accretion disc has a typical size of a few light-days, or around 100 billion kilometres across, but they lie billions of light-years away.
yyz
4.6 / 5 (10) Nov 04, 2011
@rah

"Did I miss the estimated distance of the quasar?"

The distance wasn't mentioned in the ESA press release, but the paper this story is based on gives a redshift for this quasar (HE1104-1805) of z=2.32, or about 11 Gly. The lensing galaxy is at z=0.73, approximately 6.5 Gly:

http://www.spacet...1116.pdf
roboferret
3.7 / 5 (3) Nov 04, 2011
No Omatumr? He's usually onto articles like this like a tramp on chips. I'm almost curious about how he'll handbrake turn round this one, black holes not existing and all. He'd probably just post irrelevant links to bizarre unrelated documents as usual. *nostalgic sigh*
vidyunmaya
1 / 5 (11) Nov 05, 2011
Any Data and progress beyond Black-hole concept helps spirit of Science through Astronomy to catch-up with Cosmological Index and Cosmology vedas Interlinks-Vidyardhi Nanduri
vidyunmaya
1 / 5 (11) Nov 05, 2011
the Drive function must be clear and not the upside down dogmatic logic. see Cosmology Definition in http://vidyardhic...pot.com/
Rohitasch
5 / 5 (2) Nov 05, 2011
No Omatumr? He's usually onto articles like this like a tramp on chips. I'm almost curious about how he'll handbrake turn round this one, black holes not existing and all. He'd probably just post irrelevant links to bizarre unrelated documents as usual. *nostalgic sigh*

Well, you have another one here saying things just as vague!
pauljpease
4.5 / 5 (8) Nov 05, 2011
Any Data and progress beyond Black-hole concept helps spirit of Science through Astronomy to catch-up with Cosmological Index and Cosmology vedas Interlinks-Vidyardhi Nanduri


Do any of you ever get the feeling like artificial intelligence is emerging from the internet and it is learning to speak by interacting with humans on forums like this? Like a baby babbling as it learns to communicate? Just wondering...
Twin
1 / 5 (1) Nov 05, 2011
Can anyone explain the squarish look of the image? I've seen vertical spikes in oncoming headlights during ice fog. Could this be similar?
omatumr
1 / 5 (11) Nov 06, 2011
a glowing disc of matter that is slowly being sucked into its galaxy's central black hole


That explains why the universe is contracting?

Or is that just the usual "doublespeak"? [a]

Are we in a full scale information war, as the founders of Wikileaks [b] and PrisonPlanet [c] suggest?

References:

[a] George Orwell's book, "1984"

www.online-litera...ll/1984/

[b] Wikileaks

http://wikileaks.org/

[c] PrisonPlanet

www.prisonplanet.com/

www.nytimes.com/2...ing.html

With kind regards,
Oliver K. Manuel
Former NASA Principal
Investigator for Apollo
http://myprofile....anuelo09

Ethelred
3.9 / 5 (7) Nov 06, 2011
Again Oliver attacks the honesty of all that disagree with his theory.

According to you Neutron repulsion stops the formation of Black Holes. If Black Holes are stopped by NR then Neutron stars couldn't exist either. Of course there are all those claims that NR is causing galaxies to fragment and you spammed the site with that dozens of times.>>

If it has the range to fragment galaxies and the strength and range to block the formation of ANY black holes then it not only is strong enough to stop the formation of neutron stars but also ANYTHING that is held together by gravity.

For NR to stop the formation of Black Holes and cause the fragmentation of galaxies then it is stronger than gravity at both the range of a dozen kilometers and at kiloparsecs. This means that not only does it shatter galaxies but they could not form in first place. Planets could not form and ALL gravity bound objects would be sundered by this hypothetical galaxy busting Black Hole blocking force.

Ethered
yyz
3.7 / 5 (3) Nov 06, 2011
@Twin

"Can anyone explain the squarish look of the image? I've seen vertical spikes in oncoming headlights during ice fog. Could this be similar?"

For the most part, the artefacts you see result from image processing routines (deconvolution, etc) applied to the images during analysis. The "spikes" are caused by light diffraction by the four vanes that support the secondary mirror of the HST. These effects are not physically associated with the objects being imaged.
dwickizer
not rated yet Nov 06, 2011
For the most part, the artefacts you see result from image processing routines (deconvolution, etc) applied to the images during analysis. The "spikes" are caused by light diffraction by the four vanes that support the secondary mirror of the HST. These effects are not physically associated with the objects being imaged.


Agreed. This is reminiscent of the 2D Bessell function patterns one sees when shining a highly collimated laser through a square filter and a convex lens.

Twin
1 / 5 (1) Nov 07, 2011
TY YYZ
SteveL
not rated yet Nov 11, 2011
The HST is still an awesome bit of space engineering that I'd like to see maintained and kept in use for the next 20 plus years.
MarkyMark
not rated yet Nov 12, 2011
my roomate's sister makes $68 every hour on the computer. She has been without a job for 6 months but last month her pay was $8123 just working on the computer for a few hours. Read about it on this web site doiop.com/hzjnom

Hate to say it to you bro, but your roomates sister is a Ho! And. Cheap one too at $68 per hour!

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