Starship Asterisk*

by **Chris Peterson** » Wed Aug 01, 2007 2:49 pm

starnut wrote:A suspected isolated black hole was supposedly discovered a few years ago when some astronomers noticed a small star suddenly brightened and then dimmed. It wasn't a white dwarf going nova. I can't remember offhandedly where it was reported. Of course, this claim was questioned, but finding a black hole by noticing the brightening due to gravitational lensing is still one way to do it.

Gravitational lensing could potentially be used to identify a black hole, but there's no strong evidence that we've ever seen one this way.

starnut wrote:As for gas and dust falling into the black hole, that happens only if the black hole is either a member of a close binary system, in which it is drawing matter off its companion star (usually a red giant), or a supermassive black hole at the center of a galaxy. I was talking about an isolated stellar mass black hole.

Understood. My point was that every black hole we know of falls in this category. We only consistently see black holes that make their presence known by the radiation produced by infalling material.

by **manta01** » Wed Aug 01, 2007 3:34 am

the reason I even thought it was something is if you view that one star, that black pixel stands out without even magnifying it. which was was made me notice it in the first place. and when you zoom in using the MS picture program, when you get to a certain depth it looks as if the "spec" is uniform in some fashion with a ring around it. But again I know a great deal about lossfull and loss less graphics that is why I wanted some more opinions... and again thanks very much for all the feedback, I feel edjumacated (smile)..

by **starnut** » Wed Aug 01, 2007 2:56 am

Chris Peterson wrote: I don't think there's any case of a black hole being seen as a silhouette. They are just too small, even if one did happen to pass right in front of a star (which itself is unlikely). Black holes are detected indirectly, by the radiation emitted by gas and dust falling into them. Such radiation can be very intense. In practice, all the black holes we know of are pretty bright objects. It doesn't matter that we can't see the very central part.

A suspected isolated black hole was supposedly discovered a few years ago when some astronomers noticed a small star suddenly brightened and then dimmed. It wasn't a white dwarf going nova. I can't remember offhandedly where it was reported. Of course, this claim was questioned, but finding a black hole by noticing the brightening due to gravitational lensing is still one way to do it.

As for gas and dust falling into the black hole, that happens only if the black hole is either a member of a close binary system, in which it is drawing matter off its companion star (usually a red giant), or a supermassive black hole at the center of a galaxy. I was talking about an isolated stellar mass black hole.

by **zeilouz** » Tue Jul 31, 2007 7:07 am

Okay,now i get the point,thx a lot..!

Hmmm..it does make sense to me..n learnt something new today..unless we can a closer image of the "blackhole"..

by **Chris Peterson** » Tue Jul 31, 2007 3:34 am

starnut wrote: You can detect a solitary black hole only when one passes in front of a bright background object, such as a star.

I don't think there's any case of a black hole being seen as a silhouette. They are just too small, even if one did happen to pass right in front of a star (which itself is unlikely). Black holes are detected indirectly, by the radiation emitted by gas and dust falling into them. Such radiation can be very intense. In practice, all the black holes we know of are pretty bright objects. It doesn't matter that we can't see the very central part.

by **starnut** » Tue Jul 31, 2007 1:41 am

zeilouz wrote:Black holes are transparent,arent they..?how can u detect them..?if there was a black hole..some of the pictures might be black due to the gravitational force that sucks all the matter around the black hole..

Hmmm..cant see it though..@@

If by transparent, you mean being able to see the background objects through it, the answer is no. It is called BLACK hole for a reason: all light that enters the black hole stays there. NONE will come out.

You can detect a solitary black hole only when one passes in front of a bright background object, such as a star. If you get close to one (not too close or you will be sucked in!), you might see a bright ring around it due to lights from stars being bent by the strong gravitation force. You might also be able to detect it with an infra-red detector due to thermal radiation, called Hawking radiation, being emitted just outside the event horizon. However, that remains theoretical. Anyone, correct me if I am wrong!

by **Qev** » Mon Jul 30, 2007 8:47 pm

makc wrote:
Qev wrote:If you draw a line along the plane of NGC 3628 heading towards the upper left of the picture...
Why dont YOU draw it, and post it?

I'm lazy?

by **BMAONE23** » Mon Jul 30, 2007 2:46 pm

makc wrote:
Qev wrote:If you draw a line along the plane of NGC 3628 heading towards the upper left of the picture...
Why dont YOU draw it, and post it?

I believe this is what Qev was refering to, It is between the 09:00 & 10:00 positions

by **zeilouz** » Mon Jul 30, 2007 9:48 am

Yupz..great idea..that should be great deal of help to any viewers of this topic..can someone draw it..?

by **makc** » Mon Jul 30, 2007 9:41 am

Qev wrote:If you draw a line along the plane of NGC 3628 heading towards the upper left of the picture...

Why dont YOU draw it, and post it?

by **zeilouz** » Mon Jul 30, 2007 9:13 am

Black holes are transparent,arent they..?how can u detect them..?if there was a black hole..some of the pictures might be black due to the gravitational force that sucks all the matter around the black hole..

Hmmm..cant see it though..@@

by **Qev** » Sun Jul 29, 2007 7:31 am

Astronomers have apparently imaged the surfaces of a few other stars, Altair, Mira, and Vega among them, or so I understand...

by **starnut** » Sun Jul 29, 2007 1:40 am

I doubt that is a black hole because what you called the corona of the star is just the overexposed image of the bright star spilling over to adjacent pixels. So the black hole couldn't be seen there. All stars except one (that I know of) can be seen only as points even through the largest telescopes. That one exception is Betelgeuse, the nearest red supergiant about 600 ly away.

http://apod.nasa.gov/apod/ap990605.html

I read somewhere that the only way to detect a stellar mass black hole is when one passes in front of a background star, causing the star to brighten due to gravitational lensing.

by **kfsone** » Sat Jul 28, 2007 6:44 am

Do you mean this on the right?

http://www.kfs.org/~oliver/blackspots.jpg

I marked the item on the left wondering if perhaps it was some foreground molecular cloud or something.

Remember jpeg is lossy - there are a lot of artefacts in the APOD picture as a result, and these both seem candidates.

by **BMAONE23** » Sat Jul 28, 2007 5:35 am

here's the link
http://antwrp.gsfc.nasa.gov/apod/image/ ... mandel.jpg

good eyes to spot that

by **Qev** » Sat Jul 28, 2007 4:20 am

http://antwrp.gsfc.nasa.gov/apod/ap070727.html

Okay, I know it's probably not a gravitational lens, but it does sort of look like one! If you draw a line along the plane of NGC 3628 heading towards the upper left of the picture, you'll quickly come to a bright, reddish foreground star. Straight down from that a short ways is another, somewhat dimmer foreground star with what looks like the image of a background galaxy 'wrapped' around its right side. Looks suspiciously lens-like.

I daresay it's probably just a chance alignment between a foreground star and a distorted background galaxy.

by **rigelan** » Sat Jul 28, 2007 3:44 am

Looks like a single missing pixel to me.

by **manta01** » Sat Jul 28, 2007 3:26 am

I think i found a black hole in the Astronomy picture of the day, its definitely something on the picture near a star, It may be a smudge in the glass of the telescope? or something, its in the upper right corner of the picture. the anamoly is in the corona of one of the stars in the lower left part of the corona of the star.
if you take the three star cluster and go left.. three large stars, the third large star looks to have a "smudge" in the lower part of the corona. You draw your own conclusions?

by **harry** » Fri Jul 27, 2007 12:30 pm

p1gnone wrote:regarding the The Tidal Tail of NGC 3628 of July 27: who was the galaxy that stretched the tail out? Is it out of the view of this image, or due to a no longer obvious motion of one of the other 2 [m65 m66] galaxies in the triplet?

Hello

Maybe this link may help you find

http://burro.cwru.edu/JavaLab/GalCrashWeb/links.html

This image is great

http://astrosurf.com/antilhue/m65_m66.htm

http://antwrp.gsfc.nasa.gov/apod/ap060108.html

http://www.galaxyimages.com/NGC3628.html

This image of NGC 3628 is the result of 12 hours of exposure time to bring out the faint tidal tail. The tail is the result of interaction with two nearby galaxies, M65 and M66.
You can read more about this in this Astronomical Journal article.

http://www.journals.uchicago.edu/AJ/jou ... 37999Guest

by **p1gnone** » Fri Jul 27, 2007 11:31 am

http://apod.nasa.gov/apod/ap070727.html

regarding the The Tidal Tail of NGC 3628 of July 27: who was the galaxy that stretched the tail out? Is it out of the view of this image, or due to a no longer obvious motion of one of the other 2 [m65 m66] galaxies in the triplet?

Starship Asterisk*

APOD: The Tidal Tail of NGC 3628 (2007 Jul 27)

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Expand view Topic review: APOD: The Tidal Tail of NGC 3628 (2007 Jul 27)

oh and,

Re: Gravitational lens in 2007-07-27 APOD?

Re: Gravitational lens in 2007-07-27 APOD?

Re: Gravitational lens in 2007-07-27 APOD?

Gravitational lens in 2007-07-27 APOD?

a black hole in the 7/27 image?

APOD: The Tidal Tail of NGC 3628 (2007 Jul 27)