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Re: APOD: The Jets of NGC 1097 (2013 Nov 14)
Posted: Fri Nov 15, 2013 5:15 am
by Chris Peterson
ems57fcva wrote:That ring has all of the hallmarks of an accretion disk in so far as I am concerned. What makes an accretion disk? Is it not the angular momentum of a large enough amount of gas and dust getting squeezed together as it heads into a central object?
The material needs to behave like a fluid- you need a high density so that there is viscous interaction and transfer of angular momentum. The largest accretion discs, around the black holes in AGNs, are measured in AUs. The structure in this galaxy is thousands of light years across. A structure that size with the density required to create an accretion disc would have the mass of many galaxies. A central black hole with the mass to have significant gravitational influence at that distance would have the mass of hundreds of galaxies.
There's simply no way that what we're seeing is an accretion disc. I think it's nothing more than a ring of active star formation, something not uncommonly seen in galaxies.
Re: APOD: The Jets of NGC 1097 (2013 Nov 14)
Posted: Fri Nov 15, 2013 5:57 am
by ems57fcva
geckzilla wrote:
Dude, it's just a galaxy. Accretion discs are too small to ever image directly. Go ahead and search for pictures. You won't find anything but concept art.
Then what would you say that the ring is around the center is?
Also, I will direct you to
http://en.wikipedia.org/wiki/Accretion_disc which has an HST picture of a possible accretion disk in another galaxy. The issue is not whether that thing can be an accretion disk, but rather what it would take to form and sustain in. Given enough infalling mass, you can easily have an accretion disk that big. I am wondering what that rate is, and if it is sustainable.
Re: APOD: The Jets of NGC 1097 (2013 Nov 14)
Posted: Fri Nov 15, 2013 6:07 am
by geckzilla
The keyword for that picture is may. It could also just as easily be stuff orbiting the black hole. Stuff just doesn't fall into black holes at the rate you are imagining. They don't swallow entire galaxies or even small parts of galaxies. Also, read Chris's posts. Chris is smart and makes sense especially after about the third or fourth time you read his posts.
Re: APOD: The Jets of NGC 1097 (2013 Nov 14)
Posted: Fri Nov 15, 2013 6:11 am
by Chris Peterson
ems57fcva wrote:Then what would you say that the ring is around the center is?
There is no ring. You are seeing two spiral arms which have star forming regions and young, hot stars in them.
That is a disc of cool dust, which only heats up and emits radiation near the central black hole. It is both vastly smaller than the structure you are looking at in NGC 1097, and looks nothing the same.
The issue is not whether that thing can be an accretion disk, but rather what it would take to form and sustain in. Given enough infalling mass, you can easily have an accretion disk that big.
No, you can't have an accretion disc anywhere near that size, and if you could, it would look nothing like that. The issue
is whether that thing can be an accretion disc, and the answer is no.
Re: APOD: The Jets of NGC 1097 (2013 Nov 14)
Posted: Fri Nov 15, 2013 6:13 am
by geckzilla
Oh, I almost forgot. Here is a link to an image of an ultra-closeup of that ring imaged by Hubble. As you can see, it's just a bunch of stars and stuff. Any accretion disk, if it is there, is smaller than a single pixel in the middle of the wee little core.
http://farm8.staticflickr.com/7059/6973 ... 4c89_o.jpg
Re: APOD: The Jets of NGC 1097 (2013 Nov 14)
Posted: Fri Nov 15, 2013 11:18 am
by Cousin Ricky
Ann wrote:I frankly can't spot jets 3 and 4 in today's APOD, but jets 1 and 2 are obvious.
I can see jet 3 very clearly. I cannot see jet 4.
Re: APOD: The Jets of NGC 1097 (2013 Nov 14)
Posted: Fri Nov 15, 2013 1:11 pm
by starsurfer
ems57fcva wrote:geckzilla wrote:
Dude, it's just a galaxy. Accretion discs are too small to ever image directly. Go ahead and search for pictures. You won't find anything but concept art.
Then what would you say that the ring is around the center is?
Also, I will direct you to
http://en.wikipedia.org/wiki/Accretion_disc which has an HST picture of a possible accretion disk in another galaxy. The issue is not whether that thing can be an accretion disk, but rather what it would take to form and sustain in. Given enough infalling mass, you can easily have an accretion disk that big. I am wondering what that rate is, and if it is sustainable.
The ring is what is known as a "circumnuclear starforming ring", which is found in quite a few galaxies. One of these is NGC 6951,
http://www.aanda.org/articles/aa/abs/20 ... h3186.html
You can read more about the one in NGC 1097 here:
http://iopscience.iop.org/0004-637X/736/2/129/
I think it's really confusing to call these features jets when they are clearly tidal streams/tails, they are tidal in origin and not jets of relativistic plasma as in M87 and other really active galaxies. Even scientific papers from the past 10 years have more or less concluded this. A paper about the features being the result of a minor merger:
http://iopscience.iop.org/0004-637X/585/1/281/
Re: APOD: The Jets of NGC 1097 (2013 Nov 14)
Posted: Fri Nov 15, 2013 1:17 pm
by geckzilla
starsurfer wrote:"circumnuclear starforming ring"
You don't say. That almost makes too much sense.
![Wink :wink:](./images/smilies/icon_wink.gif)
Re: APOD: The Jets of NGC 1097 (2013 Nov 14)
Posted: Fri Nov 15, 2013 1:51 pm
by Ray-Optics
Beyond wrote:I was waiting to see if anyone commented on the one in the 3 o'clock position that seems to make a 90' turn. I thought that was a bit strange. What in space makes right angles?
Exactly my question. I mean, whuh??
That should be the subject of a whole discussion if not a research project.
Re: APOD: The Jets of NGC 1097 (2013 Nov 14)
Posted: Fri Nov 15, 2013 3:03 pm
by neufer
Ray-Optics wrote:Beyond wrote:
I was waiting to see if anyone commented on the one in the 3 o'clock position that seems to make a 90' turn.
I thought that was a bit strange.
What in space makes right angles?
Exactly my question. I mean, whuh??
- A right angle is 90º (not 90')
![Arrow :arrow:](./images/smilies/icon_arrow.gif)
Re: APOD: The Jets of NGC 1097 (2013 Nov 14)
Posted: Fri Nov 15, 2013 3:37 pm
by Chris Peterson
neufer wrote:Ray-Optics wrote:Beyond wrote:
I was waiting to see if anyone commented on the one in the 3 o'clock position that seems to make a 90' turn.
I thought that was a bit strange.
What in space makes right angles?
Exactly my question. I mean, whuh??
- A right angle is 90º (not 90') :arrow:
But don't use ALT(167) to enter a degree symbol. It will not be represented properly in many browsers outside the U.S. A much better choice is ALT(0176), which will at least enter a proper Unicode symbol, accessible across many more languages. (Really, the forum code should replace either with the HTML escape character, °, but it doesn't seem to do that.)
Re: APOD: The Jets of NGC 1097 (2013 Nov 14)
Posted: Fri Nov 15, 2013 3:52 pm
by geckzilla
Weird, they aren't even the same symbol. 167 = º 0176 = °
I always forget what the dang code is and end up writing out the full word. It is totally possible to have a bbcode that will do the equivalent of °, though. I should have done this a long time ago!
90°
Re: APOD: The Jets of NGC 1097 (2013 Nov 14)
Posted: Fri Nov 15, 2013 3:55 pm
by neufer
Chris Peterson wrote:
But don't use ALT(167) to enter a degree symbol. It will not be represented properly in many browsers outside the U.S. A much better choice is ALT(0176), which will at least enter a proper Unicode symbol, accessible across many more languages. (Really, the forum code should replace either with the HTML escape character, °, but it doesn't seem to do that.)
That would explain why I have to do it in Notepad first and then copy it.
(I'm too old myself to learn a whole new set of numbers.)
Re: APOD: The Jets of NGC 1097 (2013 Nov 14)
Posted: Fri Nov 15, 2013 4:41 pm
by Beyond
90° Well, that's simple enough. Looks like the Asterisk has now entered the "Degree Correctness" program. After all, a degree is not always a degree.
Some degrees don't have either a ' or a °.
Re: APOD: The Jets of NGC 1097 (2013 Nov 14)
Posted: Fri Nov 15, 2013 5:17 pm
by neufer
Beyond wrote:
90° Well, that's simple enough.
Looks like the Asterisk has now entered the "Degree Correctness" program.
Ånn started it
Beyond wrote:
After all, a degree is not always a degree.
Some degrees don't have either a ' or a °.
Re: APOD: The Jets of NGC 1097 (2013 Nov 14)
Posted: Fri Nov 15, 2013 6:36 pm
by Beyond
But who started Ånn
![Question :?:](./images/smilies/icon_question.gif)
Re: APOD: The Jets of NGC 1097 (2013 Nov 14)
Posted: Fri Nov 15, 2013 6:45 pm
by quigley
Would "fossil star streams" be so perfectly straight, each one flaring outward as a jet would? And would they be so perfectly positioned to form an "X"? The structures seem to be so orderly, geometric, etc.
Btw, thanks for the lesson on how to type the degree symbol. For years I've been typing out "degree". This solves my problem.
Re: APOD: The Jets of NGC 1097 (2013 Nov 14)
Posted: Sat Nov 16, 2013 2:39 am
by Nitpicker
The angstrom or ångström is a unit of length equal to 10
−10 m. Its symbol is the Swedish letter Å. A typical wavelength of blue light is 4725 Å. But everybody knows about the angstrom and the colour blue.
The symbol for degrees is a royal pain in the bum to parse and convert between different hardware, software and even font definitions, given the difference between ASCII codes and the various, more modern Unicodes. I wonder if this is why Europeans favour gradians (gon) in some contexts? This makes 90 degrees equivalent to 100 gradians, 100 gon, or 100
g. Following this logic, it would make me happy if everyone would agree to specify 90 degrees as 90
d. Thanks in advance.
Edit: I'll change my avatar image if everyone agrees.
Re: APOD: The Jets of NGC 1097 (2013 Nov 14)
Posted: Sat Nov 16, 2013 4:22 am
by Beyond
I never knew about the angstrom and the color blue. I also can't type a 90 with a small d. If i copy/paste it, it comes out like this--> 90d. You can change your avatar to anything you want, as long as it's "allowed".
Re: APOD: The Jets of NGC 1097 (2013 Nov 14)
Posted: Sat Nov 16, 2013 4:46 am
by Nitpicker
Beyond wrote: I also can't type a 90 with a small d.
Use the "sup" tags for
superscript.
Re: APOD: The Jets of NGC 1097 (2013 Nov 14)
Posted: Sat Nov 16, 2013 4:50 am
by Nitpicker
Curiously, the word
Hooloovoo sounds a bit Scandinavian to me, too:
http://en.wikipedia.org/wiki/List_of_ra ... #Hooloovoo
Re: APOD: The Jets of NGC 1097 (2013 Nov 14)
Posted: Sat Nov 16, 2013 4:54 am
by Nitpicker
This is a test:
100 gradians = 100g = 90 degrees = 90 deg = 90° = 90d
(Thanks for making char tags parse "deg", geckzilla.)
Re: APOD: The Jets of NGC 1097 (2013 Nov 14)
Posted: Sat Nov 16, 2013 4:58 am
by geckzilla
Nitpicker wrote:This is a test:
100 gradians = 100g = 90 degrees = 90 deg = 90° = 90d
(Thanks for making char tags word on "deg", geckzilla.)
Char tags will work on any of these.
http://www.w3schools.com/tags/ref_entities.asp
To be honest, the [char] tag is a bit more awkward than simply using ampersand and semicolon but phpBB does have its limitations.
Re: APOD: The Jets of NGC 1097 (2013 Nov 14)
Posted: Sat Nov 16, 2013 7:21 am
by Beyond
90
d Well, how about that. Something else to not remember
![Laughing :lol2:](./images/smilies/asterisk_laugh.gif)
Re: APOD: The Jets of NGC 1097 (2013 Nov 14)
Posted: Fri Dec 20, 2013 6:09 pm
by Ron-Astro Pharmacist
Ron-Astro Pharmacist wrote:
Do active galatic bi-nuclei exist? Two supermassive black holes with dual jets. Get out your gravitational wave dectectors
http://www.nasa.gov/mission_pages/swift ... holes.html wrote:
Click to play embedded YouTube video.Zoom into Markarian 739, a nearby galaxy hosting two monster black holes.
Using NASA's Swift and Chandra, astronomers have shown that both black holes
are producing energy as gas falls into them. The object is only the second-known
binary active galactic nucleus within half-a-billion light-years. (Animation begins
with visible light view of Markarian 739 and transitions into an artistic rendering
of the two black holes. Credit: NASA's Goddard Space Flight Center)Nearby Galaxy Boasts Two Monster Black Holes, Both Active
NASA Swift, 06.10.11
<<A study using NASA's Swift satellite and the Chandra X-ray Observatory has found a second supersized black hole at the heart of an unusual nearby galaxy already known to be sporting one. The galaxy, which is known as Markarian 739 or NGC 3758, lies 425 million light-years away toward the constellation Leo. Only about 11,000 light-years separate the two cores, each of which contains a black hole gorging on infalling gas. The study will appear in a forthcoming issue of The Astrophysical Journal Letters.
"At the hearts of most large galaxies, including our own Milky Way, lies a supermassive black hole weighing millions of times the sun's mass," said Michael Koss, the study's lead author at NASA's Goddard Space Flight Center in Greenbelt, Md., and the University of Maryland in College Park (UMCP). "Some of them radiate billions of times as much energy as the sun."
Astronomers refer to galaxy centers exhibiting such intense emission as active galactic nuclei (AGN). Yet as common as monster black holes are, only about one percent of them are currently powerful AGN. Binary AGN are rarer still: Markarian 739 is only the second identified within half a billion light-years.
Since 2004, the Burst Alert Telescope (BAT) aboard Swift has been mapping high-energy X-ray sources all around the sky. The survey is sensitive to AGN up to 650 million light-years away and has uncovered dozens of previously unrecognized systems. Follow-up studies by Koss and colleagues published in 2010 reveal that about a quarter of the Swift BAT AGN were either interacting or in close pairs, with perhaps 60 percent of them poised to merge in another billion years. "If two galaxies collide and each possesses a supermassive black hole, there should be times when both black holes switch on as AGN," said coauthor Richard Mushotzky, professor of astronomy at UMCP. "We weren't seeing many double AGN, so we turned to Chandra for help."
For decades, astronomers have known that the eastern nucleus of Markarian 739 contains a black hole that is actively accreting matter and generating prodigious energy. The Chandra study shows that its western neighbor is too. This makes the galaxy one of the nearest and clearest cases of a binary AGN. The distance separating the two black holes is about a third of the distance separating the solar system from the center of our own galaxy. The dual AGN of Markarian 739 is the second-closest known, both in terms of distance from one another and distance from Earth. However, another galaxy known as NGC 6240 holds both records.
How did the second AGN remain hidden for so long? "Markarian 739 West shows no evidence of being an AGN in visible, ultraviolet and radio observations," said coauthor Sylvain Veilleux, a professor of astronomy at UMCP. "This highlights the critical importance of high-resolution observations at high X-ray energies in locating binary AGN.">>
Thanks Art - I appreciate your replies. Sometimes it takes me awhile to get back to previous questions but I eventually do and am always amazed at this groups knowledge and resource base. This site offers a wealth of continuous learning opportunities if you have time for sifting through it.
Checking out the moons rocks from "A Colorful Moon"
http://www.lpi.usra.edu/lunar/samples/ could take eons.
Ron