APOD: The Quiet Sagittarius A (2013 Sep 06)

[APOD Robot]

The Quiet Sagittarius A

Explanation: Hot gas is hard to swallow. At least that seems to be true for the supermassive black hole at the center of our Milky Way Galaxy. Known as source Sagittarius A*, the Milky Way's black hole is centered in this infrared (red and yellow hues) and X-ray (blue) composite. Based on data from an extensive campaign of observations by the orbiting Chandra X-ray telescope, the diffuse emission surrounding the black hole is seen in the close-up inset, the inset field spanning about 1/2 light-year across the galactic center some 26,000 light-years away. Astronomers have found that the X-ray emission originates in hot gas drawn from the winds of massive young stars in the region. The Chandra data indicate that only about 1% or less of the gas within the black hole's gravitational influence ever reaches the event horizon, losing enough heat and angular momentum to fall into the black hole, while the rest of the gas escapes in an outflow. The result explains why the Milky Way's black hole is so quiet, much fainter than might be expected in energetic X-rays. It likely holds for most supermassive black holes in galaxies in the nearby Universe.

<< Previous APOD

This Day in APOD

Next APOD >>

[/b]

[bystander]

http://asterisk.apod.com/viewtopic.php?t=32015
http://asterisk.apod.com/viewtopic.php?t=32048

[Ann]

It's good to see today's APOD up bright and early!

And the picture is interesting too, as well as the caption, so thanks.

Ann

[BDanielMayfield]

Ah, our friendly Super Massive Black Hole is hidden inside there. It is the anchor of the Milky Way and perhaps it's a giant recycler too.

[glueguru]

Just looking at the beautiful photo and see a right hand holding our Blackhole in its palm. The magnificent blue thumb and red fingers complete the image. Are we really being held up to the rest of the Universe?

[Boomer12k]

Interesting image....so...it needs to Burp????

I get that way too....

However...this other shot makes me think it will have nooooo trouble digesting ANYTHING!!!

:---[===] *

[bellicosity]

so, if it's such a picky eater, how'd it get so large to begin with???

[Chris Peterson]

Ah, our friendly Super Massive Black Hole is hidden inside there. It is the anchor of the Milky Way and perhaps it's a giant recycler too.

It's a trivial mass concentration compared with the mass of the galaxy. At most, a few million suns, a ten thousandth of a percent of the total galactic mass. It could go away, and the dynamics of the galaxy would be substantially unchanged. And virtually none of the mass of the galaxy will ever have a close encounter with it.

Not much of an anchor. Not much of a recycler.

[biddie67]

Since I'm not trained in this field at all, I usually struggle with the terminology and vocabulary style used here. It took me halfway through the links to realize that Sagittarius A* isn't a star but the point that marks the central black hole.

As I was reading the links, I started wondering how our galaxy could remain intact with that constant tug in the center of it. Then I wondered if the black hole could ever collapse and if it did, what would happen to our galaxy ..... if the black hole did collapse, could another one form there?

Chris's comment above was helpful ~~ I have no idea how those numbers could ever be determined but it was reassuring to this poor soul (( grin ))

[geckzilla]

Then I wondered if the black hole could ever collapse and if it did, what would happen to our galaxy ..... if the black hole did collapse, could another one form there?

You could think of a black hole as being the ultimate form of collapsed matter. I don't think it's even possible for it to collapse any further than it already has. You could have something to worry about if another large black hole were to merge with it, but the closest known one is in Andromeda.

[BDanielMayfield]

Ah, our friendly Super Massive Black Hole is hidden inside there. It is the anchor of the Milky Way and perhaps it's a giant recycler too.

It's a trivial mass concentration compared with the mass of the galaxy. At most, a few million suns, a ten thousandth of a percent of the total galactic mass. It could go away, and the dynamics of the galaxy would be substantially unchanged. And virtually none of the mass of the galaxy will ever have a close encounter with it.

Not much of an anchor. Not much of a recycler.

"Not much" is better than 'not at all.' I'll accept that with thanks.

[BDanielMayfield]

so, if it's such a picky eater, how'd it get so large to begin with???

That is an excellent question.

[geckzilla]

so, if it's such a picky eater, how'd it get so large to begin with???

That is an excellent question.

Just think of how much more massive it would be if it weren't so picky. It could engulf our whole galaxy if the human imagination had its way.

[biddie67]

Then I wondered if the black hole could ever collapse and if it did, what would happen to our galaxy ..... if the black hole did collapse, could another one form there?

You could think of a black hole as being the ultimate form of collapsed matter. I don't think it's even possible for it to collapse any further than it already has. You could have something to worry about if another large black hole were to merge with it, but the closest known one is in Andromeda.

I used the wrong word when I used "collapsed". Could a black hole run out of material within its range and lose its energy and wither away?

[Chris Peterson]

I used the wrong word when I used "collapsed". Could a black hole run out of material within its range and lose its energy and wither away?

Black holes do evaporate. A supermassive black hole has a lifetime around 10¹⁰⁰ times the age of the Universe. By the time one dissipates, there probably won't be any luminous matter left.

[Chris Peterson]

Just think of how much more massive it would be if it weren't so picky. It could engulf our whole galaxy if the human imagination had its way.

It all comes down to that imagination, and too many bad sci-fi flicks. Black holes don't need to be picky, since they don't really have any mechanism to draw much material across their event horizons.

[Ron-Astro Pharmacist]

Who knows what goes on inside a black hole but it is fun to imagine? Scientific American is co-sponsoring a flash fiction writing contest encouraging anyone to submit a fictional short story on their favorite topic involving the ideas of quantum mechanics.

http://shorts.quantumlah.org/

It seems like a good outlet for those who like thinking outside the box but may not have a professional background to backup their imagination. They post submissions and will choose the winning short story at the end of the year. Some pretty top physicists and others on the panel that will judge the competition. Check them out if interested

[whome]

Notice in the red, almost a spiral structure? I'm a professional astronomer, I've not noticed that before!

[tdcrime]

maybe it is full
or needs to burp like previous comment

[Beyond]

Just think of how much more massive it would be if it weren't so picky. It could engulf our whole galaxy if the human imagination had its way.

I can see the movie title now... The Invisible Monster That Ate The Milky Way.
YUM, Milky Way good, especially the bar. BURP

[E.E. geek]

Does this and http://apod.nasa.gov/apod/ap130728.html hint that there might be a saturation point for a black hole? Curious..

[Chris Peterson]

Does this and http://apod.nasa.gov/apod/ap130728.html hint that there might be a saturation point for a black hole? Curious..

How so? There's no suggestion that the structure of ring galaxies is related to any possible central supermassive black holes they might possess. In general, the central black holes in galaxies are insufficiently massive to significantly impact the galactic structure anywhere except very close to the center- usually in too small an area to even be resolved telescopically.

There's no reason to think black holes have any maximum mass.

[Markus Schwarz]

Does this and http://apod.nasa.gov/apod/ap130728.html hint that there might be a saturation point for a black hole? Curious..

There is no limit on how much mass a black hole can acquire and no saturation point.

[mjimih]

bellicosity wrote: so, if it's such a picky eater, how'd it get so large to begin with???

Did our black hole grow early on with a higher ratio of/more heavier material around? And now in a more mature galaxy, it consumes more light objects?

[Chris Peterson]

Did our black hole grow early on with a higher ratio of/more heavier material around? And now in a more mature galaxy, it consumes more light objects?

It's not well understood how supermassive black holes form. There is the "galaxy came first" suggestion, and the "black hole came first" suggestion. In the second case, there may have been a higher density of material, but it was certainly lighter, since this would have been before many elements heavier than hydrogen or helium would have existed.

In a mature galaxy, a central black hole only consumes objects when conditions are right for the formation of an accretion disc. Otherwise, there's no mechanism to rob orbiting material of angular momentum, and anything under the gravitational influence of the black hole will orbit, not fall inwards. There is evidence that galactic black holes go through cycles of consumption, as accretion discs form and are destroyed. Also, it's unlikely that in most cases the central black holes will ever consume more than a tiny fraction of the material in the rest of the galaxy. For the most part, their growing days are over.