APOD: The Quiet Sagittarius A (2013 Sep 06)

[mjimih]

Thanks. that whole answer blew my mind. And created an accretion disk around my head!

[owlice]

I was wondering what that was...!

[Beyond]

If you want to keep your feathers, Owlice, don't fly to close

[mjimih]

The reason I'm flabbergasted is bc my whole life I was worried about them, they're being mean with insatiable appetites and far flung influence. Now it sounds like they're not nearly as scary as I thought. dang movies
this object is the opposite of quiet tho' watch 3c321 shoot an irradiated particle beam at it's neighbor!

Click to play embedded YouTube video.

[Beyond]

I'm glad it's not hitting the

bth_MilkyWayBar.jpg (8.1 KiB) Viewed 15920 times

or we'd have a big chocolaty gooey caramel mess

[BDanielMayfield]

The reason I'm flabbergasted is bc my whole life I was worried about them, they're being mean with insatiable appetites and far flung influence. Now it sounds like they're not nearly as scary as I thought. dang movies

I like that, and I know what you mean Mark. I too had a media enhanced poor opinion of black holes (and supernovas too) at one time. But in nature destructive things can also be constructive. Like volcanoes here on earth; very bad to be next to one when it erupts, but look what they can produce, towering snow capped peaks, beautiful islands, fertile fields, etc. Black holes have their place too, it just needs to be far away.

[BDanielMayfield]

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?

I’ve read before (In a Sky and Telescope magazine article) that there is a correlation between the mass of a SMBH and the total mass of either the giant elliptical galaxy or the galactic bulge of the spiral galaxy that the SMBH is surrounded by. It’s also thought that globular clusters may contain intermediate massed BHs. I’ve also learned that it is thought by some astronomers that in open star clusters stellar massed black holes can help via gravitational interactions to disperse stars out from their places of origin.

So, since it is hard for black holes to swallow ordinary matter perhaps their main diet isn’t ordinary at all. Galaxies cannibalize each other, black holes must do so as well. Black holes must grow by swallowing whole what they cannot shred, namely, other BHs and likely neutron stars as well. Black holes are, to coin a phrase, cannibaliferous, a cannibal who’s diet is largely that of other cannibals!

[Joe New]

"...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..." Heat??? How can/does heat affect matter's reaction to gravity? Thanks!

[adam1234]

I hardly think that heat may affect matter's reaction to gravity.

[BDanielMayfield]

"...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..." Heat??? How can/does heat affect matter's reaction to gravity? Thanks!

I hardly think that heat may affect matter's reaction to gravity.

Here on Earth water spirals down drains under the influence of gravity. But if you add enough energy to the water so that it changes state from a liquid to a gas it will no longer flow down a sink drain. The material that is avoiding the pull down into BHs is ionized plasma that has been heated enormously. Also since ions are charged they can be accelerated by the a BH’s magnetic field to speeds exceeding escape velocity.

The steam not going down the drain analogy is not mine:

Scalding soup

Some scientists noted, though, that the brightness estimate assumed the gas coming from the stars was relatively cool, and that it could easily slip down the black hole's gullet, says Daniel Wang of the University of Massachusetts in Amherst. To find out what's really going on, Wang and his colleagues used NASA's Chandra X-ray Observatory to measure the temperature and brightness of gas at different distances from the black hole.

They found that the gas gets hotter and less abundant the closer it is to the black hole. The researchers estimate that less than 1 per cent of the surrounding gas ultimately comes near enough to be eaten. Wang thinks the food is just too hot.

Quasars are champion eaters because they slurp up relatively cool gas, below 1 million °C. Such gas is dense and flows in an orderly fashion into a quasar's maw, like water swirling into a drain. But the gas around Sagittarius A* is much hotter – collisions between stellar winds in the starry disc heat the gas to 10 million °C before it even starts to fall towards the black hole. This hot gas is tenuous and its particles zip around randomly, making it hard to corral.

"It's very hard to get steam into the sink," says Wang. That means the black hole should not get the blame for apparently turning up its nose at hot gas on its plate. "The black hole wants to suck it in, but it cannot," says Wang. Bizarrely, the tiny fraction of gas our black hole does imbibe may get in because it has transferred some of its jitteriness to gas particles that are thrown outwards, possibly by the black hole's own magnetic field lines.

[ErnieM]

Chris Peterson wrote:

BDanielMayfield wrote:

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.

From "Rutgers' Black Hole Discovery: The First Galaxy Without One Or The Smallest Black Hole Yet?" (http://www.sciencedaily.com/releases/20 ... 093143.htm)

Ferrarese and Merritt established a correlation between the mass of a black hole and the speed at which the stars in its galaxy are moving ("A Fundamental Relation Between Supermassive Black Holes and Their Host Galaxies," The Astrophysical Journal, 539, L9-L12 (2000)). This "M-sigma" relation is the most fundamental connection yet discovered between SBHs and their host galaxies and it has been hailed as one of the most important discoveries to come out of the Hubble Space Telescope.

If the Sagittarius A* went away, would our Sun move faster or slower? What is the over all impact on our Solar system?

[Chris Peterson]

If the Sagittarius A* went away, would our Sun move faster or slower? What is the over all impact on our Solar system?

The Sun would orbit the galactic center more slowly. However, the reduction in central mass with the elimination of Sag A* would be so small that the change would be insignificant. There would be no impact on the Solar System, and outside of a handful of stars at the galactic center, no major impact on our galaxy.

[Ann]

Yes, the central galactic coffee is just too hot!

Ann

Scalding soup

Some scientists noted, though, that the brightness estimate assumed the gas coming from the stars was relatively cool, and that it could easily slip down the black hole's gullet, says Daniel Wang of the University of Massachusetts in Amherst. To find out what's really going on, Wang and his colleagues used NASA's Chandra X-ray Observatory to measure the temperature and brightness of gas at different distances from the black hole.

They found that the gas gets hotter and less abundant the closer it is to the black hole. The researchers estimate that less than 1 per cent of the surrounding gas ultimately comes near enough to be eaten. Wang thinks the food is just too hot.

[Beyond]

There's a cure for being tooooo Hot.