Starship Asterisk*

M106 Close Up

Explanation: Close to the Great Bear (Ursa Major) and surrounded by the stars of the Hunting Dogs (Canes Venatici), this celestial wonder was discovered in 1781 by the metric French astronomer Pierre Mechain. Later, it was added to the catalog of his friend and colleague Charles Messier as M106. Modern deep telescopic views reveal it to be an island universe: a spiral galaxy around 30 thousand light-years across located only about 21 million light-years beyond the stars of the Milky Way. Along with prominent dust lanes and a bright central core, this colorful composite image highlights youthful blue star clusters and reddish stellar nurseries that trace the galaxy's spiral arms. The high resolution galaxy portrait is a mosaic of data from Hubble's sharp ACS camera combined with groundbased color image data. M106 (aka NGC 4258) is a nearby example of the Seyfert class of active galaxies, seen across the spectrum from radio to X-rays. Energetic active galaxies are powered by matter falling into a massive central black hole.

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This image shows how powerful supermassie blackholes are. Just by looking at the core of M106 you can see that it looks like a giant celestial sink hole. Lovely image.

wonderboy wrote:This image shows how powerful supermassie blackholes are. Just by looking at the core of M106 you can see that it looks like a giant celestial sink hole. Lovely image.

I don't see the slightest hint of anything suggesting that this galaxy has a central black hole. I think its effects are far too small to be seen in visible light at this image scale.

i look like a huge sink hole in the middle!

The black hole doesn't cause the spiral appearance of spiral galaxies and nothing is getting pulled to the center. I should probably keep neufer's orbital density post bookmarked...

what makes a galaxy spiral then? i always thought it was the blackhole.

wonderboy wrote:what makes a galaxy spiral then? i always thought it was the blackhole.

Density waves

wonderboy wrote:what makes a galaxy spiral then? i always thought it was the blackhole.

Keep in mind that the mass of a central black hole is only a few million stars. There are a lot more than a few million ordinary stars in the center of most spiral galaxies. The mass contribution of the black hole is only a fraction of a percent of the total.

A central black hole can have interesting effects on a galaxy if it is in an active phase, but structurally it has little impact.

Wonderful image, very detailed, hot young stars in the "arms". Thank you APOD!

Chris Peterson wrote:A central black hole can have interesting effects on a galaxy if it is in an active phase, but structurally it has little impact.

Unless we're looking at it in x-rays or radio waves? http://www.eso.org/public/images/eso0903a/ (those jets are NUTS)

geckzilla wrote:

Chris Peterson wrote:A central black hole can have interesting effects on a galaxy if it is in an active phase, but structurally it has little impact.

Unless we're looking at it in x-rays or radio waves? http://www.eso.org/public/images/eso0903a/ (those jets are NUTS)

That's why I mentioned active galaxies. Even there, however, there is little or no impact on the overall structure of the galaxy. The stars go about their orbits, spiral arms do their thing, all the same whether or not there is a black hole, and whether or not it is active.

Yeah, Centaurus A looks pretty normal in visible light. http://en.wikipedia.org/wiki/File:NGC_5128_galaxy.jpg
Well, as normal as a recently merged galaxy can look, anyway. There's no indication that the jets are affecting the stars or the dust lanes at all. It looks more like the recent merger it went through affected the jets rather than the other way around.

Chris Peterson wrote:
A central black hole can have interesting effects on a galaxy if it is in an active phase, but structurally it has little impact.

• But structurally it has some impact; e.g., an extremely bright nuclei.

http://en.wikipedia.org/wiki/Seyfert_galaxy wrote:
<<Seyfert galaxies are characterized by extremely bright nuclei, and spectra which have very bright emission lines of hydrogen, helium, nitrogen, and oxygen. These emission lines exhibit strong Doppler broadening, which implies velocities from 500 to 4000 km/s, and are believed to originate near an accretion disc surrounding the central black hole.>>

neufer wrote:

Chris Peterson wrote:A central black hole can have interesting effects on a galaxy if it is in an active phase, but structurally it has little impact.

But structurally it has some impact; e.g., an extremely bright nuclei.

"Little impact" = "some impact".

geckzilla wrote:Yeah, Centaurus A looks pretty normal in visible light. http://en.wikipedia.org/wiki/File:NGC_5128_galaxy.jpg
Well, as normal as a recently merged galaxy can look, anyway. There's no indication that the jets are affecting the stars or the dust lanes at all. It looks more like the recent merger it went through affected the jets rather than the other way around.

I've been interested in astronomy since long before astronomers knew all that much about galaxies (or rather, perhaps, before those who knew a lot about galaxies had managed to convince the all the popularizers of astronomy of their views).

So I remember something I read in a book long ago. (The Celestial Handbook?) The author noted that Centaurus A looks very strange, and he wondered if the galaxy is in the process of exploding.

I, too, think that Cen A looks strange, and it does look as if it is exploding! Of course it isn't exploding but merging, like you said, Geckzilla. Visually we see no effects of the black hole, but the galaxy looks plenty strange anyway.

Ann