Starship Asterisk*

Centaurus A

Explanation: Only 11 million light-years away, Centaurus A is the closest active galaxy to planet Earth. Spanning over 60,000 light-years, the peculiar elliptical galaxy, also known as NGC 5128, is featured in this sharp color image. Centaurus A is apparently the result of a collision of two otherwise normal galaxies resulting in a fantastic jumble of star clusters and imposing dark dust lanes. Near the galaxy's center, left over cosmic debris is steadily being consumed by a central black hole with a billion times the mass of the Sun. As in other active galaxies, that process likely generates the radio, X-ray, and gamma-ray energy radiated by Centaurus A.

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Silly me . . . I thought Andromeda was our closest galaxy. What--it's not "active?"

APOD Robot wrote: Centaurus A

Centaurus A is apparently the result of a collision of two otherwise normal galaxies resulting in a fantastic jumble of star clusters and imposing dark dust lanes. Near the galaxy's center, left over cosmic debris is steadily being consumed by a central black hole with a billion times the mass of the Sun. As in other active galaxies, that process likely generates the radio, X-ray, and gamma-ray energy radiated by Centaurus A.

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• Young Frankenstein (1974)

Dr. Frederick Frankenstein: [to Igor] Now that brain that you gave me. Was it Hans Delbruck's?

Igor: [pause, then] No.

Dr. Frederick Frankenstein: Ah! Very good. Would you mind telling me whose brain I DID put in?

Igor: Then you won't be angry?

Dr. Frederick Frankenstein: I will NOT be angry.

Igor: Abby Someone.

Dr. Frederick Frankenstein: [pause, then] Abby Someone. Abby who?

Igor: Abby Normal.

Dr. Frederick Frankenstein: [pause, then] Abby Normal?

Igor: I'm almost sure that was the name.

Dr. Frederick Frankenstein: [chuckles, then] Are you saying that I put an abnormal brain into a seven and a half foot long, fifty-four inch wide GORILLA? [grabs Igor and starts throttling him]

Dr. Frederick Frankenstein: Is that what you're telling me?

pacfandave wrote:Silly me . . . I thought Andromeda was our closest galaxy. What--it's not "active?"

Andromeda is not our closest galaxy- quite a few others are nearer. It is, however, the closest spiral galaxy. And no, Andromeda is not considered an active galaxy- it has no jets, its core isn't exceptionally bright in either the optical or radio spectrum, it isn't x-ray bright, it isn't variable. An active galaxy has some sort of accretion process occurring around its central supermassive black hole, and this isn't happening in Andromeda.

pacfandave wrote:Silly me . . . I thought Andromeda was our closest galaxy.

What--it's not "active?"

"Active" in what sense?

http://en.wikipedia.org/wiki/Andromeda_%28mythology%29 wrote:
Giorgio Vasari, Perseus and Andromeda, 1570

<<Andromeda's name is the Latinized form of the Greek Ανδρομέδη (Andromédē) meaning "to think of a man." Perseus and Andromeda had seven sons: Perseides, Perses, Alcaeus, Heleus, Mestor, Sthenelus, and Electryon, and one daughter, Gorgophone. Their descendants include the great hero Heracles and the entire Persian race.>>

pacfandave wrote:Silly me . . . I thought Andromeda was our closest galaxy. What--it's not "active?"

. The black hole in the center of a galaxy must be feed by matter to emit radiation. The galaxy is then active. Andromeda is not active because there is'nt an accretion disk around his central black hole.

According to SED's (http://seds.org/messier/Xtra/ngc/n5128.html), Centaurus A is a lenticular galaxy.

Centaurus A
Explanation: Only 11 million light-years away, Centaurus A is the closest active galaxy to planet Earth. Spanning over 60,000 light-years, the peculiar elliptical galaxy, also known as NGC 5128, is featured in this sharp color image. Centaurus A is apparently the result of a collision of two otherwise normal galaxies resulting in a fantastic jumble of star clusters and imposing dark dust lanes.

I didn't know that ellipticals had dust lanes! The pictures I've seen of them seem to have all their dust used up. Live and learn

Andromeda A is an "active galaxy", one that is,"much higher than normal luminosity over some or all of the electromagnetic spectrum (in the radio, infrared, optical, ultra-violet, X-ray and/or gamma ray wavebands" (Wiki). And more active, I presume than ours.

We are searching for life out there - would that activity prevent life starting anywhere in the Andromeda galaxy?

John

JohnD wrote:Andromeda A is an "active galaxy", one that is,"much higher than normal luminosity over some or all of the electromagnetic spectrum (in the radio, infrared, optical, ultra-violet, X-ray and/or gamma ray wavebands" (Wiki). And more active, I presume than ours.

We are searching for life out there - would that activity prevent life starting anywhere in the Andromeda galaxy?

Centaurus A you mean?

Life as we know it would have a hard time of it no doubt.

The light source is the active black hole at the galaxy's center. What is the light reflecting from to form the halo around the galaxy?

neufer wrote:Centaurus A you mean?

Life as we know it would have a hard time of it no doubt.

Doh!

Yes, Centaurus A.
John

Thanx, Chris. I should have read the blurb on Andromeda a little more closely. My bad....

zbvhs wrote:The light source is the active black hole at the galaxy's center. What is the light reflecting from to form the halo around the galaxy?

If the "halo" you're referring to is the glowing white oval, that is the galaxy. It looks like a glowing gas, more or less, because it's so far away we can't resolve the individual stars.

Rob

zbvhs wrote:The light source is the active black hole at the galaxy's center. What is the light reflecting from to form the halo around the galaxy?

The light source is the billions of stars making up the galaxy. You can't even see the active center of the galaxy- most of its output is outside optical bands- x-rays, gamma rays, radio. And most of the light from the core is being absorbed by all that dust.