Starship Asterisk*

by **neufer** » Fri Jul 13, 2018 8:46 pm

Catalina wrote: ↑Fri Jul 13, 2018 8:31 pm
I assume that we are looking at this "edge on" along the fat disc?

If we were looking at it "jet on"

I'd be more careful about calling it a "fat disc."

by **Catalina** » Fri Jul 13, 2018 8:31 pm

I assume that we are looking at this "edge on" along the fat disc?

by **Ann** » Fri Jul 13, 2018 7:20 am

bushnuts wrote: ↑Fri Jul 13, 2018 6:32 am Can you explain using the word ONLY before 11 million light years distance?

By cosmic standards, 11 million light-years to another galaxy is really close. Our own Local Group of galaxies, which includes the Milky Way, the Andromeda Galaxy, the Triangulum Galaxy and several small galaxies, is about 4 million light-years in diameter. The Virgo Cluster of galaxies, the most nearby large galaxy cluster of which the Local Group is an outlier, is about 50 million light-years away, almost 5 times farther away than Centaurus A.

So 11 million light-years is certainly nearby as distances to galaxies go!

Ann

by **bushnuts** » Fri Jul 13, 2018 6:32 am

Can you explain using the word ONLY before 11 million light years distance?

by **Ann** » Fri Jul 13, 2018 5:46 am

After all the humor, I'm going to be painfully serious again. (What a bore!)

: Click to view full size image

Centaurus A. Source: https://www.jpl.nasa.gov/spaceimages/de ... d=PIA07912

: Click to view full size image

NGC 4402. Source: https://www.spacetelescope.org/images/heic0911c/

Note how gas seems to stream away from Centaurus A to the upper left. To me, that makes the appearance of this galaxy slightly similar to the appearance of NGC 4402, whose gas is also streaming away from it. Of course, NGC 4402 is losing its gas due to ram pressure, because the galaxy isn't colliding with another galaxy but just moving through the hot dense gas of the Virgo Cluster of galaxies. The forces acting on the gas in the spiral component of Cen A must be different.

Ann

by **neufer** » Thu Jul 12, 2018 8:13 pm

MarkBour wrote: ↑Thu Jul 12, 2018 7:23 pm
neufer wrote: ↑Thu Jul 12, 2018 12:16 pm
https://apod.nasa.gov/apod/ap080110.html
Interesting. Today's APOD caption lists Centaurus A's central black hole at around 1 billion Sols. In the caption of the APOD from January of 2008, that you kindly linked here, it estimates 10 million Sols. Wikipedia picks yet a different size:
<<https://en.wikipedia.org/wiki/Centaurus_A>>:

The center of the galaxy contains a supermassive black hole with a mass equivalent to 55 million solar masses,
referencing this estimate from a source dated in 2012:
"Radio Telescopes Capture Best-Ever Snapshot of Black Hole Jets". NASA. Retrieved 2012-10-02.

Click to play embedded YouTube video.

.

Billion Sol black holes seem mostly to populate:
- the centers of giant elliptical galaxies
  near the centers of giant galactic clusters:
https://en.wikipedia.org/wiki/List_of_m ... lack_holes

by **MarkBour** » Thu Jul 12, 2018 8:02 pm

ta152h0 wrote: ↑Thu Jul 12, 2018 6:22 pm They will test the Webb Telescope optics before launching, right?

LOL. I'm not sure I get the humor, exactly, but it made me emit a pained laugh, anyway.

by **MarkBour** » Thu Jul 12, 2018 7:23 pm

neufer wrote: ↑Thu Jul 12, 2018 12:16 pm https://apod.nasa.gov/apod/ap080110.html

Interesting. Today's APOD caption lists Centaurus A's central black hole at around 1 billion Sols. In the caption of the APOD from January of 2008, that you kindly linked here, it estimates 10 million Sols. Wikipedia picks yet a different size:

<<https://en.wikipedia.org/wiki/Centaurus_A>>:
The center of the galaxy contains a supermassive black hole with a mass equivalent to 55 million solar masses,

referencing this estimate from a source dated in 2012:

"Radio Telescopes Capture Best-Ever Snapshot of Black Hole Jets". NASA. Retrieved 2012-10-02.

So, talk about "active". It seems to be accreting at an incredible rate.

(Yes, @DL MARTIN, you may subtract 11 million years from that ...)

by **DL MARTIN** » Thu Jul 12, 2018 6:30 pm

If what we are seeing occurred 11 million years ago, then why is 'time since' not accorded the same obscurant status as, for example, dust. Otherwise, how is the term 'active galaxy' justified? It would seem that the term archeological artifact is more appropriate.

by **ta152h0** » Thu Jul 12, 2018 6:22 pm

They will test the Webb Telescope optics before launching, right?

by **ta152h0** » Thu Jul 12, 2018 6:03 pm

Ah, if only human observers could only go there( or not )

by **Ann** » Thu Jul 12, 2018 5:51 pm

orin stepanek wrote: ↑Thu Jul 12, 2018 11:08 am With all that dust; why is it called an elliptical? I would call it an irregular!

Art's explanation is correct, but he was somewhat long-winded. So think of Centaurus A as a galactic train wreck. A smallish spiral galaxy with a fat dust lane is crashing into an elliptical galaxy, dust fragments and shrapnel flying. And hey presto, you have Centaurus A!

: Click to view full size image

Centaurus A. Photo: NASA, JPL, GALEX.

And I just found this picture! I think it is unfair that I didn't find it before!

Ann

by **neufer** » Thu Jul 12, 2018 12:28 pm

orin stepanek wrote: ↑Thu Jul 12, 2018 11:08 am
With all that dust; why is it called an elliptical? I would call it an irregular!

https://en.wikipedia.org/wiki/Centaurus_A

Click to play embedded YouTube video.
<<In 1954, Walter Baade and Rudolph Minkowski suggested that the peculiar structure is the result of a merge event of a giant elliptical galaxy and a small spiral galaxy. Centaurus A may be described as having a peculiar morphology. As seen from Earth, the galaxy looks like a lenticular or elliptical galaxy with a superimposed dust lane. The peculiarity of this galaxy was first identified in 1847 by John Herschel, and the galaxy was included in Halton Arp's Atlas of Peculiar Galaxies (published in 1966) as one of the best examples of a "disturbed" galaxy with dust absorption. The galaxy's strange morphology is generally recognized as the result of a merger between two smaller galaxies. The bulge of this galaxy is composed mainly of evolved red stars. The dusty disk, however, has been the site of more recent star formation; over 100 star formation regions have been identified in the disk.>>
.
https://apod.nasa.gov/apod/ap160629.html

by **neufer** » Thu Jul 12, 2018 12:16 pm

starsurfer wrote: ↑Thu Jul 12, 2018 8:27 am
I love this image by the Ciel Austral team that shows its jet.

https://apod.nasa.gov/apod/ap080110.html

by **orin stepanek** » Thu Jul 12, 2018 11:08 am

With all that dust; why is it called an elliptical? I would call it an irregular!

by **starsurfer** » Thu Jul 12, 2018 8:27 am

I love this image by the Ciel Austral team that shows its jet.

by **Ann** » Thu Jul 12, 2018 5:15 am

I love this (blurry) picture of Centaurus A by GALEX, highlighting the ultraviolet light of the galaxy, concentrated in the broad, tattered dust lane. The entire dust lane seems to be aglow.

Ann

by **APOD Robot** » Thu Jul 12, 2018 4:05 am

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 telescopic view. 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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