APOD: The Outer Shells of Centaurus A (2012 Jul 01)

Comments and questions about the APOD on the main view screen.
User avatar
APOD Robot
Otto Posterman
Posts: 4166
Joined: Fri Dec 04, 2009 3:27 am

APOD: The Outer Shells of Centaurus A (2012 Jul 01)

Post by APOD Robot » Mon Jul 02, 2012 2:23 am

Image The Outer Shells of Centaurus A

Explanation: What causes the surrounding shells in peculiar galaxy Cen A? In 2002 a fascinating image of peculiar galaxy Centaurus A was released, processed to highlight a faint blue arc indicating an ongoing collision with a smaller galaxy. Another interesting feature of Cen A, however, is the surrounding system of shells, better visible here in this recently released wider pan from the four meter Blanco telescope at Cerro Tololo Inter-American Observatory. Faint shells around galaxies are not unusual and considered by themselves as evidence of a previous galaxy merger, analogous to water ripples on a pond. An unexpected attribute of these shells is the abundance of gas, which should become separated from existing stars during the collision.

<< Previous APOD This Day in APOD Next APOD >>
[/b]

User avatar
geckzilla
Ocular Digitator
Posts: 9151
Joined: Wed Sep 12, 2007 12:42 pm
Location: Modesto, CA

Re: APOD: The Outer Shells of Centaurus A (2012 Jul 01)

Post by geckzilla » Mon Jul 02, 2012 2:33 am

Just call me "geck" because "zilla" is like a last name.

nstahl
Science Officer
Posts: 233
Joined: Mon Nov 29, 2004 4:08 am

Re: APOD: The Outer Shells of Centaurus A (2012 Jul 01)

Post by nstahl » Mon Jul 02, 2012 2:22 pm

I take it there's a problem with the usual APOD computer. Nothing serious I hope.

This is a great APOD, btw.

User avatar
orin stepanek
Plutopian
Posts: 5937
Joined: Wed Jul 27, 2005 3:41 pm
Location: Nebraska

Re: APOD: The Outer Shells of Centaurus A (2012 Jul 01)

Post by orin stepanek » Mon Jul 02, 2012 6:17 pm

Interesting story about the shells during a galactic merger! 8-)
And I've heard of hermit crabs using shells for a home! But kitties? Hermit Kitties? :wink: :roll: :mrgreen:
Orin

Smile today; tomorrow's another day!

pssacks@hotmail.com

Re: APOD: The Outer Shells of Centaurus A (2012 Jul 01)

Post by pssacks@hotmail.com » Mon Jul 02, 2012 7:40 pm

Could the outer shells of Centaurus A be the result of two black holes from the merging galaxies circling one another and setting off gravity waves?

User avatar
neufer
Vacationer at Tralfamadore
Posts: 17753
Joined: Mon Jan 21, 2008 1:57 pm
Location: Alexandria, Virginia

Re: APOD: The Outer Shells of Centaurus A (2012 Jul 01)

Post by neufer » Mon Jul 02, 2012 7:56 pm

pssacks@hotmail.com wrote:
Could the outer shells of Centaurus A be the result of
two black holes from the merging galaxies circling one another and setting off gravity waves?
I was thinking more on the lines of:
two or more black holes from the merging galaxies circling one another and ejecting stars in all directions.
Art Neuendorffer

User avatar
Moonlady
Selenian
Posts: 665
Joined: Fri Apr 13, 2012 9:06 pm

Re: APOD: The Outer Shells of Centaurus A (2012 Jul 01)

Post by Moonlady » Tue Jul 03, 2012 6:47 pm

neufer wrote:
pssacks@hotmail.com wrote:
Could the outer shells of Centaurus A be the result of
two black holes from the merging galaxies circling one another and setting off gravity waves?
I was thinking more on the lines of:
two or more black holes from the merging galaxies circling one another and ejecting stars in all directions.
Oh you guys are phenomenal!


My brain stopped working when I saw this stunning Apod and I made this sound: woooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooow!

User avatar
Ann
4725 Å
Posts: 11076
Joined: Sat May 29, 2010 5:33 am

Re: APOD: The Outer Shells of Centaurus A (2012 Jul 01)

Post by Ann » Tue Jul 03, 2012 9:09 pm

Photo: Wanderingdivers
I want to return to the idea of "ripples in a pond". Astrophtographer David Malin was, or so I think, the first person to notice that large elliptical galaxies are surrounded by faint shells. David Malin interpreted these shells as signs of mergers. When a smaller galaxy fell into a larger galaxy, the larger galaxy would respond by expanding. But as the galaxy rebounded and contracted again, shells of stars would remain outside the galaxy, like debris washed up on a shore.
Image
The Cartwheel Galaxy. Photo: Hubble
The Cartwheel galaxy was hit by another galaxy, and the Cartwheel responded by taking on this strange shape. As the Cartwheel rebounds and contracts again, remnants of its outer shell will likely remain.

When large ellipticals have many outer shells, that is probably a sign that they have undergone many mergers.



Ann
Color Commentator

User avatar
Beyond
500 Gigaderps
Posts: 6889
Joined: Tue Aug 04, 2009 11:09 am
Location: BEYONDER LAND

Re: APOD: The Outer Shells of Centaurus A (2012 Jul 01)

Post by Beyond » Tue Jul 03, 2012 9:34 pm

Now that's something to pond-der, ripples.
To find the Truth, you must go Beyond.

User avatar
StarCuriousAero
Ensign
Posts: 59
Joined: Tue Apr 12, 2011 10:20 pm
Location: California Desert

Re: APOD: The Outer Shells of Centaurus A (2012 Jul 01)

Post by StarCuriousAero » Tue Jul 03, 2012 9:53 pm

Beautiful picture, Centaurus A has always been incredibly fascinating. I'm also glad to see it finally described as a "peculiar" galaxy... since none of those other galaxy descriptions seem to adequately fit.