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APOD: Galaxies in the River (2016 Feb 10)
Posted: Wed Feb 10, 2016 5:05 am
by APOD Robot
Galaxies in the River
Explanation: Large galaxies grow by eating small ones.
Even our own galaxy practices galactic
cannibalism, absorbing small galaxies that get too close and are
captured by the Milky Way's gravity. In fact, the practice is common in the universe and illustrated by this striking pair of interacting galaxies from the banks of the southern constellation
Eridanus,
The River. Located over 50 million light years away, the large, distorted spiral NGC 1532 is seen locked in a
gravitational struggle with dwarf galaxy NGC 1531 (right of center), a struggle the smaller galaxy
will eventually lose. Seen edge-on, spiral NGC 1532 spans about 100,000 light-years. Nicely detailed
in this sharp image, the NGC 1532/1531 pair is thought to be similar to the well-studied system of face-on spiral and small companion
known as M51.
[/b]
Re: APOD: Galaxies in the River (2016 Feb 10)
Posted: Wed Feb 10, 2016 5:43 am
by daddyo
like the title's metaphor
Re: APOD: Galaxies in the River (2016 Feb 10)
Posted: Wed Feb 10, 2016 6:21 am
by Nitpicker
APOD Robot wrote:a struggle the smaller galaxy will eventually lose.
It depends how you define winning and losing. There may be fine citizens in the smaller galaxy, quietly hopeful of a new home.
Re: APOD: Galaxies in the River (2016 Feb 10)
Posted: Wed Feb 10, 2016 10:21 am
by heehaw
Just wait till we take on Andromeda!
Re: APOD: Galaxies in the River (2016 Feb 10)
Posted: Wed Feb 10, 2016 4:30 pm
by neufer
heehaw wrote:
Just wait till we take on Andromeda!
https://en.wikipedia.org/wiki/Andromeda_Galaxy wrote:
<<Being approximately 220,000 light years across, the Andromeda Galaxy is the largest galaxy of the Local Group, which also contains the Milky Way, the Triangulum Galaxy, and about 44 other smaller galaxies.
Despite earlier findings that suggested that the Milky Way contains more dark matter and could be the largest in the grouping, the 2006 observations by the Spitzer Space Telescope revealed that Andromeda contains one trillion (10
12) stars: at least twice the number of stars in the Milky Way, which is estimated to be 200–400 billion.
The Andromeda Galaxy is estimated to be 1.5×10
12 solar masses, while the mass of the Milky Way is estimated to be 8.5×10
11 solar masses. The Milky Way and Andromeda are expected to collide in 3.75 billion years, eventually merging to form a giant elliptical galaxy or perhaps a large disk galaxy.>>
Re: APOD: Galaxies in the River (2016 Feb 10)
Posted: Wed Feb 10, 2016 4:41 pm
by Ann
heehaw wrote:Just wait till we take on Andromeda!
First we take Manhattan, then we take Berlin, then we take Andromeda...
(I don't know, the meter just doesn't sound right. Maybe we don't take Andromeda.)
But this is a great APOD of a fascinating pair of interacting galaxies. Note the elongated outer arm of NGC 1532 at lower right. It's been stretched by tidal forces like a rubber band.
Mountain lion. Photo: myheimu.
Also note how the inner arms of NGC 1532 at right are raised up like a pouncing predator, intent on catching its prey. And the prey is of course the hapless dwarf galaxy, NGC 1531. Note the large yellow bulge of NGC 1532 and the bright star formation in a part of its inner arm.
M51 and NGC 5195. Photo: R. Jay GaBany.
But I disagree that NGC 1531/1532 is very similar to M51 and NGC 5195. Even though M51 is obviously larger than its companion, NGC 5195, the two galaxies might be relatively similar in mass. Note the small yellow bulge of M51, which is considerably smaller than the bulge of NGC 5195. We expect to find most of a galaxy's baryonic matter in its bulge.
But when it comes to NGC 1531 and 1532, there can be no doubt that NGC 1532 is not only bigger but also far more massive than its small dwarf companion-prey. The large yellow bulge of NGC 1532 is testament to that.
Ann
Re: APOD: Galaxies in the River (2016 Feb 10)
Posted: Wed Feb 10, 2016 4:44 pm
by isoparix
A Pedant writes:
'Even our own galaxy practices galactic cannibalism...' ==> 'Even our own galaxy practises galactic cannibalism...'
'....the practice is common...' Correct!
Think advise (verb)/advice (noun)...
Re: APOD: Galaxies in the River (2016 Feb 10)
Posted: Wed Feb 10, 2016 5:25 pm
by starsurfer
I would love to see an artist's impression of the Milky Way that shows all its currently known tidal streams. I find galaxy interactions very interesting and I'm constantly dazzled by the sheer array of shapes and forms peculiar galaxies can take.
Re: APOD: Galaxies in the River (2016 Feb 10)
Posted: Wed Feb 10, 2016 5:52 pm
by bystander
isoparix wrote:A Pedant writes:
'Even our own galaxy practices galactic cannibalism...' ==> 'Even our own galaxy practises galactic cannibalism...'
'....the practice is common...' Correct!
Think advise (verb)/advice (noun)...
In American English
practices is correct.
Practice vs. practise
In the main varieties of English from outside North America, practice is the noun, and practise is the verb. For instance, we would say that a doctor with a private practice practises privately. There is no such distinction in American English, where practice is both a noun and a verb, and
practise is not used at all. Canadian English also favors practise as the verb, but practice appears with relative frequency as a verb (about a third as often as practise).
Re: APOD: Galaxies in the River (2016 Feb 10)
Posted: Wed Feb 10, 2016 6:45 pm
by Ron-Astro Pharmacist
Those merging galaxies show up "
all over the place".
Nice image Geck!! But sometimes you don't get
credit?
Oh - I guess you did and I didn't see it the first time.
The River is so full of
them.
Re: APOD: Galaxies in the River (2016 Feb 10)
Posted: Wed Feb 10, 2016 7:20 pm
by Tekija
bystander wrote:isoparix wrote:A Pedant writes:
'Even our own galaxy practices galactic cannibalism...' ==> 'Even our own galaxy practises galactic cannibalism...'
'....the practice is common...' Correct!
Think advise (verb)/advice (noun)...
In American English
practices is correct.
Practice vs. practise
In the main varieties of English from outside North America, practice is the noun, and practise is the verb. For instance, we would say that a doctor with a private practice practises privately. There is no such distinction in American English, where practice is both a noun and a verb, and
practise is not used at all. Canadian English also favors practise as the verb, but practice appears with relative frequency as a verb (about a third as often as practise).
A good example to people whose English is painful to your ears?
The Scotch and the Irish leave you close to tears.
There even are places where English completely disappears.
In America, they haven't used it for years!
George B. Shaw
My Fair Lady (Pygmalion)
Re: APOD: Galaxies in the River (2016 Feb 10)
Posted: Wed Feb 10, 2016 8:28 pm
by neufer
Tekija wrote:
A good example to people whose English is painful to your ears?
The Scotch and the Irish leave you close to tears.
There even are places where English completely disappears.
In America, they haven't used it for years!
George B. Shaw - My Fair Lady (Pygmalion)
https://en.wikipedia.org/wiki/Shavian_alphabet wrote:
<<The Shavian alphabet (also known as the Shaw alphabet) is an alphabet conceived as a way to provide simple, phonetic orthography for the English language to replace the difficulties of conventional spelling. It was posthumously funded by and named after Irish playwright George Bernard Shaw. Shaw set three main criteria for the new alphabet: it should be (1) at least 40 letters; (2) as "phonetic" as possible (that is, letters should have a 1:1 correspondence to phonemes); and (3) distinct from the Latin alphabet to avoid the impression that the new spellings were simply "misspellings".
Shaw had served from 1926 to 1939 on the BBC's Advisory Committee on Spoken English, which included several exponents of phonetic writing. All of his interest in spelling and alphabet reform was made clear in Shaw's will of June 1950, in which provision was made for Isaac Pitman, with a grant in aid from the Public Trustee, to establish a Shaw Alphabet. Following Shaw's death in November 1950, and after some legal dispute, the Trustee announced a worldwide competition to design such an alphabet, with the aim of producing a system which would be an economical way of writing and of printing the English language. A contest for the design of the new alphabet was won by four people, including Mr. Ronald Kingsley Read. Read was then appointed to amalgamate the four designs to produce the new alphabet.
Due to the contestation of Shaw's will, the trust charged with developing the new alphabet could only afford to publish one book: a version of Shaw's play Androcles and the Lion, in a bi-alphabetic edition with both conventional and Shavian spellings. In 2013 an edition of Alice's Adventures in Wonderland, transcribed into Shavian by Thomas Thurman, was published.>>
Re: APOD: Galaxies in the River (2016 Feb 10)
Posted: Wed Feb 10, 2016 10:07 pm
by geckzilla
Ron-Astro Pharmacist wrote:Those merging galaxies show up "
all over the place".
Nice image Geck!! But sometimes you don't get
credit?
Oh - I guess you did and I didn't see it the first time.
The River is so full of
them.
The crediting is all wonky. I get credit where none is due on some of ESA's images where I found and did process my own versions, but then ESA processed their own and they just look similar and the credit is for me finding the image not the processing. I have to repeatedly explain this to people. Very few of my images are in use outside of Wikipedia.
Re: APOD: Galaxies in the River (2016 Feb 10)
Posted: Wed Feb 10, 2016 10:18 pm
by Ron-Astro Pharmacist
geckzilla wrote:Ron-Astro Pharmacist wrote:Those merging galaxies show up "
all over the place".
Nice image Geck!! But sometimes you don't get
credit? The River is so full of
them.
The crediting is all wonky. I get credit where none is due on some of ESA's images where I found and did process my own versions, but then ESA processed their own and they just look similar and the credit is for me finding the image not the processing. I have to repeatedly explain this to people. Very few of my images are in use outside of Wikipedia.
You'd think the(y) could get
their "copy" right!
Re: APOD: Galaxies in the River (2016 Feb 10)
Posted: Wed Feb 10, 2016 10:51 pm
by geckzilla
Ron-Astro Pharmacist wrote:You'd think the could get
their "copy" right!
Most people try but what "acknowledgement" means isn't clear to anyone but the person who wrote it.
Re: APOD: Galaxies in the River (2016 Feb 10)
Posted: Thu Feb 11, 2016 1:14 am
by Ann
geckzilla wrote:Ron-Astro Pharmacist wrote:Those merging galaxies show up "
all over the place".
Nice image Geck!! But sometimes you don't get
credit?
Oh - I guess you did and I didn't see it the first time.
The River is so full of
them.
The crediting is all wonky. I get credit where none is due on some of ESA's images where I found and did process my own versions, but then ESA processed their own and they just look similar and the credit is for me finding the image not the processing. I have to repeatedly explain this to people.
So did you or did you not process that new, fascinating picture of NGC 1487? And if you didn't, did you process your own version of it?
Very few of my images are in use outside of Wikipedia.
Wow. I'm impressed. It's like, OK, where can I see some of your images? Oh, they're on Wikipedia.
Ann
Re: APOD: Galaxies in the River (2016 Feb 10)
Posted: Thu Feb 11, 2016 11:14 am
by geckzilla
Ann wrote:So did you or did you not process that new, fascinating picture of NGC 1487? And if you didn't, did you process your own version of it?
Very few of my images are in use outside of Wikipedia.
Wow. I'm impressed. It's like, OK, where can I see some of your images? Oh, they're on Wikipedia.
Ann
I did, it's here:
https://www.flickr.com/photos/geckzilla ... ist-jdcQaL
As far as Wikipedia goes, there is one user in particular who I noticed adding some of my images. It's a hobby for some people to maintain and add new stuff to it. No doubt my pictures will get replaced with newer ones released by ESA and the Hubble Site people.
Re: APOD: Galaxies in the River (2016 Feb 10)
Posted: Thu Feb 11, 2016 2:45 pm
by Ann
Very interesting, Geck. There is an obvious color difference between your image and the one Ron linked to.
Would you say that your color balance is the "truest" to what the filters show, or is the other image the truest?
Ann
Re: APOD: Galaxies in the River (2016 Feb 10)
Posted: Thu Feb 11, 2016 8:56 pm
by geckzilla
Well, almost everyone out there tends to ramp up the saturation. I do it sometimes, but usually I don't. I do not know what to call true. They are both representations of the same data. The increased saturation one might say is just to aid our human eyes in seeing what are quite minor colors. You could say mine is slightly closer to raw or less processed.
