APOD: Galaxies in the River (2020 Jan 08)

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APOD: Galaxies in the River (2020 Jan 08)

Post by APOD Robot » Wed Jan 08, 2020 5:07 am

Image Galaxies in the River

Explanation: Large galaxies grow by eating small ones. Even our own galaxy engages in a sort of galactic cannibalism, absorbing small galaxies that are 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.

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Ann
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Re: APOD: Galaxies in the River (2020 Jan 08)

Post by Ann » Wed Jan 08, 2020 6:31 am

I first saw a picture of this pair of galaxies in my trusted The Color Atlas of Galaxies by James D Wray. The atlas is from the 1980s and the quality of the pictures is poor indeed, compared with what modern photography can do. But what you get in Wray's atlas is an honest depiction of the luminance of various parts of the galaxies. Bright parts look bright and faint parts look faint or are invisible.

So what struck me when I looked at Wray's picture of NGC 1532 was a row of intensely bright regions of star formation. You can make them out in today's APOD on the right side of the inner arm, starting with a pair of bright white "eyes" (or maybe those bulging white mounds are more reminiscent of some other part of the human anatomy).

Anyway, I can say this: The star formation that goes on in that part of the inner arm of NGC 1532 is bright. And intense.

But apart from calling attention to the brightness distribution across NGC 1531 and 1532 (and bringing out the difference between ultraviolet-rich O-type stars and blue A-type stars), Wray's image of this interacting pair is obviously inferior in every way to today's APOD by Star Shadows Remote Observatory, PROMPT, CTIO. (What a coincidence: Wray took many of his pictures with the CTIO telescope.)

Really, though: Today's APOD is beautifully colored and superbly detailed. I love it! :D

Ann
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Re: APOD: Galaxies in the River (2020 Jan 08)

Post by Boomer12k » Wed Jan 08, 2020 7:46 am

Ok... maybe it is not "cannibalism"... maybe it goes this way... the smaller "female" galaxy 'WINKS' a come hither look... and the larger male galaxy pulls her closer to him... and...um... well... BOTH WIN....

It is "Attraction"... after all...It's "Galactic Love"...

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Re: APOD: Galaxies in the River (2020 Jan 08)

Post by JRoc » Wed Jan 08, 2020 1:36 pm

If you enlarge the image just above the left edge of NGC1532, above the puff of stars, you will see a triangle of stars with a red start at the apex. Look to the left of the top most star and you will see a blur. Magnify the blur and there are two galaxies, the smaller appearing to be devoured by the larger. I realize this could be a superposition, but finding it was a real joy for me.

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Re: APOD: Galaxies in the River (2020 Jan 08)

Post by sillyworm 2 » Wed Jan 08, 2020 1:56 pm

Ann..I just found a beautiful copy of GALAXIES by Timothy Ferris...for $3.99..dated for sure...but so fun & informative.

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Re: APOD: Galaxies in the River (2020 Jan 08)

Post by TheOtherBruce » Wed Jan 08, 2020 2:03 pm

APOD Robot wrote:
Wed Jan 08, 2020 5:07 am
dwarf galaxy NGC 1531 (right of center),
Was this written by someone looking at a rotated picture? What I assume is NGC1531 is above the larger spiral's core, right in the middle of the picture.

An interesting kink in the inner spiral arm — it's really been yanked up hard by the dwarf galaxy's gravity.
This universe shipped by weight, not by volume.
Some expansion of the contents may have occurred during shipment.

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Re: APOD: Galaxies in the River (2020 Jan 08)

Post by orin stepanek » Wed Jan 08, 2020 2:28 pm

:D Beautiful merger; as the two become one! :b: 😉
Orin

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Re: APOD: Galaxies in the River (2020 Jan 08)

Post by neufer » Wed Jan 08, 2020 5:31 pm

Boomer12k wrote:
Wed Jan 08, 2020 7:46 am

Ok... maybe it is not "cannibalism"... maybe it goes this way... the smaller "female" galaxy 'WINKS' a come hither look... and the larger male galaxy pulls her closer to him... and...um... well... BOTH WIN....
:arrow: Or, perhaps, the LARGER "female" galaxy 'WINKS' a come hither look...
https://en.wikipedia.org/wiki/Sexual_di ... rentiation

<<Size dimorphism shows a correlation with sexual cannibalism, which is prominent in spiders (it is also found in insects such as praying mantises). In the size dimorphic wolf spider, food-limited females cannibalize more frequently. Therefore, there is a high risk of low fitness for males due to pre-copulatory cannibalism, which led to male selection of larger females for two reasons: higher fecundity and lower rates of cannibalism. In addition, female fecundity is positively correlated with female body size and large female body size is selected for, which is seen in the family Araneidae. All Argiope species, including Argiope bruennichi, use this method. Some males evolved ornamentation including binding the female with silk, having proportionally longer legs, modifying the female's web, mating while the female is feeding, or providing a nuptial gift in response to sexual cannibalism. Male body size is not under selection due to cannibalism in all spider species such as Nephila pilipes, but is more prominently selected for in less dimorphic species of spiders, which often selects for larger male size.>>
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Re: APOD: Galaxies in the River (2020 Jan 08)

Post by MarkBour » Wed Jan 08, 2020 5:44 pm

APOD Robot wrote:
Wed Jan 08, 2020 5:07 am
Image Galaxies in the River

Explanation: Large galaxies grow by eating small ones ... galactic cannibalism ... absorbing ... captured ... locked in a gravitational struggle ... the smaller galaxy will eventually lose ...
I think this metaphor of "eating" for the process is quite strained and is being imposed onto this process by a competitive biological creature. Interesting that the name of the constellation is the river. When 2 rivers join, we don't really think of one as absorbing the other. They merge and continue together.

So, I like Boomer's and Orin's comments on the process.
Mark Goldfain

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Pro & confluences

Post by neufer » Wed Jan 08, 2020 6:35 pm

MarkBour wrote:
Wed Jan 08, 2020 5:44 pm

I think this metaphor of "eating" for the process is quite strained and is being imposed onto this process by a competitive biological creature. Interesting that the name of the constellation is the river. When 2 rivers join, we don't really think of one as absorbing the other. They merge and continue together.
https://en.wikipedia.org/wiki/River_Mersey wrote:
Click to play embedded YouTube video.
  • The quality of Mersey is not strained.
    It droppeth as the gentle rain from heaven
    Upon the place beneath. It is twice blest:
    It blesseth him that gives and him that takes.
<<Mersey river sediments from outer to inner estuary contain a variety of common organic pollutants, including polyaromatic hydrocarbons (PAH) with concentrations which fall in the middle of the range of similarly industrial-urban river-estuaries. The distribution of individual PAH compounds suggests that the Mersey has contaminants mainly derived from combustion sources such as vehicle exhaust as well as coal burning. The distribution of the toxic heavy metal Mercury (Hg) has been assessed by measuring 203 sediments taken from shallow cores extracted from both the main river and adjacent salt marshes. The average amount of Hg in the Mersey was found to be 2 mg/kg with the highest amounts of 5 mg/kg occurring below the surface at concentrations harmful to sediment dwelling biota. The vertical rise and fall in Hg pollution observed at four Mersey salt marshes indicated a decline in metal pollution since the 1980s.

[However,] salmon have returned to the Mersey river and have been seen jumping at Woolston and Howley Weirs between September and November.>>
Art Neuendorffer

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Re: APOD: Galaxies in the River (2020 Jan 08)

Post by ta152h0 » Thu Jan 09, 2020 1:53 am

Those numbers, with 3-4 !'s I need an ice old one.
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Re: Pro & confluences

Post by TheZuke! » Thu Jan 09, 2020 2:51 pm

neufer wrote:
Wed Jan 08, 2020 6:35 pm
MarkBour wrote:
Wed Jan 08, 2020 5:44 pm

I think this metaphor of "eating" for the process is quite strained and is being imposed onto this process by a competitive biological creature. Interesting that the name of the constellation is the river. When 2 rivers join, we don't really think of one as absorbing the other. They merge and continue together.
https://en.wikipedia.org/wiki/River_Mersey wrote:
Click to play embedded YouTube video.
  • The quality of Mersey is not strained.
    It droppeth as the gentle rain from heaven
    Upon the place beneath. It is twice blest:
    It blesseth him that gives and him that takes.
<<Mersey river sediments from outer to inner estuary contain a variety of common organic pollutants, including polyaromatic hydrocarbons (PAH) with concentrations which fall in the middle of the range of similarly industrial-urban river-estuaries. The distribution of individual PAH compounds suggests that the Mersey has contaminants mainly derived from combustion sources such as vehicle exhaust as well as coal burning. The distribution of the toxic heavy metal Mercury (Hg) has been assessed by measuring 203 sediments taken from shallow cores extracted from both the main river and adjacent salt marshes. The average amount of Hg in the Mersey was found to be 2 mg/kg with the highest amounts of 5 mg/kg occurring below the surface at concentrations harmful to sediment dwelling biota. The vertical rise and fall in Hg pollution observed at four Mersey salt marshes indicated a decline in metal pollution since the 1980s.

[However,] salmon have returned to the Mersey river and have been seen jumping at Woolston and Howley Weirs between September and November.>>
I didn't even click the link, neufer, and that song is stuck in my head!
B^)

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Re: Pro & confluences

Post by neufer » Thu Jan 09, 2020 3:52 pm

TheZuke! wrote:
Thu Jan 09, 2020 2:51 pm

I didn't even click the link, neufer, and that song is stuck in my head! B^)
  • You're welcome.
Art Neuendorffer

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Re: Pro & confluences

Post by MarkBour » Thu Jan 09, 2020 5:50 pm

neufer wrote:
Thu Jan 09, 2020 3:52 pm
TheZuke! wrote:
Thu Jan 09, 2020 2:51 pm

I didn't even click the link, neufer, and that song is stuck in my head! B^)
  • You're welcome.
Me too. It is a very fine song.

... the Shakespeare ain't bad, either. ;-)
Mark Goldfain