APOD: Arp 194: Merging Galaxy Group (2019 Mar 25)

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Re: APOD: Arp 194: Merging Galaxy Group (2019 Mar 25)

Post by Chris Peterson » Mon Mar 25, 2019 4:46 pm

zendae1 wrote: Mon Mar 25, 2019 4:21 pm Is there no way to perhaps see this amalgamation from 'the side'? We have had simulations that offer supposed views before. I do wonder what this looks like from any perpendicular location! From the real view, it looks like a train wreck.
Not really. The radial velocities of different components can be determined, which can provide input to simulations, and the possibility of calculating possible orbits. But that's about it. There's not a lot we can determine about the 3D structure.
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Re: APOD: Arp 194: Merging Galaxy Group (2019 Mar 25)

Post by neufer » Mon Mar 25, 2019 7:52 pm

https://scitechdaily.com/hubble-image-of-arp-194-cosmic-optical-illusions-in-ursa-major/ wrote: Hubble Image of Arp 194 – Cosmic Optical Illusions in Ursa Major
By NASA, ESA and the Hubble Heritage Team (STScI/AURA)
September 21, 2015

<<The galaxies at the top and bottom of the frame are named PGC 37639 and PGC 101374 respectively. Although it may look as if the two are in the middle of a galactic tug-of-war, connected by the prominent stream of blue through the center of the image, PGC 37639 lies somewhat closer to Earth than its companion, and the two are not physically connected.

In another optical trick, this image does not contain two galaxies, but at least four. The upper left patch actually hosts two galaxies in the early stages of merging. Their bright centers can still be seen separately, glowing amid a maelstrom of gas and dust. A smaller and relatively intact spiral galaxy, known as SDSSCGB 19.4, can be seen to the right of the merging duo. This trio of galaxies comprises Arp 194, a galaxy group just under 600 million light-years away from Earth in the constellation of Cepheus.

The blue stream is thought to have formed through the turbulent gravitational interactions occurring at the top of the frame — the uppermost galaxy clump is a whirl of flailing once-spiral arms. The stream is some 100,000 light-years long, and made up of gas, dust and many millions of newborn stars. These stars, which are clumped together to form star clusters, which in turn later accumulate as superclusters, are responsible for the striking blue hue visible here. They are mostly young, hot and massive, a combination that causes them to emit blue light.>>
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Re: APOD: Arp 194: Merging Galaxy Group (2019 Mar 25)

Post by neufer » Mon Mar 25, 2019 8:27 pm

Nitpicker wrote: Mon Mar 25, 2019 5:37 am
Another curious puzzle ... I've just noticed a number of different websites that say that Arp 194 is in Cepheus, when it is nowhere near Cepheus. It is in Ursa Major. I wonder who was the initial culprit to so successfully propagate this misinformation?
Hubble Celebrates Its 19th Anniversary with a "Fountain of Youth"
was probably released by non-astronomer NASA PR department
and contains a number of errors.
http://sci.esa.int/hubble/44682-constellation-region-near-arp-194/ wrote:
:arrow: This picture, taken with a small ground-based camera, highlights the part of the northern sky that includes: Ursa Major, Coma Berenices, Canes Venatici and Cepheus [sic]. Arp 194 lies within the constellation of Cepheus [sic], just below and to the left of the "foot" of the Great Bear (Ursa Major).
Arp 194 lies within the constellation of Ursa Majors ,
just below and to the left of the "foot" of the Great Bear
https://en.wikipedia.org/wiki/UGC_6945 wrote:
UGC 6945 (also known as Arp 194)

Right ascension 11h 57m 54.87s
Declination +36° 23′ 32.8″
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Re: APOD: Arp 194: Merging Galaxy Group (2019 Mar 25)

Post by Fred the Cat » Mon Mar 25, 2019 9:38 pm

I was reading an article and noticed a reference to a 1982 article in Sci-Am “Charge-coupled Devices in Astronomy”. So, I ran downstairs and found the old journal. :clap: (They don't make even the old stuff available for us web surfers) :( It stated,” A single pictures made by a CCD imager 500 pixels on a side holds the same amount of raw information as a 100,000 word book..” I have no idea how today’s CCD’s might stack up. :roll:

It seems hard to imagine it’s been almost 40 years since CCD’s have been around to make images available like we see today.
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Re: APOD: Arp 194: Merging Galaxy Group (2019 Mar 25)

Post by Chris Peterson » Mon Mar 25, 2019 10:05 pm

Fred the Cat wrote: Mon Mar 25, 2019 9:38 pm I was reading an article and noticed a reference to a 1982 article in Sci-Am “Charge-coupled Devices in Astronomy”. So, I ran downstairs and found the old journal. :clap: (They don't make even the old stuff available for us web surfers) :( It stated,” A single pictures made by a CCD imager 500 pixels on a side holds the same amount of raw information as a 100,000 word book..” I have no idea how today’s CCD’s might stack up. :roll:

It seems hard to imagine it’s been almost 40 years since CCD’s have been around to make images available like we see today.
I made this CCD image in 1977, a year out of high school. The sensor was a 100x100 element array made by Fairchild. Had to build the camera myself, and cool it with ice and alcohol. It's a 10 minute exposure with an autoguided 6-inch Newtonian (had to make the autoguider, too). Can't believe it was that long ago!

(Not much available in terms of display devices, either. I output this as a slow scan frame on an oscilloscope, a few seconds top to bottom, captured on a Polaroid camera. Scanned off the print years later. The digital data, if it still exists, must be floating around in a stored box of 8-inch floppy disks somewhere. I might have even output it to paper tape. 100x100x8-bit is only 10 kB, between 1% and 10% of a typical book in simple ASCII.)
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Re: APOD: Arp 194: Merging Galaxy Group (2019 Mar 25)

Post by Nitpicker » Mon Mar 25, 2019 10:29 pm

Chris, that sounds like typical teenage behaviour in the 70s ... abusing alcohol and messing around with psychedelics like CCD, to make the stars look pixelated. 😀

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Re: APOD: Arp 194: Merging Galaxy Group (2019 Mar 25)

Post by Ann » Mon Mar 25, 2019 11:33 pm

Chris Peterson wrote: Mon Mar 25, 2019 10:05 pm
Fred the Cat wrote: Mon Mar 25, 2019 9:38 pm I was reading an article and noticed a reference to a 1982 article in Sci-Am “Charge-coupled Devices in Astronomy”. So, I ran downstairs and found the old journal. (They don't make even the old stuff available for us web surfers) :( It stated,” A single pictures made by a CCD imager 500 pixels on a side holds the same amount of raw information as a 100,000 word book..” I have no idea how today’s CCD’s might stack up.

It seems hard to imagine it’s been almost 40 years since CCD’s have been around to make images available like we see today.
I made this CCD image in 1977, a year out of high school. The sensor was a 100x100 element array made by Fairchild. Had to build the camera myself, and cool it with ice and alcohol. It's a 10 minute exposure with an autoguided 6-inch Newtonian (had to make the autoguider, too). Can't believe it was that long ago!

(Not much available in terms of display devices, either. I output this as a slow scan frame on an oscilloscope, a few seconds top to bottom, captured on a Polaroid camera. Scanned off the print years later. The digital data, if it still exists, must be floating around in a stored box of 8-inch floppy disks somewhere. I might have even output it to paper tape. 100x100x8-bit is only 10 kB, between 1% and 10% of a typical book in simple ASCII.)
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ccd101.jpg
:clap:

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Re: APOD: Arp 194: Merging Galaxy Group (2019 Mar 25)

Post by orin stepanek » Tue Mar 26, 2019 11:57 am

I think I see 4 main galaxies in the picture! the 2 on top colliding; The one on the bottom interacting; the one on the viewers sight farther in the background and not involved. There maybe more that are hard to distinguish from stars! But it is just my humble opinion! :D
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Re: APOD: Arp 194: Merging Galaxy Group (2019 Mar 25)

Post by bystander » Tue Mar 26, 2019 3:45 pm

neufer wrote: Mon Mar 25, 2019 7:52 pm
SciTechDaily wrote:
Hubble Image of Arp 194 – Cosmic Optical Illusions in Ursa Major
By NASA, ESA and the Hubble Heritage Team (STScI/AURA)
September 21, 2015

This is actually a copy of an article at ESA Space Images. The image there is from Hubble Heritage and HubbleSite in April of 2009. There was also a write-up at the ESA Hubble site.

Interacting Galaxies Arp 194
Hubble Heritage (STScI/AURA) | 2009 Apr 21
Over the past 19 years Hubble has taken dozens of exotic pictures of galaxies going “bump in the night” as they collide with each other and have a variety of close encounters of the galactic kind. Just when you thought these interactions couldn’t look any stranger, this image of a trio of galaxies, called Arp 194, looks like one of the galaxies has sprung a leak. The bright blue streamer is really a stretched spiral arm full of newborn blue stars. This typically happens when two galaxies interact and gravitationally tug at each other.

Resembling a pair of owl eyes, the two nuclei of the colliding galaxies can be seen in the process of merging at the upper left. The bizarre blue bridge of material extending out from the northern component looks like it connects to a third galaxy but in reality the galaxy is in the background and not connected at all. Hubble’s sharp view allows astronomers to try and visually sort out what are foreground and background objects when galaxies, superficially, appear to overlap.

The blue "fountain" is the most striking feature of this galaxy troupe and it contains complexes of super star clusters, that may have as many as dozens of individual young star clusters in them. It formed as a result of the interactions among the galaxies in the northern component of Arp 194. The gravitational forces involved in a galaxy interaction can enhance the star formation rate and give rise to brilliant bursts of star formation in merging systems.

Hubble's resolution shows clearly that the stream of material lies in front of the southern component of Arp 194, as evidenced by the dust that is silhouetted around the star cluster complexes.

The details of the interactions among the multiple galaxies that make up Arp 194 are complex. The system was most likely disrupted by a previous collision or close encounter. The shapes of all galaxies involved have been distorted by their gravitational interactions with one another.

Arp 194, located in the constellation Cepheus, resides approximately 600 million light years away from Earth. Arp 194 is one of thousands of interacting and merging galaxies known in our nearby Universe. These observations were taken in January of 2009 with the Wide Field Planetary Camera 2. Blue, green and red filters were composited together to form the rather picturesque image of a galaxy interaction.
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Re: APOD: Arp 194: Merging Galaxy Group (2019 Mar 25)

Post by neufer » Tue Mar 26, 2019 4:11 pm

bystander wrote: Tue Mar 26, 2019 3:45 pm
Interacting Galaxies Arp 194
Hubble Heritage (STScI/AURA) | 2019 Apr 21 [sic]
Arp 194, located in the constellation Cepheus, resides approximately 600 million light years away from Earth. Arp 194 is one of thousands of interacting and merging galaxies known in our nearby Universe. These observations were taken in January of 2009 with the Wide Field Planetary Camera 2. Blue, green and red filters were composited together to form the rather picturesque image of a galaxy interaction.
http://asterisk.apod.com/viewtopic.php? ... 25#p290857
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Re: APOD: Arp 194: Merging Galaxy Group (2019 Mar 25)

Post by Ann » Tue Mar 26, 2019 5:37 pm

neufer wrote: Tue Mar 26, 2019 4:11 pm
bystander wrote: Tue Mar 26, 2019 3:45 pm
Interacting Galaxies Arp 194
Hubble Heritage (STScI/AURA) | 2019 Apr 21 [sic]
Arp 194, located in the constellation Cepheus, resides approximately 600 million light years away from Earth. Arp 194 is one of thousands of interacting and merging galaxies known in our nearby Universe. These observations were taken in January of 2009 with the Wide Field Planetary Camera 2. Blue, green and red filters were composited together to form the rather picturesque image of a galaxy interaction.
http://asterisk.apod.com/viewtopic.php? ... 25#p290857
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Re: APOD: Arp 194: Merging Galaxy Group (2019 Mar 25)

Post by Nitpicker » Tue Mar 26, 2019 11:15 pm

The initial error (by whoever) of locating Arp 194 in Cepheus was fairly minor. That it has been copy-pasted so many times, on so many different sites (more sites than listed by Art and bystander), over a decade, with no verification, is a bit poor.

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Re: APOD: Arp 194: Merging Galaxy Group (2019 Mar 25)

Post by Nitpicker » Wed Mar 27, 2019 12:02 am

The HST image of Arp 194, recorded in Jan 2009, must have been one of the last to be recorded with the WFPC2 camera, which was removed in May 2009, and replaced with the WFC3 camera.

The 2002 paper than Ann provided a link to, and the 2016 paper in the "because of" link in the APOD caption, are both clear in their assertions that the southern galaxy "recently" passed through the northern galaxy (of two close components). Both these papers were based on detailed spectral observations using large, ground-based telescopes.

I am not sure of the basis for the alternative assertion, that the southern galaxy is more distant and unrelated to the bridge between the northern and southern components. The only basis I have read was something along the lines of "the higher resolution of the Hubble image shows the bridge to be clearly in front of the southern galaxy". This seems like a weak basis to form an alternative assertion. I don't profess to be very good at interpreting images of galaxies, but it is certainly not obvious to me that the bridge is "clearly" in front of the southern galaxy in this APOD, to the point that they are only a chance alignment.