APOD: Peculiar Galaxies of Arp 273 (2017 Jan 05)

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APOD: Peculiar Galaxies of Arp 273 (2017 Jan 05)

Postby APOD Robot » Thu Jan 05, 2017 1:25 pm

Image Peculiar Galaxies of Arp 273

Explanation: The spiky stars in the foreground of this sharp cosmic portrait are well within our own Milky Way Galaxy. The two eye-catching galaxies lie far beyond the Milky Way, at a distance of over 300 million light-years. Their distorted appearance is due to gravitational tides as the pair engage in close encounters. Cataloged as Arp 273 (also as UGC 1810), the galaxies do look peculiar, but interacting galaxies are now understood to be common in the universe. In fact, the nearby large spiral Andromeda Galaxy is known to be some 2 million light-years away and approaching the Milky Way. Arp 273 may offer an analog of their far future encounter. Repeated galaxy encounters on a cosmic timescale can ultimately result in a merger into a single galaxy of stars. From our perspective, the bright cores of the Arp 273 galaxies are separated by only a little over 100,000 light-years.

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Ann
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Re: APOD: Peculiar Galaxies of Arp 273 (2017 Jan 05)

Postby Ann » Thu Jan 05, 2017 3:47 pm

I am full of admiration for Wolfgang Ries and Stefan Heutz for producing such a fine portrait of a fascinating interacting pair of galaxies that more than 300 million light-years from the Earth. As if that wasn't enough, two moderately bright stars - 9th and 10th magnitude - complicate matters by lining up right next to the faint 13th magnitude galaxies.

So you did extremely well, Wolfgang and Stefan!

Arp 273. NASA/ESA and Hubble Space Telescope.
Arp 272. NASA, ESA, the Hubble Heritage (STScI/AURA)
ESA/Hubble Collaboration, and K. Noll (STScI)

For all of that, today's APOD can't compete with the Hubble portrait of the same galaxies, and I don't see how it could be otherwise.
















The Hubble portrait of Arp 273 (the picture at left) shows a fascinating detail in the larger galaxy. At 1 o'clock, there is what looks like a tiny barred galaxy tangled in the large spiral's outer arm. Colorwise, the small barred object is non-red enough to be at the same general distance as Arp 273. Personally I believe that this object really is a small intruder, and that it has affected the large galaxy's structure. Note the numerous large and small blue clusters that seem to emanate from the general vicinity of the small trespasser and flow left, until they merge with the long, sweeping arm of the large galaxy. Similar clusters are found in a shorter arm of the large galaxy as well, an arm that seems to point directly at the intruder.

An even more striking example of a very small galaxy entering the "battle" between two larger galaxies is Arp 272, the galaxy pair at right. You can't miss the small galaxy that seems to sit smack in the middle of an "overhead arm" joining NGC 6050 and IC 1179.

I'd like to add, speaking of today's APOD, that Wolfgang Ries and Stefan Heutz' image sheds light on the Hubble portrait bringing out the colors of NGC 273 in a way that is really illuminating. You can see the small intruder as a tiny orange dot in today's APOD, and you can also see a long line of strikingly blue clusters in the vicinity of the intruder. The very regular arms of the large galaxy suggests that they are affected more by tidal forces than by the ravages of runaway star formation, but the color gradient of the arms still let us see clearly what parts of the arm are forming new stars and what parts aren't.

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Re: APOD: Peculiar Galaxies of Arp 273 (2017 Jan 05)

Postby starsurfer » Thu Jan 05, 2017 5:02 pm

Shouldn't the copyright also include Michael Breite since he is a member of the team?

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Re: APOD: Peculiar Galaxies of Arp 273 (2017 Jan 05)

Postby Ann » Thu Jan 05, 2017 5:35 pm

Arp 273. NASA/ESA and Hubble Space Telescope.
Arp 272. NASA, ESA, the Hubble Heritage (STScI/AURA)
ESA/Hubble Collaboration, and K. Noll (STScI)


























I apologize for showing these two galaxy pictures once again, but I just realized a fascinating similarity when it comes to the star formation of these interacting galaxies. In my other post, I pointed out the regularly spaced blue clusters being churned out in the top arm of the large spiral of the interacting pair Arp 273, UGC 1810. Well, please note that the smaller spiral of the interacting pair Arp 272, IC 1179 (at right), is also churning out bright blue clusters at regular intervals!

Fascinating! I have long wondered why IC 1179 acted that way, but now I can see that UGC 1810 is doing something similar! Maybe it has something to do with a galactic threesome after all?

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Re: APOD: Peculiar Galaxies of Arp 273 (2017 Jan 05)

Postby Ann » Fri Jan 06, 2017 7:05 pm

I was going to edit my post above, but I was too late, so... Please note that the galaxies involved in making such waves and such "sequential clusters" are spectacularly barred. The little galaxy interloper tangled in the outer arm of UGC 1810 in Arp 273 is "all bar". The galaxy sitting between NGC 6050 and IC 1179 is pretty much "all bar", too. And IC 1179 is also spectacularly barred. It doesn't seem to have a core at all, just a bar running along its middle. And amazingly, its bar is really no brighter than the bar of the little galaxy at top.

You can see another, really nice version of this galactic threesome here.

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Re: APOD: Peculiar Galaxies of Arp 273 (2017 Jan 05)

Postby MarkBour » Fri Jan 06, 2017 7:24 pm

Ann wrote: ... spectacularly barred.

I'm reading this on my cell phone. Always nice to get three or more bars. :D
Mark Goldfain


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