by Ann » Tue May 17, 2022 5:18 am
NGC 1316 and NGC 1317 are a fascinating pair of interacting galaxies!
NGC 1316 is a portrait of the aftermath of some sort of collision (which certainly involved NGC 1317 to the upper right of NGC 1316 in the APOD), whereas NGC 1275 is a portrait of the collision as it is happening (and the hapless smaller galaxy is no longer visible as an independent entity).
There is another galactic pair that is somewhat similar to NGC 1316/NGC 1317, namely NGC 474/NGC 470. There is a large elliptical that shows severe signs of upheaval, paired with a much more calm-looking spiral galaxy sporting a prominent ring:
The main difference between NGC 1316 and NGC 474 is that the tidal shells of NGC 1316 look rather messy, whereas in NGC 474 they look more elegant and "sculpted". And there are a number of "nested shells" in NGC 474.
A fascinating aspect of the NGC 1316/NGC 1317 pair is that NGC 1316 is classified as a (barred) lenticular galaxy, a galaxy with a disk but with little dust and no star formation, whereas NGC 1317 is classified as a barred spiral galaxy. But you can tell at a glance that these two galaxies are pretty much exactly the same color, the same shade of completely dominant yellow. Their color indexes confirm it: Both have a B-V index of +0.89! Their U-B indexes are also very similar, if not identical: +0.29 for NGC 1317 and +0.39 for NGC 1316.
The reason why NGC 1317 is a little more ultraviolet than than NGC 1316 is that NGC 1317 sports a nuclear ring of star formation, the only place in NGC 1317 where (any sort of substantial) star formation is taking place:
Note that NGC 1317 is another of those two-ringed galaxies: There is a nuclear ring encircling the core and a larger ring encircling the galactic bar. There was
another APOD showing such a two-ringed galaxy just a little more than a week ago. Do you remember?
Ann
NGC 1316 and NGC 1317 are a fascinating pair of interacting galaxies!
[float=left][img3="NGC 1316: After Galaxies Collide. Image Credit & Copyright: Capture: Greg Turgeon; Processing: Kiko Fairbairn"]https://apod.nasa.gov/apod/image/2205/Ngc1316_Turgeon_960.jpg[/img3][/float][float=right][img3="Elliptical galaxy NGC 1275 in the process of merging with a small spiral galaxy, producing dust, star formation and threads of ionized gas in the large elliptical. Image: NASA, ESA, and the Hubble Heritage."]https://upload.wikimedia.org/wikipedia/commons/thumb/0/0a/NGC_1275_Hubble.jpg/1280px-NGC_1275_Hubble.jpg[/img3][/float]
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NGC 1316 is a portrait of the aftermath of some sort of collision (which certainly involved NGC 1317 to the upper right of NGC 1316 in the APOD), whereas NGC 1275 is a portrait of the collision as it is happening (and the hapless smaller galaxy is no longer visible as an independent entity).
There is another galactic pair that is somewhat similar to NGC 1316/NGC 1317, namely NGC 474/NGC 470. There is a large elliptical that shows severe signs of upheaval, paired with a much more calm-looking spiral galaxy sporting a prominent ring:
[float=left][img3="Galaxy NGC 474: Cosmic Blender. Credit & Copyright: Mischa Schirmer."]https://apod.nasa.gov/apod/image/0710/ngc474_schirmer.jpg[/img3][/float]
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The main difference between NGC 1316 and NGC 474 is that the tidal shells of NGC 1316 look rather messy, whereas in NGC 474 they look more elegant and "sculpted". And there are a number of "nested shells" in NGC 474.
A fascinating aspect of the NGC 1316/NGC 1317 pair is that NGC 1316 is classified as a (barred) lenticular galaxy, a galaxy with a disk but with little dust and no star formation, whereas NGC 1317 is classified as a barred spiral galaxy. But you can tell at a glance that these two galaxies are pretty much exactly the same color, the same shade of completely dominant yellow. Their color indexes confirm it: Both have a B-V index of +0.89! Their U-B indexes are also very similar, if not identical: +0.29 for NGC 1317 and +0.39 for NGC 1316.
The reason why NGC 1317 is a little more ultraviolet than than NGC 1316 is that NGC 1317 sports a nuclear ring of star formation, the only place in NGC 1317 where (any sort of substantial) star formation is taking place:
[float=left][attachment=0]NGC 1317 detail from APOD 17 May 2022.png[/attachment][/float][float=right][img3="The nuclear ring of star formation in NGC 1317. Image: ESA/Hubble & NASA, J. Lee and the PHANGS-HST Team."]https://cdn.spacetelescope.org/archives/images/screen/potw2148a.jpg[/img3][/float]
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Note that NGC 1317 is another of those two-ringed galaxies: There is a nuclear ring encircling the core and a larger ring encircling the galactic bar. There was [url=https://apod.nasa.gov/apod/ap220508.html]another APOD[/url] showing such a two-ringed galaxy just a little more than a week ago. Do you remember?
[img3="Spiral Galaxy NGC 1512: The Inner Rings. Image Credit: NASA, ESA, Hubble Space Telescope"]https://apod.nasa.gov/apod/image/2205/NGC1512inner_Hubble_960.jpg[/img3]
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Ann