by Ann » Wed Nov 09, 2022 5:32 am
johnnydeep wrote: ↑Tue Nov 08, 2022 10:45 pm
AVAO wrote: ↑Tue Nov 08, 2022 6:15 am
...The description is misleading. Only two of the three galaxies are shown in today's APOD image...
http://www.caelumobservatory.com/mlsc/wilds.jpg
Credit / Copyright: Adam Block/Mount Lemmon SkyCenter/University of Arizona
I had noticed that discrepancy as well, but what's the true story here? Are the three galaxies in the image at the Wikipedia page really interacting or not? From the clear trails of stars connecting them, I would say yes. Yet this APOD implies that only two of the galaxies in the "Wild Triple" are interacting, which is clearly the actual case if the three galaxies are instead the ones in this APOD.
Wikipedia wrote:
Wild's Triplet is a group of three small, interacting spiral galaxies. The galaxies are visible in the constellation Virgo. The triplet has luminous connecting bridges and is located some 200 million light-years away.
The Wikipedia stub is illustrated with the same Adam Block image that AVAO posted here. Clearly the background galaxy in the APOD has never been a member of Wild's Triplet.
You can tell that the two galaxies seen in the APOD are small:
As for this member of Wild's Triplet, note that its huge region of star formation (at lower right) is probably brighter, or at least as bright, as its center. Only low-mass galaxies can have regions of star formation brighter than their centers. Note in the picture of the low-mass, highly disturbed galaxy NGC 1313 that its pink and blue arms are brighter than its center.
The other member of Wild's Triplet imaged in the APOD appears to be a little more massive, or at least its center is a little brighter. The core is somewhat large and "abruptly brighter" than its yellow-orange surroundings, which suggests that it is encircled by a bright ring of formation, similar to what we see in galaxy NGC 4314.
To me, the two galaxies of Wild's Triplet seen in the APOD also look small because they are "coarse" and not so elegant. Let's compare them with another galaxy that is actually not very big, but I find it quite elegant:
NGC 5054. Image: Mark Hanson and Mike Selby.
Note the beautifully shaped yellow inner region of NGC 5054, with fine dust lanes winding inside it. The core may be surrounded by regions of star formation. The yellow inner disk is ring-shaped and well separated from the arms, whose inner parts are delineated by elegant thin dust lanes. The spiral arms are quite long, elegantly curved and full of regions of star formation of pink and blue. I would not be entirely surprised if the small edge-on blue galaxy at right is a satellite galaxy of NGC 5054, which interacts with the larger galaxy.
But the members of Wild's Triplet are much coarser. The stellar populations of their centers and arms are not nearly as well separated, and their dust lanes are nowhere near as thin and long. They do look small to me - and they are.
Ann
[quote=johnnydeep post_id=327031 time=1667947546 user_id=132061]
[quote=AVAO post_id=327014 time=1667888149 user_id=144694]
[quote="APOD Robot" post_id=327013 time=1667884125 user_id=128559]
[url=https://apod.nasa.gov/apod/ap221108.html] [img]https://apod.nasa.gov/apod/calendar/S_221108.jpg[/img] [size=150]Galaxies: Wild's Triplet from Hubble[/size][/url]
...[b]This grouping of galaxies[/b] is called the [url=https://en.wikipedia.org/wiki/Wild's_Triplet]Wild Triplet[/url], not only for the [url=https://en.wikipedia.org/wiki/Paul_Wild_(Australian_scientist)]discoverer[/url], but for the number of bright galaxies that appear. It had been assumed [b]that all three galaxies[/b], collectively cataloged as [url=https://ned.ipac.caltech.edu/level5/Arp/Arp_contents.html]Arp[/url] 248, are [url=https://apod.nasa.gov/apod/ap130514.html]interacting[/url], but more [url=https://i.insider.com/55a67a7a371d22ce178b6624]recent investigations[/url] reveal that only the brightest two galaxies are sparring gravitationally: the big galaxies at the top and bottom.
...
[/quote]
...The description is misleading. Only two of the three galaxies are shown in today's APOD image...
[img]https://upload.wikimedia.org/wikipedia/commons/9/99/Wildss.jpg[/img]
[url]http://www.caelumobservatory.com/mlsc/wilds.jpg[/url]
[size=50] Credit / Copyright: Adam Block/Mount Lemmon SkyCenter/University of Arizona[/size]
[/quote]
I had noticed that discrepancy as well, but what's the true story here? Are the three galaxies in the image at the Wikipedia page really interacting or not? From the clear trails of stars connecting them, I would say yes. Yet this APOD implies that only two of the galaxies in the "Wild Triple" are interacting, which is clearly the actual case if the three galaxies are instead the ones in this APOD.
[/quote]
[quote][url=https://en.wikipedia.org/wiki/Wild%27s_Triplet]Wikipedia[/url] wrote:
Wild's Triplet is a group of three small, interacting spiral galaxies. The galaxies are visible in the constellation Virgo. The triplet has luminous connecting bridges and is located some 200 million light-years away. [/quote]
The Wikipedia stub is illustrated with the same Adam Block image that AVAO posted here. Clearly the background galaxy in the APOD has never been a member of Wild's Triplet.
You can tell that the two galaxies seen in the APOD are small:
[float=right][img3="NGC 1313, imaged on ATEO-3 by Franck Jobard and processed by Utkarsh Mishra from Deep Sky Chile." ]https://1.bp.blogspot.com/-rUNgq_IlSYQ/YIQod3UhukI/AAAAAAAADPo/jDZ3AfeqLG8pFSrdXGGXUV6fBL7oECbRwCNcBGAsYHQ/s2048/ateo-3_ngc1313_umishra.jpg[/img3][/float][attachment=2]APOD 8 November 2022 Wilds Triplet galaxy 2.png[/attachment]
[clear][/clear]
As for this member of Wild's Triplet, note that its huge region of star formation (at lower right) is probably brighter, or at least as bright, as its center. Only low-mass galaxies can have regions of star formation brighter than their centers. Note in the picture of the low-mass, highly disturbed galaxy NGC 1313 that its pink and blue arms are brighter than its center.
[float=left][attachment=1]APOD 8 November 2022 Wilds Triplet galaxy 1.png[/attachment][/float][float=right][img3="The core of galaxy NGC 4314, surrounded by a ring of star formation. Credit: G. Fritz Benedict, Andrew Howell, Inger Jorgensen, David Chapell (University of Texas), Jeffery Kenney (Yale University), and Beverly J. Smith (CASA, University of Colorado), and NASA "]https://upload.wikimedia.org/wikipedia/commons/3/39/NGC_4314HST1998-21-b-full.jpg[/img3][/float]
[clear][/clear]
The other member of Wild's Triplet imaged in the APOD appears to be a little more massive, or at least its center is a little brighter. The core is somewhat large and "abruptly brighter" than its yellow-orange surroundings, which suggests that it is encircled by a bright ring of formation, similar to what we see in galaxy NGC 4314.
To me, the two galaxies of Wild's Triplet seen in the APOD also look small because they are "coarse" and not so elegant. Let's compare them with another galaxy that is actually not very big, but I find it quite elegant:
[float=left][attachment=0]NGC 5054 Mark Hanson.png[/attachment][c][size=85][color=#0040FF]NGC 5054. Image: Mark Hanson and Mike Selby.[/color][/size][/c][/float]
[clear][/clear]
Note the beautifully shaped yellow inner region of NGC 5054, with fine dust lanes winding inside it. The core may be surrounded by regions of star formation. The yellow inner disk is ring-shaped and well separated from the arms, whose inner parts are delineated by elegant thin dust lanes. The spiral arms are quite long, elegantly curved and full of regions of star formation of pink and blue. I would not be entirely surprised if the small edge-on blue galaxy at right is a satellite galaxy of NGC 5054, which interacts with the larger galaxy.
But the members of Wild's Triplet are much coarser. The stellar populations of their centers and arms are not nearly as well separated, and their dust lanes are nowhere near as thin and long. They do look small to me - and they are.
Ann