by Ann » Tue Jan 23, 2024 7:35 pm
Okay! This is a great APOD, but at the same time, it's really hard to make head or tails of some of the deep-sky objects here!
One thing that I absolutely love about this APOD is how it shows us that the nebulosities here seem to be connected and form huge shells!
But I frankly can't identify all the nebulas here - in fact, not by a long shot! But let's take a look at some of the stars and nebulas and see what I
think they are!
As you can see, I tried to identify only parts of the APOD, and I wasn't able to identify all the nebulas
at all. But let's look at some of the sights here:
Let's talk a little about the what the APOD really reveals to us. The photographer, Alistair Symon, is a master at bringing out even very faint red hydrogen alpha emission (even if it looks yellow in today's APOD). That's why we see so many nebulas in this APOD. Many of the nebulas here are so faint that they are very rarely photographed.
But Alistair Symon is showing us something else too, namely that long stretches of the Milky Way are
not home to visible red nebulas or visible star formation. Take a look at this picture of the northern Milky Way:
What we can learn from this is that, while dust seems to be necessary to create the right conditions for star formation in the nearby universe, the presence of dust does not guarantee the presence of star formation at all. Long dust lanes can indeed be "sterile":
There is more than meets the eye in the parts of the Milky Way that are rich in gas and dust. But there are also parts of the Milky Way that appear as "barren" as a desert, or as barren as a dusty but non-starforming elliptical galaxy. Like NGC 1316.
So to summarize, galaxies are mysterious. Sometimes they rejuvenate themselves by birthing new stars, and sometimes they don't.
Ah yes, sometimes things happen and sometimes they don't. Completely off topic, here is a bonus video.
Click to play embedded YouTube video.
Ann
Okay! This is a great APOD, but at the same time, it's really hard to make head or tails of some of the deep-sky objects here!
[img3="Deep Nebulas: From Seagull to California.
Image Credit & Copyright: Alistair Symon"]https://apod.nasa.gov/apod/image/2401/SeagullToCalifornia_Symon_960_Annotated.jpg[/img3]
One thing that I absolutely love about this APOD is how it shows us that the nebulosities here seem to be connected and form huge shells!
[attachment=0]APOD 23 January 2024 annotated.png[/attachment]
But I frankly can't identify all the nebulas here - in fact, not by a long shot! But let's take a look at some of the stars and nebulas and see what I [b][i]think[/i][/b] they are!
[attachment=1]APOD 23 January 2024 detail annotated.png[/attachment]
As you can see, I tried to identify only parts of the APOD, and I wasn't able to identify all the nebulas [b][i]at all[/i][/b]. But let's look at some of the sights here:
[img3="IC 2162. Isn't this one funny? It looks like a pair of red alien eyes in front of, perhaps, a red skull or something! Credit: Bernhard Hubl."]https://lh5.googleusercontent.com/proxy/wq0k41QsoGoieP3JMgEBlrD5nvjmMphNMPV7WYvgkhDoaMcjBR_rFGqeLU36GHyZfs6ulIEUEDHwgWTWXLhwv5QpXHPT[/img3]
👀 :D
[float=left][img3="Sharpless 261. The annotated APOD calls it Sh2-262, but that's another nebula. Sharpless 261 looks like a half-closed eye, doesn't it? Credit: Steve Milne."]https://cdn.astrobin.com/thumbs/oGlGc4eseZH8_1824x0_5KAh9wxn.jpg[/img3][/float][float=right][img3="This half-closed eye looks like nebula Sharpless 261, doesn't it?"]https://thumbs.dreamstime.com/z/half-closed-eye-woman-white-background-half-closed-eye-woman-white-background-drawing-160154998.jpg[/img3][/float]
[clear][/clear]
[img3="I like this picture, because it shows us where things are located relative to one another. The Jellyfish Nebula is at upper center, just above orange star Eta Geminorum. Blue reflection nebula is to the upper right of the Jellyfish Nebula, and orange Mu Geminorum is at top, next to another red nebula. At far left is the Monkeyhead Nebula, and at far right is star cluster M35. To the lower left of M35, you can see small whitish blob. That's rich old cluster NGC 2158. In this picture, north is to the right. Credit: Scott Rosen."]http://www.astronomersdoitinthedark.com/images/product/images/NGC2174-IC443-200-450D-Ha-1600-2013-0130-0131--40x600-28x300--RGB-0203-70x180-32x300--640x.jpg[/img3]
[img3="I love pictures that show the connection between the Rosette Nebula and the Cone Nebula and Christmas Tree Cluster. In this picture, the Rosette Nebula is at center right, and the Cone Nebula and Christmas Tree Cluster at center left. Credit: Ahmed Waddah."]https://live.staticflickr.com/65535/53479921499_837b6fd300.jpg[/img3]
[float=left][img3="I love this picture! The large red shape is the Seagull Nebula, looking most impressive indeed, and the small blue 'insect' or 'butterfly' is Thor's Helmet! Credit: Ali Alobaidly"]https://astrob.in/tjqbld/0/rawthumb/regular/get.jpg?insecure[/img3]
[/float][float=right][img3="Not quite like this but something like this!"]https://as2.ftcdn.net/v2/jpg/05/28/60/07/1000_F_528600771_ifVQU7RQrzhIojjD6oqMpyNrIIRtGkeP.jpg[/img3][/float]
[clear][/clear]
Let's talk a little about the what the APOD really reveals to us. The photographer, Alistair Symon, is a master at bringing out even very faint red hydrogen alpha emission (even if it looks yellow in today's APOD). That's why we see so many nebulas in this APOD. Many of the nebulas here are so faint that they are very rarely photographed.
But Alistair Symon is showing us something else too, namely that long stretches of the Milky Way are [b][i]not[/i][/b] home to visible red nebulas or visible star formation. Take a look at this picture of the northern Milky Way:
[img3="In this picture, red hydrogen alpha is indeed shown as red. At far left you can see NGC 7822. To the right of NGC 7822 are many nebulas in Cepheus, among them IC 1396. Then there is a black 'gap' and after that we have the North America Nebula and the Veil Nebula among others. 'Below' the band of the Milky Way in the Lacerta nebula. But please note the long stretch of Milky Way that does not contain any red nebulas at all! At far right, though, you can spot some tiny nebulas in Serpens and Sagittarius, among them the Lagoon Nebula. Credit: Alistair Symon."]https://www.woodlandsobservatory.com/MilkyWaytoCassiopeia/Full%20Milky%20Way%201000%20400K.jpg[/img3]
What we can learn from this is that, while dust seems to be necessary to create the right conditions for star formation in the nearby universe, the presence of dust does not guarantee the presence of star formation at all. Long dust lanes can indeed be "sterile":
[img3="AM 1316-241 is a pair of overlapping galaxies. one arm of the spiral galaxy at left is lit from behind by the light from from the elliptical galaxy at right. Note the long stretch of arm that contains dust only and no star clusters or nebulas at all. Credit: NASA, ESA, the Hubble Heritage (STScI/AURA)-ESA/Hubble Collaboration, and W. Keel (University of Alabama, Tuscaloosa)"]https://d2pn8kiwq2w21t.cloudfront.net/images/jpegPIA10389.width-1600.jpg[/img3]
There is more than meets the eye in the parts of the Milky Way that are rich in gas and dust. But there are also parts of the Milky Way that appear as "barren" as a desert, or as barren as a dusty but non-starforming elliptical galaxy. Like NGC 1316.
[img3="Elliptical galaxy NGC 1316. There is dust here, but no young star clusters or nebulas. The gas and dust in NGC 1316 is 'sterile'. Credit: NASA, ESA, and The Hubble Heritage Team (STScI/AURA)"]https://upload.wikimedia.org/wikipedia/commons/thumb/a/a4/Ngc1316_hst.jpg/1024px-Ngc1316_hst.jpg[/img3]
So to summarize, galaxies are mysterious. Sometimes they rejuvenate themselves by birthing new stars, and sometimes they don't.
Ah yes, sometimes things happen and sometimes they don't. Completely off topic, here is a bonus video.
[youtube]https://www.youtube.com/watch?v=lwLLFbC1H0c[/youtube]
Ann