APOD: Stairway to the Milky Way (2024 May 29)

[APOD Robot]

Stairway to the Milky Way

Explanation: What happens if you ascend this stairway to the Milky Way? Before answering that, let's understand the beautiful sky you will see. Most eye-catching is the grand arch of the Milky Way Galaxy, the band that is the central disk of our galaxy which is straight but distorted by the wide-angle nature of this composite image. Many stars well in front of the Milk Way will be visible, with the bright white star just below the stellar arch being Altair, and the bright blue star above it being Vega. The air glows green on the left, just above the yellow cloud deck. The featured image was taken last month on Portugal's Madeira Island in the North Atlantic Ocean. Oh, and what happens after you reach the top of these stairs and admire the amazing sky is, quite probably, that you then descend down the stairs on the other side.

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[Ann]

Yes, that's a nice Milky Way image (with stairs)!

Stairway to the Milky Way. Image Credit & Copyright: Marcin Rosadziński

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Me being me, I obviously love the blue zing of bright star Vega at top!


But I'd also like to call your attention to the reddish patch of nebulosity around Deneb:

I believe that this reddish patch is the northern bar-end enhancement of the Milky Way. So what's a galactic bar-end enhancement? It's the part of a barred spiral galaxy where the bar meets the spiral arm. This particular part of a barred spiral often displays enhanced levels of star formation, like this:

NGC 6217 with bar and bar-end enhancement.
Credit: NASA/ESA/Hubble.

Astronomer and astrophotographer David Malin told me once, in private conversation, that there are two parts along the band of the Milky Way where the bar meets the spiral arms, and these two sites display enhanced star formation. One of these sites is in Cygnus near Deneb and Sadr. The other one is in Carina.

Bar-end enhancement in Carina (the Carina Nebula). Credit: Alan Dyer.

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Or perhaps it is NGC 3603 (and maybe NGC 3576) that are the bar-end enhancements of the southern Milky Way? Well, we are still in Carina.

NGC 3603 at left, NGC 3576 at right. Credit: ESO.

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And when the galactic evolution has run its course, and star formation has long since come to an end, the bar-end enhancements may still be visible.

NGC 936. Credit: SDSS/Donald Pelletier.

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Ann

[Sa Ji Tario]

Is the object under the letters "Air Glow" Andromeda?

[Ann]

Is the object under the letters "Air Glow" Andromeda?

Yes, it looks like that!

Ann

[desertengineer2]

Wow! I remember walking this EXACT bridge back in my days of exploring this beautiful island.

The weather is unpredictable in the Azores, but sometimes when the sky IS clear, it is REALLY clear! I remember walking out at 1 AM and watching the Perseids for about an hour that the sky had parted. At the time, they turned lights off at night to conserve electricity, so the sky was one of the darkest in the world, when clear.

[desertengineer2]

So, this is a trail that takes you up to an overlook of both the island and a peak on the side of the old remnants of the shield volcano. The whole island is actually just a collection of BIG volcanic cones. From the top, on a clear day, you get an amazing view of a partially collapsed cinder cone of the highest peak, plus a majestic view of the island. ON A CLEAR DAY. Most of the time, the 45 minute drive up, climbing about 6000 ft, starts clear, but turns into cold rain and fog. I remember being there one summer and freezing in wet rain when we got to the top. Because the Atlantic air is humid, it almost always gets foggy and rainy when lifted up the mountain. But the park is still really beautiful to visit.

There are also MANY other sites to see there. From amazing beaches of jagged rock to heavenly fields of cows, ancient rock walls, and cows. The food is the best I've ever had. The festivals in August are really fun to see in Funchal, which I think is the city lights under the cloud deck. Amazing cathedral. You will never get a better coffee than here.

I know the island has really grown in the last ten years, and may have become a bit more "touristy", but is still worth a trip. Being a 4-hour flight from the US, this is pretty much the closest to "old Europe" you will find. Late Spring to Late Summer is pretty much the only window you'll get to visit, as when winter comes, it's nothing but howling wind and cold rain for most of the cold season. Still, go see it if you get a chance. LOTS of history. LOTS of small vineyards with AMAZING wines they DO NOT export, so what you mail home and bring back is all you are going to get. Oh, did I mention the food?

[johnnydeep]

Or perhaps it is NGC 3603 (and maybe NGC 3576) that are the bar-end enhancements of the southern Milky Way? Well, we are still in Carina.

Do the distances (from Wikipedia) to NGC 3603 (20,000 ly) and NGC 3576 (9,000 ly) jibe with either or both of them being physically in the "bar-end"?

EDIT: I suppose so, based on this map of the Milky Way, where the circular lines are 5,000 ly wide. But maybe they're not in the SAME bar-end!

Bystander's replacement link:
https://science.nasa.gov/wp-content/upl ... ormat=webp

*** EDIT: About the edit from bystander about my hot-linking to a large image. I thought I linked to the one below, which is only 895 kb in size. Do the dimensions matter too?

https://science.nasa.gov/wp-content/upl ... ormat=webp

[Ann]

Or perhaps it is NGC 3603 (and maybe NGC 3576) that are the bar-end enhancements of the southern Milky Way? Well, we are still in Carina.

Do the distances (from Wikipedia) to NGC 3603 (20,000 ly) and NGC 3576 (9,000 ly) jibe with either or both of them being physically in the "bar-end"?

EDIT: I suppose so, based on this map of the Milky Way, where the circular lines are 5,000 ly wide. But maybe they're not in the SAME bar-end!

NGC 3603 is definitely far more distant than NGC 3576. They are not close to one another at all, but at least they are in the same general bar-end overall region of the Milky Way (or so I believe anyway). However, we must bear in mind that we can only see a relatively small part of the Milky Way. So we could be missing the real bar ends!

My guess is that at least one of these nebulas marks the general position of one of the galactic bar ends, and NGC 3603 is definitely the likeliest culprit. It is one of the largest star forming regions in our galaxy, actually (I think) the largest.

Image of the NGC 3603 region were obtained in three near-IR filter bands (Js, H and Ks) with the ISAAC instrument at the ANTU telescope. Credit: ESO.

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But I guess it's possible that the "shearing motion" of the bar stirs up gas further out from the bar end (or, alternatively, further out along the bar), and thus triggers massive star formation further out as well.

You can see in NGC 1672 that it is forming stars at different distances from the outer parts of the bar.

This NASA Hubble Space Telescope view of the nearby barred spiral galaxy NGC 1672 unveils details in the galaxy’s star-forming clouds and dark bands of interstellar dust. Credit: NASA, ESA, and The Hubble Heritage Team

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Ann

[johnnydeep]

Thanks, Ann!

[Guest]

The galaxy is not bent unless you distort the photo. The galaxy seen from within the disk is straight. This is improper to make laymen think this arch actually exists. These photos of bent Milky Ways are improper and shouldn’t be posted.

[Case]

The galaxy is not bent unless you distort the photo. The galaxy seen from within the disk is straight. This is improper to make laymen think this arch actually exists. These photos of bent Milky Ways are improper and shouldn’t be posted.

One has to compromise, when projecting a “dome” to a 2D surface. Do you also object to flat whole Earth maps?

[Chris Peterson]

The galaxy is not bent unless you distort the photo. The galaxy seen from within the disk is straight. This is improper to make laymen think this arch actually exists. These photos of bent Milky Ways are improper and shouldn’t be posted.

If you are standing on the ground when the Milky Way is overhead, it is certainly seen as an arch, curving from one side of the horizon, passing through the zenith, and then down to the opposite horizon.

Geometrically, the Milky Way is not a line. It is a circle, which we view from the interior.

Of course, the image could be remapped so the Milky Way appears linear. In which case we'd have a weirdly curved horizon.