APOD: A 10,000 Kilometer Galactic Bridge (2022 Jun 03)

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APOD: A 10,000 Kilometer Galactic Bridge (2022 Jun 03)

Post by APOD Robot » Fri Jun 03, 2022 4:05 am

Image A 10,000 Kilometer Galactic Bridge

Explanation: With this creative astro-collaboration you can follow the plane of our Milky Way Galaxy as it bridges northern and southern hemisphere skies. To construct the expansive composite nightscape, skies over Observatorio El Sauce in Chile (top) were imaged on the same date but 6 hours later than the skies over the Saint-Veran observatory in the French Alps. The 6 hour time-lag allowed Earth's rotation to align the Milky Way above domes at the two sites. All exposures were made with similar cameras and lenses mounted on simple tripods. A faint greenish airglow is visible in the dark Chilean sky that also features the Large and Small Magellanic Clouds near the observatory dome. In the French Alps light pollution is apparent, but the distant Andromeda Galaxy can still be spotted near the horizon in the northern night. On planet Earth the two observatories are separated by about 10,000 kilometers.

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Re: APOD: A 10,000 Kilometer Galactic Bridge (2022 Jun 03)

Post by VictorBorun » Fri Jun 03, 2022 5:20 am

make it 3 frames and create full 360° Milky Way sky above 3 landscapes

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Re: APOD: A 10,000 Kilometer Galactic Bridge (2022 Jun 03)

Post by Ann » Fri Jun 03, 2022 5:50 am

Oudoux-and-Jeff-Graphy-with10000km_c[1].jpg
A 10,000 Kilometer Galactic Bridge.
Image Credit & Copyright: Maxime Oudoux, Jean-Francois GELY

It is interesting to contemplate how different the southern Milky Way is compared with the northern Milky Way. It is obvious from the APOD that there is a lot more scattered red (or pink-looking) hydrogen alpha in the northern Milky Way than in the southern Milky Way. On the other hand, the southern Milky Way is a lot brighter than its northern counterpart, because the center of the Milky Way is located in the southern constellation of Sagittarius.

It is really true that there is more red hydrogen alpha in the northern hemisphere than in the southern:

Milky Way from Orion to Scorpius Alistair Symon.png
Hydrogen Alpha in the Milky Way from Orion to Scorpius. Credit and copyright:
Alistair Symon. Note all the red stuff to the left, and the yellow stuff to the right.


In the southern Milky Way, the "swollen" all-yellow background bulge is an imposing presence, and pink emission nebulas are confined to the central dust lane (apart from the Rho Ophiuchi region).

Look at NGC 7814 to see how a yellow bulge can dominate, and look at NGC 1448 to see how a galaxy's outer disk can "flare out" and be full of star formation:


Let's conclude with the Gaia space telescope's portrait of the Milky Way. Please note that Gaia "suppresses" bright blue stars, because all stars are seen as individual dots of the same size (and saturation?), unless I am very much mistaken. But the overall shape of the edge-on Milky Way, as well as the distribution of dust lanes, is seen very clearly:


Ann

Edit: All right, I admit it. The most likely explanation as to why we see so many red nebulas in the northern Milky Way is because these nebulas are quite literally closer to us, whereas the bright nebulas of the south, such as the Lagoon Nebula, are further away from us and located in a more distant spiral arm.
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Re: APOD: A 10,000 Kilometer Galactic Bridge (2022 Jun 03)

Post by orin stepanek » Fri Jun 03, 2022 12:22 pm

Oudoux-and-Jeff-Graphy-with10000km_c.jpg
Nice job connecting the two observatories pictures all together!
Kudos! 8-)
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Re: APOD: A 10,000 Kilometer Galactic Bridge (2022 Jun 03)

Post by johnnydeep » Fri Jun 03, 2022 3:54 pm

Maybe I missed it, but what is the significance of the blurry background image? It appears to be a blown up portion of the southern half.
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Re: APOD: A 10,000 Kilometer Galactic Bridge (2022 Jun 03)

Post by johnnydeep » Fri Jun 03, 2022 4:28 pm

APOD Robot wrote: Fri Jun 03, 2022 4:05 am Image A 10,000 Kilometer Galactic Bridge

Explanation: With this creative astro-collaboration you can follow the plane of our Milky Way Galaxy as it bridges northern and southern hemisphere skies. To construct the expansive composite nightscape, skies over Observatorio El Sauce in Chile (top) were imaged on the same date but 6 hours later than the skies over the Saint-Veran observatory in the French Alps. The 6 hour time-lag allowed Earth's rotation to align the Milky Way above domes at the two sites. All exposures were made with similar cameras and lenses mounted on simple tripods. A faint greenish airglow is visible in the dark Chilean sky that also features the Large and Small Magellanic Clouds near the observatory dome. In the French Alps light pollution is apparent, but the distant Andromeda Galaxy can still be spotted near the horizon in the northern night. On planet Earth the two observatories are separated by about 10,000 kilometers.
I tried to compare this APOD with the linked-to one from two years ago, but it's doesn't make sense to me. How do the two stretches of the Milky Way map to each other?

milky way north and south merged - two varieties.JPG
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Re: APOD: A 10,000 Kilometer Galactic Bridge (2022 Jun 03)

Post by Chris Peterson » Fri Jun 03, 2022 4:29 pm

johnnydeep wrote: Fri Jun 03, 2022 3:54 pm Maybe I missed it, but what is the significance of the blurry background image? It appears to be a blown up portion of the southern half.
No significance. Just a technique to produce a final image with a more conventional aspect ratio.
Chris

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Re: APOD: A 10,000 Kilometer Galactic Bridge (2022 Jun 03)

Post by Ann » Fri Jun 03, 2022 5:05 pm

johnnydeep wrote: Fri Jun 03, 2022 4:28 pm
APOD Robot wrote: Fri Jun 03, 2022 4:05 am Image A 10,000 Kilometer Galactic Bridge

Explanation: With this creative astro-collaboration you can follow the plane of our Milky Way Galaxy as it bridges northern and southern hemisphere skies. To construct the expansive composite nightscape, skies over Observatorio El Sauce in Chile (top) were imaged on the same date but 6 hours later than the skies over the Saint-Veran observatory in the French Alps. The 6 hour time-lag allowed Earth's rotation to align the Milky Way above domes at the two sites. All exposures were made with similar cameras and lenses mounted on simple tripods. A faint greenish airglow is visible in the dark Chilean sky that also features the Large and Small Magellanic Clouds near the observatory dome. In the French Alps light pollution is apparent, but the distant Andromeda Galaxy can still be spotted near the horizon in the northern night. On planet Earth the two observatories are separated by about 10,000 kilometers.
I tried to compare this APOD with the linked-to one from two years ago, but it's doesn't make sense to me. How do the two stretches of the Milky Way map to each other?

Actually, Johnny, I think Sagittarius and the center of the galaxy are missing in today's APOD.

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Re: APOD: A 10,000 Kilometer Galactic Bridge (2022 Jun 03)

Post by johnnydeep » Fri Jun 03, 2022 8:45 pm

Ann wrote: Fri Jun 03, 2022 5:05 pm
johnnydeep wrote: Fri Jun 03, 2022 4:28 pm
APOD Robot wrote: Fri Jun 03, 2022 4:05 am Image A 10,000 Kilometer Galactic Bridge

Explanation: With this creative astro-collaboration you can follow the plane of our Milky Way Galaxy as it bridges northern and southern hemisphere skies. To construct the expansive composite nightscape, skies over Observatorio El Sauce in Chile (top) were imaged on the same date but 6 hours later than the skies over the Saint-Veran observatory in the French Alps. The 6 hour time-lag allowed Earth's rotation to align the Milky Way above domes at the two sites. All exposures were made with similar cameras and lenses mounted on simple tripods. A faint greenish airglow is visible in the dark Chilean sky that also features the Large and Small Magellanic Clouds near the observatory dome. In the French Alps light pollution is apparent, but the distant Andromeda Galaxy can still be spotted near the horizon in the northern night. On planet Earth the two observatories are separated by about 10,000 kilometers.
I tried to compare this APOD with the linked-to one from two years ago, but it's doesn't make sense to me. How do the two stretches of the Milky Way map to each other?

Actually, Johnny, I think Sagittarius and the center of the galaxy are missing in today's APOD.

Ann
So, would the two pics line up like so (using the LMC and SMC as guide "stars" and scaling and rotating today's pic to match them up in both images)?:

milky way north and south merged - two varieties oriented.JPG
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Re: APOD: A 10,000 Kilometer Galactic Bridge (2022 Jun 03)

Post by dushyant » Sat Jun 04, 2022 4:25 am

Good way to counter the opacity of the earth. Perhaps there should be a frugal tripod mounted camera at each pole to give us a real time scan of the cosmos.

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Re: APOD: A 10,000 Kilometer Galactic Bridge (2022 Jun 03)

Post by Ann » Sat Jun 04, 2022 5:45 am

johnnydeep wrote: Fri Jun 03, 2022 8:45 pm
Ann wrote: Fri Jun 03, 2022 5:05 pm
johnnydeep wrote: Fri Jun 03, 2022 4:28 pm

I tried to compare this APOD with the linked-to one from two years ago, but it's doesn't make sense to me. How do the two stretches of the Milky Way map to each other?

Actually, Johnny, I think Sagittarius and the center of the galaxy are missing in today's APOD.

Ann
So, would the two pics line up like so (using the LMC and SMC as guide "stars" and scaling and rotating today's pic to match them up in both images)?:


Johnny, check this out:

APOD 3 June 2022 Galactic Bridge annotated.png
Milky Way from Orion to Crux Alan Dyer annotated.png
Milky Way from Orion to Crux. Photo: Alan Dyer.

Ann
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Re: APOD: A 10,000 Kilometer Galactic Bridge (2022 Jun 03)

Post by johnnydeep » Sat Jun 04, 2022 12:33 pm

Ann wrote: Sat Jun 04, 2022 5:45 am
johnnydeep wrote: Fri Jun 03, 2022 8:45 pm
Ann wrote: Fri Jun 03, 2022 5:05 pm

Actually, Johnny, I think Sagittarius and the center of the galaxy are missing in today's APOD.

Ann
So, would the two pics line up like so (using the LMC and SMC as guide "stars" and scaling and rotating today's pic to match them up in both images)?:


Johnny, check this out:

APOD 3 June 2022 Galactic Bridge annotated.png
Milky Way from Orion to Crux Alan Dyer annotated.png
Milky Way from Orion to Crux. Photo: Alan Dyer.

Ann
So I think my overlay is correct then, and today's APOD shows much less of the entire band of the Milky Way than the one from 2020. Right?
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Re: APOD: A 10,000 Kilometer Galactic Bridge (2022 Jun 03)

Post by Ann » Sat Jun 04, 2022 2:37 pm

johnnydeep wrote: Sat Jun 04, 2022 12:33 pm
Ann wrote: Sat Jun 04, 2022 5:45 am
johnnydeep wrote: Fri Jun 03, 2022 8:45 pm

So, would the two pics line up like so (using the LMC and SMC as guide "stars" and scaling and rotating today's pic to match them up in both images)?:


Johnny, check this out:

Milky Way from Orion to Crux. Photo: Alan Dyer.

Ann
So I think my overlay is correct then, and today's APOD shows much less of the entire band of the Milky Way than the one from 2020. Right?
That's right, Johnny!

Ann
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Re: APOD: A 10,000 Kilometer Galactic Bridge (2022 Jun 03)

Post by alter-ego » Sun Jun 05, 2022 5:23 am

By the numbers, compared to today's visible ~205° MW swath, the 2020 APOD displays about 265°, or about 30% larger,
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