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Astronomy Picture of the Day - Gaia Reconstructs a Top View of our Galaxy
NASA ^ | 13 May, 2025 | Illustration Credit: ESA, Gaia, DPAC, Stefan Payne-Wardenaar

Posted on 05/13/2025 1:16:19 PM PDT by MtnClimber

Explanation: What does our Milky Way Galaxy look like from the top? Because we are on the inside, humanity can’t get an actual picture. Recently, however, just such a map has been made using location data for over a billion stars from ESA’s Gaia mission. The resulting featured illustration shows that just like many other spiral galaxies, our Milky Way has distinct spiral arms. Our Sun and most of the bright stars we see at night are in just one arm: Orion. Gaia data bolsters previous indications that our Milky Way has more than two spiral arms. Our Galaxy's center sports a prominent bar. The colors of our Galaxy's thin disk derive mostly from dark dust, bright blue stars, and red emission nebula. Although data analysis is ongoing, Gaia was deactivated in March after a succession mission.


TOPICS: Astronomy; Astronomy Picture of the Day; Science
KEYWORDS: apod; nasa

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To be added or removed from the Astronomy Picture of the Day ping list please send me a request via "Private Reply" (Mail).

For more detail go to the link and click on the image for a high definition image. You can then move the magnifying glass cursor then click to zoom in and click again to zoom out. When zoomed in you can scan by moving the side bars on the bottom and right side of the image.

1 posted on 05/13/2025 1:16:19 PM PDT by MtnClimber
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To: MtnClimber

2 posted on 05/13/2025 1:16:51 PM PDT by MtnClimber (For photos of scenery, wildlife and climbing, click on my screen name for my FR home page.)
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To: MtnClimber

3 posted on 05/13/2025 1:17:21 PM PDT by MtnClimber (For photos of scenery, wildlife and climbing, click on my screen name for my FR home page.)
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To: 21stCenturion; 21twelve; 4everontheRight; A Navy Vet; A_perfect_lady; abb; AFB-XYZ; AFPhys; ...
Pinging the APOD list

🪐 🌟 🌌 🍔

4 posted on 05/13/2025 1:18:09 PM PDT by MtnClimber (For photos of scenery, wildlife and climbing, click on my screen name for my FR home page.)
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To: MtnClimber

Our solar system is on the bottom of the second image just below the “O” in Orion.


5 posted on 05/13/2025 1:20:23 PM PDT by MtnClimber (For photos of scenery, wildlife and climbing, click on my screen name for my FR home page.)
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To: MtnClimber
The side view from yesterday:


6 posted on 05/13/2025 1:22:18 PM PDT by MtnClimber (For photos of scenery, wildlife and climbing, click on my screen name for my FR home page.)
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To: MtnClimber

We’re in the Galactic Boondocks................


7 posted on 05/13/2025 1:24:17 PM PDT by Red Badger (Homeless veterans camp in the streets while illegals are put up in 5 Star hotels....................)
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To: MtnClimber

8 posted on 05/13/2025 1:26:42 PM PDT by Red Badger (Homeless veterans camp in the streets while illegals are put up in 5 Star hotels....................)
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To: MtnClimber

What is “The Bar”?


9 posted on 05/13/2025 1:26:46 PM PDT by Paladin2 (YMMV)
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To: MtnClimber

I can see my house! :)


10 posted on 05/13/2025 1:32:24 PM PDT by Diana in Wisconsin (I don't have, 'Hobbies.' I'm developing a robust Post-Apocalyptic skill set.)
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To: Red Badger
To put it bluntly, ain't NONE of us very important in, 'The Grand Scheme of Things!'


11 posted on 05/13/2025 1:36:43 PM PDT by Diana in Wisconsin (I don't have, 'Hobbies.' I'm developing a robust Post-Apocalyptic skill set.)
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To: MtnClimber

Wow.


12 posted on 05/13/2025 1:39:24 PM PDT by No name given ( Anonymous is who you’ll know me as)
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To: MtnClimber

Cool.


13 posted on 05/13/2025 1:39:35 PM PDT by No name given ( Anonymous is who you’ll know me as)
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To: MtnClimber

Galactic UFO.


14 posted on 05/13/2025 1:41:49 PM PDT by Paladin2 (YMMV)
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To: Paladin2
Barred vs Unbarred Spiral Galaxies (The Differences!)

Scientists use four terms to differentiate the different types of galaxies: spiral galaxies, barred spiral galaxies, elliptical galaxies, and irregular galaxies. This article assesses the similarities and differences of the barred spiral galaxy vs. an unbarred spiral galaxy. The main difference between a barred spiral and unbarred spiral galaxy is the large bar that runs through the center of the former. While the structure of both galaxies is largely similar, this elongated bar suggests that the galaxy is a more mature version of the spiral galaxy. Continue reading to learn about the similarities and differences between barred and unbarred spiral galaxies.

This is the barred NGC 1300 Galaxy

Spiral galaxies are flat, rotating disc composed of gas, dust, and stars. A barred spiral galaxy is that which has a bar-shaped structure made from stars at its center. Edwin Hubble first discovered these galaxies in the early part of the twentieth century, and scientists use the classification SB to differentiate them. And we can break this classification down even further. An SBa galaxy contains very tightly bound arms, whereas an SBc galaxy has significantly more loosely bound arms. As many as 65% of spiral galaxies contain bars; these affect the movement of the gas, dust, and stars that surround them. Scientists believe the bar acts similarly to a funnel, pulling matter into the disc’s bulge. This leads to starbursts in the center of the galaxy. The central bar in a galaxy provides information about the age of that galaxy, with scientists estimating that a bar takes around two billion years to form. Our galaxy is a barred spiral; while the largest Barred Spiral that we can see is the Condor Galaxy, found in the Pavo constellation. The so called “bar” isn’t a solid object. Instead, its formation is due to a range of unstable stars at the center of a galaxy that give the appearance of a solid object thanks to their high density.

What Is An Unbarred Spiral Galaxy?

This is the unbarred Whirlpool Galaxy

An unbarred spiral galaxy is a variety of spiral galaxy that lacks a central bar; scientists use the classification SA to differentiate them from other galaxy types. The arms of a spiral galaxy contain numerous amounts of gas and dust, plus a range of young stars that shine brightly but briefly. The formation of spiral arms remains to be something of a puzzle for scientists. One theory is that high-density waves traveling through the outer disc could be responsible for these formations, but no one knows. Scientists also believe that spiral galaxies eventually evolve into elliptical galaxies as they age. But the latter is difficult to measure thanks to their abundance of older, dimmer stars that give them less visibility in the night sky. The bigger a galaxy is, the faster it will spin, with the arms of a large galaxy spinning at up to two million kilometers per hour. A different version of the unbarred spiral galaxy is the unbarred lenticular galaxy. A lenticular galaxy is one whose structure sits somewhere between a spiral and elliptical gallery. It contains a large disc, but its arms are not the same magnitude as a spiral galaxy. Scientists denote this type of galaxy as SA0.

The Similarities Between Unbarred And Barred Galaxies.

The physical structure of barred and unbarred galaxies is similar in many ways. Most spiral galaxies possess a bulge at their center, with a rotating disc of stars surrounding it. Both galaxies have a defined shape, which bulges in the middle. Another characteristic shared by both types of galaxies is that the older stars reside closer to the nucleus, while the younger stars spread out across the arms. Stars contained in the bulge of a spiral galaxy tend to be redder (as well as older) than the rest. This bulge is created by an incredibly dense nucleus that draws matter into its center. Scientists classify unbarred and barred galaxies by how tightly the spiral arms are wound. SAa or SBa galaxies are those that possess tight arms, whereas a SAc or SBc galaxy is one with a loose formation.

Differences Between Barred and Unbarred Spiral Galaxies.

While a barred spiral galaxy holds many of the same characteristics as an unbarred spiral galaxy, there is one obvious difference. The barred galaxy has a huge bar running through its center that affects everything from the movement of the stars to the arms of the galaxy’s spiral. 2008 studies demonstrated that barred spiral galaxies are the older of the two types as a central bar indicates that a galaxy has reached its full maturity. A barred galaxy forms when the orbits within a spiral galaxy become unstable and deviate from their circular path. These divergences in the star’s orbit gradually elongate its path, which eventually locks into a bar. A bar is thought to be the last significant process of a spiral galaxy which forces a large amount of gas towards its center while fuelling the formation of new stars and feeding supermassive black holes.

Summary

Barred and unbarred spiral galaxies share the same basic shape and many of the same characteristics. They have a large central disc, around which massive arms of gas and dust swirl. The difference between the two is the presence of a large bar. This bar is formed due to the unstable nature of the orbits within that galaxy and signifies that the galaxy in question is older than an unbarred spiral galaxy.

15 posted on 05/13/2025 1:49:48 PM PDT by MtnClimber (For photos of scenery, wildlife and climbing, click on my screen name for my FR home page.)
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To: Red Badger
Given the size of our universe...that 'you are here' dot is about 50 million times too small. The pic is of our galaxy.

But...I get the point.

16 posted on 05/13/2025 1:54:46 PM PDT by Bloody Sam Roberts (Perfection is impossible. But if you pursue perfection...you may achieve excellence.)
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To: MtnClimber

Thanks for the info.

Does having my house in a Barred Galaxy increase its value?

[We seem to be deep in the ‘burbs.]


17 posted on 05/13/2025 1:58:38 PM PDT by Paladin2 (YMMV)
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To: Paladin2

I think the unbarred spirals have the highest home values. They are newer.


18 posted on 05/13/2025 2:05:39 PM PDT by MtnClimber (For photos of scenery, wildlife and climbing, click on my screen name for my FR home page.)
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To: Diana in Wisconsin

Well, there goes the neighborhood.


19 posted on 05/13/2025 2:26:40 PM PDT by Noumenon (You can evade reality, but you cannot evade the consequences of evading reality. KTF)
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To: MtnClimber

“The side view from yesterday:”

This image raises a curiosity. What is pulling on it to make it Asymmetric like that rather than flat and Symmetric? Whatever it is, it is affecting all the bodies on the right opposite from all the bodies on the left. Extremely interesting...


20 posted on 05/13/2025 2:48:09 PM PDT by Openurmind
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