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NGC 3521: Galaxy in a Bubble

Explanation: Gorgeous spiral galaxy NGC 3521 is a mere 35 million light-years away, toward the northern springtime constellation Leo. Relatively bright in planet Earth's sky, NGC 3521 is easily visible in small telescopes but often overlooked by amateur imagers in favor of other Leo spiral galaxies, like M66 and M65. It's hard to overlook in this colorful cosmic portrait though. Spanning some 50,000 light-years the galaxy sports characteristic patchy, irregular spiral arms laced with dust, pink star forming regions, and clusters of young, blue stars. This deep image also finds NGC 3521 embedded in fainter, gigantic, bubble-like shells. The shells are likely tidal debris, streams of stars torn from satellite galaxies that have undergone mergers with NGC 3521 in the distant past.

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This pic shows especially well that a galaxy isn't a neat and tidy spiral. Many pics of other galaxies suggest a cloud of stars, relatively disorganised, around the main structure, but not as clearly as this. So the Milky Way will have a shell of stars. Do we know this, or only infer it?

John

JohnD wrote: ↑Thu May 05, 2022 8:05 am This pic shows especially well that a galaxy isn't a neat and tidy spiral. Many pics of other galaxies suggest a cloud of stars, relatively disorganised, around the main structure, but not as clearly as this. So the Milky Way will have a shell of stars. Do we know this, or only infer it?

John

We know it as they have been directly observed…

Milky Way Leftover Shell Stars Discovered In Galactic Halo
Like tantalizing tidbits stored in the vast recesses of one’s refrigerator, astronomers using NASA’s Hubble Space Telescope have evidence of a shell of stars left over from one of the Milky Way’s meals. In a study which will appear in an upcoming issue of the Astrophysical Journal researchers have revealed a group of stars moving sideways – a motion which points to the fact our galaxy may have consumed another during its evolution.

“Hubble’s unique capabilities are allowing astronomers to uncover clues to the galaxy’s remote past. The more distant regions of the galaxy have evolved more slowly than the inner sections. Objects in the outer regions still bear the signatures of events that happened long ago,” said Roeland van der Marel of the Space Telescope Science Institute (STScI) in Baltimore, Maryland.

As curious as this shell of stars is, they offer even more information by revealing a chance to study the mysterious hidden mass of Milky Way – dark matter. With more than a hundred billion galaxies spread over the Universe, what better place to get a closer look than right here at home? The team of astronomers led by Alis Deason of the University of California, Santa Cruz, and van der Marel studied the outer halo, a region roughly 80,000 light years from our galaxy’s center, and identified 13 stars which may have come to light at the very beginning of the Milky Way’s formation.

https://www.universetoday.com/100158/m ... ctic-halo/

Star Map of the Milky Way's Outer Halo

Images of the Milky Way and the Large Magellanic Cloud (LMC) are overlaid on a map of the surrounding area, our galaxy's galactic halo. Dark blue represents a low concentration of stars; lighter blues indicate increasing stellar density. The map spans from about 200,000 light-years to 325,000 light-years from the galactic center and provides the first clear view of the major features in this region.

The LMC is orbiting the Milky Way and will eventually merge with it. The high concentration in the lower half is a wake created by the LMC as it sails through the galactic halo.

In the upper half of the image, astronomers observed an apparent excess of stars compared to the southern hemisphere. This is evidence that the Large Magellanic Cloud has pulled the Milky Way disk significantly off-center. The galactic halo can be thought of as a bubble surrounding the disk. The number of stars per area is highest near the center of the bubble, and drops off moving away from the center. If the Milky Way were in the center of the halo, astronomers would see an approximately equal number of stars in both hemispheres. But because the Milky Way has been pulled away from the center, when astronomers look into the northern hemisphere, they see more of the central, highly populated area. Comparing these two views, there is an apparent excess of stars in the northern hemisphere.
https://www.jpl.nasa.gov/images/pia2457 ... outer-halo

Ancient Halo Stars Cast the Milky Way’s First Light
We inhabit a giant spiral-shaped galaxy that glows with hundreds of billions of stars, a colossus so massive that at least two dozen lesser galaxies revolve around it. But how did this enormous entity arise? Clues come from the Milky Way's oldest and wisest stars—those in the stellar halo, the galactic component that envelops the bright disk housing the sun.
Halo stars stand out because they formed before supernova explosions had scattered a large amount of heavy elements into the galaxy, so halo stars possess little iron. The brightest halo members are iron-poor globular star clusters, spectacular objects that can pack hundreds of thousands of old stars into a sphere just a few dozen light-years across.
Now the Hubble Space Telescope has found that an individual halo star is even older than these ancient star cities and is thus an ideal time capsule passed down from the Milky Way's birth. "This is a really elegant piece of work," says Gerry Gilmore, an astronomer at the University of Cambridge in England who was not affiliated with the researchers. "They've done as good a job as it is possible to do."

Despite its importance, the stellar halo constitutes just a thousandth of the Milky Way's total mass. Although the halo extends far beyond the disk, most of its stars lie closer to the galaxy's center than we do, so globular clusters abound in constellations toward the galactic center, such as Scorpius and Sagittarius.
https://www.scientificamerican.com/art ... rst-light/

As Johnny Carson might say “that is some wild, weird stuff!”

Eric

Thank you, XgeoX!

The idea of primitive, hill-billy stars out in the boondocks is intriguing! When looking at a galaxy's portrait, I always wonder what the view would be in a planet's sky, and if there might be anyone to see it. From what you say, despite the age of halo stars, the lack of heavy elements may make life less likely.
John

I like this picture of stellar streams orbiting the Milky Way. I couldn't help drawing dots along the streams to make them stand out more in the picture at left. In the picture at right, you can see some of the dwarf galaxies that have "donated" the streams of stars that are orbiting our galaxy.


Ann

Kinda looks as though it is in a cloud;or bubble as the title says!
Maybe the Galaxy is still growing; what with al the fodder around it!
Beautiful; isn't it!

Russ

more than enveloped in a bubble there appears a distinctly red column, obliquely aimed at the galactic center to the left, ad perhaps from behind also to the right. Is this a anomaly of the imaging or active galactic center ? M82 has messy jets, and the artists conceive columnar jets always orthogonal to galactic plane. So is this a galactic feature or am I imagining too much?

NGC 3521 is a fascinating galaxy, and today's APOD is very fine. Please compare the Hanson/Selby image with the one by R. Jay GaBany at right. Note how "thick" the yellow streams are, and how they seem to rise from the central part of the galaxy like "smoke". This sort of thing isn't "normal", or at least, it isn't at all common. It's not the streams themselves that are unusual, but their brightness is.

For myself, I find the streams' deep yellow-orange color remarkable, too. Streams usually originate from dwarf galaxies that have been captured by a larger galaxy and have been cannibalized by the larger bully. But dwarf galaxies, even those that consists of old stars only, aren't usually so red. That's because dwarf galaxies tend to be relatively metal-poor, and metal-poor stars are a little bluer (or more non-red) than metal-rich ones at the same spectral class and temperature.

Note in the Hanson/Selby image that one of the yellow streams seems to contain a truly red component too, as if it contained some ionized hydrogen. It would be interesting if that was the case.

To me the yellow streams rising from the center of NGC 3521 appear somewhat similar to water splashing from a pond when you have thrown a stone into it. Is it possible that something similar is going on in NGC 3521? Can the yellow stars of the streams actually be yellow stars from the bulge of NGC 3521 itself that are "splashing" from center because something has been "thrown" into it? (I can hear Chris say no. Because when a galaxy hits another galaxy the result looks like, say, the Tadpole galaxy, not like water splashing from a pond.)


I keep insisting that the shells of NGC 3521 are unusually yellow. Let's compare it with two shell galaxies in Pisces, NGC 474 and NGC 467:

Ann: from the apod link:

”Also, notice the rarely seen Hydrogen Alpha jets emanation from this galaxy.”

Ann wrote: ↑Thu May 05, 2022 3:38 pm

NGC 3521. Image Credit & Copyright: Mark Hanson and Mike Selby.

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NGC 3521. Image: R. Jay GaBany.

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red alpha Hydrogen jet? Yellow stellar chimney?
Let's try to fit the two images.

at least you could change the title...... see my post and my picture of 03/02/2020

https://www.flickr.com/photos/17910585@ ... 167213281/

Ngc 3521 Galaxy - Luminance from T2 of CHILESCOPE + RGB from my previous pictures

Iaffaldano Giuseppe Carmine wrote: ↑Tue May 10, 2022 6:25 am at least you could change the title...... see my post and my picture of 03/02/2020

https://www.flickr.com/photos/17910585@ ... 167213281/

Ngc 3521 Galaxy - Luminance from T2 of CHILESCOPE + RGB from my previous pictures

That's a lovely picture, Iaffaldano, but I'm not sure what you mean by changing the title (of the APOD?).

Ann

i am not practiced and able with software but if you see my post of March 2 2020 you can see that the title of my post was NGC 3521 Galaxy in a Bubble and you give me a kind appraciation; now after 2 years you give apod to a picture that Bubble doesn't show but shows the tidal stream; so if you want give apod to the Bubble give apod to me....... or change the title .....i joke..obviously

Iaffaldano Giuseppe Carmine wrote: ↑Tue May 10, 2022 10:06 am i am not practiced and able with software but if you see my post of March 2 2020 you can see that the title of my post was NGC 3521 Galaxy in a Bubble and you give me a kind appraciation; now after 2 years you give apod to a picture that Bubble doesn't show but shows the tidal stream; so if you want give apod to the Bubble give apod to me....... or change the title .....i joke..obviously

Well, I didn't get the joke either, but I guess it has to do with a "first use" claim to using "Galaxy in a Bubble" as a title. In any event, jokes are best indicated as such by using an emoji, or "smiley", like this one: That serves as a clue to the humor challenged.

Regardless of all that, your picture of NGC 3521 is indeed lovely!

Be honoured, Iaffaldeno!

As Oscar said, "“Imitation is the sincerest form of flattery that mediocrity can pay to greatness.”

My name is Iaffaldano ..... i don't know Oscar ...who is? I certainly don't imitate anyone; i think that whoever gave to this Apod this title suffers from limited vision and poor imagination or it is possible that my image stayed in his mind. Much better the title given by Hanson : Marquise in the sky https://www.hansonastronomy.com/ngc3521-1meter

Iaffaldano Giuseppe Carmine wrote: ↑Tue May 10, 2022 4:46 pm My name is Iaffaldano ..... i don't know Oscar ...who is? I certainly don't imitate anyone; i think that whoever gave to this Apod this title suffers from limited vision and poor imagination or it is possible that my image stayed in his mind. Much better the title given by Hanson : Marquise in the sky https://www.hansonastronomy.com/ngc3521-1meter

"Oscar" is Oscar Wilde, famous Irish writer and wry wit extraordinaire. For more on his quote:

https://thewordcounter.com/what-does-imitation-is-the-sincerest-form-of-flattery-mean/ wrote: <b>The Origin of the Expression</b>
The cleric and writer Charles Caleb Colton appears to be the first person to have stated the saying exactly as we know and use it today, in his 1820 work Lacon: Or, Many Things in Few Words. But the idea shared by the phrase was expressed before then. Versions of the popular saying conveying the same thought can be found in works from the 1700s, including a biography of Marcus Aurelius and a piece by the writer and politician Eustace Budgell, in which he said, “Imitation is a kind of artless flattery.” Although artless sounds negative in this context, because Budgell’s statement does seem to have inspired the phrase we use today, the adjective likely has more to do with the idea that one can imitate without even being aware they’re doing so, making the imitation a pure or sincere form of flattery.
...
The Irish poet Oscar Wilde weighed in on the debate, elaborating on the proverb and concluding, “Imitation is the sincerest form of flattery that mediocrity can pay to greatness.”

Though to some the truthfulness of the saying is in question, as a proverb, it serves to express a universal idea: that in general, imitation conveys some sense of admiration.

As for where the APOD writers came up with the title, perhaps they were inspired by the one in this page from 2019, which predates your use of the title:

"NGC3521: The Bubble Galaxy"

https://astrodrudis.com/ngc-3521-the-bubble-galaxy/

I'd post the pic itself, but it's huge, so here are just the details of it from the site (also as a pic since cut-and-paste from the site itself is verbotten!


[ PS - feeling inspired by Neufer today... ]

generally as an Italian I am more accustomed to the writings of Dante Alighieri and Alessandro Manzoni, but I prefer my simple paraphrases born from my humble mind to the famous phrases of other minds; if there is a bubble around this galaxy my bubble is the most beautiful ... remember that.

Iaffaldano Giuseppe Carmine wrote: ↑Wed May 11, 2022 7:32 am generally as an Italian I am more accustomed to the writings of Dante Alighieri and Alessandro Manzoni, but I prefer my simple paraphrases born from my humble mind to the famous phrases of other minds; if there is a bubble around this galaxy my bubble is the most beautiful ... remember that.

Well, that doesn't seem very "humble" of you!