GOTD: Galaxy Of The Day

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Re: GOTD: Galaxy Of The Day

Post by AVAO » Tue Apr 02, 2024 8:49 pm

03.02.2024 I HST: Arp 72 - Two’s company NGC 5996 & NGC 5994
universe today | Original release 2024 April 01
A large spiral galaxy with a smaller neighbouring galaxy. The spiral galaxy is wide and distorted, with colourful dust. Its companion lies close by it at the end of a spiral arm, to the lower left. A long, faint tail of stars reaches up from the right side of the spiral galaxy to the top of the image. Several small, distant galaxies can be seen in the background, as well as one bright star in the foreground.

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Re: GOTD: Galaxy Of The Day

Post by AVAO » Mon Apr 22, 2024 7:05 pm

Hubble captures a bright galactic and stellar duo
phys.org | Original release 2024 April 22
While the focus of this image is the spiral galaxy NGC 3783, the eye is equally drawn to the very bright object in the lower right part of this image. This is the star HD 101274. The perspective in this image makes the star and the galaxy look like close companions, but this is an illusion. HD 101274 lies only about 1,530 light-years from Earth, it is about 85,000 times closer than NGC 3783. This explains how a single star can appear to outshine an entire galaxy!

NGC 3783 is a type-1 Seyfert galaxy, which is a galaxy with a bright central region. Hubble captures it in incredible detail, from its glowing central bar to its narrow, winding arms and the dust threaded through them, thanks to five separate images taken in different wavelengths of light. In fact, the galactic center is so bright that it exhibits diffraction spikes, normally only seen on stars such as HD 101274.

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Re: GOTD: Galaxy Of The Day

Post by AVAO » Tue Apr 23, 2024 5:46 am

AVAO wrote: Mon Apr 22, 2024 7:05 pm Hubble captures a bright galactic and stellar duo
phys.org | Original release 2024 April 22
While the focus of this image is the spiral galaxy NGC 3783, the eye is equally drawn to the very bright object in the lower right part of this image. This is the star HD 101274. The perspective in this image makes the star and the galaxy look like close companions, but this is an illusion. HD 101274 lies only about 1,530 light-years from Earth, it is about 85,000 times closer than NGC 3783. This explains how a single star can appear to outshine an entire galaxy!

NGC 3783 is a type-1 Seyfert galaxy, which is a galaxy with a bright central region. Hubble captures it in incredible detail, from its glowing central bar to its narrow, winding arms and the dust threaded through them, thanks to five separate images taken in different wavelengths of light. In fact, the galactic center is so bright that it exhibits diffraction spikes, normally only seen on stars such as HD 101274.

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GOTD4Y Jac
Click to view full size image 1 or image 2
jac berne (flickr) Original data: HST

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Re: GOTD: Galaxy Of The Day

Post by Ann » Tue Apr 23, 2024 6:08 am

AVAO wrote: Mon Apr 22, 2024 7:05 pm Hubble captures a bright galactic and stellar duo
phys.org | Original release 2024 April 22
While the focus of this image is the spiral galaxy NGC 3783, the eye is equally drawn to the very bright object in the lower right part of this image. This is the star HD 101274. The perspective in this image makes the star and the galaxy look like close companions, but this is an illusion. HD 101274 lies only about 1,530 light-years from Earth, it is about 85,000 times closer than NGC 3783. This explains how a single star can appear to outshine an entire galaxy!

NGC 3783 is a type-1 Seyfert galaxy, which is a galaxy with a bright central region. Hubble captures it in incredible detail, from its glowing central bar to its narrow, winding arms and the dust threaded through them, thanks to five separate images taken in different wavelengths of light. In fact, the galactic center is so bright that it exhibits diffraction spikes, normally only seen on stars such as HD 101274.

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GOTD4Y Jac
Nice galaxy, but I have to talk about the star, HD 101274. According to Simbad, this is a star of spectral class A0V. Its colors are a little bit red for its spectral class, 0.106, but there could be various reasons for that, such as a flattened shape of the star (common in A-type stars), and we might be viewing it equator-on. I don't think that the star is particularly dust-reddened (unless it is somehow self-reddened), in view of the crystal clarity of the background galaxies.

The distance to HD 101274 is some 1,530 light-years, and the luminosity of the star is ~40 times solar. That's normal.

Okay, now to what I wanted to say: I'm the owner of a fat old catalog, Sky Catalogue 2000.0, Volume 1, Stars to Magnitude 8.0.

Sky Catalogue 2000 Volume 1.jpg

This catalog lists some 50,000 stars, but HD 101274 is not one of them, because its V magnitude is 9.12. Interestingly, though, this catalog lists the most common types of magnitude 8 and brighter stars according to their spectral class. The most common of these stars are spectral class K, and there are 7638 stars of spectral class K listed in Sky Catalogue 2000.0, Volume 1, Stars to Magnitude 8.0. The second most common type of star listed in this catalog is spectral class A, and there are 4440 stars of spectral class A listed here.

That figures. And it says something about the nature and color of the Milky Way. Most of its light is going to come from its brightest stars, and these are, mainly, red giant stars of spectral class K. The second most important contributors to the light of the Milky Way are the main sequence A-type stars.

That doesn't mean that main sequence A-type stars are common in the Milky Way. Only 0.6% of all main sequence stars in our galaxy are spectral class A! But they make a difference because they are bright. No, not tremendously bright, of course, typically probably around 20 times solar, but since only 0.12003% of the main sequence stars in our galaxy are brighter than the Vegas and Siriuses and 98.6% are fainter, you can see that the contribution of the A stars is definitely not negligible!

https://en.wikipedia.org/wiki/Stellar_c ... sification

Galaxy NGC 3783 is cosying up to one of our own galaxy most common types of bright stars!

Ann
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Re: GOTD: Galaxy Of The Day

Post by AVAO » Wed May 15, 2024 5:09 am

HST: Close up of the irregular galaxy NGC 4753
NASA/ESA | Original release 2024 May 13
This image is the object's sharpest view to date, showcasing Hubble’s incredible resolving power and ability to reveal complex dust structures. NGC 4753 resides around 60 million light-years from Earth in the constellation Virgo and was first discovered by the astronomer William Herschel in 1784. It is a member of the NGC 4753 Group of galaxies within the Virgo II Cloud, which comprises roughly 100 galaxies and galaxy clusters.

This galaxy is believed to be the result of a galactic merger with a nearby dwarf galaxy roughly 1.3 billion years ago. NGC 4753’s distinct dust lanes around its nucleus are believed to have been accreted from this merger event.

[...]

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Re: GOTD: Galaxy Of The Day

Post by Ann » Wed May 15, 2024 5:54 pm

AVAO wrote: Wed May 15, 2024 5:09 am HST: Close up of the irregular galaxy NGC 4753
NASA/ESA | Original release 2024 May 13
This image is the object's sharpest view to date, showcasing Hubble’s incredible resolving power and ability to reveal complex dust structures. NGC 4753 resides around 60 million light-years from Earth in the constellation Virgo and was first discovered by the astronomer William Herschel in 1784. It is a member of the NGC 4753 Group of galaxies within the Virgo II Cloud, which comprises roughly 100 galaxies and galaxy clusters.

This galaxy is believed to be the result of a galactic merger with a nearby dwarf galaxy roughly 1.3 billion years ago. NGC 4753’s distinct dust lanes around its nucleus are believed to have been accreted from this merger event.

[...]

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GOTD4Y Jac
NGC 4753 looks like a typical lenticular galaxy, with a few elegant strands of dust weaving across the core, as if the clothing of the galaxy has been unraveled and only a few thin strands are left.

Thank you so much for updating us about the Galaxy of the Week! :D

Ann
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Re: GOTD: Galaxy Of The Day

Post by AVAO » Wed May 15, 2024 7:17 pm

Ann wrote: Wed May 15, 2024 5:54 pm
AVAO wrote: Wed May 15, 2024 5:09 am HST: Close up of the irregular galaxy NGC 4753
NASA/ESA | Original release 2024 May 13

[...]

GOTD4Y Jac
NGC 4753 looks like a typical lenticular galaxy, with a few elegant strands of dust weaving across the core, as if the clothing of the galaxy has been unraveled and only a few thin strands are left.

Thank you so much for updating us about the Galaxy of the Week! :D

Ann

ThanX Ann too!

That's a very nice and fitting description.

Jac

Enviroment DSS10

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Original data: NASA/ESA (HST) jac berne (flickr)

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Re: GOTD: Galaxy Of The Day

Post by AVAO » Sat Jun 01, 2024 8:35 am

HST: Broad and sweeping spiral galaxy NGC 4731 - The lights of a galactic bar
NASA/ESA | Original release 2024 May 27

A close-in view of a barred spiral galaxy. The bright, glowing bar crosses the centre of the galaxy, with spiral arms curving away from its ends and continuing out of view. It’s surrounded by bright patches of light where stars are forming, as well as dark lines of dust. The galaxy’s clouds of gas spread out from the arms and bar, giving way to a dark background with some foreground stars and small, distant galaxies.


[...] This highly detailed image was created using six different filters. The abundance of colour illustrates the galaxy's billowing clouds of gas, dark dust bands, bright pink star-forming regions and, most obviously, the long, glowing bar with trailing arms.

Barred spiral galaxies outnumber both regular spirals and elliptical galaxies put together, numbering around 60% of all galaxies. [...] The orbital patterns and the gravitational interactions within a galaxy that sustain the bar also transport matter and energy into it, fuelling star formation. Indeed, the observing programme studying NGC 4731 seeks to investigate this flow of matter in galaxies.

Beyond the bar, the spiral arms of NGC 4731 stretch out far past the confines of this close-in Hubble view. The galaxy’s elongated arms are thought to result from gravitational interactions with other, nearby galaxies in the Virgo cluster.


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Re: GOTD: Galaxy Of The Day

Post by AVAO » Wed Jun 26, 2024 7:44 pm

HST: NGC 3059 - A broad and narrow galactic view
NASA/ESA | Original release 2024 June 3
A spiral galaxy seen face-on, so that its many arms and its glowing, bar-shaped core can be easily seen. The arms are filled with bluish patches of older stars, pink patches where new stars are forming, and dark threads of dust. A few bright stars with cross-shaped diffraction spikes lie in the foreground.

This Picture of the Week features the barred spiral galaxy NGC 3059, which lies about 57 million light-years from Earth. The data used to compose this image were collected by Hubble in May 2024, as part of an observing programme that studied a number of galaxies. All the observations were made using the same range of filters: partially transparent materials that allow only very specific wavelengths of light to pass through.

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Re: GOTD: Galaxy Of The Day

Post by Ann » Thu Jun 27, 2024 6:48 am

AVAO wrote: Wed Jun 26, 2024 7:44 pm HST: NGC 3059 - A broad and narrow galactic view
NASA/ESA | Original release 2024 June 3
A spiral galaxy seen face-on, so that its many arms and its glowing, bar-shaped core can be easily seen. The arms are filled with bluish patches of older stars, pink patches where new stars are forming, and dark threads of dust. A few bright stars with cross-shaped diffraction spikes lie in the foreground.

This Picture of the Week features the barred spiral galaxy NGC 3059, which lies about 57 million light-years from Earth. The data used to compose this image were collected by Hubble in May 2024, as part of an observing programme that studied a number of galaxies. All the observations were made using the same range of filters: partially transparent materials that allow only very specific wavelengths of light to pass through.

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GOTD4Y Jac

Oh wow, Jac, that's gorgeous! That's glorious! I have to say it: There is no beating Hubble when it comes to producing beautiful space porn! All right, okay: There are some truly stunning Webb images of dust structures in spiral galaxies. (Thanks, Judy!)

But all in all, Hubble makes the most beautiful space images (when it makes good use of its filters). For this image, it used no fewer than six filters: Two ultraviolet ones, one blue, one green, one infrared and one narrowband one designed to detect hydrogen alpha which is such a characteristic byproduct of star formation and the ultraviolet light of hot stars on gas clouds.

A few notes here. NGC 3059 is found in Carina, relatively close to the band of the Milky Way. It is the second brightest galaxy in Carina, even though NGC 3059 is probably small-ish, and we can conclude that many other galaxies in this constellation are hidden behind the band of the Milky Way, also known as the Zone of Avoidance.


Let's return to NGC 3059. The galaxy has a short bar which is full of star formation! Note the large dust cloud in the rightmost part of the bar. But also note that the bar itself is blue-white in color, which means that the light of the bar is predominately emitted by hot blue-white stars. That's unusual, because most bars are very yellow in color and full of old red and yellow stars.

Bar of NGC 3059 ESA Hubble NASA D Thilker.png
The bar of NGC 3059 is peppered with hot blue-white stars.

The bar of NGC 3059 looks like it is in the process of forming. It is very different from the bar of NGC 1300. Mature bars, such as the one in NGC 1300, are not only yellow in color, but they also contain two dust lanes stretching from the core of the galaxy to the beginning of the spiral arms. The bar of NGC 3059 contains no dust lanes, and, remarkably, the galaxy has no visible core. The fact that NGC 3059 lacks a visible core suggests to me that this galaxy can't be too big, and it can't contain a very big central black hole.


We have reason to believe that the bar of NGC 3059 is quite bright, considering it is quite full of very bright hot stars. For comparison, let's look at another galaxy whose bar contains star formation, but also contains old yellow stars:


Finally, I note that Hubble photographed NGC 3059 in May 2024, after it started having major problems with its gyros. Hooray! Hubble may not be operating at full capacity - it may be slower than before - but it is, at least, definitely back in business! 😀 🥳

Ann
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Re: GOTD: Galaxy Of The Day

Post by AVAO » Sat Jun 29, 2024 4:32 pm

Ann wrote: Thu Jun 27, 2024 6:48 am
Finally, I note that Hubble photographed NGC 3059 in May 2024, after it started having major problems with its gyros. Hooray! Hubble may not be operating at full capacity - it may be slower than before - but it is, at least, definitely back in business! 😀 🥳

Ann

ThanX 4 your detailed comments.

I like HUBBLE too because it has our eyes.
WEBB on the other hand is a vamp :evil:

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Re: GOTD: Galaxy Of The Day

Post by AVAO » Sat Jun 29, 2024 4:56 pm

Follow the leader
NASA/ESA | Original release 2024 June 23
This line of galaxies is a cosmic coincidence behind the interacting system Arp-Madore 2105-332, which is a pair of galaxies 200 million light years away in the suitably small constellation of Microscopium. Gravitational tendrils from each galaxy reach out to one another, pulling stars and galaxies out and unravelling both galaxies. It’s all fairly standard as far as interacting galaxies go, but what is remarkable is that line of numerous galaxies in the background. These galaxies are completely unrelated to Arp-Madore 2105-332 – it’s just a chance alignment, but it makes for a remarkable vista. Some of the distant galaxies in the line appear red, drained of star-forming gas and with only older stars left. One is a classic blue spiral perhaps like our own galaxy. Looking around the image, the objects with diffraction spikes are stars in our Milky Way. Everything else in this image is a galaxy, mostly too faint or too far away to be resolved as anything but a smudge of light.

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Re: GOTD: Galaxy Of The Day

Post by Ann » Wed Jul 17, 2024 5:31 am

AVAO wrote: Sat Jun 29, 2024 4:56 pm Follow the leader
NASA/ESA | Original release 2024 June 23
This line of galaxies is a cosmic coincidence behind the interacting system Arp-Madore 2105-332, which is a pair of galaxies 200 million light years away in the suitably small constellation of Microscopium. Gravitational tendrils from each galaxy reach out to one another, pulling stars and galaxies out and unravelling both galaxies. It’s all fairly standard as far as interacting galaxies go, but what is remarkable is that line of numerous galaxies in the background. These galaxies are completely unrelated to Arp-Madore 2105-332 – it’s just a chance alignment, but it makes for a remarkable vista. Some of the distant galaxies in the line appear red, drained of star-forming gas and with only older stars left. One is a classic blue spiral perhaps like our own galaxy. Looking around the image, the objects with diffraction spikes are stars in our Milky Way. Everything else in this image is a galaxy, mostly too faint or too far away to be resolved as anything but a smudge of light.

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GOTD4Y Jac
Fantastic, Jac! I haven't been good enough at paying attention to your posts here. Well, Arp-Madore 2105-332 is a fascinating pair! They both look like lenticular galaxies that are undergoing a "dry merger", one that doesn't result in any star formation. I note, however, that the galaxy on the right, 2MASX J21080362-3313196, contains either a starburst, or more likely, a post-starburst region in its very center. The galaxy on the left, 2MASX J21080362-3313197, displays a little hint of blue in its weak arm below its center. Probably F-type stars, possibly with some late A-type stars among them.

I can't make sense of the background galaxies!

Background galaxies from potw2350a 11 December 2023.png

The topmost galaxy is small and reddened by dust in the foreground galaxy, 2MASX J21080362-3313197. The two orange galaxies near bottom are very orange and could be background galaxies. But what about the two spirals in the middle? One is orange and one is blue, yet even the orange one shows signs of star formation and star clusters. Why are these galaxies so different in color, when they are so similar in size and overall shape?

Could the blue galaxy be in the foreground relative to the other, orange-colored galaxies here? But the blue galaxy looks quite large and well-formed. It's hard to believe that it is much smaller than the orange galaxies seen (in projection?) close to it, and that a noticeable difference in redshift would account for the difference in color!

Ann
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Re: GOTD: Galaxy Of The Day

Post by AVAO » Wed Jul 17, 2024 7:59 am

Ann wrote: Wed Jul 17, 2024 5:31 am
AVAO wrote: Sat Jun 29, 2024 4:56 pm Follow the leader
NASA/ESA | Original release 2024 June 23
This line of galaxies is a cosmic coincidence behind the interacting system Arp-Madore 2105-332, which is a pair of galaxies 200 million light years away in the suitably small constellation of Microscopium. Gravitational tendrils from each galaxy reach out to one another, pulling stars and galaxies out and unravelling both galaxies. It’s all fairly standard as far as interacting galaxies go, but what is remarkable is that line of numerous galaxies in the background. These galaxies are completely unrelated to Arp-Madore 2105-332 – it’s just a chance alignment, but it makes for a remarkable vista. Some of the distant galaxies in the line appear red, drained of star-forming gas and with only older stars left. One is a classic blue spiral perhaps like our own galaxy. Looking around the image, the objects with diffraction spikes are stars in our Milky Way. Everything else in this image is a galaxy, mostly too faint or too far away to be resolved as anything but a smudge of light.

... read more
... big
GOTD4Y Jac
Fantastic, Jac! I haven't been good enough at paying attention to your posts here. Well, Arp-Madore 2105-332 is a fascinating pair! They both look like lenticular galaxies that are undergoing a "dry merger", one that doesn't result in any star formation. I note, however, that the galaxy on the right, 2MASX J21080362-3313196, contains either a starburst, or more likely, a post-starburst region in its very center. The galaxy on the left, 2MASX J21080362-3313197, displays a little hint of blue in its weak arm below its center. Probably F-type stars, possibly with some late A-type stars among them.

I can't make sense of the background galaxies!


Background galaxies from potw2350a 11 December 2023.png


The topmost galaxy is small and reddened by dust in the foreground galaxy, 2MASX J21080362-3313197. The two orange galaxies near bottom are very orange and could be background galaxies. But what about the two spirals in the middle? One is orange and one is blue, yet even the orange one shows signs of star formation and star clusters. Why are these galaxies so different in color, when they are so similar in size and overall shape?

Could the blue galaxy be in the foreground relative to the other, orange-colored galaxies here? But the blue galaxy looks quite large and well-formed. It's hard to believe that it is much smaller than the orange galaxies seen (in projection?) close to it, and that a noticeable difference in redshift would account for the difference in color!

Ann
ThanX Ann

For your detailed comment! I feel the same way. I can't really believe that this chain of background galaxies should be spatially random.

Jac