APOD: M63: Sunflower Galaxy Wide Field (2016 Aug 04)

Comments and questions about the APOD on the main view screen.
User avatar
APOD Robot
Otto Posterman
Posts: 4786
Joined: Fri Dec 04, 2009 3:27 am

APOD: M63: Sunflower Galaxy Wide Field (2016 Aug 04)

Post by APOD Robot » Thu Aug 04, 2016 4:07 am

Image M63: Sunflower Galaxy Wide Field

Explanation: The Sunflower Galaxy blooms near the center of this wide field telescopic view. The scene spans about 2 degrees or 4 full moons on the sky toward the loyal constellation Canes Venatici. More formally known as Messier 63, the majestic island universe is nearly 100,000 light-years across, about the size of our own Milky Way Galaxy. Surrounding its bright yellowish core, sweeping spiral arms are streaked with cosmic dust lanes and dotted with star forming regions. A dominant member of a known galaxy group, M63 has faint, extended features that could be the the remains of dwarf satellite galaxies, evidence that large galaxies grow by accreting small ones. M63 shines across the electromagnetic spectrum and is thought to have undergone bursts of intense star formation.

<< Previous APOD This Day in APOD Next APOD >>
[/b]

ShaileshS

Re: APOD: M63: Sunflower Galaxy Wide Field (2016 Aug 04)

Post by ShaileshS » Thu Aug 04, 2016 5:11 am

If spiral galaxy comes in contact with a dwarf galaxy then the resultant will be still spiral (just a bigger version). Right ? If 2 spiral medium size galaxies collide (e.g. Andromeda and Milky way), then resultant will be eliptical, I heard. Why ? Why not bigger spiral ? And, what happens when 2 elliptical galaxies collide OR when 1 elliptical and 1 spiral collide ? Thanks in advance for all the answers and comments.

User avatar
geckzilla
Ocular Digitator
Posts: 9173
Joined: Wed Sep 12, 2007 12:42 pm
Location: Modesto, CA

Re: APOD: M63: Sunflower Galaxy Wide Field (2016 Aug 04)

Post by geckzilla » Thu Aug 04, 2016 8:23 am

ShaileshS wrote:If spiral galaxy comes in contact with a dwarf galaxy then the resultant will be still spiral (just a bigger version). Right ? If 2 spiral medium size galaxies collide (e.g. Andromeda and Milky way), then resultant will be eliptical, I heard. Why ? Why not bigger spiral ? And, what happens when 2 elliptical galaxies collide OR when 1 elliptical and 1 spiral collide ? Thanks in advance for all the answers and comments.
These could be considered general rules of thumb. Not always true, but they sound about right in many cases. If you have a collection of matter that's already in a disc, it would take a much larger collection of matter to change it from being a disc, hence #1. A dwarf galaxy would not be massive enough to disrupt an established spiral from its disc-shaped organization. Two spirals may or may not be discs in the end. Surely it would depend upon how the angular momentum combined in the end. Elliptical galaxies tend to be quite massive, but they do sometimes come in disc shapes or have the remnants of a disc in them, but those are usually classified as lenticular galaxies. A lot of elliptical galaxies retain evidence of distant mergers in the form of faint shells. To be honest, I don't know exactly why they lose their rotation and become spheroids.
Just call me "geck" because "zilla" is like a last name.

User avatar
Ann
4725 Å
Posts: 12259
Joined: Sat May 29, 2010 5:33 am

Re: APOD: M63: Sunflower Galaxy Wide Field (2016 Aug 04)

Post by Ann » Thu Aug 04, 2016 9:04 am

ShaileshS wrote:If spiral galaxy comes in contact with a dwarf galaxy then the resultant will be still spiral (just a bigger version). Right ? If 2 spiral medium size galaxies collide (e.g. Andromeda and Milky way), then resultant will be eliptical, I heard. Why ? Why not bigger spiral ? And, what happens when 2 elliptical galaxies collide OR when 1 elliptical and 1 spiral collide ? Thanks in advance for all the answers and comments.
Sometimes spiral galaxies can apparently merge in such a way that the end product is a larger spiral galaxy, even a super spiral galaxy.
Super spiral galaxies, two with double nuclei.
Photo: SDSS.
http://www.nasa.gov/feature/jpl/astrono ... l-galaxies wrote:
A strange new kind of galactic beast has been spotted in the cosmic wilderness. Dubbed "super spirals," these unprecedented galaxies dwarf our own spiral galaxy, the Milky Way, and compete in size and brightness with the largest galaxies in the universe...

In a sample of approximately 800,000 galaxies no more than 3.5 billion light-years from Earth, 53 of the brightest galaxies intriguingly had a spiral, rather than elliptical, shape...

A vital hint about the potential origin of super spirals is that four out of the 53 seen by Ogle and colleagues clearly contain two galactic nuclei, instead of just one as usual. Double nuclei, which look like two egg yolks frying in a pan, are a telltale sign of two galaxies having just merged together. Conventionally, mergers of spiral galaxies are destined to become bloated, elliptical galaxies. Yet Ogle and colleagues speculate that a special merger involving two, gas-rich spiral galaxies could see their pooled gases settle down into a new, larger stellar disk -- presto, a super spiral...
Ann
Color Commentator

User avatar
Ann
4725 Å
Posts: 12259
Joined: Sat May 29, 2010 5:33 am

Re: APOD: M63: Sunflower Galaxy Wide Field (2016 Aug 04)

Post by Ann » Thu Aug 04, 2016 9:40 am

M83 is a so-called flocculent galaxy, one that doesn't have long elegant spiral arms, but rather many short arm segments.

An interesting aspect of today's APOD is that it demonstrates that M63 has an extended halo.

Other flocculent galaxies also have extended halos:
NGC 3521. Photo: R Jay GaBany, David Martinez-Delgado et al.
NGC 4414. Photo: Adam Block.


















My own guess is that the somewhat chaotic nature of the spiral pattern of flocculent galaxies, as well as their huge extended halos, may be products of mergers and collisions.

Ann
Color Commentator

User avatar
neufer
Vacationer at Tralfamadore
Posts: 18805
Joined: Mon Jan 21, 2008 1:57 pm
Location: Alexandria, Virginia

Re: APOD: M63: Sunflower Galaxy Wide Field (2016 Aug 04)

Post by neufer » Thu Aug 04, 2016 10:38 am

ShaileshS wrote:
If 2 spiral medium size galaxies collide (e.g. Andromeda and Milky way), then resultant will be eliptical, I heard. Why ? Why not bigger spiral ? And, what happens when 2 elliptical galaxies collide OR when 1 elliptical and 1 spiral collide ?
Probably about the only thing one can say for sure is that when two galaxies collide they will lose a lot of dark matter and become more active.

It could be that spiral galaxies originally formed "like beads on a string" along the filaments of dark matter condensations while elliptical galaxies formed at the tangles of dark matter condensations:
https://en.wikipedia.org/wiki/Spiral_galaxy#Alignment_of_spin_axis_with_cosmic_voids wrote:
<<Recent results suggest that the orientation of the spin axis of spiral galaxies is not a chance result, but instead they are preferentially aligned along the surface of cosmic voids. That is, spiral galaxies tend to be oriented at a high angle of inclination relative to the large-scale structure of the surroundings. They have been described as lining up like "beads on a string," with their axis of rotation following the filaments around the edges of the voids.>>
https://en.wikipedia.org/wiki/Void_(astronomy) wrote: <<Cosmic voids are the vast empty spaces between filaments (the largest-scale structures in the Universe), which contain very few or no galaxies. Voids typically have a diameter of 10 to 100 megaparsecs; particularly large voids, defined by the absence of rich superclusters, are sometimes called supervoids. They have less than one-tenth of the average density of matter abundance that is considered typical for the observable Universe.

Voids are believed to have been formed by baryon acoustic oscillations in the Big Bang, collapses of mass followed by implosions of the compressed baryonic matter. Starting from initially small anisotropies from quantum fluctuations in the early Universe, the anisotropies grew larger in scale over time. Regions of higher density collapsed more rapidly under gravity, eventually resulting in the large-scale, foam-like structure or “cosmic web” of voids and galaxy filaments seen today. Voids located in high-density environments are smaller than voids situated in low-density spaces of the universe.

Voids appear to correlate with the observed temperature of the cosmic microwave background (CMB) because of the Sachs–Wolfe effect. Colder regions correlate with voids and hotter regions correlate with filaments because of gravitational redshifting. As the Sachs–Wolfe effect is only significant if the Universe is dominated by radiation or dark energy, the existence of voids is significant in providing physical evidence for dark energy.>>
Art Neuendorffer

Boomer12k
:---[===] *
Posts: 2691
Joined: Sun Apr 22, 2007 12:07 am

Re: APOD: M63: Sunflower Galaxy Wide Field (2016 Aug 04)

Post by Boomer12k » Thu Aug 04, 2016 3:22 pm

Great wide shot...

:---[===] *

User avatar
Ann
4725 Å
Posts: 12259
Joined: Sat May 29, 2010 5:33 am

Re: APOD: M63: Sunflower Galaxy Wide Field (2016 Aug 04)

Post by Ann » Thu Aug 04, 2016 6:30 pm

There is a thick, dark, elongated dust lane separating the finely patterned part of M63's disk from the galaxy's outer, smooth features. This dust lane is very obvious in today's APOD, because the outer features are brighter in this picture than they usually are.

Other galaxies also have dust lanes separating different parts of the galaxy. In the case of M64, I believe that the inner and the outer parts rotate in different directions. Interestingly, the dust lane of M64 also looks kind of flocculent.

Ann
Color Commentator

chuckster
Ensign
Posts: 66
Joined: Sat Mar 08, 2014 2:02 am

Re: APOD: M63: Sunflower Galaxy Wide Field (2016 Aug 04)

Post by chuckster » Thu Aug 04, 2016 7:06 pm

Spiral structure in galaxies- from what does it arise? Intuitively, it seems to come from spinning, but that can't be right,
based on all the other flavors of galactic structure. I've read (or heard) that spiral structure is massaged into the galactic disc by gravity waves propagating out from a central black hole.

User avatar
Chris Peterson
Abominable Snowman
Posts: 16925
Joined: Wed Jan 31, 2007 11:13 pm
Location: Guffey, Colorado, USA

Re: APOD: M63: Sunflower Galaxy Wide Field (2016 Aug 04)

Post by Chris Peterson » Thu Aug 04, 2016 7:38 pm

chuckster wrote:Spiral structure in galaxies- from what does it arise? Intuitively, it seems to come from spinning, but that can't be right,
based on all the other flavors of galactic structure. I've read (or heard) that spiral structure is massaged into the galactic disc by gravity waves propagating out from a central black hole.
It has nothing to do with gravitational waves. You can read about the more well accepted ideas here.
Chris

*****************************************
Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

User avatar
Ann
4725 Å
Posts: 12259
Joined: Sat May 29, 2010 5:33 am

Re: APOD: M63: Sunflower Galaxy Wide Field (2016 Aug 04)

Post by Ann » Thu Aug 04, 2016 7:46 pm

chuckster wrote:Spiral structure in galaxies- from what does it arise? Intuitively, it seems to come from spinning, but that can't be right,
based on all the other flavors of galactic structure. I've read (or heard) that spiral structure is massaged into the galactic disc by gravity waves propagating out from a central black hole.
Black holes don't give galaxies spiral structures.

Check out this list of massive black holes in other galaxies. I haven't bothered trying to identify the galaxies with the fancy designations, but my software easily recognizes the NGC and the Messier galaxies. Most of the NGC and the Messier galaxies in that list are elliptical galaxies, without spiral structure. The spiral galaxies in that list, such as the Andromeda galaxy, the Sombrero galaxy and M81, don't host the most massive black holes.

Ann
Color Commentator

User avatar
Ann
4725 Å
Posts: 12259
Joined: Sat May 29, 2010 5:33 am

Re: APOD: M63: Sunflower Galaxy Wide Field (2016 Aug 04)

Post by Ann » Thu Aug 04, 2016 8:44 pm

The amount of star formation in a galaxy affects its appearance.
UGC 12158. Credit: ESA/Hubble & NASA.
M101. Image credit: Reuters / BJ Fulton (Las Cumbres) and the Palomar Transient Factor.


















UGC 12158 at left contains a lot less star formation than M101 at right. In UGC 12158, star formation follows the spiral arms very closely, and the (smallish) star clusters and nebulas are very evenly distributed along the elegant spiral arms. In M101, star formation is popping off like firecrackers almost uncontrollably, so that the galaxy almost seems to be coming apart at the seams.

It seems very likely that M101 has been affected by mergers or interactions with one or several dwarf galaxies quite recently. UGC 12158, by contrast, looks undisturbed, like Sleeping Beauty before the prince awakens her with a kiss.

Ann
Color Commentator

starsurfer
Stellar Cartographer
Posts: 4873
Joined: Thu Mar 15, 2012 7:25 pm

Re: APOD: M63: Sunflower Galaxy Wide Field (2016 Aug 04)

Post by starsurfer » Mon Aug 08, 2016 3:53 pm

Ann wrote:M83 is a so-called flocculent galaxy, one that doesn't have long elegant spiral arms, but rather many short arm segments.

An interesting aspect of today's APOD is that it demonstrates that M63 has an extended halo.

Other flocculent galaxies also have extended halos:
NGC 3521. Photo: R Jay GaBany, David Martinez-Delgado et al.
NGC 4414. Photo: Adam Block.


















My own guess is that the somewhat chaotic nature of the spiral pattern of flocculent galaxies, as well as their huge extended halos, may be products of mergers and collisions.

Ann
What you describe as haloes in these particular galaxies are actually examples of tidal shells.

User avatar
Ann
4725 Å
Posts: 12259
Joined: Sat May 29, 2010 5:33 am

Re: APOD: M63: Sunflower Galaxy Wide Field (2016 Aug 04)

Post by Ann » Mon Aug 08, 2016 5:05 pm

starsurfer wrote:
Ann wrote:M83 is a so-called flocculent galaxy, one that doesn't have long elegant spiral arms, but rather many short arm segments.

An interesting aspect of today's APOD is that it demonstrates that M63 has an extended halo.

Other flocculent galaxies also have extended halos:

My own guess is that the somewhat chaotic nature of the spiral pattern of flocculent galaxies, as well as their huge extended halos, may be products of mergers and collisions.

Ann
What you describe as haloes in these particular galaxies are actually examples of tidal shells.
Okay! :wink:

So do you think that the chaotic nature of the spiral pattern of flocculent galaxies as well as their extended tidal shells can be products of mergers and collisions?

Ann
Color Commentator

User avatar
neufer
Vacationer at Tralfamadore
Posts: 18805
Joined: Mon Jan 21, 2008 1:57 pm
Location: Alexandria, Virginia

Re: APOD: M63: Sunflower Galaxy Wide Field (2016 Aug 04)

Post by neufer » Mon Aug 08, 2016 5:52 pm

Ann wrote:
My own guess is that the somewhat chaotic nature of the spiral pattern of flocculent galaxies, as well as their huge extended halos, may be products of mergers and collisions.
https://en.wikipedia.org/wiki/Triangulum_Galaxy wrote: <<In 2004, evidence was announced of a clumpy stream of hydrogen gas linking the Andromeda Galaxy [~1 trillion stars] with Triangulum [~40 billion stars], suggesting that the two may have tidally interacted in the past. This discovery was confirmed in 2011. A distance of less than 300 kiloparsecs between the two supports this hypothesis. A past interaction between these two galaxies took place from 2 to 8 billion years ago, and a more violent encounter will occur 2.5 billion years in the future.>>

http://apod.nasa.gov/apod/ap150926.html
http://apod.nasa.gov/apod/ap121220.html
Art Neuendorffer

chuckster
Ensign
Posts: 66
Joined: Sat Mar 08, 2014 2:02 am

Re: APOD: M63: Sunflower Galaxy Wide Field (2016 Aug 04)

Post by chuckster » Mon Aug 08, 2016 6:52 pm

Chris Peterson wrote:
chuckster wrote:Spiral structure in galaxies- from what does it arise? Intuitively, it seems to come from spinning, but that can't be right,
based on all the other flavors of galactic structure. I've read (or heard) that spiral structure is massaged into the galactic disc by gravity waves propagating out from a central black hole.
It has nothing to do with gravitational waves. You can read about the more well accepted ideas here.
Thanks for pointing me in the right direction.

chuckster
Ensign
Posts: 66
Joined: Sat Mar 08, 2014 2:02 am

Re: APOD: M63: Sunflower Galaxy Wide Field (2016 Aug 04)

Post by chuckster » Mon Aug 08, 2016 6:56 pm

Ann wrote:
chuckster wrote:Spiral structure in galaxies- from what does it arise? Intuitively, it seems to come from spinning, but that can't be right,
based on all the other flavors of galactic structure. I've read (or heard) that spiral structure is massaged into the galactic disc by gravity waves propagating out from a central black hole.
Black holes don't give galaxies spiral structures.

Check out this list of massive black holes in other galaxies. I haven't bothered trying to identify the galaxies with the fancy designations, but my software easily recognizes the NGC and the Messier galaxies. Most of the NGC and the Messier galaxies in that list are elliptical galaxies, without spiral structure. The spiral galaxies in that list, such as the Andromeda galaxy, the Sombrero galaxy and M81, don't host the most massive black holes.

Ann
So much for that black hole/spiral structure false relationship of mine ! Thanks for straightening me out.

starsurfer
Stellar Cartographer
Posts: 4873
Joined: Thu Mar 15, 2012 7:25 pm

Re: APOD: M63: Sunflower Galaxy Wide Field (2016 Aug 04)

Post by starsurfer » Tue Aug 09, 2016 4:11 pm

Ann wrote:
starsurfer wrote:
Ann wrote:M83 is a so-called flocculent galaxy, one that doesn't have long elegant spiral arms, but rather many short arm segments.

An interesting aspect of today's APOD is that it demonstrates that M63 has an extended halo.

Other flocculent galaxies also have extended halos:

My own guess is that the somewhat chaotic nature of the spiral pattern of flocculent galaxies, as well as their huge extended halos, may be products of mergers and collisions.

Ann
What you describe as haloes in these particular galaxies are actually examples of tidal shells.
Okay! :wink:

So do you think that the chaotic nature of the spiral pattern of flocculent galaxies as well as their extended tidal shells can be products of mergers and collisions?

Ann
Isn't it generally accepted that the spiral structure in galaxies is a result of density waves? I think collisions would affect density waves and therefore the overall structure. You can easily see this in the visual appearance of interacting and peculiar galaxies.

User avatar
Ann
4725 Å
Posts: 12259
Joined: Sat May 29, 2010 5:33 am

Re: APOD: M63: Sunflower Galaxy Wide Field (2016 Aug 04)

Post by Ann » Wed Aug 10, 2016 3:34 am

starsurfer wrote:
Ann wrote:
starsurfer wrote: What you describe as haloes in these particular galaxies are actually examples of tidal shells.
Okay! :wink:

So do you think that the chaotic nature of the spiral pattern of flocculent galaxies as well as their extended tidal shells can be products of mergers and collisions?

Ann
Isn't it generally accepted that the spiral structure in galaxies is a result of density waves? I think collisions would affect density waves and therefore the overall structure. You can easily see this in the visual appearance of interacting and peculiar galaxies.
M51, a grand design galaxy with long arms, and companion NGC 5195. Photo: Bill Snyder.
NGC 2775, a flocculent galaxy with patchy, broken spiral fragments. Photo: Adam Block.




















It is certainly true that interactions can enhance the spiral structure of disk galaxies. M51, the Whirlpool galaxy, is the poster child for this sort of enhanced spiral structure through interactions with another galaxy. Bill Snyder's picture also shows large tidal shells surrounding both M51 and its companion, NGC 5195. These shells are clearly also caused by the mutual interactions.

But take a look at Adam Block's picture of NGC 2775. Go to this page to see a full size image of it. Here you can also see a huge tidal shell surrounding NGC 2775.

NGC 2775 could be considered a poster child for flocculent galaxies. Its spiral structure is extremely broken up and patchy.

But NGC 2775 doesn't have any sort of companion that is in any way comparable to the Whirlpool Galaxy's NGC 5195. Adam Block's full size image shows two small blue galaxies at upper right of NGC 2775; they could be at the same distance as NGC 2775 and possibly be interacting with it, but being small and blue, they are quite clearly not very massive. A small yellowish galaxy is visible in the lower left corner of the full size image. Being yellowish, it is a bit more massive than the small blue ones, but no tidal bridge can be seen between this galaxy and NGC 2775.

I'm wondering if NGC 2775 could have interacted rather violently with another galaxy and perhaps merged with it. That would explain the huge tidal shell. It could also possibly explain NGC 2775's extremely patchy and almost disintegrated spiral structure.

My point is that interactions can both enhance, disrupt and perhaps destroy a galaxy's spiral structure.

Ann
Color Commentator

starsurfer
Stellar Cartographer
Posts: 4873
Joined: Thu Mar 15, 2012 7:25 pm

Re: APOD: M63: Sunflower Galaxy Wide Field (2016 Aug 04)

Post by starsurfer » Wed Aug 10, 2016 12:43 pm

Ann wrote:
starsurfer wrote:
Ann wrote:
Okay! :wink:

So do you think that the chaotic nature of the spiral pattern of flocculent galaxies as well as their extended tidal shells can be products of mergers and collisions?

Ann
Isn't it generally accepted that the spiral structure in galaxies is a result of density waves? I think collisions would affect density waves and therefore the overall structure. You can easily see this in the visual appearance of interacting and peculiar galaxies.
M51, a grand design galaxy with long arms, and companion NGC 5195. Photo: Bill Snyder.
NGC 2775, a flocculent galaxy with patchy, broken spiral fragments. Photo: Adam Block.




















It is certainly true that interactions can enhance the spiral structure of disk galaxies. M51, the Whirlpool galaxy, is the poster child for this sort of enhanced spiral structure through interactions with another galaxy. Bill Snyder's picture also shows large tidal shells surrounding both M51 and its companion, NGC 5195. These shells are clearly also caused by the mutual interactions.

But take a look at Adam Block's picture of NGC 2775. Go to this page to see a full size image of it. Here you can also see a huge tidal shell surrounding NGC 2775.

NGC 2775 could be considered a poster child for flocculent galaxies. Its spiral structure is extremely broken up and patchy.

But NGC 2775 doesn't have any sort of companion that is in any way comparable to the Whirlpool Galaxy's NGC 5195. Adam Block's full size image shows two small blue galaxies at upper right of NGC 2775; they could be at the same distance as NGC 2775 and possibly be interacting with it, but being small and blue, they are quite clearly not very massive. A small yellowish galaxy is visible in the lower left corner of the full size image. Being yellowish, it is a bit more massive than the small blue ones, but no tidal bridge can be seen between this galaxy and NGC 2775.

I'm wondering if NGC 2775 could have interacted rather violently with another galaxy and perhaps merged with it. That would explain the huge tidal shell. It could also possibly explain NGC 2775's extremely patchy and almost disintegrated spiral structure.

My point is that interactions can both enhance, disrupt and perhaps destroy a galaxy's spiral structure.

Ann
Not only does Adam Block's image of NGC 2775 show a shell, the full frame image also shows a long tidal tail! It is generally accepted that these additional structures are the result of minor mergers with dwarf galaxies. See more here.

User avatar
rstevenson
Quis custodiet ipsos custodes?
Posts: 2677
Joined: Fri Mar 28, 2008 1:24 pm
Location: Halifax, NS, Canada

Re: APOD: M63: Sunflower Galaxy Wide Field (2016 Aug 04)

Post by rstevenson » Wed Aug 10, 2016 1:03 pm

Ann wrote:My point is that interactions can both enhance, disrupt and perhaps destroy a galaxy's spiral structure.
I suspect that the angle at which the planes of two spiral galaxies approach and pass through each other will have a strong effect on which of those scenarios plays out. Picture them coming together with nearly parallel spiral planes, then compare your mental picture of the result with them coming together with one plane tilted at about 90° to the other. I believe the results in those two cases will be drastically different, but I can't quite decide which would disrupt the spiral shapes more.

Also, the degree of interpenetration will have a major effect. If the galaxys' central bulges closely overlap, the result will surely be different than if the central bulge of one galaxy passes through the outer region of the other.

Finally, I think that the angle of intersection of the trajectories of the two galaxies will have a strong effect. There should be quite a difference between the results if the galaxies are travelling at about 90° to each other, compared to if their paths were intersecting at only a slight angle.

Rob

Rakeera

Re: APOD: M63: Sunflower Galaxy Wide Field (2016 Aug 04)

Post by Rakeera » Mon Aug 15, 2016 10:56 pm

I noticed what appears to be a foreground star to the lower right of M63 that seems to be affecting the sunflower Galaxy. Could this star be hiding a dwarf galaxy behind it?

User avatar
Ann
4725 Å
Posts: 12259
Joined: Sat May 29, 2010 5:33 am

Re: APOD: M63: Sunflower Galaxy Wide Field (2016 Aug 04)

Post by Ann » Tue Aug 16, 2016 1:19 am

Rakeera wrote:I noticed what appears to be a foreground star to the lower right of M63 that seems to be affecting the sunflower Galaxy. Could this star be hiding a dwarf galaxy behind it?
M63. Photo: NASA and GALEX.
Antennae galaxies. Photo: Rolf Olsen.

















No. Take a look at the ultraviolet image of M63 at left. In this image, the foreground star in question has shrunk to a tiny yellow dot at 3 o'clock. Why is it so tiny? It is because this star is relatively cool, a bit cooler than the Sun, and therefore it emits only small amounts of ultraviolet light. But another yellow foreground star looks bright, because that star is a bit hotter than the Sun.

In this ultraviolet image, the very hot stars of M63 are shown in blue light. You can see that there are many (often faint) blue "arm fragments" surrounding M63. These are areas of star formation in the outer arms of M63. The brightest blue fragment is directly below the tiny yellow dot of the foreground star. This blue fragment is unusually rich in hot stars, stars similar to Rigel and Deneb and the stars in Orion's Belt.

The blue fragment is a part of M63 itself and not a dwarf galaxy. But it certainly does happen that a starforming feature that originally belonged to a parents galaxy "comes loose" and turns into a dwarf galaxy of its own. Take a look at the image at right. It shows two colliding galaxies, the Antennae Galaxies. They have been named the Antennae because of the very long tidal tails that have been thrown out from each galaxy because of the collision. The tidal tail on the left is longer than the one at right, and it ends in regions of star formation (blue clumps). These newborn clusters of hot bright stars are so far away from their parent galaxy that they might well turn into a dwarf galaxy of their own.

Ann
Color Commentator