Starship Asterisk*

The Stars of the Triangulum Galaxy

Explanation: Like grains of sand on a cosmic beach, stars of the Triangulum Galaxy are resolved in this sharp mosaic from the Hubble Space Telescope's Advanced Camera for Surveys (ACS). The inner region of the galaxy spanning over 17,000 light-years is covered at extreme resolution, the second largest image ever released by Hubble. At its center is the bright, densely packed galactic core surrounded by a loose array of dark dust lanes mixed with the stars in the galactic plane. Also known as M33, the face-on spiral galaxy lies 3 million light-years away in the small northern constellation Triangulum. Over 50,000 light-years in diameter, the Triangulum Galaxy is the third largest in the Local Group of galaxies after the Andromeda Galaxy (M31), and our own Milky Way. Of course, to fully appreciate the Triangulum's stars, star clusters, and bright nebulae captured in this Hubble mosaic, you'll need to use a zoom tool.

<< Previous APOD

This Day in APOD

Next APOD >>

Are all the "big" stars here part of the Milky Way? There's one bright one coincidentally appearing very near the center of M33 ... that's not in M33 right?


Closeup of the center

Love the big nebula at the bottom of the picture and the "blue, one-eyed 'puppy dog' " in the upper right...

Here is my shot with my 6" Celestron Evolution...not as bright...I forget how long the exposures were, or the number of frames...maybe 10-20 at 30 secs or so...not real sure but that would be common...maybe longer.

My image would be rotated to our left, you can see the "y" shape of stars, and the triangle of stars in the hub...as well as some "globby" features.

This was from 9-27-2018. It was an awesome night, if I remember.

:---[===] *

Zooming does give one an appreciation for the number of stars in any galaxy! Of course it takes quintillions of 'tries' to produce even ONE single example of life appearing, and doing what we do. Sure lucky it was us! Hmmm...

So any galaxies, with so many stars, with so many planets! I can't imagine how many!

The "use a zoom tool" link is an overwhelming view. Looks difficult to call interstellar space empty. Maybe intergalactic now.

BobStein-VisiBone wrote: ↑Sat Feb 23, 2019 7:51 am Are all the "big" stars here part of the Milky Way? There's one bright one coincidentally appearing very near the center of M33 ... that's not in M33 right?


Closeup of the center

Any bright spot with radiating spikes will be a star in our Milky Way galaxy. Any that does not have them should be associated with M33. (There are lots of examples of both throughout the image.) The bright spot in your close-up seems to be the central region of M33 -- not an individual star.

Rob

Astounding image!!!! Wow just WOW!!! So much detail .I esp like the figure 8ish curly star patterns around 9:00 in the outer arm.

The distances to stars and galaxies is mind melting.The closest star in The Milky Way is incredibly far away....our galactic core? Ridiculously distant.Our neighboring galaxies? Galaxies "out there" ? Unfathomable distances ...Sure we can throw numbers at them...analyze their light frequencies..monitor gravitational waves....dang..fantastic achievements! But frustrating still!!!! I want to touch them!

The Triangulum Galaxy has at least an order of magnitude less stars than the Milky Way and two orders of magnitude less than Andromeda. These numbers are hard to grasp when already in this image 10 to 15 million individual stars are visible.

Amazingly, running the math, the number stars visible in the original image are only about one tenth of a percent of the stars in this galaxy. (However, I find it hard to believe that there is an order of magnitude difference between the Milky Way and M31.) And even the hi-res version of this image shows only a fraction of those 10 – 15 million stars, at it has only 9 million pixels.

rstevenson wrote: ↑Sat Feb 23, 2019 2:38 pm

BobStein-VisiBone wrote: ↑Sat Feb 23, 2019 7:51 am Are all the "big" stars here part of the Milky Way? There's one bright one coincidentally appearing very near the center of M33 ... that's not in M33 right?


Closeup of the center

Any bright spot with radiating spikes will be a star in our Milky Way galaxy. Any that does not have them should be associated with M33. (There are lots of examples of both throughout the image.) The bright spot in your close-up seems to be the central region of M33 -- not an individual star.

Rob

Would all the stars have diffraction spikes if they could be resolved?

Fred the Cat wrote: ↑Sat Feb 23, 2019 3:57 pm

rstevenson wrote: ↑Sat Feb 23, 2019 2:38 pm

BobStein-VisiBone wrote: ↑Sat Feb 23, 2019 7:51 am Are all the "big" stars here part of the Milky Way? There's one bright one coincidentally appearing very near the center of M33 ... that's not in M33 right?


Closeup of the center

Any bright spot with radiating spikes will be a star in our Milky Way galaxy. Any that does not have them should be associated with M33. (There are lots of examples of both throughout the image.) The bright spot in your close-up seems to be the central region of M33 -- not an individual star.

Rob

Would all the stars have diffraction spikes if they could be resolved?

That looks like the center of the galaxy to me. The core. Not a foreground Milky Way star, in my opinion. (But I might be wrong.)

Ann

Fred the Cat wrote: ↑Sat Feb 23, 2019 3:57 pm

rstevenson wrote: ↑Sat Feb 23, 2019 2:38 pm

BobStein-VisiBone wrote: ↑Sat Feb 23, 2019 7:51 am Are all the "big" stars here part of the Milky Way? There's one bright one coincidentally appearing very near the center of M33 ... that's not in M33 right?


Closeup of the center

Any bright spot with radiating spikes will be a star in our Milky Way galaxy. Any that does not have them should be associated with M33. (There are lots of examples of both throughout the image.) The bright spot in your close-up seems to be the central region of M33 -- not an individual star.

Rob

Would all the stars have diffraction spikes if they could be resolved?

All the stars do have diffraction spikes. As do the extended sources like galaxies and galaxy cores. There just aren't enough photons being diffracted to rise above the instrumental noise floor and be visible.

Fred the Cat wrote: ↑Sat Feb 23, 2019 3:57 pm
Would all the stars have diffraction spikes if they could be resolved?

ALL Hubble observed stars produce unresolved Airy disk images with accompanying diffraction spikes (caused by inference from the struts holding the convex hyperbolic secondary mirror).

Overexposure of the brightest stars turns those Airy disks into wide circles with noticeably bright diffraction spikes.

Boomer12k wrote: ↑Sat Feb 23, 2019 8:50 am Love the big nebula at the bottom of the picture and the "blue, one-eyed 'puppy dog' " in the upper right...

Here is my shot with my 6" Celestron Evolution...not as bright...I forget how long the exposures were, or the number of frames...maybe 10-20 at 30 secs or so...not real sure but that would be common...maybe longer.

My image would be rotated to our left, you can see the "y" shape of stars, and the triangle of stars in the hub...as well as some "globby" features.

This was from 9-27-2018. It was an awesome night, if I remember.

:---[===] *

Thanks, Boomer, your image gives a very helpful way to relate to the Hubble image.

I too, like that "one-eyed puppy-dog" in the Hubble image (the Zoom tool link is awesome).

So very blue, I guess it must be a reflection nebula.

MarkBour wrote: ↑Sat Feb 23, 2019 6:36 pm

Boomer12k wrote: ↑Sat Feb 23, 2019 8:50 am Love the big nebula at the bottom of the picture and the "blue, one-eyed 'puppy dog' " in the upper right...

Here is my shot with my 6" Celestron Evolution...not as bright...I forget how long the exposures were, or the number of frames...maybe 10-20 at 30 secs or so...not real sure but that would be common...maybe longer.

My image would be rotated to our left, you can see the "y" shape of stars, and the triangle of stars in the hub...as well as some "globby" features.

This was from 9-27-2018. It was an awesome night, if I remember.

:---[===] *

Thanks, Boomer, your image gives a very helpful way to relate to the Hubble image.

Capture1.png

I too, like that "one-eyed puppy-dog" in the Hubble image (the Zoom tool link is awesome).

So very blue, I guess it must be a reflection nebula.

I guess that the blue nebula at top right might be the huge emission nebula NGC 604.

Brian Ventrudo of Slooh.com wrote:

The largest star forming region in this galaxy, a patch known as NGC 604, is bright enough to be visible in small backyard telescopes under good conditions, and offers you a chance to see for yourself a star factory in a galaxy some 3 million light years away.


How big is NGC 604? It’s 1,500 light years across, about forty times larger than the famous Orion Nebula (M42) and about as large as the Orion Nebula is distant from us. It’s also some 6,000 times brighter than M42. If NGC 604 replaced the Orion Nebula in our galaxy, it would shine as bright as the planet Venus and its light would fill a patch of sky as large as your outstretched hand.

I'm not absolutely sure that the blue nebula at top right in the APOD is really NGC 604. But it is absolutely certain that the nebula in question is an emission nebula and that its dominant color is red.

It could be that the blue nebula at top right in the APOD is one of these nebulas instead: NGC 588 at left in the picture at left, NGC 592 in the center and NGC 595 at right.

What do you think?


Ann

Ann wrote: ↑Sat Feb 23, 2019 7:59 pm

MarkBour wrote: ↑Sat Feb 23, 2019 6:36 pm

Boomer12k wrote: ↑Sat Feb 23, 2019 8:50 am Love the big nebula at the bottom of the picture and the "blue, one-eyed 'puppy dog' " in the upper right...

Here is my shot with my 6" Celestron Evolution...not as bright...I forget how long the exposures were, or the number of frames...maybe 10-20 at 30 secs or so...not real sure but that would be common...maybe longer.

My image would be rotated to our left, you can see the "y" shape of stars, and the triangle of stars in the hub...as well as some "globby" features.

This was from 9-27-2018. It was an awesome night, if I remember.

:---[===] *

Thanks, Boomer, your image gives a very helpful way to relate to the Hubble image.

Capture1.png

I too, like that "one-eyed puppy-dog" in the Hubble image (the Zoom tool link is awesome).

So very blue, I guess it must be a reflection nebula.

Click to view full size image

NGC 604, giant stellar nursery.
Hubble Legacy Archive, ESA, NASA; Processing - Donald Waid

I guess that the blue nebula at top right might be the huge emission nebula NGC 604.

Brian Ventrudo of Slooh.com wrote:

The largest star forming region in this galaxy, a patch known as NGC 604, is bright enough to be visible in small backyard telescopes under good conditions, and offers you a chance to see for yourself a star factory in a galaxy some 3 million light years away.


How big is NGC 604? It’s 1,500 light years across, about forty times larger than the famous Orion Nebula (M42) and about as large as the Orion Nebula is distant from us. It’s also some 6,000 times brighter than M42. If NGC 604 replaced the Orion Nebula in our galaxy, it would shine as bright as the planet Venus and its light would fill a patch of sky as large as your outstretched hand.

I'm not absolutely sure that the blue nebula at top right in the APOD is really NGC 604. But it is absolutely certain that the nebula in question is an emission nebula and that its dominant color is red.

Click to view full size image

NGC 588 (left), NGC 592 (center) and NGC 595 (right).
Copyright: J. Shuder.

It could be that the blue nebula at top right in the APOD is one of these nebulas instead: NGC 588 at left in the picture at left, NGC 592 in the center and NGC 595 at right.

What do you think?


Ann

I think it is NGC588... in your image it is sideways...the "top" or "Ears"...are on the right side... but it does show that it seems to be an emission nebula...maybe today's image is a bit false colored?

:---[===] *

It is interesting that there are soooo many Dwarf Galaxies close by us... might there not also be D.G.'s around other galaxies that we simply don't see due to lack of brightness???

:---[===] *

Ann wrote: ↑Sat Feb 23, 2019 7:59 pm I'm not absolutely sure that the blue nebula at top right in the APOD is really NGC 604. But it is absolutely certain that the nebula in question is an emission nebula and that its dominant color is red.

Yes, it is NGC 604. If you follow “the second largest image ever released” link, you’ll see a thumbnail of that blue nebula identified as NGC 604, which links to this page. I didn’t see an explanation of the color — why an H-II region is blue rather than the usual pinkish-red.

I checked the "zoom" tool.. what a view at 2nd most zoomed level.. stars are next to eachother as if they are sand grains on a beach.. I wonder what's the smallest distance between any 2 stars in the densest region.. and, will there be darkness on any planet in one of those star's solar system ? They might be seeing multiple stars in their sky - all time. No ?

Cousin Ricky wrote: ↑Sat Feb 23, 2019 3:25 pm

The Triangulum Galaxy has at least an order of magnitude less stars than the Milky Way and two orders of magnitude less than Andromeda. These numbers are hard to grasp when already in this image 10 to 15 million individual stars are visible.

Amazingly, running the math, the number stars visible in the original image are only about one tenth of a percent of the stars in this galaxy. (However, I find it hard to believe that there is an order of magnitude difference between the Milky Way and M31.) And even the hi-res version of this image shows only a fraction of those 10 – 15 million stars, at it has only 9 million pixels.

According to the second largest image link (in reference to the original hubble image),

spacetelescope.org wrote:This new image of the Triangulum Galaxy — also known as Messier 33 or NGC 598 — has a staggering 665 million pixels

Boomer12k wrote: ↑Sat Feb 23, 2019 9:05 pm
I think it is NGC588... in your image it is sideways...the "top" or "Ears"...are on the right side... but it does show that it seems to be an emission nebula...maybe today's image is a bit false colored?

:---[===] *

You bet it is!

Ann

Joe Stieber wrote: ↑Sat Feb 23, 2019 9:54 pm

Ann wrote: ↑Sat Feb 23, 2019 7:59 pm I'm not absolutely sure that the blue nebula at top right in the APOD is really NGC 604. But it is absolutely certain that the nebula in question is an emission nebula and that its dominant color is red.

Yes, it is NGC 604. If you follow “the second largest image ever released” link, you’ll see a thumbnail of that blue nebula identified as NGC 604, which links to this page. I didn’t see an explanation of the color — why an H-II region is blue rather than the usual pinkish-red.

It is blue because it is false colored. Groan. Why do you think you hear me complain about the color of Hubble images (and other astroimages) all the time?

One reason why this APOD is false colored is because of the filters used when the image was produced. If the Hubble people didn't use an Hα filter for this image, the Hα emission nebulas won't come out as red in an image like this. I checked the filters used for the picture of M33. One was a wideband blue filter, centered at 475 nm (which is blue but pretty far from ultraviolet), and one was a wideband near infrared filter centered at 814 nm, which is very far from the Hα line at about 656 nm.

Emission nebulas always contain Hβ as well as Hα, although Hα dominates. None of the filters used for this image can detect Hα at 656 nm, but Hβ at 486 nm is almost smack in the middle of the wideband blue 475 nm filter. So the less dominant blue 486 nm Hβ line from the dominant red Hα emission nebulas in M33 will stick out like a sore thumb and paint all those nebulas an incredibly vibrant shade of blue.

Here we can also find the explanation for the unnaturally orange color of M33. All stars emit appreciable amounts of infrared light. But many cool stars emit practically no blue light at all. A two-filter image using a blue and an infrared filter will preferentially detect the infrared light of huge numbers of cool stars. The infrared light from all these cool stars will then be shown as visual red in the image and make the galaxy appear much more orange than, say, a comparison with the color of the Sun would make it appear.

Ann

shaileshs wrote: ↑Sun Feb 24, 2019 1:54 am I checked the "zoom" tool.. what a view at 2nd most zoomed level.. stars are next to eachother as if they are sand grains on a beach.. I wonder what's the smallest distance between any 2 stars in the densest region.. and, will there be darkness on any planet in one of those star's solar system ? They might be seeing multiple stars in their sky - all time. No ?

Anyone can shed light (enlighten me) on my above query ? Thanks in advance!