APOD: Cosmic Clouds in the Unicorn (2020 Feb 08)

Comments and questions about the APOD on the main view screen.
User avatar
APOD Robot
Otto Posterman
Posts: 3830
Joined: Fri Dec 04, 2009 3:27 am

APOD: Cosmic Clouds in the Unicorn (2020 Feb 08)

Post by APOD Robot » Sat Feb 08, 2020 5:05 am

Image Cosmic Clouds in the Unicorn

Explanation: Interstellar clouds of hydrogen gas and dust abound in this gorgeous skyscape. The 3 degree wide field of view stretches through the faint but fanciful constellation Monoceros, the Unicorn. A star forming region cataloged as NGC 2264 is centered, a complex jumble of cosmic gas, dust and stars about 2,700 light-years distant. It mixes reddish emission nebulae excited by energetic light from newborn stars with dark dust clouds. Where the otherwise obscuring dust clouds lie close to hot, young stars they also reflect starlight, forming blue reflection nebulae. A few light-years across, a simple sculpted shape known as the Cone Nebula is near center. Outlined by the red glow of hydrogen gas, the cone points toward the left and bright, blue-white S Monocerotis. Itself a multiple system of massive, hot stars S Mon is adjacent to bluish reflection nebulae and the convoluted Fox Fur nebula. Expansive dark markings on the sky are silhouetted by a larger region of fainter emission with yellowish open star cluster Trumpler 5 near the top of the frame. The curious compact cometary shape right of center is known as Hubble's Variable Nebula.

<< Previous APOD This Day in APOD Next APOD >>

User avatar
neufer
Vacationer at Tralfamadore
Posts: 16805
Joined: Mon Jan 21, 2008 1:57 pm
Location: Alexandria, Virginia

Re: APOD: Cosmic Clouds in the Unicorn (2020 Feb 08)

Post by neufer » Sat Feb 08, 2020 5:23 am

https://en.wikipedia.org/wiki/NGC_2264 wrote:

Newborn stars, hidden behind thick dust, are revealed in this image of a section of the Christmas Tree Cluster from NASA's Spitzer Space Telescope. The newly revealed infant stars appear as pink and red specks toward the center and appear to have formed in regularly spaced intervals along linear structures in a configuration that resembles the spokes of a wheel or the pattern of a snowflake. Hence, astronomers have nicknamed this the "Snowflake Cluster." Star-forming clouds like this one are dynamic and evolving structures. Since the stars trace the straight line pattern of spokes of a wheel, scientists believe that these are newborn stars, or "protostars." At a mere 100,000 years old, these infant structures have yet to "crawl" away from their location of birth. Over time, the natural drifting motions of each star will break this order, and the snowflake design will be no more. While most of the visible-light stars that give the Christmas Tree Cluster its name and triangular shape do not shine brightly in Spitzer's infrared eyes, all of the stars forming from this dusty cloud are considered part of the cluster. Like a dusty cosmic finger pointing up to the newborn clusters, Spitzer also illuminates the optically dark and dense Cone Nebula, the tip of which can be seen towards the bottom left corner of the image. Image Credit: NASA/JPL-Caltech/P.S. Teixeira (Center for Astrophysics)
Art Neuendorffer

User avatar
Ann
4725 Å
Posts: 10163
Joined: Sat May 29, 2010 5:33 am

Re: APOD: Cosmic Clouds in the Unicorn (2020 Feb 08)

Post by Ann » Sat Feb 08, 2020 6:27 am

Nice APOD ! It really shows all kinds of nebulas, emission, reflection, dark dust and, of course, the strange Hubble Variable Nebula. See it vary here! :D

Christmas Tree and Trumpler 5.png
Christmas Tree Cluster (bottom left), Trumpler 5 (center)
and IC 447 (top right). Photo: Lynn Hillborn.




















The attachment I posted at left is a drastically reduced sized version of the APOD, and it doesn't do it justice in any way. The full size image - almost 10 MB! - however, contains the best portrait of cluster Trumpler 5 that I think I've ever seen.

Trumpler 5.png





P. Donati et al. wrote:

As part of a long-term programme, we analyse the evolutionary status and properties of the old and populous open cluster Trumpler 5 (Tr 5), located in the Galactic anticentre direction, almost on the Galactic plane.
...
Our analysis shows that Tr 5 has subsolar metallicity, with [Fe/H] = −0.403 ± 0.006 dex (derived from spectroscopy), age between 2.9 and 4 Gyr (the lower age is found using stellar models without core overshooting), reddening E(B − V) in the range 0.60–0.66 mag complicated by a differential pattern (of the order of ∼±0.1 mag), and distance modulus (m − M)0 = 12.4 ± 0.1 mag.

I find Trumpler 5 so interesting, because the cluster is so obviously very rich - just look at the number of stars in it!! - and very many of the stars appear to be the same luminosity, which is to say that there are no truly luminous stars inside it. The large numbers of stars in the cluster can be a sign of youth, because the stars have not had time to disperse. But the lack of very bright stars in the cluster is a sign of (relatively) old age, because the most massive (and therefore brightest) stars have already died.

Of course, for me as a color commentator, the uniformly orange color of the stars in Trumpler 5 is fascinating, too. The color-magnitude diagram of Trumpler 5 at right shows how red the stars are. Let's compare them with the Sun. The Sun has a B-V index of about 0.65, but as you can see in the diagram at right, the top of the main sequence of Trumpler 5 (the top of the thick diagonal line of black dots) ends at a B-V index of about 1.0, which is about the color of Pollux.

(There are a few blue stragglers in Trumpler 5, stars that stay on the main sequence and are brighter and bluer than all the other main sequence stars. They are at top left in the diagram.)

Pollux (left) and Castor. Photo: Rogelio Bernal Andreo.





But it is still true that almost all the stars in Trumpler 5 are at least as red as Pollux! Well, not quite, because the stars are reddened by dust. They are reddened by about 0.6 magnitudes, which means, if I get it correctly, that the top of the main sequence of Trumpler 5 really ends at a B-V index of about 0.4 instead of a B-V index of 1.0. So instead of saying that almost all the stars in Trumpler 5 are at least as red as Pollux, we can say that only a small number of stars in Trumpler 5 are at all bluer than the Sun.

So there can be no doubt that Trumpler 5 is old, rich and rather red. I find the cluster fascinating, and I love the picture of it in today's APOD.

Ann
You do not have the required permissions to view the files attached to this post.
Color Commentator

Boomer12k
:---[===] *
Posts: 2641
Joined: Sun Apr 22, 2007 12:07 am

Re: APOD: Cosmic Clouds in the Unicorn (2020 Feb 08)

Post by Boomer12k » Sat Feb 08, 2020 7:57 am

Wonderful image...

:---[===] *

sillyworm 2

Re: APOD: Cosmic Clouds in the Unicorn (2020 Feb 08)

Post by sillyworm 2 » Sat Feb 08, 2020 1:32 pm

Trumpler 5 steals the show!

User avatar
neufer
Vacationer at Tralfamadore
Posts: 16805
Joined: Mon Jan 21, 2008 1:57 pm
Location: Alexandria, Virginia

Re: APOD: Cosmic Clouds in the Unicorn (2020 Feb 08)

Post by neufer » Sat Feb 08, 2020 2:03 pm

sillyworm 2 wrote:
Sat Feb 08, 2020 1:32 pm

Trumpler 5 steals the show!
  • Barron :?:
Art Neuendorffer

User avatar
orin stepanek
Plutopian
Posts: 5282
Joined: Wed Jul 27, 2005 3:41 pm
Location: Nebraska

Re: APOD: Cosmic Clouds in the Unicorn (2020 Feb 08)

Post by orin stepanek » Sat Feb 08, 2020 4:18 pm

Very nice! :D
Orin

Smile today; tomorrow's another day!

User avatar
Cousin Ricky
Science Officer
Posts: 282
Joined: Mon Aug 26, 2013 4:08 pm
Location: St. Thomas, U.S. Virgin Islands (+18.3, -64.9)

Re: APOD: Cosmic Clouds in the Unicorn (2020 Feb 08)

Post by Cousin Ricky » Sat Feb 08, 2020 4:39 pm

I’m trying to find out how Tr 5 is so orange and still an open cluster, but I can’t find anything on the Web that isn’t an abstruse science paper or behind a subscription wall.

sillyworm 2

Re: APOD: Cosmic Clouds in the Unicorn (2020 Feb 08)

Post by sillyworm 2 » Sat Feb 08, 2020 6:53 pm

neufer wrote:
Sat Feb 08, 2020 2:03 pm
sillyworm 2 wrote:
Sat Feb 08, 2020 1:32 pm

Trumpler 5 steals the show!
  • Barron :?:
Ha Ha who knows....

User avatar
Ann
4725 Å
Posts: 10163
Joined: Sat May 29, 2010 5:33 am

Re: APOD: Cosmic Clouds in the Unicorn (2020 Feb 08)

Post by Ann » Sat Feb 08, 2020 9:26 pm

Cousin Ricky wrote:
Sat Feb 08, 2020 4:39 pm
I’m trying to find out how Tr 5 is so orange and still an open cluster, but I can’t find anything on the Web that isn’t an abstruse science paper or behind a subscription wall.
The orange color of Tumpler 5 is due to two reasons. One, the cluster is old enough that all the really blue stars that originally belonged to it have already died. Two, there is quite a lot of dust between us and the cluster that reddens the stars. As you can see from the picture at right, when there is dust between us and the stars, the light from the stars gets redder and dimmer.

Hyades.png


















Take a look at the picture at left of the Hyades Cluster. The Hyades is a much younger cluster than Trumpler 5, about 625 million years, while Trumpler 5 is at least two billion years. Also Trumpler 5 is much farther away than the Hyades, because the Hyades is a nearby cluster at only about 153 light-years, while Trumpler 5 is certainly at least a thousand light-years away, and probably more.

Young Pleiades (top right) and much older Hyades (bottom).
Photo: Amir H. Abolfath (TWAN).
To get an even better idea of the non-blue nature of the circa 625-million-year-old Hyades cluster, compare it with the circa 100-million-year-old Pleiades cluster. The Pleiades is actually abnormally blue, because a cluster like the Pleiades would normally contain at least one red giant. The Pleiades actually did contain at least one red giant in the past, but this red giant has died and left a white dwarf behind.

Even so, you can see how very much bluer the young Pleiades cluster is compared with the much older Hyades. Note, too, that the Hyades is much closer to us (at about 153 light-years) compared with circa 440 light-years for the Pleiades.

The dust that you can see in the vicinity of the Hyades is probably mostly located behind the cluster from our point of view, so that it doesn't provide much reddening. There is definitely a lot more dust between us and Trumpler 5 than between us and the Hyades, so that Trumpler 5 is a lot more reddened that the Hyades.

Another difference between the Hyades and Trumpler 5 is that Hyades is a relatively poor cluster, containing relatively few stars, whereas Trumpler 5 is a very rich open cluster indeed.

Ann
You do not have the required permissions to view the files attached to this post.
Color Commentator

User avatar
Cousin Ricky
Science Officer
Posts: 282
Joined: Mon Aug 26, 2013 4:08 pm
Location: St. Thomas, U.S. Virgin Islands (+18.3, -64.9)

Re: APOD: Cosmic Clouds in the Unicorn (2020 Feb 08)

Post by Cousin Ricky » Sun Feb 09, 2020 4:19 pm

neufer wrote:
Sat Feb 08, 2020 2:03 pm
sillyworm 2 wrote:
Sat Feb 08, 2020 1:32 pm

Trumpler 5 steals the show!
  • Barron :?:
:roll:

User avatar
Cousin Ricky
Science Officer
Posts: 282
Joined: Mon Aug 26, 2013 4:08 pm
Location: St. Thomas, U.S. Virgin Islands (+18.3, -64.9)

Re: APOD: Cosmic Clouds in the Unicorn (2020 Feb 08)

Post by Cousin Ricky » Sun Feb 09, 2020 4:41 pm

Ann wrote:
Sat Feb 08, 2020 9:26 pm
Cousin Ricky wrote:
Sat Feb 08, 2020 4:39 pm
I’m trying to find out how Tr 5 is so orange and still an open cluster, but I can’t find anything on the Web that isn’t an abstruse science paper or behind a subscription wall.
Take a look at the picture at left of the Hyades Cluster. The Hyades is a much younger cluster than Trumpler 5, about 625 million years, while Trumpler 5 is at least two billion years. Also Trumpler 5 is much farther away than the Hyades, because the Hyades is a nearby cluster at only about 153 light-years, while Trumpler 5 is certainly at least a thousand light-years away, and probably more.
Thanks. I didn’t realize open clusters could last 2 billion years without dispersing.
Ann wrote:
Sat Feb 08, 2020 9:26 pm
Young Pleiades (top right) and much older Hyades (bottom).
Photo: Amir H. Abolfath (TWAN).
To get an even better idea of the non-blue nature of the circa 625-million-year-old Hyades cluster, compare it with the circa 100-million-year-old Pleiades cluster. The Pleiades is actually abnormally blue, because a cluster like the Pleiades would normally contain at least one red giant. The Pleiades actually did contain at least one red giant in the past, but this red giant has died and left a white dwarf behind.
I get a 403 (“forbidden”) on this photo. Anyhow, I was looking at these two Friday night, although I didn’t think to compare their colors. That would have been difficult anyway with the near-full Moon nearby. I was showing the Pleiades to people in my telescope, and I end up looking at the Hyades regularly because Aldebaran is in the line-of-sight to the cluster, and Aldebaran being brighter than Betelgeuse is still freaking me out.

Also, someone with me thought that the Sun was a K star, so I showed him Aldebaran as an example.

User avatar
Chris Peterson
Abominable Snowman
Posts: 14816
Joined: Wed Jan 31, 2007 11:13 pm
Location: Guffey, Colorado, USA

Re: APOD: Cosmic Clouds in the Unicorn (2020 Feb 08)

Post by Chris Peterson » Sun Feb 09, 2020 5:13 pm

Cousin Ricky wrote:
Sun Feb 09, 2020 4:41 pm
Ann wrote:
Sat Feb 08, 2020 9:26 pm
Cousin Ricky wrote:
Sat Feb 08, 2020 4:39 pm
I’m trying to find out how Tr 5 is so orange and still an open cluster, but I can’t find anything on the Web that isn’t an abstruse science paper or behind a subscription wall.
Take a look at the picture at left of the Hyades Cluster. The Hyades is a much younger cluster than Trumpler 5, about 625 million years, while Trumpler 5 is at least two billion years. Also Trumpler 5 is much farther away than the Hyades, because the Hyades is a nearby cluster at only about 153 light-years, while Trumpler 5 is certainly at least a thousand light-years away, and probably more.
Thanks. I didn’t realize open clusters could last 2 billion years without dispersing.
How long a cluster survives is largely a function of its mass (barring significant external gravitational encounters). All clusters dissolve over time, including globulars. But those that are more massive have stronger gravitational ties and need more time to dissolve. T5 is a massive cluster, out on the tail of the open cluster mass distribution, representative of probably less than 10% of all open clusters.
Chris

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

User avatar
Ann
4725 Å
Posts: 10163
Joined: Sat May 29, 2010 5:33 am

Re: APOD: Cosmic Clouds in the Unicorn (2020 Feb 08)

Post by Ann » Sun Feb 09, 2020 6:00 pm

Cousin Ricky wrote:
Sun Feb 09, 2020 4:41 pm
Ann wrote:
Sat Feb 08, 2020 9:26 pm
Cousin Ricky wrote:
Sat Feb 08, 2020 4:39 pm
I’m trying to find out how Tr 5 is so orange and still an open cluster, but I can’t find anything on the Web that isn’t an abstruse science paper or behind a subscription wall.
Take a look at the picture at left of the Hyades Cluster. The Hyades is a much younger cluster than Trumpler 5, about 625 million years, while Trumpler 5 is at least two billion years. Also Trumpler 5 is much farther away than the Hyades, because the Hyades is a nearby cluster at only about 153 light-years, while Trumpler 5 is certainly at least a thousand light-years away, and probably more.
Thanks. I didn’t realize open clusters could last 2 billion years without dispersing.
Note that Trumpler 5 is an anticenter cluster:
P. Donati et al. wrote:

As part of a long-term programme, we analyse the evolutionary status and properties of the old and populous open cluster Trumpler 5 (Tr 5), located in the Galactic anticentre direction, almost on the Galactic plane.
I think this means that Trumpler 5 is located in the very outskirts of the spiral system of the Milky Way, which in that case would place it in a position where it would enjoy an unusual amount of "peace and quiet" and little harassment of giant molecular clouds and other obstacles which would normally hasten the demise of an open cluster.


There is another interesting open cluster which we may compare Trumpler 5 to, which is even older than Tr 5. It's the fascinating open cluster M67.

M67. Processing: Noel Carboni, Imaging: Greg Parker.
M67. Image credit: Palomar Observatory / STScI / WikiSky.



















M67 is believed to be 4 billion years old, which is extremely old for an open cluster. As you can see it is rich, and like Trumpler 5, it is located in a "peaceful" part of the galaxy, far away from the galactic center. Unlike Trumper 5, it is relatively unreddened.

According to Messier Monday, there are about 500 stars in M67 (after 4 billion years!) and all the A-type stars have evolved off the main sequence, leaving only F-type and later main sequence stars left.

I want to protest a little there, however. As you can see, there is one strikingly blue star in M67. The way this star stands out is seen better in another picture:

Ultraviolet image of M67. Photo: GALEX.
The bright blue star in M67 is called HIP 43465. Note the GALEX image, which measured the ultraviolet light emanating from the stars of M67. All the yellow stars in the GALEX image are non-blue, but the very blue star is UV-bright, hot and blue. Without a doubt, this is a B-type star, otherwise it couldn't possibly be so blue. (It is in fact a B8V-type star with a B-V index of -0.07.)

How can a 4 billion-year-old cluster contain a B8V star, which should have died when M67 was perhaps a tenth of its current age? In my opinion, HIP 43465 can only be a blue straggler star. It has gained mass from another star, gradually or suddenly becoming massive enough (at least 3 solar masses) to shine with the blue light of a B-type star. It wouldn't surprise me in the slightest if HIP 4365 is (or was) an Algol-type star, where a main sequence star is close enough to its red giant companion (which must have filled its Roche lobe) to start accreting matter from its swollen companion, eventually almost sucking it dry while putting on more and more mass itself.

So M67 is somewhat similar to Trumpler 5, but it is even older. M67 is also relatively unreddened, unlike Trumpler 5, and it contains a very hot and blue "blue straggler", which Trumpler 5 doesn't.

Ann
Color Commentator

imtiyana
Asternaut
Posts: 3
Joined: Mon Feb 10, 2020 5:45 am

Re: APOD: Cosmic Clouds in the Unicorn (2020 Feb 08)

Post by imtiyana » Mon Feb 10, 2020 5:54 am

Hi great day to you all, I am new to this community.
I noticed an unusual object in "Cosmic Clouds in the Unicorn (2020 Feb 08)" at right centre of the frame, it looks like a "Dora cake". was just curious to know what it is. Looks something very strange.

User avatar
geckzilla
Ocular Digitator
Posts: 9034
Joined: Wed Sep 12, 2007 12:42 pm
Location: Modesto, CA

Re: APOD: Cosmic Clouds in the Unicorn (2020 Feb 08)

Post by geckzilla » Mon Feb 10, 2020 7:28 am

imtiyana wrote:
Mon Feb 10, 2020 5:54 am
Hi great day to you all, I am new to this community.
I noticed an unusual object in "Cosmic Clouds in the Unicorn (2020 Feb 08)" at right centre of the frame, it looks like a "Dora cake". was just curious to know what it is. Looks something very strange.
Does it look like this
Image

or like this?
Image
Just call me "geck" because "zilla" is like a last name.

imtiyana
Asternaut
Posts: 3
Joined: Mon Feb 10, 2020 5:45 am

Re: APOD: Cosmic Clouds in the Unicorn (2020 Feb 08)

Post by imtiyana » Mon Feb 10, 2020 12:45 pm

Hi Geck,
I am not sure how to upload my cropped image here. you can distinctly see it on the right side of 8th Feb APOD

User avatar
Cousin Ricky
Science Officer
Posts: 282
Joined: Mon Aug 26, 2013 4:08 pm
Location: St. Thomas, U.S. Virgin Islands (+18.3, -64.9)

Re: APOD: Cosmic Clouds in the Unicorn (2020 Feb 08)

Post by Cousin Ricky » Mon Feb 10, 2020 6:16 pm

imtiyana wrote:
Mon Feb 10, 2020 5:54 am
Hi great day to you all, I am new to this community.
I noticed an unusual object in "Cosmic Clouds in the Unicorn (2020 Feb 08)" at right centre of the frame, it looks like a "Dora cake". was just curious to know what it is. Looks something very strange.
What is a “Dora cake”? A Web search turns up literally nothing but cakes featuring Dora the Explorer, and they all look different.

Of Geck’s images, the first one is Hubble’s Variable Nebula (NGC 2261), and the second is the Cone Nebula (a part of NGC 2264).

User avatar
Ann
4725 Å
Posts: 10163
Joined: Sat May 29, 2010 5:33 am

Re: APOD: Cosmic Clouds in the Unicorn (2020 Feb 08)

Post by Ann » Mon Feb 10, 2020 7:05 pm

imtiyana wrote:
Mon Feb 10, 2020 5:54 am
Hi great day to you all, I am new to this community.
I noticed an unusual object in "Cosmic Clouds in the Unicorn (2020 Feb 08)" at right centre of the frame, it looks like a "Dora cake". was just curious to know what it is. Looks something very strange.
Like the others here, I'm clueless as to what a Dora cake is.

Cone Nebula and Hubbles variable nebula.png
The Cone Nebula (lower left) and Hubble's Variable Nebula (upper right).
The Cone Nebula. Photo: Adam Block/Mount Lemmon SkyCenter/
University of Arizona.

















But I guess that you are talking about one of the two nebulas that you can see in the picture at left. The dark nebula with a white tip, seen against a red background (at lower left) is the Cone Nebula.

You can see the Cone Nebula better in the picture at right. As you can see, the Cone Nebula is almost "lying down" in the APOD but "standing up" in Adam Block's image.




The Cone Nebula is simply a "pillar" of gas and dust. The Cone Nebula is the only thing left "standing" after the strong stellar winds and harsh ultraviolet photons from the bright blue stars in the vicinity have eroded the rest of the "gaseous wall" that once surrounded this birth place of young stars. The reason why the Cone Nebula is still standing when the rest of the gas structures have eroded away is that the gas and dust happened to be thicker and denser than average in the Cone Nebula.

The reason why the Cone Nebula has a white tip is because at least two and maybe three stars are in the process of forming there. You can see the stars at the tip of the Cone Nebula in the picture at left. The red background of the Cone Nebula is also caused by the hot blue stars, whose harsh ultraviolet light tears electrons from hydrogen atoms and makes them glow red.




Hubble's Variable Nebula. Animation: Tom and Jennifer Polakis.

















The other object you may have been asking about is Hubble's Variable Nebula. This is a nebula that is illuminated by a very young star that has not yet "cast off" its birth cocoon. Winds from the star make the gas cloud rotate irregularly. As the gas rotates, different parts of it gets illuminated by the star. That is why it is called a variable nebula.

Ann
You do not have the required permissions to view the files attached to this post.
Color Commentator

imtiyana
Asternaut
Posts: 3
Joined: Mon Feb 10, 2020 5:45 am

Re: APOD: Cosmic Clouds in the Unicorn (2020 Feb 08)

Post by imtiyana » Tue Feb 11, 2020 7:44 am

Hi Ann,
That's a lot of info, thank you for clarification and taking me for a walk through.
A dora cake resembles flying disk bulged at the centre. it is the very same variable nebula