APOD: Star Cluster NGC 362 from Hubble (2017 Oct 11)

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APOD: Star Cluster NGC 362 from Hubble (2017 Oct 11)

Postby APOD Robot » Wed Oct 11, 2017 4:10 am

Image Star Cluster NGC 362 from Hubble

Explanation: If our Sun were near the center of NGC 362, the night sky would glow like a jewel box of bright stars. Hundreds of stars would glow brighter than Sirius, and in many different colors. Although these stars could become part of breathtaking constellations and intricate folklore, it would be difficult for planetary inhabitants there to see -- and hence understand -- the greater universe beyond. NGC 362 is one of only about 170 globular clusters of stars that exist in our Milky Way Galaxy. This star cluster is one of the younger globulars, forming likely well after our Galaxy. NGC 362 can be found with the unaided eye nearly in front of the Small Magellanic Cloud, and angularly close to the second brightest globular cluster known, 47 Tucanae. The featured image was taken with the Hubble Space Telescope to help better understand how massive stars end up near the center of some globular clusters.

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Re: APOD: Star Cluster NGC 362 from Hubble (2017 Oct 11)

Postby Boomer12k » Wed Oct 11, 2017 9:13 am

Awesome... too bad I am not in the southern hemisphere... but then I CAN rent a scope in Australia, I suppose...hmmmmmm.....

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Re: APOD: Star Cluster NGC 362 from Hubble (2017 Oct 11)

Postby starsurfer » Wed Oct 11, 2017 10:42 am

Boomer12k wrote:Awesome... too bad I am not in the southern hemisphere... but then I CAN rent a scope in Australia, I suppose...hmmmmmm.....

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How about renting a scope in Chile? :D

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Re: APOD: Star Cluster NGC 362 from Hubble (2017 Oct 11)

Postby starsurfer » Wed Oct 11, 2017 10:43 am

Aww poor NGC 362, gets hardly any attention! :cry:
Also there's hardly any Hubble shots of planetary nebulae nowadays? :?

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Re: APOD: Star Cluster NGC 362 from Hubble (2017 Oct 11)

Postby Donna » Wed Oct 11, 2017 12:48 pm

This must be the place Isaac Asimov wrote his story "Nightfall" about.

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Re: APOD: Star Cluster NGC 362 from Hubble (2017 Oct 11)

Postby neufer » Wed Oct 11, 2017 1:00 pm

Donna wrote:
This must be the place Isaac Asimov wrote his story "Nightfall" about.

A sky filled with "Jupiters" & "Saturns" would be like a sky with a permanent full moon:
    it's still night even if there's enough light to read by.
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Re: APOD: Star Cluster NGC 362 from Hubble (2017 Oct 11)

Postby Fred the Cat » Wed Oct 11, 2017 1:23 pm

All those suns emitting all that light and we can’t even say what light is. Of course, back here on Earth we have all these consciousnesses and we can’t say what they are either. Even the universe we may exit in is debated. Seems like we really don’t know much. :?

Good news is we still have plenty of light to read about what we don’t know and lots to think about where ever we are. :ssmile:
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Re: APOD: Star Cluster NGC 362 from Hubble (2017 Oct 11)

Postby De58te » Wed Oct 11, 2017 1:38 pm

Asimov's Nightfall was about a planet that had 6 suns in the sky. At least one or two were always up so the inhabitants had always daylight ever since they were born. However every 20,000 years or so, the astronomy mechanics were such that all stars would set out of the sky and not another star would rise, even if it was only for 15 minutes. The last time it happened their history spoke of a breakdown of society that nearly ended their race. Hence the title Nightfall, which would make people mad because nobody alive had ever seen darkness. [Apparently there were no caves on the planet.] I suppose if the Nighfall planet was in the center of NGC 362, then a planet having 6 suns is very reasonable, but they probably wouldn't see any darkness when the 'night' fell.

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Re: APOD: Star Cluster NGC 362 from Hubble (2017 Oct 11)

Postby Chris Peterson » Wed Oct 11, 2017 2:09 pm

Fred the Cat wrote:All those suns emitting all that light and we can’t even say what light is.

We have a very, very good idea what light is.
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Re: APOD: Star Cluster NGC 362 from Hubble (2017 Oct 11)

Postby Ann » Wed Oct 11, 2017 2:57 pm

Chris Peterson wrote:
Fred the Cat wrote:All those suns emitting all that light and we can’t even say what light is.

We have a very, very good idea what light is.


Photons. Massless particles of a certain wavelength. :yes:

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Re: APOD: Star Cluster NGC 362 from Hubble (2017 Oct 11)

Postby starbrush » Wed Oct 11, 2017 3:08 pm

What I notice about this picture is the lace-doily appearance: despite its 3D globular aspect, there are many little 'hollows' in the outer reaches, reminiscent of grass tussocks in an arid landscape. It's a lovely texture, an overall smoothness composed of distinct clumpiness. Is this a feature of the 'mass segregation' process that is supposed to be at work in globular clusters?

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Re: APOD: Star Cluster NGC 362 from Hubble (2017 Oct 11)

Postby Chris Peterson » Wed Oct 11, 2017 3:25 pm

Ann wrote:
Chris Peterson wrote:
Fred the Cat wrote:All those suns emitting all that light and we can’t even say what light is.

We have a very, very good idea what light is.

Photons. Massless particles of a certain wavelength. :yes:

Photons. Particles with a rest mass of zero and a certain momentum (or energy).
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Re: APOD: Star Cluster NGC 362 from Hubble (2017 Oct 11)

Postby neufer » Wed Oct 11, 2017 3:27 pm

Ann wrote:
Chris Peterson wrote:
We have a very, very good idea what light is.

Photons. Massless particles of a certain wavelength. :yes:

1) Gravitons are also massless particles.
2) It is possible that at least one type of neutrino might be massless.
3) Locatable particles must contain multiple wavelengths.
Last edited by neufer on Wed Oct 11, 2017 3:28 pm, edited 1 time in total.
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Re: APOD: Star Cluster NGC 362 from Hubble (2017 Oct 11)

Postby Chris Peterson » Wed Oct 11, 2017 3:27 pm

starbrush wrote:What I notice about this picture is the lace-doily appearance: despite its 3D globular aspect, there are many little 'hollows' in the outer reaches, reminiscent of grass tussocks in an arid landscape. It's a lovely texture, an overall smoothness composed of distinct clumpiness. Is this a feature of the 'mass segregation' process that is supposed to be at work in globular clusters?

I think it's a perceptual illusion combined with the statistics of a large population of stars. What appear to be voids or richer areas are transient.
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Re: APOD: Star Cluster NGC 362 from Hubble (2017 Oct 11)

Postby Tszabeau » Wed Oct 11, 2017 4:42 pm

Chris Peterson wrote:
starbrush wrote:What I notice about this picture is the lace-doily appearance: despite its 3D globular aspect, there are many little 'hollows' in the outer reaches, reminiscent of grass tussocks in an arid landscape. It's a lovely texture, an overall smoothness composed of distinct clumpiness. Is this a feature of the 'mass segregation' process that is supposed to be at work in globular clusters?

I think it's a perceptual illusion combined with the statistics of a large population of stars. What appear to be voids or richer areas are transient.


I had a similar question to starbush but in terms of pixels. When I zoom into the center of the cluster, there are absolutely no black pixels... when I zoom into a darker corner of the high-res image there are still very few, if any, truly black pixels. I’ve noticed this with other APODs, as well (not just clusters). Is that merely a photographic or pixelization limitation or is it because every single point we look at has something (visible matter) in it, at some depth or other, within our field of view? I hope that makes sense.

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Re: APOD: Star Cluster NGC 362 from Hubble (2017 Oct 11)

Postby neufer » Wed Oct 11, 2017 4:45 pm

Chris Peterson wrote:
starbrush wrote:
What I notice about this picture is the lace-doily appearance: despite its 3D globular aspect, there are many little 'hollows' in the outer reaches, reminiscent of grass tussocks in an arid landscape. It's a lovely texture, an overall smoothness composed of distinct clumpiness. Is this a feature of the 'mass segregation' process that is supposed to be at work in globular clusters?

I think it's a perceptual illusion combined with the statistics of a large population of stars. What appear to be voids or richer areas are transient.
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Re: APOD: Star Cluster NGC 362 from Hubble (2017 Oct 11)

Postby Chris Peterson » Wed Oct 11, 2017 4:47 pm

Tszabeau wrote:
Chris Peterson wrote:
starbrush wrote:What I notice about this picture is the lace-doily appearance: despite its 3D globular aspect, there are many little 'hollows' in the outer reaches, reminiscent of grass tussocks in an arid landscape. It's a lovely texture, an overall smoothness composed of distinct clumpiness. Is this a feature of the 'mass segregation' process that is supposed to be at work in globular clusters?

I think it's a perceptual illusion combined with the statistics of a large population of stars. What appear to be voids or richer areas are transient.


I had a similar question to starbush but in terms of pixels. When I zoom into the center of the cluster, there are absolutely no black pixels... when I zoom into a darker corner of the high-res image there are still very few, if any, truly black pixels. I’ve noticed this with other APODs, as well (not just clusters). Is that merely a photographic or pixelization limitation or is it because every single point we look at has something (visible matter) in it, at some depth or other, within our field of view? I hope that makes sense.

It is generally not considered good processing to set the darkest pixels to black (value = 0). Not only will this result in many people losing dark but nonzero pixels on their displays, but bringing the dark level up to just below the noise floor gives a more realistic window on the data.
Chris

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Re: APOD: Star Cluster NGC 362 from Hubble (2017 Oct 11)

Postby rparks3141 » Wed Oct 11, 2017 5:15 pm

Are the stars being drawn into the center of the cluster, or are they drifting out of the cluster after being formed inside the cluster?

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Re: APOD: Star Cluster NGC 362 from Hubble (2017 Oct 11)

Postby Chris Peterson » Wed Oct 11, 2017 5:22 pm

rparks3141 wrote:Are the stars being drawn into the center of the cluster, or are they drifting out of the cluster after being formed inside the cluster?

Neither. The stars are individually in orbit around the center of mass of the cluster (although subject to significant perturbation when passing near other stars). A popular, and generally accurate analogy of a globular cluster is a swarm of bees.
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Re: APOD: Star Cluster NGC 362 from Hubble (2017 Oct 11)

Postby Evenstar » Wed Oct 11, 2017 5:40 pm

Is it at all understood why clusters like this form with no rotation in our Milky Way? What did their past and future look like?

Has one found any planets around any of these stars using any means?

Can things like clusters and nebulas be at all detected in other galaxies? Perhaps most notably Andromeda?
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Re: APOD: Star Cluster NGC 362 from Hubble (2017 Oct 11)

Postby neufer » Wed Oct 11, 2017 5:53 pm

Evenstar wrote:
Has one found any planets around any of these stars using any means?
https://en.wikipedia.org/wiki/Globular_cluster#Planets wrote:
<<In 2000, the results of a search for giant planets in the globular cluster 47 Tucanae were announced. The lack of any successful discoveries suggests that the abundance of elements (other than hydrogen or helium) necessary to build these planets may need to be at least 40% of the abundance in the Sun. Terrestrial planets are built from heavier elements such as silicon, iron and magnesium. The very low abundance of these elements in globular clusters means that the member stars have a far lower likelihood of hosting Earth-mass planets, when compared to stars in the neighborhood of the Sun. Hence the halo region of the Milky Way galaxy, including globular cluster members, are unlikely to host habitable terrestrial planets.

In spite of the lower likelihood of giant planet formation, just such an object has been found in the globular cluster Messier 4. This planet was detected orbiting a pulsar in the binary star system PSR B1620-26. The eccentric and highly inclined orbit of the planet suggests it may have been formed around another star in the cluster, then was later "exchanged" into its current arrangement. The likelihood of close encounters between stars in a globular cluster can disrupt planetary systems, some of which break loose to become free floating planets. Even close orbiting planets can become disrupted, potentially leading to orbital decay and an increase in orbital eccentricity and tidal effects.>>
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Re: APOD: Star Cluster NGC 362 from Hubble (2017 Oct 11)

Postby Chris Peterson » Wed Oct 11, 2017 5:55 pm

Evenstar wrote:Is it at all understood why clusters like this form with no rotation in our Milky Way? What did their past and future look like?

The origin, history, and evolution of globular clusters is not well understood. They do not orbit inside the galaxy with stars, but outside the galaxy in the halo.

Has one found any planets around any of these stars using any means?

I don't think so. It is likely that this environment would not make stable planetary systems very common. Multiple close encounters between stars would tend to result in planets eventually being ejected.

Can things like clusters and nebulas be at all detected in other galaxies? Perhaps most notably Andromeda?

We see globular clusters around most spiral galaxies (including Andromeda). And we detect nebulas of different types in many other galaxies, as well.
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You've got Mayall!

Postby neufer » Wed Oct 11, 2017 6:03 pm

Evenstar wrote:
Can things like clusters and nebulas be at all detected in other galaxies?

Perhaps most notably Andromeda?
https://en.wikipedia.org/wiki/Mayall_II wrote:
<<Mayall II, also known as NGC-224-G1, SKHB 1, GSC 2788:2139, HBK 0-1, M31GC J003247+393440 or Andromeda's Cluster, is a globular cluster orbiting M31, the Andromeda Galaxy.

It is located 130,000 light-years (40 kpc) from the Andromeda Galaxy's galactic core, and is the brightest (by absolute magnitude) globular cluster in the Local Group, having an apparent magnitude of 13.7. Mayall II is considered to have twice the mass of Omega Centauri, and may contain a central, intermediate-mass (∼ 2×104M⊙) black hole.

It was first identified as a possible globular cluster by American astronomers Nicholas Mayall and Olin J. Eggen in 1953 using a Palomar 48-inch (1.2 m) Schmidt plate exposed in 1948.

Because of the widespread distribution of metallicity, indicating multiple star generations and a large stellar creation period, many contend that it is not a true globular cluster, but is actually the galactic core that remains of a dwarf galaxy consumed by Andromeda.>>
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Re: APOD: Star Cluster NGC 362 from Hubble (2017 Oct 11)

Postby neufer » Wed Oct 11, 2017 6:45 pm

Evenstar wrote:
Is it at all understood why clusters like this form with no rotation in our Milky Way?

    1) They revolve around the center of the Milky Way.
    2) Their internal rotation is evident in their ellipticities:

Code: Select all

 Galaxy        Ellipticity of globular clusters
-----------------------------------------------------
Milky Way        0.07±0.04
LMC              0.16±0.05
SMC              0.19±0.06
M31              0.09±0.04

Globular Clusters are effectively mini elliptical galaxies that quickly soaked up all the gas that would have made them disk shaped:

https://en.wikipedia.org/wiki/Elliptical_galaxy wrote:
:arrow: This image from NASA's Hubble Space Telescope shows the diverse collection of galaxies in the cluster Abell S0740 that is over 450 million light-years away in the direction of the constellation Centaurus. The giant elliptical ESO 325-G004 looms large at the cluster's center. The galaxy is as massive as 100 billion of our suns. Hubble resolves thousands of globular star clusters orbiting ESO 325-G004. Globular clusters are compact groups of hundreds of thousands of stars that are gravitationally bound together. At the galaxy's distance they appear as pinpoints of light contained within the diffuse halo. Other fuzzy elliptical galaxies dot the image. Some have evidence of a disk or ring structure that gives them a bow-tie shape.

<<An elliptical galaxy is a type of galaxy having an approximately ellipsoidal shape and a smooth, nearly featureless brightness profile. Elliptical galaxies are characterized by several properties that make them distinct from other classes of galaxy. They are spherical or ovoid masses of stars, starved of star-making gases. Unlike flat spiral galaxies with organization and structure, they are more three-dimensional, without much structure, and their stars are in somewhat random orbits around the center. Originally Edwin Hubble hypothesized that elliptical galaxies evolved into spiral galaxies, which was later discovered to be false. Stars found inside of elliptical galaxies are on average much older than stars found in spiral galaxies.

Most elliptical galaxies are composed of older, low-mass stars, with a sparse interstellar medium and minimal star formation activity, and they tend to be surrounded by large numbers of globular clusters. Elliptical galaxies are believed to make up approximately 10%–15% of galaxies in the Virgo Supercluster, and they are not the dominant type of galaxy in the universe overall. They are preferentially found close to the centers of galaxy clusters. Elliptical galaxies are (together with lenticular galaxies) also called "early-type" galaxies (ETG), due to their location in the Hubble sequence, and are found to be less common in the early Universe.>>
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Re: APOD: Star Cluster NGC 362 from Hubble (2017 Oct 11)

Postby NCTom » Wed Oct 11, 2017 8:22 pm

Thanks, Ann, Chris, and Neuf, for your comments. I miss your input when you don't show up.


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