Starship Asterisk*

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

• it's still night even if there's enough light to read by.

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

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.

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:

Ann wrote:

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

Photons. Massless particles of a certain wavelength.

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?

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.

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.

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.

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?

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.>>

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?

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?

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:

[b][color=#0000FF]Hubble Telescope image of Mayall II, colour picture assembled from separate images taken in visible and near-infrared wavelengths in July 1994. Credit: Michael Rich, Kenneth Mighell, and James D. Neill (Columbia University), and Wendy Freedman (Carnegie Observatories) and NASA[/color][/b]

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<<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.>>

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:

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

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

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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.>>