Pleiades and Stardust (2009 Oct 14)

[tytower]

http://apod.nasa.gov/apod/ap091014.html

Who is it that is making these absolute statements as if they know?

If this is the ejected material of one side of a black hole spewing new stars forth and we are watching directly over a pole then the gas could be a very big part of the new star formation process.

Deep in the heart of a black hole type star at some point something has to give. It stands to reason that when it does give material at super pressure and temp are going to come from the poles first and you will see nothing until the matter is far enough away from the center for light to survive too.

[pcstarship]

Compare today's image of the Seven Sisters with this one, the second-ever post on APOD:

http://antwrp.gsfc.nasa.gov/apod/ap950620.html

It's amazing how imaging technology has advanced since 1995. How good do you think this cluster will this look in 2023?

[Chris Peterson]

Who is it that is making these absolute statements as if they know?

People who have the knowledge and education to know that the statements are substantively correct with a high degree of certainty.

If this is the ejected material of one side of a black hole spewing new stars forth and we are watching directly over a pole then the gas could be a very big part of the new star formation process.

There is no underlying theory, or observational evidence, to suggest such a thing is even possible. So it is hard to take the idea seriously, unless you can frame it rigorously in a way that fits in with our existing knowledge of physics.

[Chris Peterson]

Compare today's image of the Seven Sisters with this one, the second-ever post on APOD:

http://antwrp.gsfc.nasa.gov/apod/ap950620.html

It's amazing how imaging technology has advanced since 1995. How good do you think this cluster will this look in 2023?

Probably not as much as you might think. Sensors are already recording most of the photons that strike them, and optics are diffraction limited. Lucky imaging techniques will become available that allow for some additional resolution (but no more than two or three times), but that wouldn't even be apparent at the image scale of this APOD.

Improvements could be more significant for professional images, since we may have much larger space-based telescopes observing over a wide range of wavelengths. Such imagery will provide a wealth of data, but I doubt will be much different aesthetically than the images being produced today.

[geckzilla]

I don't much like the post processing done on this image today. Too much color bleeding, for lack of a better way to describe it. I think it'd be fun to have the original and try myself at ramping up the colors. I don't know if I could do any better but it'd be nice to try.

[DonAVP]

I don't much like the post processing done on this image today. Too much color bleeding, for lack of a better way to describe it. I think it'd be fun to have the original and try myself at ramping up the colors. I don't know if I could do any better but it'd be nice to try.

Got me thinking??? What format do these images come in or are first made from the data? I would guess RAW. But don't know. Photoshop has some very powerful tools to manipulate images. What other software is used? I too would like to be given the RAW data to play with.

Don

[bystander]

They look much the same as APOD: 2008 December 9 - M45: The Pleiades Star Cluster.
The photographers information page http://blog.deepskycolors.com/archive/2 ... s-M45.html

[geckzilla]

Really, by? I thought they'd look less colorful than even that older APOD.

[neufer]

http://antwrp.gsfc.nasa.gov/apod/ap070611.html

<<In the well known Pleiades star cluster, starlight is slowly destroying this wandering cloud of gas and dust. The star Merope lies just off the upper left edge of this picture from the Hubble Space Telescope. In the past 100,000 years, part of the cloud has by chance moved so close to this star - only 3,500 times the Earth-Sun distance - that the starlight itself is having a very dramatic effect. Pressure of the star's light significantly repels the dust in the reflection nebula, and smaller dust particles are repelled more strongly. As a result, parts of the dust cloud have become stratified, pointing toward Merope. The closest particles are the most massive and the least affected by the radiation pressure. A longer-term result will be the general destruction of the dust by the energetic starlight.>>

• Merope's radiation pressure at 3,500 AU
  
  ~ the Sun's radiation pressure at 200 AU

[orin stepanek]

And the 7 sisters! http://www.naic.edu/~gibson/pleiades/pleiades_myth.html

Orin

[harry]

G'day

It is a fantastic image.

The question is:

If the universe is expanding.

What makes stars cluster?

[neufer]

The question is:
If the universe is expanding. What makes stars cluster?

The stars "cluster" primarily because they were born together and they haven't had time to leave the cradle.

http://en.wikipedia.org/wiki/Open_cluster

<<An open cluster is a group of up to a few thousand stars that were formed from the same giant molecular cloud, and are still loosely gravitationally bound to each other. In contrast, globular clusters are very tightly bound by gravity. Open clusters have been found only in spiral and irregular galaxies, in which active star formation is occurring. They are usually less than a few hundred million years old: they become disrupted by close encounters with other clusters and clouds of gas as they orbit the galactic center, as well as losing cluster members through internal close encounters. Young open clusters may still be contained within the molecular cloud from which they formed, illuminating it to create an H II region. Over time, radiation pressure from the cluster will disperse the molecular cloud. Typically, about 10% of the mass of a gas cloud will coalesce into stars before radiation pressure drives the rest away.>>

Universal expansion is separating the Pleiades cluster at about 1 mph.

Random star motion is separating the Pleiades cluster at a much faster rate.

<<The Pleiades cluster core radius is about 8 light years and tidal radius is about 43 light years. The cluster's relative motion will eventually lead it to be located, as seen from Earth many millennia in the future, passing below the feet of what is currently the constellation of Orion. Also, like most open clusters, the Pleiades will not stay gravitationally bound forever, as some component stars will be ejected after close encounters and others will be stripped by tidal gravitational fields. Calculations suggest that the cluster will take about 250 million years to disperse, with gravitational interactions with giant molecular clouds and the spiral arms of our galaxy also hastening its demise.>>

[harry]

G'day Neufer

you said

Universal expansion is separating the Pleiades cluster at about 1 mph.

Where on earth do you get that evidence?

[neufer]

Universal expansion is separating the Pleiades cluster at about 1 mph.

Where on earth do you get that evidence?

Hubble Constant = 74.2 (km/s)/Mpc = 267,000 (km/hr)/Mpc = 0.267 (km/hr)/pc ~ 1 mph / (6 pc)

The Pleiades cluster ~ 6 parsecs in diameter.

<<The Pleiades cluster core radius is about 8 light years and tidal radius is about 43 light years.>>

[Chris Peterson]

Hubble Constant = 74.2 (km/s)/Mpc = 267,000 (km/hr)/Mpc = 0.267 (km/hr)/pc ~ 1 mph / (6 pc)

The Pleiades cluster ~ 6 parsecs in diameter.

<<The Pleiades cluster core radius is about 8 light years and tidal radius is about 43 light years.>>

The value is theoretically correct, but gravity is much stronger than the "force" of universal expansion. Areas with mass concentrations don't expand, which includes galaxies. The Pleiades cluster is, of course, deeply embedded in the Milky Way; space is not expanding between its components.

[harry]

G'day

I agree with you Chris.

The principle of clustering was shown in space, by throwing small objects that clustered together.

Even with the small objects, now imagine the larger objects like Stars and planets.

[canuck100]

Areas with mass concentrations don't expand, which includes galaxies. The Pleiades cluster is, of course, deeply embedded in the Milky Way; space is not expanding between its components.

I have read this elsewhere. I believe that superclusters are the largest structures in the universe. Are they also the largest structures whose components are not expanding with respect to each other?

[Chris Peterson]

I have read this elsewhere. I believe that superclusters are the largest structures in the universe. Are they also the largest structures whose components are not expanding with respect to each other?

I don't think that superclusters are gravitationally bound; I think they just reflect residual structure from the very early Universe, and are the size they are because they are expanding with space. A supercluster has extremely low density; it doesn't seem likely that gravity has much effect.

[canuck100]

Thanks.

I googled "Are superclusters expanding" and found an abstract from a 2002 paper at http://arxiv.org/abs/astro-ph/0204121.

I don't get the details of their abstract . . .

We investigate the dynamical state of superclusters in Lambda cold dark matter ($\Lambda$CDM) cosmological models, where the density parameter $\Omega_0=0.2-0.4$ and $\sigma_8$ (the rms fluctuation on the $8h^{-1}$Mpc scale) is $0.7-0.9$. To study the nonlinear regime, we use N-body simulations. We define superclusters as maxima of the density field smoothed on the scale $R=10h^{-1}$Mpc. Smaller superclusters defined by the density field smoothed on the scale $R=5h^{-1}$Mpc are also investigated. We find the relations between the radially averaged peculiar velocity and the density contrast in the superclusters for different cosmological models. These relations can be used to estimate the dynamical state of a supercluster on the basis of its density contrast. In the simulations studied, all the superclusters defined with the $10h^{-1}$Mpc smoothing are expanding by the present epoch. Only a small fraction of the superclusters defined with $R=5h^{-1}$Mpc has already reached their turnaround radius and these superclusters have started to collapse. In the model with $\Omega_0=0.3$ and $\sigma_8=0.9$, the number density of objects which have started to collapse is $5 \times 10^{-6}h^3$Mpc$^{-3}$. The results for superclusters in the N-body simulations are compared with the spherical collapse model. We find that the radial peculiar velocities in N-body simulations are systematically smaller than those predicted by the spherical collapse model ($\sim 25$% for the $R=5h^{-1}$Mpc superclusters).

. . . but what I take from it is that according to their simulations, most superclusters are expanding as they state that their model suggests that 'Only a small fraction of the superclusters defined with . . . has already reached their turnaround radius and these superclusters have started to collapse.' I note that this is a simulation that suggests a result, not an observation that confirms a result.

Also, my comment about superclusters being the largest structure in the universe is debatable according to the wikipedia article at
http://en.wikipedia.org/wiki/Supercluster
On the one hand

Once thought to be the largest structures in nature, superclusters are now understood to be subordinate to enormous walls or sheets, usually called "filaments", sometimes called "super cluster complexes", "walls" or "sheets", that can span a billion light-years in length, more than 5% of the observable universe.

On the other hand

According to some astronomers, no clusters of super clusters (“hyperclusters”) are known; the existence of structures larger than superclusters is debated (see Galaxy filament). Interspersed among super clusters are large voids of space in which few galaxies exist. Even though superclusters are the largest structures confirmed, the total number of superclusters leaves possibilities for structural distribution; the total number of super clusters in the universe is believed to be close to 10 million.

Just posting this in interests of accuracy.

[Chris Peterson]

I googled "Are superclusters expanding" and found an abstract from a 2002 paper at http://arxiv.org/abs/astro-ph/0204121.

I don't get the details of their abstract ...
... but what I take from it is that according to their simulations, most superclusters are expanding as they state that their model suggests that 'Only a small fraction of the superclusters defined with . . . has already reached their turnaround radius and these superclusters have started to collapse.' I note that this is a simulation that suggests a result, not an observation that confirms a result.

My reading is that they have produced a set of results from a model, and have varied a particular parameter that does not have a well established value. They point out that measurement techniques are becoming good enough to test these predictions with actual observation, which will then allow the density parameter in question to be determined with greater accuracy.

This is a standard method in astronomy and cosmology in particular, since most observations can't be tested in the laboratory!

[harry]

G'day

What is large and what is small?

Think of it this way.

Atom
Earth
Solar System
Galaxy
Local group of galaxies
Larger group of local galaxies
Huge group of Larger group of local galaxies
Super cluster of huge groups of galaxies
Super dooper cluster of super clusters.

All have a connection in one way or another.

You may find this quite interesting.

http://arxiv.org/abs/0801.2965
Cosmology and Cosmogony in a Cyclic Universe

Authors: Jayant V. Narlikar, Geoffrey Burbidge, R.G. Vishwakarma
(Submitted on 18 Jan 2008)

Abstract: In this paper we discuss the properties of the quasi-steady state cosmological model (QSSC) developed in 1993 in its role as a cyclic model of the universe driven by a negative energy scalar field. We discuss the origin of such a scalar field in the primary creation process first described by F. Hoyle and J. V. Narlikar forty years ago. It is shown that the creation processes which takes place in the nuclei of galaxies are closely linked to the high energy and explosive phenomena, which are commonly observed in galaxies at all redshifts.
The cyclic nature of the universe provides a natural link between the places of origin of the microwave background radiation (arising in hydrogen burning in stars), and the origin of the lightest nuclei (H, D, He$^3$ and He$^4$). It also allows us to relate the large scale cyclic properties of the universe to events taking place in the nuclei of galaxies. Observational evidence shows that ejection of matter and energy from these centers in the form of compact objects, gas and relativistic particles is responsible for the population of quasi-stellar objects (QSOs) and gamma-ray burst sources in the universe.
In the later parts of the paper we briefly discuss the major unsolved problems of this integrated cosmological and cosmogonical scheme. These are the understanding of the origin of the intrinsic redshifts, and the periodicities in the redshift distribution of the QSOs.

[Maj_sm_jz]

Hello to all.
I've heard a claim that the stars that make up the constellation of Orion are gravitationally bound to each other, and those of Pleiades too. Is this true? If so, how was it confirmed? Are there any research papers available on the internet? Are there any other such naked-eye-observable constellations that are gravitationally linked?

Thanks for your answers.