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fuagf

01/14/12 9:07 AM

#165443 RE: F6 #165402

F6, that totally spaced me out, lol, even now i found myself wondering how dark matter was 'found' ..

Dark matter ..

In astronomy and cosmology, dark matter is matter that neither emits nor scatters light or other electromagnetic radiation, and so cannot be directly seen with telescopes. Dark matter is believed to constitute 83% of the matter in the universe and 23% of the mass-energy.

Dark matter was postulated by Fritz Zwicky in 1933 to account for evidence of "missing mass" in the orbital velocities of galaxies in clusters. Subsequently, other observations have indicated the presence of dark matter in the universe; these observations include the rotational speeds of galaxies, gravitational lensing of background objects by galaxy clusters such as the Bullet Cluster, and the temperature distribution of hot gas in galaxies and clusters of galaxies. Dark matter is widely believed to be composed primarily of a new, not yet characterized, type of subatomic particle. The search for this particle, by a variety of means, is one of the major efforts in particle physics today.[5] Though the existence of dark matter is generally accepted by the mainstream scientific community, some alternative theories have been proposed to explain the anomalies that dark matter is intended to account for, without hypothesizing dark matter.

Dark matter's existence is inferred from gravitational effects on visible matter and gravitational lensing of background radiation, and was originally hypothesized to account for discrepancies between calculations of the mass of galaxies, clusters of galaxies and the entire universe made through dynamical and general relativistic means, and calculations based on the mass of the visible "luminous" matter these objects contain: stars and the gas and dust of the interstellar and intergalactic medium. The most widely accepted explanation for these phenomena is that dark matter exists and that it is most likely composed of heavy particles that interact only through gravity and possibly the weak force; however, alternate explanations have been proposed, and there is not yet sufficient experimental evidence to determine which is correct. Many experiments to detect proposed dark matter particles through non-gravitational means are underway. .. http://en.wikipedia.org/wiki/Dark_matter

Dark Energy

In physical cosmology, astronomy and celestial mechanics, dark energy is a hypothetical form of energy that permeates all of space and tends to accelerate the expansion of the universe. Dark energy is the most accepted theory to explain observations since the 1990s that indicate that the universe is expanding at an increasing rate. In the standard model of cosmology, dark energy currently accounts for 73% of the total mass-energy of the universe.

Two proposed forms for dark energy are the cosmological constant, a constant energy density filling space homogeneously, and scalar fields such as quintessence or moduli, dynamic quantities whose energy density can vary in time and space. Contributions from scalar fields that are constant in space are usually also included in the cosmological constant. The cosmological constant is physically equivalent to vacuum energy. Scalar fields which do change in space can be difficult to distinguish from a cosmological constant because the change may be extremely slow. .. http://en.wikipedia.org/wiki/Dark_energy

starry eyed and spaced out .. what the heck is the difference between dark matter (some 83% of the
matter of the universe, above) and dark energy "73% of the total mass-energy of the universe."

===============



Dark matter vs dark energy

Hoosier (below) is a bit confused between Dark Matter and Dark Energy, and
unconvinced by the whole shebang. This is very common, so let’s have a post on it..

Dark matter .. http://en.wikipedia.org/wiki/Dark_matter .. is thought to account for 20% of all the matter/energy of the universe. Although we can’t see it, we’re pretty sure it exists, because its gravitational effect on visible matter can be seen. Put differently, we don’t insist that all existing matter must be ‘visible’ (i.e. emit or reflect electromagnetic radiation). Instead , we include the possibility that some matter may be seen only by its gravitational effect on neighbouring matter. The idea was first postulated by Fritz Zwicky .. http://en.wikipedia.org/wiki/Fritz_Zwicky .. in the 1930s – today, the known motion of certain spiral galaxies suggests that dark matter makes up 22% of all matter/energy, while ordinary (visible) matter makes up only 4% .

Of course, like the MOND .. http://en.wikipedia.org/wiki/Modified_Newtonian_dynamics .. crowd suggest, there is always the possibility is that our laws of gravity (both Newtonian and Einsteinian) are simply wrong. But most physicists consider this unlikely, as the predictions of our theory of gravity match observation in so many other instances…

Dark energy .. http://en.wikipedia.org/wiki/Dark_energy .. is a lot more speculative, and a lot more recent. It’s simply the name we give to whatever is causing the expansion of the universe to speed up (since 1998, it has been known that the expansion rate is currently increasing). The physical cause for dark energy is thought to be some sort of vacuum energy, but nobody’s sure yet. (From the point of view of theory, the phenomenon suggests that Einstein’s equations need an extra term, known technically as the ‘positive cosmological constant’.)

Putting the two together, cosmologists postulate that ordinary matter, dark matter and dark energy all add up to the critical density required for the geometry of the universe to be flat (which is what observation suggests). In other words, the current model of the universe can be summed up by

Density ord matter (4%) + Dens dark matter (22%) + Dens dark energy (74%) = 100%

More

The strongest evidence .. http://www.msnbc.msn.com/id/14453775/ .. yet for dark matter was reported last summer. In the passage of one galaxy through another, one might expect the dark matter of one galaxy to interact differently than its ordinary matter, and researchers at the University of Arizona are pretty sure this is exactly they saw.

Galaxy collision seen by the CHANDRA space telescope



It is also reported here .. http://apetrov.wordpress.com/2008/04/16/damalibra-claims-to-see-dark-matter/ .. and here .. http://www.symmetrymagazine.org/breaking/2008/04/12/dark-matter-discovered-aps-april-2008/ .. that another group, the DAMA-LIBRA collaboration, have observed separate evidence of dark matter, but this claim is more controversial.

17 Comments »

1. Thanks so much for taking time out of your day to help explain the mysteries of the universe Doctor C.
I really do appreciate it!
a couple more things..That’s a beeautiful picture..but what do the colors of red and blue mean? what does it represent? How does it show dark matter when it can’t be seen? Is that gasses of some sort? how does that prove dark matter?
Also..I read something somewhere about this guy that put forth the idea that dark energy doesn’t really exist.. the reason it appears to us the the universe is expanding faster and faster is because the speed of light over time is slowing down and makes the red shift skewed to us observers. Have you read that also? Maybe at the big bang light was twice as fast as today..Boy if that was true ole albert would be spinning in his grave! :)
but if true then e=mc squared would mean that the energy levels near the big bang would have been twice of what we would calculate and slowly everything would be degrading.
I’ll try to find that link for you to check out.
Again..thanks for answering my dumb questions..
I went to one web page and the guy bragged about how smart he was and how stupid i was..I don’t get that alot when speaking in person.. They don’t have the courage to insult you when they know I’d kick thier ass..But this is the beauty of the internet..people can call you stupid and get away with it. Some people are smart..some play sports well..Some know how to fix stuff..why the ego?
I dunno..thanks again Doc.


Comment by HoosierHoops | May 23, 2008 | Reply

and

4. btw, regarding the red and blue in the picture. If I recall that correctly, it’s an overlay of two data-sets (and both over the Hubble image with the stars). The red one shows the mass-distribution of visible matter (can’t recall which parts of the spectrum precisely), the blue one shows the mass-distribution as inferred from gravitational lensing data. What you see is that both are offset from each other. The interpretation is that the bulk of the matter which causes the gravitational lensing is not where the visible matter is. The reason why the visible matter is lagging behind is that it interacts more strongly than the dark matter (usually thought to consist of WIMPs – weakly interacting massive particles). Best,

B. .. http://coraifeartaigh.wordpress.com/2008/05/22/dark-matter-and-dark-energy/

Thanks for all your hard work F6. Even though it often leaves me galaxy eyed and universally out of touch. LOL

How can it be considered that our universe, starting from nothing and expanding in all directions, could be flat?

I feel about 6 years old.





F6

01/20/12 11:34 AM

#165863 RE: F6 #165402

Cataract in a gravitational lens may be a tiny galaxy


Left: Hubble Space Telescope infrared image of Einstein ring B1938+666; right: Einstein ring in radio light

By Matthew Francis | Published January 19, 2012 6:25 AM

The Universe seems to be built from the bottom up: small structures combine to make larger and larger objects. In the best models cosmologists have developed, dark matter is the architect, providing the gravitational foundations on which the gas and dust that form stars can collect. Large-scale dark matter simulations of the Universe produce results that match the observed populations of large galaxies such as Milky Way. But they also predict far too many low-mass galaxies compared to what we've seen in population surveys.

One possible resolution to the problem is that at least some low-mass galaxies may be lacking much ordinary matter. If a galaxy has few or no stars and little gas, it won't produce much light, making it difficult to observe. Nevertheless, all mass has a gravitational effect that can reveal itself under certain circumstances. A recent analysis by S. Vegetti, D. J. Lagatutta, J. P. McKean, M. W. Auger, C. D. Fassnacht, and L. V. E. Koopmans found a small anomaly in a gravitational lens that may be a small satellite galaxy that's too faint to be seen via direct observation.

The Milky Way, M31 (Andromeda Galaxy), and many other observed galaxies have satellite galaxies surrounding them. Some of these are relatively large and bright (like the Large and Small Magellanic Clouds), but many are very faint and relatively low mass, such as the Sagittarius dwarf elliptical galaxy. Standard dark matter models predict large numbers of these dwarf satellites, far more than we've actually observed.

Mass affects the path of light, as a consequence of the general theory of relativity. For a sufficiently large mass, the light's shift may be sufficiently large that we can measure it, and it can produce lensed images of the original light source. In gravitational lensing, the lens is a galaxy or galaxy cluster lying between Earth and a distant source, itself typically a galaxy. If the lens is directly in the line of sight, the image of the source galaxy can be distorted into an Einstein ring, a circular image of the source. By studying the shape and other characteristics of the image, observers can reconstruct details about both the lens and the source galaxies.

A particular lens system, JVAS B1938+666, is a distant elliptical galaxy that produced a bright Einstein ring image of an even more remote source galaxy. Independent observations by the W. M. Keck Telescope's Near Infrared Camera 2 and the Near Infrared Camera aboard the Hubble Space Telescope provided the basis to reconstruct the mass distribution in the lens galaxy. The analysis by Vegetti and colleagues found an anomaly in the results; explaining it requires either an extra bit of mass in the lens or some intervening dust to block the light from parts of the image. However, dust absorbs light in a particular way, changing the spectrum of the image, and the team failed to find the appropriate signature.

That leaves the most likely culprit being another clump of mass that isn't part of the main lens galaxy. Subtracting a reasonable model for the elliptical galaxy leaves the image pattern that would be produced by this hypothetical clump of mass. If you assume that this lensing isn't from an unconnected galaxy with a smaller effect, then the clump of mass can be characterized fairly easily apart from the larger elliptical galaxy. Starting with assumptions taken from standard dark matter simulations, the researchers attempted to fit the location and mass of the clump, and found something consistent with an object in the same mass category as the Sagittarius dwarf galaxy.

Although the research letter published today in Nature calls this dwarf galaxy candidate "dark" both in the title and description (implying no emitted light), the authors do point out that they can only put a ceiling on the luminosity on the object. That maximum limit is still brighter than several of the Milky Way's dwarf satellite galaxies. In other words, it's premature to declare that a dark galaxy has been found, even if the mass estimate holds up under further investigation.

Nevertheless, the presence of this candidate has other important implications for dark matter models. The lens galaxy (and hence the perturbing lump of matter) is about 3 billion parsecs away, meaning the light we observe from it was emitted when the Universe was roughly half its current age. (Recall that the Universe is expanding, so the galaxy is carried farther from us by the expansion even as the light travels between it and Earth.) Detecting any small galaxy at that distance is not only an impressive feat, but also gives us some hints about the history of the formation of galaxies farther back in time. Since the candidate dwarf galaxy was found using parameters from dark matter simulations, the authors argue that the simulations may not be as far off as they have seemed.

Nature, 2012. DOI: 10.1038/nature10669 [ http://www.nature.com/nature/journal/v481/n7381/full/nature10669.html ( http://dx.doi.org/10.1038/nature10669 )]

Ars Technica © 2012 Condé Nast Digital

http://arstechnica.com/science/news/2012/01/cataract-in-a-gravitational-lens-may-be-a-tiny-galaxy.ars [with comments]


===


Dark matter galaxy hints seen 10bn light-years away

18 January 2012
http://www.bbc.co.uk/news/science-environment-16610153


===


Dwarf galaxies: breakthrough in bid to find 'fossils' of early universe
A team of astronomers reports that it has detected the most distant dwarf galaxy yet discovered orbiting an enormous elliptical galaxy some 10 billion light-years away.
January 18, 2012
http://www.csmonitor.com/Science/2012/0118/Dwarf-galaxies-breakthrough-in-bid-to-find-fossils-of-early-universe [no comments yet]


===


Do Invisible Galaxies Swirl Around the Milky Way?
Jan. 19, 2012
http://www.time.com/time/health/article/0,8599,2104740,00.html [with comments]


F6

02/26/12 8:30 AM

#168616 RE: F6 #165402

Milky Way May Have 100,000 Times More Nomad Planets Than Stars

Posted on February 26, 2012

There may be 100,000 times more “nomad planets” in the Milky Way than stars, according to a new study by researchers at the Kavli Institute for Particle Astrophysics and Cosmology [ http://kipac.stanford.edu/ ] (KIPAC), a joint institute of Stanford University and the SLAC National Accelerator Laboratory. How amazing is that. Science is so cool. I had no idea this was the case.

If observations confirm the estimate, this new class of celestial objects will affect current theories of planet formation and could change our understanding of the origin and abundance of life.

“If any of these nomad planets are big enough to have a thick atmosphere, they could have trapped enough heat for bacterial life to exist,” said Louis Strigari, leader of the team that reported the result in a paper: Nomads of the Galaxy [ http://arxiv.org/abs/1201.2687 ]. Although nomad planets don’t bask in the warmth of a star, they may generate heat through internal radioactive decay and tectonic activity.

Searches over the past two decades have identified more than 500 planets outside our solar system, almost all of which orbit stars. Last year, researchers detected about a dozen nomad planets, using a technique called gravitational microlensing, which looks for stars whose light is momentarily refocused by the gravity of passing planets.

The research produced evidence that roughly two nomads exist for every typical, so-called main-sequence star in our galaxy. The new study estimates that nomads may be up to 50,000 times more common than that.

To arrive at what Strigari himself called “an astronomical number,” the KIPAC team took into account the known gravitational pull of the Milky Way galaxy, the amount of matter available to make such objects and how that matter might divvy itself up into objects ranging from the size of Pluto to larger than Jupiter. Not an easy task, considering no one is quite sure how these bodies form. According to Strigari, some were probably ejected from solar systems, but research indicates that not all of them could have formed in that fashion.

“To paraphrase Dorothy from The Wizard of Oz, if correct, this extrapolation implies that we are not in Kansas anymore, and in fact we never were in Kansas,” said Alan Boss of the Carnegie Institution for Science, author of The Crowded Universe: The Search for Living Planets, who was not involved in the research. “The universe is riddled with unseen planetary-mass objects that we are just now able to detect.”

A good count, especially of the smaller objects, will have to wait for the next generation of big survey telescopes, especially the space-based Wide-Field Infrared Survey Telescope and the ground-based Large Synoptic Survey Telescope, both set to begin operation in the early 2020s.

A confirmation of the estimate could lend credence to another possibility mentioned in the paper – that as nomad planets roam their starry pastures, collisions could scatter their microbial flocks to seed life elsewhere.

Additional authors included KIPAC member Matteo Barnabè and affiliate KIPAC member Philip Marshall of Oxford University. The research was supported by NASA, the National Science Foundation and the Royal Astronomical Society.

*

Related:

full press release
http://news.stanford.edu/news/2012/february/slac-nomad-planets-022312.html

Astronomers Find a Planet Denser Than Lead
http://engineering.curiouscatblog.net/2008/10/07/astronomers-find-a-planet-denser-than-lead/

Hot Ice Planet
http://engineering.curiouscatblog.net/2007/05/17/hot-ice-planet/

NASA’s Mars Curiosity Rover
http://engineering.curiouscatblog.net/2011/06/16/nasas-mars-curiosity-rover/

Planet, Less Dense Than Cork, Is Discovered
http://engineering.curiouscatblog.net/2006/09/15/planet-less-dense-than-cork-is-discovered/

*

© curiouscat.com 2012

http://engineering.curiouscatblog.net/2012/02/26/milky-way-may-have-100000-times-more-nomad-planets-than-stars/ [no comments yet] [also at http://www.ecnmag.com/News/Feeds/2012/02/blogs-the-cutting-edge-milky-way-may-have-100-000-times-more-nomad-planet/ (no comments yet)]

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fuagf

07/03/12 12:45 AM

#178553 RE: F6 #165402

New Planet Found: Could a Super-Earth plus Triple Stars Equal Life?

F6, this post basically because a search and a glance at all your links re new exoplanets i
didn't see GJ667Cc .. hope there is other stuff here not covered in your exoplanet library.


By Michael D. Lemonick Friday, Feb. 03, 2012


An artist depiction of the planet GJ667Cc and the
three stars it orbits .. Carnegie Institution / UCSC

The search for exoplanets, or worlds orbiting other stars, is evolving so fast that discoveries that seemed exotic just a few months ago have become commonplace. Multiple-planet solar systems? Astronomers expected to find just a handful; now we know of more than 200. Planets orbiting double or even triple stars? It was big news when just one was announced back in September; we've already got several more examples in hand. In short, the unexpected is something planet hunters have learned to expect — and in most cases, these surprises have tended to expand the possibilities for finding worlds where life might thrive.

It's just happened again: astronomers from the Carnegie Institution of Washington and the University of California, Santa Cruz, writing in the Astrophysical Journal Letters, have announced the discovery of yet another new world that defies everyone's expectations. Not only does the new planet orbit one of the suns in a triple-star system — rare enough in itself — but the stars in this system have surprisingly low levels of the heavy elements planets are made from. Theory suggests that such stars shouldn't form planets in the first place, so if this isn't a fluke, there may be many more planets in the Milky Way than anyone thought. (See the best photos from space in 2011.) .. http://www.time.com/time/photogallery/0,29307,2101995,00.html

That's not all: the new planet, called GJ667Cc, is just 4.5 times Earth's mass. That's big enough to qualify it for the astronomical label "super-Earth" but still quite small by exoplanet standards. Indeed, it's so small that GJ667Cc is thought to be made of earthlike rock rather than gas — even if those rocks had to coalesce from a smaller supply of raw material circling the parent sun. Beyond that, it orbits in its star's habitable zone: if there's water there, that water could be in life-friendly liquid form. GJ667Cc whips around its star once every 28 days or so; in our solar system, that would put it so scorchingly close to the sun that water would boil off. But the star in this case is an M-dwarf, much dimmer and redder than our own. Given its mass and its temperature, says co-discoverer Steve Vogt, of UC Santa Cruz, "I think it's going to be pretty historic. We've been gnawing at the bone of an earthlike planet in the habitable zone for years now, and I think we're just about there."

Actually, this isn't the first time he's said something like that. A bit over a year ago, Vogt and Paul Butler, of Carnegie, announced a similarly earthlike planet they called Gliese 581g, .. http://www.time.com/time/health/article/0,8599,2022489,00.html .. but other astronomers were (and remain) dubious about the legitimacy of the find. "We haven't backed off," says Vogt, "but that one will always be controversial, because it's a difficult measurement."

This one, he says, is a much more clear-cut case. Along with Butler, lead author Guillem Anglada-Escudé (now at the University of Göttingen, in Germany) and several others, Vogt combined data from three different ground-based telescopes, dating back 10 years, to come up with the solid signal of a planet. "We were basically able to say, stick a fork in this one and put it in a referred journal — it's done." (See photos of a new planetary nebula that dazzles astronomers.) ..
http://www.time.com/time/photogallery/0,29307,2085617,00.html

[GOOD .. at least some of these links are new on the board. I think .. lol]

What's most exciting of all about GJ667Cc, though, is not just that it's a super-Earth in its star's habitable zone, nor that it was found in a solar system where planets have no right to be. It's that this new world is impressively close to our own Earth. The great majority of exoplanets known to date have been found by the Kepler space probe, but most of these are hundreds of light-years away. That's much too far away to search for even indirect signs of alien life — and that will continue to be true after the James Webb Space Telescope, Hubble's successor, launches in 2018.

But GJ667Cc is a mere 22 light-years away — practically next door — and while the planet can't be seen directly yet, it's not impossible that the next generation of ground or space telescopes could take readings of its atmosphere to look for telltale signs of life. And we have the technology today, says Vogt, "to send a Droid cell phone out there to take closeup images. It would take about 200 years, plus another 20 to send the pictures back." (See photos of the universe, to scale.) ..
http://www.time.com/time/photogallery/0,29307,2079745,00.html

Nobody's actually planning to do that, but the fact that it's even possible speaks volumes about how close astronomers are to finding and studying places in the universe where life might be thriving at this very moment. In the world of exoplanet science, the improbable things don't seem to stay improbable for very long.

Watch TIME's video "Mars Rover Opportunity Celebrates Its Eighth Birthday."
http://www.time.com/time/video/player/0,32068,1424087054001_2105746,00.html

Read "A Telescope as Sharp as Hubble — but On the Ground
http://www.time.com/time/health/article/0,8599,2105816,00.html

http://www.time.com/time/health/article/0,8599,2106061,00.html

This article is also linked here
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fuagf

07/11/12 11:36 PM

#179213 RE: F6 #165402

Dark Energy, Dark Matter [NASA Astrophysics]

In the early 1990's, one thing was fairly certain about the expansion of the Universe. It might have enough energy density to stop its expansion and recollapse, it might have so little energy density that it would never stop expanding, but gravity was certain to slow the expansion as time went on. Granted, the slowing had not been observed, but, theoretically, the Universe had to slow. The Universe is full of matter and the attractive force of gravity pulls all matter together. Then came 1998 and the Hubble Space Telescope (HST) observations of very distant supernovae that showed that, a long time ago, the Universe was actually expanding more slowly than it is today. So the expansion of the Universe has not been slowing due to gravity, as everyone thought, it has been accelerating. No one expected this, no one knew how to explain it. But something was causing it.

Eventually theorists came up with three sorts of explanations. Maybe it was a result of a long-discarded version of Einstein's theory of gravity, one that contained what was called a "cosmological constant." Maybe there was some strange kind of energy-fluid that filled space. Maybe there is something wrong with Einstein's theory of gravity and a new theory could include some kind of field that creates this cosmic acceleration. Theorists still don't know what the correct explanation is, but they have given the solution a name. It is called dark energy.

What Is Dark Energy?


Universe Dark Energy-1 Expanding Universe
http://hubblesite.org/newscenter/archive/releases/2001/09/image/g/

This diagram reveals changes in the rate of expansion since the universe's birth 15 billion years ago. The more shallow the curve, the faster the rate of expansion. The curve changes noticeably about 7.5 billion years ago, when objects in the universe began flying apart as a faster rate. Astronomers theorize that the faster expansion rate is due to a mysterious, dark force that is pulling galaxies apart. .. NASA/STSci/Ann Feild

More is unknown than is known. We know how much dark energy there is because we know how it affects the Universe's expansion. Other than that, it is a complete mystery. But it is an important mystery. It turns out that roughly 70% .. http://map.gsfc.nasa.gov/news/5yr_release.html .. of the Universe is dark energy. Dark matter makes up about 25%. The rest - everything on Earth, everything ever observed with all of our instruments, all normal matter - adds up to less than 5% of the Universe. Come to think of it, maybe it shouldn't be called "normal" matter at all, since it is such a small fraction of the Universe.

One explanation for dark energy is that it is a property of space. Albert Einstein was the first person to realize that empty space is not nothing. Space has amazing properties, many of which are just beginning to be understood. The first property that Einstein discovered is that it is possible for more space to come into existence. Then one version of Einstein's gravity theory, the version that contains a cosmological constant, .. http://hubblesite.org/newscenter/archive/releases/2009/08/ .. makes a second prediction: "empty space" can possess its own energy. Because this energy is a property of space itself, it would not be diluted as space expands. As more space comes into existence, more of this energy-of-space would appear. As a result, this form of energy would cause the Universe to expand faster and faster. Unfortunately, no one understands why the cosmological constant should even be there, much less why it would have exactly the right value to cause the observed acceleration of the Universe.


Dark Matter Core Defies Explanation
http://hubblesite.org/newscenter/archive/releases/2012/10/full/

This image shows the distribution of dark matter, galaxies, and hot gas in the core of the merging
galaxy cluster Abell 520. The result could present a challenge to basic theories of dark matter.

Another explanation for how space acquires energy comes from the quantum theory of matter. In this theory, "empty space" is actually full of temporary ("virtual") particles that continually form and then disappear. But when physicists tried to calculate how much energy this would give empty space, the answer came out wrong - wrong by a lot. The number came out 10120 times too big. That's a 1 with 120 zeros after it. It's hard to get an answer that bad. So the mystery continues.

Another explanation for dark energy is that it is a new kind of dynamical energy fluid or field, something that fills all of space but something whose effect on the expansion of the Universe is the opposite of that of matter and normal energy. Some theorists have named this "quintessence," after the fifth element of the Greek philosophers. But, if quintessence is the answer, we still don't know what it is like, what it interacts with, or why it exists. So the mystery continues.

A last possibility is that Einstein's theory of gravity is not correct. That would not only affect the expansion of the Universe, but it would also affect the way that normal matter in galaxies and clusters of galaxies behaved. This fact would provide a way to decide if the solution to the dark energy problem is a new gravity theory or not: we could observe how galaxies come together in clusters. But if it does turn out that a new theory of gravity is needed, what kind of theory would it be? How could it correctly describe the motion of the bodies in the Solar System, as Einstein's theory is known to do, and still give us the different prediction for the Universe that we need? There are candidate theories, but none are compelling. So the mystery continues.

The thing that is needed to decide between dark energy possibilities - a property of space, a new dynamic fluid, or a new theory of gravity - is more data, better data.

What Is Dark Matter?


Abell 2744: Pandora's Cluster Revealed
http://chandra.harvard.edu/photo/2011/a2744/

One of the most complicated and dramatic collisions between galaxy clusters ever seen is captured in this new composite image of Abell 2744. The blue shows a map of the total mass concentration (mostly dark matter).

By fitting a theoretical model of the composition of the Universe to the combined set of cosmological observations, scientists have come up with the composition that we described above, ~70% dark energy, ~25% dark matter, ~5% normal matter. What is dark matter?

We are much more certain what dark matter is not than we are what it is. First, it is dark, meaning that it is not in the form of stars and planets that we see. Observations show that there is far too little visible matter in the Universe to make up the 25% required by the observations. Second, it is not in the form of dark clouds of normal matter, matter made up of particles called baryons. We know this because we would be able to detect baryonic clouds by their absorption of radiation passing through them. Third, dark matter is not antimatter, because we do not see the unique gamma rays that are produced when antimatter annihilates with matter. Finally, we can rule out large galaxy-sized black holes on the basis of how many gravitational lenses we see. High concentrations of matter bend light passing near them from objects further away, but we do not see enough lensing events to suggest that such objects to make up the required 25% dark matter contribution.

However, at this point, there are still a few dark matter possibilities that are viable. Baryonic matter could still make up the dark matter if it were all tied up in brown dwarfs or in small, dense chunks of heavy elements. These possibilities are known as massive compact halo objects, or "MACHOs". .. http://imagine.gsfc.nasa.gov/docs/teachers/galaxies/imagine/dark_matter.html .. But the most common view is that dark matter is not baryonic at all, but that it is made up of other, more exotic particles like axions or WIMPS (Weakly Interacting Massive Particles). .. http://imagine.gsfc.nasa.gov/docs/teachers/galaxies/imagine/dark_matter.html

Recent Discoveries

April 2, 2012 Fermi Observations of Dwarf Galaxies Provide New Insights on Dark Matter
http://www.nasa.gov/mission_pages/GLAST/news/dark-matter-insights.html

March 14, 2012 Mapping the Dark Matter in Abell 383
http://chandra.harvard.edu/photo/2012/a383/

March 2, 2012 Dark Matter Core Defies Explanation
http://hubblesite.org/newscenter/archive/releases/2012/10/

January 10, 2012 El Gordo
http://chandra.harvard.edu/photo/2012/elgordo/

January 10, 2012 Farthest Protocluster of Galaxies Ever Seen
http://hubblesite.org/newscenter/archive/releases/2012/2012/05/full/results/50/

October 13, 2011 New Dark Matter Census Survey
http://hubblesite.org/newscenter/archive/releases/2011/2011/25/results/100/

June 22, 2011 Abell 2744: Pandora's Cluster Revealed
http://chandra.harvard.edu/photo/2011/a2744/

May 19, 2011 GALEX Helps Confirm Nature of Dark Energy
http://www.galex.caltech.edu/newsroom/glx2011-01r.html

April 12, 2011 Abell 383
http://www.spitzer.caltech.edu/images/3579-ssc2011-05a-Annotated-View-of-Abell-383

March 14, 2011 Hubble Rules Out One Alternative to Dark Energy
http://hubblesite.org/newscenter/archive/releases/2011/2011/08/results/100/

http://science.nasa.gov/astrophysics/focus-areas/what-is-dark-energy/

F6

09/27/12 4:58 AM

#186833 RE: F6 #165402

Hubble Space Telescope Lets Us Look Back 13.2-Billion Years Into Our Past (VIDEO)


Over 5,500 galaxies, including one created just 450-million years after the universe's creation 13.7-billion years ago.
(Photo: http://HubbleSite.org )


By Keerthi Chandrashekar | First Posted: Sep 25, 2012 06:26 PM EDT

Scientists have assembled a series of photos together from the Hubble Space Telescope in order to create what is the deepest view into space ever. The image shows light from galaxies that are so old, they existed just a mere 450 million years after the universe's creation 13.7-billion-years ago.

The photo has been dubbed eXtreme Deep Field [ http://hubblesite.org/newscenter/archive/releases/2012/37 ], or XDF, and even though it is a tiny portion of the angular diameter of the moon (the constellation Fornax) one can still see around 5,500 galaxies.

Over 10 years of Hubble photographs were used in order to create XDF, including those from Hubble's new infrared camera, which allows it to peer deep into space to detect red light.

"The XDF is the deepest image of the sky ever obtained and reveals the faintest and most distant galaxies ever seen. XDF allows us to explore further back in time than ever before," said Garth Illingworth from University of California at Santa Cruz and lead scientist of the Hubble Ultra Deep Field 2009 program.

Before the Hubble Telescope, scientists could not really see beyond 7-billion light-years. Now, the XDF, comprised of Hubble photographs, peers back 13.2-billion years into our universe's past, allowing astronomers to gain a better understanding of the early universe and galaxies were formed.

The images also help scientists better prepare for the Hubble's successor, the James Webb Space Telescope.

A web seminar on September 27, 2012 at 1:00 p.m. titled "Meet the Hubble eXtreme Deep Field Observing Team [ https://plus.google.com/events/c1sh631k56ep2t4pjnkqifmkks4 ]" will allow the public to listen to three astronomers talk about assembling the landmark image.

© 2012 Latinos Post

http://www.latinospost.com/articles/4580/20120925/hubble-space-telescope-lets-look-back-13.htm [with the video below embedded; no comments yet]


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Fly Through the Hubble eXtreme Deep Field
Published on Sep 25, 2012 by HubbleSiteChannel [ http://www.youtube.com/user/HubbleSiteChannel ]

This video takes you through Hubble's deepest view of the universe, from its location in the sky to the dimmest, most distant galaxies.

http://www.youtube.com/watch?v=odprMkzOst8


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