12-11-10

Hubble Provides Most Detailed Dark Matter Map Yet

 

11th November 2010

 

DarkMatterAbell.jpg

 

Nasa Hubble Space Telescope shows the distribution of dark matter in the center of the giant galaxy cluster Abell 1689. (more than 1000 galaxies with trillions of stars).

 

Credit: NASA, ESA, D. Coe (NASA Jet Propulsion Laboratory/California Institute of Technology,
and Space Telescope Science Institute), N. Benitez (Institute of Astrophysics of Andalusia, Spain), T. Broadhurst (University of the Basque Country, Spain), and H. Ford (Johns Hopkins University).

 

Credits :

 

http://www.universetoday.com/78309/hubble-provides-most-d...

 

10-11-10

Cosmology Video - The Hubble Ultra Deep Field in 3D


 

Animation Credit:

 

Hubble Cosmological Redshift Animation Courtesy:

 

Mike Gallis

 

http://phys23p.sl.psu.edu/phys_anim/Phys_anim.htm

 

http://www.youtube.com/watch?v=e6G2Z6iD-9M

 

Music Used in this video was purchased from stockmusic.net and belongs to the Spirit Legends Collection.

 

The tunes I used were:

 

Voice Redo B

 

Voice in the Dark

 

Link to demos:

 

http://www.stockmusic.net/index.cfm/page/main.collectionD...

 

Category:

 

Science & Technology

 

 

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15-05-09

Astronomers Closing in on Dark Energy with Refined Hubble Constant

The name “dark energy” is just a placeholder for the force — whatever it is — that is causing the Universe to expand. But astronomers are perhaps getting closer to understanding this force. New observations of several Cepheid variable stars by the Hubble Space Telescope has refined the measurement of the Universe’s present expansion rate to a precision where the error is smaller than five percent. The new value for the expansion rate, known as the Hubble constant, or H0 (after Edwin Hubble who first measured the expansion of the universe nearly a century ago), is 74.2 kilometers per second per megaparsec (error margin of ± 3.6). The results agree closely with an earlier measurement gleaned from Hubble of 72 ± 8 km/sec/megaparsec, but are now more than twice as precise.The Hubble measurement, conducted by the SHOES (Supernova H0 for the Equation of State) Team and led by Adam Riess, of the Space Telescope Science Institute and the Johns Hopkins University, uses a number of refinements to streamline and strengthen the construction of a cosmic “distance ladder,” a billion light-years in length, that astronomers use to determine the universe’s expansion rate.Hubble observations of the pulsating Cepheid variables in a nearby cosmic mile marker, the galaxy NGC 4258, and in the host galaxies of recent supernovae, directly link these distance indicators. The use of Hubble to bridge these rungs in the ladder eliminated the systematic errors that are almost unavoidably introduced by comparing measurements from different telescopes. Steps to the Hubble Constant. Credit: NASA, ESA, and A. Feild (STScI)Riess explains the new technique: “It’s like measuring a building with a long tape measure instead of moving a yard stick end over end. You avoid compounding the little errors you make every time you move the yardstick. The higher the building, the greater the error.” Lucas Macri, professor of physics and astronomy at Texas A&M, and a significant contributor to the results, said, “Cepheids are the backbone of the distance ladder because their pulsation periods, which are easily observed, correlate directly with their luminosities. Another refinement of our ladder is the fact that we have observed the Cepheids in the near-infrared parts of the electromagnetic spectrum where these variable stars are better distance indicators than at optical wavelengths.”This new, more precise value of the Hubble constant was used to test and constrain the properties of dark energy, the form of energy that produces a repulsive force in space, which is causing the expansion rate of the universe to accelerate.By bracketing the expansion history of the universe between today and when the universe was only approximately 380,000 years old, the astronomers were able to place limits on the nature of the dark energy that is causing the expansion to speed up. (The measurement for the far, early universe is derived from fluctuations in the cosmic microwave background, as resolved by NASA’s Wilkinson Microwave Anisotropy Probe, WMAP, in 2003.)Their result is consistent with the simplest interpretation of dark energy: that it is mathematically equivalent to Albert Einstein’s hypothesized cosmological constant, introduced a century ago to push on the fabric of space and prevent the universe from collapsing under the pull of gravity. (Einstein, however, removed the constant once the expansion of the universe was discovered by Edwin Hubble.) Detail from NGC 3021. Credit: NASA, ESA, and A. Riess (STScI/JHU)“If you put in a box all the ways that dark energy might differ from the cosmological constant, that box would now be three times smaller,” says Riess. “That’s progress, but we still have a long way to go to pin down the nature of dark energy.” Though the cosmological constant was conceived of long ago, observational evidence for dark energy didn’t come along until 11 years ago, when two studies, one led by Riess and Brian Schmidt of Mount Stromlo Observatory, and the other by Saul Perlmutter of Lawrence Berkeley National Laboratory, discovered dark energy independently, in part with Hubble observations. Since then astronomers have been pursuing observations to better characterize dark energy.Riess’s approach to narrowing alternative explanations for dark energy—whether it is a static cosmological constant or a dynamical field (like the repulsive force that drove inflation after the big bang)—is to further refine measurements of the universe’s expansion history.Before Hubble was launched in 1990, the estimates of the Hubble constant varied by a factor of two. In the late 1990s the Hubble Space Telescope Key Project on the Extragalactic Distance Scale refined the value of the Hubble constant to an error of only about ten percent. This was accomplished by observing Cepheid variables at optical wavelengths out to greater distances than obtained previously and comparing those to similar measurements from ground-based telescopes.The SHOES team used Hubble’s Near Infrared Camera and Multi-Object Spectrometer (NICMOS) and the Advanced Camera for Surveys (ACS) to observe 240 Cepheid variable stars across seven galaxies. One of these galaxies was NGC 4258, whose distance was very accurately determined through observations with radio telescopes. The other six galaxies recently hosted Type Ia supernovae that are reliable distance indicators for even farther measurements in the universe. Type Ia supernovae all explode with nearly the same amount of energy and therefore have almost the same intrinsic brightness.By observing Cepheids with very similar properties at near-infrared wavelengths in all seven galaxies, and using the same telescope and instrument, the team was able to more precisely calibrate the luminosity of supernovae. With Hubble’s powerful capabilities, the team was able to sidestep some of the shakiest rungs along the previous distance ladder involving uncertainties in the behavior of Cepheids.Riess would eventually like to see the Hubble constant refined to a value with an error of no more than one percent, to put even tighter constraints on solutions to dark energy.Source: Space Telescope Science Institutecopyright http://www.universetoday.com/2009/05/07/astronomers-closing-in-on-dark-energy-with-refined-hubble-constant/hubble-constant/dark matter

25-05-08

Hubble Survey Finds Missing Matter, Probes Intergalactic Web

Although the universe contains billions of galaxies, only a small amount of its matter is locked up in these behemoths. Most of the universe's matter that was created during and just after the Big Bang must be found elsewhere.Now, in an extensive search of the local universe, astronomers say they have definitively found about half of the missing normal matter, called baryons, in the spaces between the galaxies. This important component of the universe is known as the "intergalactic medium," or IGM, and it extends essentially throughout all of space, from just outside our Milky Way galaxy to the most distant regions of space observed by astronomers.The questions "where have the local baryons gone, and what are their properties?" are being answered with greater certainty than ever before."We think we are seeing the strands of a web-like structure that forms the backbone of the universe," Mike Shull of the University of Colorado explained. "What we are confirming in detail is that intergalactic space, which intuitively might seem to be empty, is in fact the reservoir for most of the normal, baryonic matter in the universe."Hubble observations made nearly a decade ago by Todd Tripp and colleagues first reported finding the hottest portion of this missing matter in the local universe. That study utilized spectroscopic observations of one quasar to look for absorbing intergalactic gas along the path to the quasar.In the May 20 issue of The Astrophysical Journal, Charles Danforth and Shull report on observations taken along sight-lines to 28 quasars. Their analysis represents the most detailed observations to date of how the IGM looks within about four billion light-years of Earth.Baryons are protons, neutrons, and other subatomic particles that make up ordinary matter such as hydrogen, helium, and heavier elements. Baryonic matter forms stars, planets, moons, and even the interstellar gas and dust from which new stars are born.Astronomers caution that the missing baryonic matter is not to be confused with "dark matter," a mysterious and exotic form of matter that is only detected via its gravitational pull.Danforth and Shull, of the Department of Astrophysical and Planetary Sciences at the University of Colorado in Boulder, looked for the missing baryonic matter by using the light from distant quasars (the bright cores of galaxies with active black holes) to probe spider-web-like structure that permeates the seemingly invisible space between galaxies, like shining a flashlight through fog.Using the Space Telescope Imaging Spectrograph (STIS) aboard NASA's Hubble Space Telescope and NASA's Far Ultraviolet Spectroscopic Explorer (FUSE), the astronomers found hot gas, mostly oxygen and hydrogen, which provide a three-dimensional probe of intergalactic space. STIS and FUSE found the spectral "fingerprints" of intervening oxygen and hydrogen superimposed on the quasars' light.The bright quasar light was measured to penetrate more than 650 filaments of hydrogen in the cosmic web. Eighty-three filaments were found laced with highly ionized oxygen in which five electrons have been stripped away.The presence of highly ionized oxygen (and other elements) between the galaxies is believed to trace large quantities of invisible, hot, ionized hydrogen in the universe. These vast reservoirs of hydrogen have largely escaped detection because they are too hot to be seen in visible light, yet too cool to be seen in X-rays.The oxygen "tracer" was probably created when exploding stars in galaxies spewed the oxygen back into intergalactic space where it mixed with the pre-existing hydrogen via a shockwave which heated the oxygen to very high temperatures.The team also found that about 20 percent of the baryons reside in the voids between the web-like filaments. Within these voids could be faint dwarf galaxies or wisps of matter that could turn into stars and galaxies in billions of years.Probing this vast cosmic web will be a key goal for the Cosmic Origins Spectrograph (COS), a new science instrument that astronauts plan to install on Hubble during Servicing Mission 4 later this year."COS will allow us to make more robust and more detailed core samples of the cosmic web," Shull said. "We predict that COS will find considerably more of the missing baryonic matter.""Our goal is to confirm the existence of the cosmic web by mapping its structure, measuring the amount of heavy metals found in it, and measuring its temperature. Studying the cosmic web gives us information on how galaxies built up over time."The COS team hopes to observe 100 additional quasars and build up a survey of more than 10,000 hydrogen filaments in the cosmic web, many laced with heavy elements from early stars. Copyright http://hubblesite.org/newscenter/archive/releases/2008/20/full/cosmic web

13-02-08

Jong, helder sterrenstelsel ontdekt van 12,8 miljoen jaar oud.

Nasa’s Hubble en Spitzer ruimtetelescopen hebben één van de jongste en helderste sterrenstelsels ontdekt die zo’n 700 miljoen jaar na de Big Bang ontstaan is.Astronoom Garth Illingworth van the University of California, Santa Cruz zegt dat de leden van het team verbaasd waren dat ze dergelijk helder sterrenstelsel van 12,8 miljard jaar oud gevonden hebben. Het stelsel kan meer informatie geven over het ontstaan en evolutie van dergelijke sterrenstelsels. De James Webb ruimtetelescoop die gelanceerd wordt in 2013 zal zeker het object aan verder onderzoek onderwerpen.youngestgalaxies

22-01-08

Hubble Ruimtetelescoop ontdekt donkere materie

DONKEREMATERIEOpnames van de Hubble Ruimtetelescoop hebben een spookachtige ring van donkere materie aangetoond die zeer lang geleden gevormd werd tijdens een geweldige botsing tussen twee massieve melkwegclusters. De ontdekking van de ring is een van de sterkste bewijzen dat donkere materie bestaat. Astronomen hebben lange tijd gedacht dat die donkere materie een extra bron van zwaartekracht is bij melkwegclusters. Men weet niet juist wat donkere materie is. Men veronderstelt dat het een soort van elementaire deeltjes zijn. De ontdekking was onverwacht...Het gebeurde toen men de melkwegcluster Cl 0024 +17 (ZwCl 0024 +1652), gelegen op 5 miljard lichtjaar vanaf de Aarde bekeek. Het bestaan van de donkere materie kan afgeleid worden door het observeren van hoe de zwaartekracht het licht van verre melkwegstelsels afbuigt.Donkere materie vormt samen met donkere energie het grootste deel van het heelal. Gewone materie, zoals sterren en planeten, omvat slechts een paar procent. Donkere materie opsporen is geen gemakkelijke opgave omdat er geen lichtbron of lichtweerkaatsing is. Astronomen kunnen alleen detecteren hoe de zwaartekracht het licht beïnvloedt.