November 29, 2007, 10:27 PM CT

Scientists solve cosmological puzzle

Hamilton, ON. November 29, 2007 Scientists using supercomputer simulations have exposed a very violent and critical relationship between interstellar gas and dark matter when galaxies are born one that has been largely ignored by the current model of how the universe evolved.

The findings, published recently in Science, solve a longstanding problem of the widely accepted model Cold Dark Matter cosmology which suggests there is much more dark matter in the central regions of galaxies than actual scientific observations suggest.

This standard model has been hugely successful on the largest of scalesthose above a few million light-yearsbut suffers from several persistent difficulties in predicting the internal properties of galaxies, says Sergey Mashchenko, research associate in the Department of Physics & Astronomy at McMaster University. One of the most troublesome issues concerns the mysterious dark matter that dominates the mass of most galaxies.

Supercomputer cosmological simulations prove that indeed, this problem can be resolved. Scientists modeled the formation of a dwarf galaxy to illustrate the very violent processes galaxies suffer at their births, a process in which dense gas clouds in the galaxy form massive stars, which, at the ends of their lives, blow up as supernovae......... Posted by: Sean      Read more         Source

November 27, 2007, 10:27 PM CT

Researchers examine Einstein's theories on the universe

Einsteins self-proclaimed biggest blunder his postulation of a cosmological constant (a force that opposes gravity and keeps the universe from collapsing) may not be such a blunder after all, as per the research of an international team of researchers that includes two Texas A&M University researchers.

The team is working on a project called ESSENCE that studies supernovae (exploding stars) to figure out if dark energy the accelerating force of the universe is consistent with Einsteins cosmological constant.

Texas A&M scientists Nicholas Suntzeff and Kevin Krisciunas are part of the project, which began in October of 2002 and is scheduled to end next month after achieving its goal of discovering and studying 200 supernovae. The team uses a 4-meter diameter telescope in Chile during the observing season of October to December to find the supernovae.

In 1917, Einstein was working on his Theory of General Relativity and was trying to come up with an equation that describes a static universe one that stands still and does not collapse under the force of gravity in a big crunch. In order to keep the universe static in his theory, Einstein introduced a cosmological constant a force that opposes the force of gravity.

Then, 12 years later, Edwin Hubble discovered that the universe is not static it is actually expanding. So Einstein scrapped his idea of a cosmological constant and dismissed it as his biggest blunder......... Posted by: Sean      Read more         Source

November 27, 2007, 9:05 PM CT

Voyager 2 will reach major milestone in space

Using a computer model simulation, Haruichi Washimi, a physicist at UC Riverside, has predicted when the interplanetary spacecraft Voyager 2 will cross the termination shock, the spherical shell around the solar system that marks where the solar wind slows down to subsonic speed.

As per Washimis simulations, the spacecraft is set to cross the termination shock in late 2007-early 2008. To make this forecast, Washimi and colleagues used data from Voyager 2 and performed a global magneto-hydrodynamic simulation a method that allows for precise and quantitative predictions of geomagnetic disturbances caused by solar activities.

Because Voyager 2s crossing of the shock is expected to be an abrupt and relatively brief event, researchers are working to ensure that the most is made of the opportunity. With an idea of when the spacecraft will cross the shock, they are better able to maximize coverage of the crossing.

Study results appear in the Dec. 1 issue of The Astrophysical Journal

Washimis model has predicted the location of a boundary that is approximately 90 times farther from the sun than is the Earth, to within a few percent, said Gary Zank, the director of the Institute of Geophysics and Planetary Physics and one of the coauthors of the research paper. This is truly remarkable given the enormous complexity of the physics involved, the temporal and spatial scales involved, and the variability of the solar wind conditions......... Posted by: Sean      Read more         Source

November 18, 2007, 9:05 PM CT

The Moon and Europe

As Rosetta closed in on Earth, swung by and then left on its course again, several instruments on the spacecraft were busy taking snaps. As it swung away, the OSIRIS camera also caught glimpses of the Moon.

The Moon was imaged with the OSIRIS Narrow Angle Camera (NAC) at 07:36 CET, about nine hours after Rosetta's closest approach to Earth.

OSIRIS has been designed to image faint objects, so a neutral density filter was placed in the optical path to reduce the sensitivity of the camera to one-fiftieth. The above image was acquired through the far-focus red filter of the camera (750 nanometres).

The below image of Earth is targeted roughly at Greece. It was taken with the OSIRIS Wide Angle Camera (WAC) during the swing-by......... Posted by: Sean      Read more         Source

November 15, 2007, 10:35 PM CT

Hubble zooms in on heart of mystery comet

The NASA/ESA Hubble Space Telescope has probed the bright core of Comet 17P/Holmes which, to the delight of sky watchers, mysteriously brightened by nearly a million-fold in a 24-hour period beginning October 23, 2007.

Astronomers have used Hubble's powerful resolution to study Comet Holmes' core for clues about how the comet brightened. The orbiting observatory's Wide Field Planetary Camera 2 (WFPC2) monitored the comet for several days, snapping images on 29 Oct., 31 Oct. and 4 Nov. Hubble's crisp "eye" can see details as small as 54 kilometres across, providing the sharpest view yet of the source of the spectacular brightening.

The Hubble image at right, taken on 4 Nov., shows the heart of the comet. The central portion of the image has been specially processed to highlight variations in the dust distribution near the nucleus. About twice as much dust lies along the east-west direction (the horizontal direction) as along the north-south direction (the vertical direction), giving the comet a "bow tie" appearance.

The composite colour image at left, taken Nov. 1 by the amateur astronomer Alan Dyer, shows the complex structure of the entire coma, consisting of concentric shells of dust and a faint tail emanating from the comet's right side.

The nucleus - the small solid body that is the source of the comet's activity - is still swaddled in bright dust, even 12 days after the spectacular outburst. "Most of what Hubble sees is sunlight scattered from microscopic particles," explained Hal Weaver of The Johns Hopkins University Applied Physics Laboratory of Laurel, Maryland in the USA, who led the Hubble investigation. "But we may finally be starting to detect the emergence of the nucleus itself in this final Hubble image"......... Posted by: Sean      Read more         Source

November 15, 2007, 10:25 PM CT

Planets forming in Pleiades star cluster

Rocky terrestrial planets, perhaps like Earth, Mars or Venus, appear to be forming or to have recently formed around a star in the Pleiades ("seven sisters") star cluster, the result of "monster collisions" of planets or planetary embryos.

Astronomers using the Gemini Observatory in Hawaii and the Spitzer Space Telescope report their findings in an upcoming issue of the Astrophysical Journal, the premier journal in astronomy.

"This is the first clear evidence for planet formation in the Pleiades, and the results we are presenting may well be the first observational evidence that terrestrial planets like those in our solar system are quite common," said Joseph Rhee, a UCLA postdoctoral scholar in astronomy and lead author of the research.

The Pleiades star cluster, in the constellation Taurus, is well-known in a number of cultures. It is named for the seven daughters of Atlas and Pleione, who were placed by Zeus among the stars in Greek mythology and is cited in the Bible "Can you bind the beautiful Pleiades" Can you loose the cords of Orion"" (Job 38:31). The automaker Subaru's name is the Japanese word for the Pleiades, Rhee said.

The Pleiades is probably the best known star cluster and the most striking to the naked eye. "You've seen it a number of times, and it's now easily visible in the evening sky," said research co-author Benjamin Zuckerman, UCLA professor of physics and astronomy......... Posted by: Sean      Read more         Source

November 14, 2007, 9:50 PM CT

How to make the brightest supernova eve

A supernova observed last year was so bright--about 100 times as luminous as a typical supernova--that it challenged the theoretical understanding of what causes supernovae. But Stan Woosley, professor of astronomy and astrophysics at the University of California, Santa Cruz, had an idea that he thought could account for it--an extremely massive star that undergoes repeated explosions. When Woosley and two colleages worked out the detailed calculations for their model, the results matched the observations of the supernova known as SN 2006gy, the brightest ever recorded.

The scientists describe the model in a paper would be reported in the November 15 issue of the journal Nature. Woosley's coauthors are Sergei Blinnikov, a visiting researcher at UCSC from the Institute of Theoretical and Experimental Physics in Moscow, and Alexander Heger of Los Alamos National Laboratory.

"This was a stupendously bright supernova, and we think we have the leading model to explain it. It's a new mechanism for making a supernova, and for doing it again and again in the same star," Woosley said. "We commonly think of a supernova as the death of a star, but in this case the same star can blow up half a dozen times".

The first explosion throws off the star's outer shell and produces a not-very-bright supernova-like display. The second explosion puts another supernova's worth of energy into a second shell, which expands at high velocity until it collides with the first shell, producing an extraordinarily brilliant display......... Posted by: Sean      Read more         Source

November 13, 2007, 9:50 PM CT

Rosetta right on track for Earth swing-by

Preparations for Rosetta's Earth swing-by scheduled for tonight, 21:57 CET, are well underway. The manoeuvre executed on 18 October 2007 has been accurate enough to not require any additional trajectory corrections today.

This means that the most critical operational procedures for the success of the swing-by are now over. However, the operations teams are constantly on the watch to make sure that nothing disturbs the spacecraft's velocity and direction and that its stability is maintained throughout the observations.

The core observations will start only in the afternoon, but the instruments are already being prepared for the delicate procedures. The spacecraft has been pointed to certain areas in the sky for calibration and this will continue for about 24 hours. During the swing-by, Rosetta will first point to Earth and will observe the Earth-Moon system as a whole afterwards......... Posted by: Sean      Read more         Source

November 13, 2007, 9:49 PM CT

New Planet Discovered Around Nearby Star

Astronomers funded in part by the National Science Foundation (NSF) today announced their discovery of a fifth planet around the nearby star 55 Cancri, making it the only star aside from the sun known to have five planets.

The research results have been accepted for publication in the Astrophysical Journal. Lead author Debra Fischer, assistant professor of astronomy at San Francisco State University, said the fifth planet is within the star's habitable zone, in which water could exist as a liquid. Eventhough the planet is a ball of gas, liquid water could exist on the surface of a moon or on other rocky planets that may yet be found within the zone.

"This work marks an exciting next step in the search for worlds like our own," said Michael Briley, astronomer and director of the stellar astronomy and astrophysics program at NSF. "To go from the first detections of planets around the sun-like stars to finding a full-fledged solar system with a planet in the habitable zone in just 12 years is an amazing accomplishment and a testament to the years of hard work by these investigators".

The unique 55 Cancri system, located 41 light-years away in the direction of the constellation Cancer, resembles our own solar system with a clutch of four inner planets and one giant outer planet, eventhough it's missing an Earth or Mars......... Posted by: Sean      Read more         Source

November 8, 2007, 9:50 PM CT

Most Massive Stellar Black Hole Ever Found

An international team, including astronomers from Tel Aviv University, has uncovered the most massive stellar black hole found to date in a binary system.

Reported in the prestigious journal Nature this week, the research was conducted by an international team including Professor Tsevi Mazeh, who is the director of the Sackler Institute of Astronomy at Tel Aviv University and holds the Oren Family Chair of Experimental Physics, and his Ph.D. student Avi Shporer.

The newly-discovered black hole is about 16 times the mass of our sun and located three million light-years away in a distant galaxy called Messier 33. The finding is unique because the black hole, named M33 X-7, is linked to an uncommonly large companion star (its binary pair), with a mass about 70 times the mass of our sun. The two objects move one around the other in space once every 3.5 days in an everlasting dance.

A stellar black hole is formed from the collapse of the core of a massive star at the end of its life. The collapse creates an intense gravitational force, where not even rays of light can escape its gravitational pull, rendering the phenomenon invisible. Matter transferred from the companion star into the black hole falls into the hole's gravitational attraction and emits X-ray radiation that the astronomers have detected by using special satellites......... Posted by: Sean      Read more         Source