September 6, 2006, 9:56 PM CT

No Proof For Dark Matter Proof

When Douglas Clowe of the University of Arizona in Tucson announced on 21 August that his team had "direct proof of dark matter's existence", it seemed the issue had been settled. Now proponents of the so-called modified theories of gravity, who explain the motion of stars and galaxies without resorting to dark matter, have hit back and are suggesting that Clowe's team has jumped the gun.

"One should not draw premature conclusions about the existence of dark matter without a careful analysis of alternative gravity theories," writes John Moffat, of the University of Waterloo in Ontario, Canada, who pioneered an alternative theory of gravity known as MOG (www.arxiv.org/astro-ph/0608675).

The controversy centres on the pattern of gravitational lensing, or the bending of light, around the Bullet cluster of galaxies, which formed from the collision of two clusters. While most of the Bullet cluster's visible mass lies in a pool of hot gas near the centre, galaxies can also be seen on either side. Clowe's study of lensing indicates that most of the mass is contained in the two lobes, rather than in the pool of gas. The team says this is evidence of dark matter surrounding the galaxies.

Moffat claims that his MOG theory can explain the Bullet cluster without an ounce of dark matter. In MOG, gravity acts as predicted by Newton's inverse square law up to a certain distance from the gravitating mass, after which it gets a little stronger. In the Bullet cluster, the complex arrangement of galaxies and hot gas combines to make gravity strongest in the lobes, so that is where the lensing would be most apparent. Moffat has worked this out for the Bullet cluster using a.........

Posted by: Kevin      Permalink         Source

September 5, 2006, 9:21 PM CT

Stages Of Star Formation

The Japan Aerospace Exploration Agencys (JAXA) AKARI Infrared Space Telescope has returned spectacular new images showing the earliest stages of star formation and the final stages of the death of stars in our Galaxy. The results released recently (August 30th) depict scenes showing infrared pictures of the birth and death of stars. The quality of this data has delighted the Japanese, UK and Dutch Team members and shown the power of this new telescope for studies of astronomical objects of our own Galaxy.

AKARI was launched on February 21st 2006 from Uchinoura Space Centre, Japan, and is now about half way to completing its first map of the sky in infrared light. UK astronomers, who are collaborating with Japanese, Korean and Dutch Partners in the far-infrared all sky survey experiment on the satellite, have been supported by the Particle Physics and Astronomy Research Council (PPARC) to develop the software used to process the data returned from the telescope. The European Space Agency contributes technical and ground station support in return for access to some of the observations.

Star-birth in Cepheus.

An area of approximately 3 square degrees around the reflection nebula IC 1396 in the constellation Cepheus has been observed by the AKARI Infrared Camera (IRC) in its scanning mode at wavelengths of 9 and 18 micrometres (10-6 metres).........

Posted by: Brooke      Permalink         Source

September 3, 2006, 7:08 AM CT

Life of Stardust

A new image from NASA's Spitzer Space Telescope is helping astronomers understand how stardust is recycled in galaxies.

The cosmic portrait shows the Large Magellanic Cloud, a nearby dwarf galaxy named after Ferdinand Magellan, the seafaring explorer who observed the murky object at night during his fleet's historic journey around Earth. Now, nearly 500 years after Magellan's voyage, astronomers are studying Spitzer's view of this galaxy to learn more about the circular journey of stardust, from stars to space and back again.

The Large Magellanic Cloud is like an open book," said Dr. Margaret Meixner of the Space Telescope Science Institute, Baltimore, Md. "We can see the entire lifecycle of matter in a galaxy in this one snapshot." Meixner is lead author of a paper on the findings to appear in the November 2006 issue of the Astronomical Journal.

The vibrant false-color image, a mosaic of approximately 300,000 individual frames, shows a central blue sea of stars amidst lots of colorful, choppy waves of dust. It can be viewed at: http://www.spitzer.caltech.edu/Media/releases/ssc2006-17/ssc2006-17b.shtml.

Space dust is important for making stars, planets and even people. The tiny particles -- flecks of minerals, ices and carbon-rich molecules -- are everywhere in the universe. Developing stars and solar systems are constantly consuming dust, while older stars shed dust back into space, where it will one day provide the ingredients for new generations of stars.........

Posted by: Brooke      Permalink         Source

September 3, 2006, 6:56 AM CT

NASA Names Orion Contractor

Lessons from the past are guiding NASA's next step into the future, as the space agency prepares to replace the space shuttle with an Apollo-style vehicle for human explorers.

The vehicle is Orion, named for one of the brightest and most recognizable star formations in the sky. It will be a multi-purpose capsule -- the central member of a family of spacecraft and shuttle-derived launchers that NASA's Constellation Program is developing to carry astronauts back to the moon and later to Mars. The first flight with astronauts aboard is planned for no later than 2014. Orion's first flight to the moon is planned for no later than 2020.

NASA has selected Lockheed Martin Corp. as the prime contractor to design, develop, and build Orion, America's spacecraft for a new generation of explorers.

The Orion crew capsule will carry astronauts back to the moon and later to Mars. The first flight with astronauts aboard is planned for no later than 2014. Orion's first flight to the moon is planned for no later than 2020.

In what amounts to one of the most significant NASA procurements in more than 30 years, two industry teams, Northrop Grumman/Boeing and Lockheed Martin, spent the past 13 months refining concepts, analyzing requirements and sketching designs for Orion. On Thursday, managers of NASA's Exploration Systems Mission Directorate revealed that Lockheed Martin Corp. of Bethesda, Md., has been chosen to build it.........

Posted by: Brooke      Permalink         Source

August 28, 2006, 9:58 PM CT

Rare high-altitude clouds found on Mars

Planetary scientists have discovered the highest clouds above any planetary surface. They found them above Mars using the SPICAM instrument on board ESA's Mars Express spacecraft. The results are a new piece in the puzzle of how the Martian atmosphere works.

Until now, scientists had been aware only of the clouds that hug the Martian surface and lower reaches of the atmosphere. Thanks to data from the SPICAM Ultraviolet and Infrared Atmospheric Spectrometer onboard Mars Express, a fleeting layer of clouds have been discovered at an altitude between 80 and 100 kilometres. The clouds are most likely composed of carbon dioxide.

SPICAM made the discovery by observing distant stars just before they disappeared behind Mars. By looking at the effects on the starlight as it travelled through the Martian atmosphere, SPICAM built up a picture of the molecules at different altitudes. Each sweep through the atmosphere is called a profile.

The first hints of the new cloud layer came when certain profiles showed that the star dimmed noticeably when it was behind the 90100 kilometre high atmospheric layer. Although this happened in only one percent of the profiles, by the time the team had collected 600 profiles, they were confident that the effect was real.

"If you wanted to see these clouds from the surface of Mars, you would probably have to wait until after sunset" says Franck Montmessin, a SPICAM scientist with Service d'Aeronomie du CNRS, Verrires-le-Buisson, France, and lead author of the results. This is because the clouds are very faint and can only be seen reflecting sunlight against the darkness of the night sky. In that respect, they look similar to the mesospheric clouds, also known as noctilucent clouds, on Earth. These occur at 80 kilometres altitude above our planet, where the density of the atmosphere is similar to that of Mars' at 35 kilometres. The newly discovered Martian clouds therefore occur in a much more rarefied atmospheric location.........

Posted by: Brooke      Permalink         Source

August 24, 2006, 10:01 PM CT

One-Two Particle Punch Poses Greater Risk

It doesn't just matter how much radiation an astronaut is exposed to, time and the order in which charged particles strike human cells are important factors as well. That's the main finding of a study simulating radiation exposure conducted at the U.S. Department of Energy's Brookhaven National Laboratory and published in the September 2006 edition of Radiation Research. In the study, human cells were three times more likely to develop properties similar to those in the initial stages of cancer when they were exposed to two types of high-energy particles in a short period of time.

The radiation field in space contains high levels of high-energy protons and much lower levels of high atomic number, high-energy (HZE) particles such as iron and titanium.

"Most people studying the effects of space radiation have looked at the effects of just one type of particle, either the protons or the HZE particles," said Brookhaven biologist Betsy Sutherland, the paper's lead author. "This is one of the first studies to try to imitate real space radiation conditions closely, where, on average, a cell will be hit by a proton first and then by an HZE particle. We decided to examine what this does to human cells".

To test the effect of dual-particle irradiation, Sutherland's team at the NASA Space Radiation Laboratory, a facility built at Brookhaven Lab specifically for space radiation studies, first exposed normal human cells to a beam of protons. Then, anywhere from 2.5 minutes to 48 hours later, they exposed the cells to iron or titanium particles.........

Posted by: Brooke      Permalink         Source

August 24, 2006, 9:20 PM CT

Smackdown in the Lake of Excellence

The European Space Agency's Smart-1 mission ends on September 3rd 2006. Appropriately for such a successful mission, its final resting place will be an area of the Moon known as the 'Lake of Excellence'. During its 3-year lifespan, Europe's first mission to the Moon has advanced both lunar science and the technology that underpins it.

UK participation in Smart-1 was funded by the Particle Physics and Astronomy Research Council with additional funds from the British National Space Centre. PPARC CEO Professor Keith Mason hailed the mission's success "Smart-1 has been amazingly successful, both in proving new technologies that will help shape how Europe explores space in the future and in dramatically increasing our understanding of the Moon. With Smart-1 UK and European scientists and engineers have made a significant contribution to future international lunar exploration programmes".

Scientific Success

Smart-1's scientific instruments have subjected the Moon to new scrutiny and worked so well that the mission was extended by an additional year. The UK instrument D-CIXS (a demonstrator compact X-ray spectrometer) has obtained mineral maps of the Moon's composition, looking at the distribution of calcium, magnesium, aluminium, silicon and iron. These will help to determine if the Moon was formed from terrestrial debris after a collision or mostly from a planet-sized object that crashed into the Earth.........

Posted by: Brooke      Permalink         Source

August 24, 2006, 9:10 PM CT

Pluto is not a planet

The "United Nations" of astronomers has announced a new definition of what a planet is, slightly revising the description preferred by an international panel including an MIT professor that was tasked with the challenge.

Members of the International Astronomical Union (IAU) voted on August 24 to define a planet as an object that is in orbit around the sun, is large enough for its own gravity to pull it into a nearly spherical shape, and has cleared the neighborhood around its orbit -- in other words, it has no other large bodies crossing its path.

The third condition was added to the draft definition of a planet submitted to the IAU about a week ago by MIT's Richard Binzel and colleagues. Binzel, a professor of planetary science in the Department of Earth, Atmospheric and Planetary Sciences, took responsibility for presenting the final version of the resolution at the time of the final vote.

This means that while Pluto will still be considered a planet, it will technically be a dwarf planet because it is smaller than Mercury. It will be joined in that category by Ceres and 2003 UB313 (a temporary name for an object discovered only three years ago). More "dwarf planets" are expected to be announced by the IAU in the coming months and years.

As a result of the new definition, our solar system now contains eight planets: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, plus the three dwarf planets led by Pluto.........

Posted by: Brooke      Permalink         Source

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