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TW Hydrae: There’s More To Astronomers’ Favorite Planetary Nursery Than Previously Thought

February 6, 2013 Leave a comment

Artist's impression. Image credit: Axel M. Quetz (MPIA)

Artist’s impression. Image credit: Axel M. Quetz (MPIA)

Using ESA’s Herschel Space Telescope, astronomers including Thomas Henning from the Max Planck Institute for Astronomy in Heidelberg have used a new method to determine the mass of the planetary nursery around the star TW Hydrae. At a distance of merely 176 light-years from Earth, this is the closest star that is currently forming new planets – hence one of the most important objects for astronomers studying planet formation. The precise new measurement shows a much larger mass for TW Hydrae’s disk than in previous studies, indicating that the system could be forming planets similar to those of our own Solar System. The study is published in the January 31 issue of the journal Nature.

TW Hydrae has one of the most frequently observed protoplanetary disks of all, and its observations are a key to testing current models of planet formation. That’s why it was especially vexing that one of the fundamental parameters of the disk remained fairly uncertain: The total mass of the molecular hydrogen gas contained within the disk. This mass value is crucial in determining how many and what kinds of planets can be expected to form.

Full Story: http://www.mpia.de/Public/menu_q2e.php?Aktuelles/PR/2013/PR130130/PR_130130_en.html
Also: http://www.ns.umich.edu/new/releases/21145-how-planets-form-astronomers-weigh-a-protoplanetary-disk-with-unprecedented-accuracy

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Ridges On Mars Suggest Ancient Flowing Water

February 6, 2013 Leave a comment

Credit: NASA Mars Reconnaissance Orbiter

Credit: NASA Mars Reconnaissance Orbiter

Networks of narrow ridges found in impact craters on Mars appear to be the fossilized remnants of underground cracks through which water once flowed, according to a new analysis by researchers from Brown University.

The study, in press in the journal Geophysical Research Letters, bolsters the idea that the subsurface environment on Mars once had an active hydrology and could be a good place to search for evidence of past life. The research was conducted by Lee Saper, a recent Brown graduate, with Jack Mustard, professor of geological sciences.

The ridges, many of them hundreds of meters in length and a few meters wide, had been noted in previous research, but how they had formed was not known. Saper and Mustard thought they might once have been faults and fractures that formed underground when impact events rattled the planet’s crust. Water, if present in the subsurface, would have circulated through the cracks, slowly filling them in with mineral deposits, which would have been harder than the surrounding rocks. As those surrounding rocks eroded away over millions of years, the seams of mineral-hardened material would remain in place, forming the ridges seen today.

Full Story: http://news.brown.edu/pressreleases/2013/01/marswater

When A Planet Behaves Like A Comet

February 6, 2013 Leave a comment

A comparison of the ionosphere of Venus under different solar wind conditions. Credit: ESA/Wei et al. (2012)

A comparison of the ionosphere of Venus under different solar wind conditions. Credit: ESA/Wei et al. (2012)

ESA’s Venus Express has made unique observations of Venus during a period of reduced solar wind pressure, discovering that the planet’s ionosphere balloons out like a comet’s tail on its nightside. The ionosphere is a region of weakly electrically charged gas high above the main body of a planet’s atmosphere. Its shape and density are partly controlled by the internal magnetic field of the planet.

For Earth, which has a strong magnetic field, the ionosphere is relatively stable under a range of solar wind conditions. By comparison, Venus does not have its own internal magnetic field and relies instead on interactions with the solar wind to shape its ionosphere. The extent to which this shaping depends on the strength of the solar wind has been controversial, but new results from Venus Express reveal for the first time the effect of a very low solar wind pressure on the ionosphere of an unmagnetised planet.

As this significantly reduced solar wind hit Venus, Venus Express saw the planet’s ionosphere balloon outwards on the planet’s ‘downwind’ nightside, much like the shape of the ion tail seen streaming from a comet under similar conditions.

Full Story: http://www.esa.int/Our_Activities/Space_Science/When_a_planet_behaves_like_a_comet
Also: http://sci.esa.int/science-e/www/object/index.cfm?fobjectid=51315

Stellar Effervescence On Display

February 6, 2013 Leave a comment

DEM L50: A superbubble located in the Large Magellanic Cloud about 160,000 light years from Earth.Credit: X-ray: NASA/CXC/Univ of Michigan/A.E.Jaskot, Optical: NOAO/CTIO/MCELS

DEM L50: A superbubble located in the Large Magellanic Cloud about 160,000 light years from Earth.
Credit: X-ray: NASA/CXC/Univ of Michigan/A.E.Jaskot, Optical: NOAO/CTIO/MCELS

This composite image shows the superbubble DEM L50 (a.k.a. N186) located in the Large Magellanic Cloud about 160,000 light years from Earth. Superbubbles are found in regions where massive stars have formed in the last few million years. The massive stars produce intense radiation, expel matter at high speeds, and race through their evolution to explode as supernovas . The winds and supernova shock waves carve out huge cavities called superbubbles in the surrounding gas.

Like another superbubble in the LMC, N44, DEM L50 gives off about 20 times more X-rays than expected from standard models for the evolution of superbubbles. A Chandra study published in 2011 showed that there are two extra sources of the bright X-ray emission: supernova shock waves striking the walls of the cavities, and hot material evaporating from the cavity walls.

Full Story: http://www.chandra.harvard.edu/photo/2013/deml50/

Thawing ‘Dry Ice’ Drives Groovy Action On Mars

February 6, 2013 Leave a comment

Image Credit: NASA/JPL-Caltech/Univ. of Arizona

Image Credit: NASA/JPL-Caltech/Univ. of Arizona

Researchers using NASA’s Mars Reconnaissance Orbiter see seasonal changes on far-northern Martian sand dunes caused by warming of a winter blanket of frozen carbon dioxide.

Earth has no naturally frozen carbon dioxide, though pieces of manufactured carbon-dioxide ice, called “dry ice,” sublime directly from solid to gas on Earth, just as the vast blankets of dry ice do on Mars. A driving factor in the springtime changes where seasonal coverings of dry ice form on Mars is that thawing occurs at the underside of the ice sheet, where it is in contact with dark ground being warmed by early-spring sunshine through translucent ice. The trapped gas builds up pressure and breaks out in various ways.

Transient grooves form on dunes when gas trapped under the ice blanket finds an escape point and whooshes out, carrying out sand with it. The expelled sand forms dark fans or streaks on top of the ice layer at first, but this evidence disappears with the seasonal ice, and summer winds erase most of the grooves in the dunes before the next winter. The grooves are smaller features than the gullies that earlier research linked to carbon-dioxide sublimation on steeper dune slopes.

Full Story: http://www.jpl.nasa.gov/news/news.php?release=2013-034
Also: http://www.psi.edu/news/press-releases#marscotwo

Red Explosions Reveal Secret Life Of Binary Stars

February 6, 2013 Leave a comment

Hubble space telescope images show an expanding burst of light from a red supergiant star. Image: NASA/ESA

Hubble space telescope images show an expanding burst of light from a red supergiant star. Image: NASA/ESA

A University of Alberta professor has revealed the workings of a celestial event involving binary stars that produce an explosion so powerful its luminosity ranks close to that of a supernova, an exploding star.

Theoretical astrophysicist Natalia Ivanova says researchers have long debated about what happens when binary stars, two stars that orbit one another, come together in a “common envelope.” “When this dramatic cannibalizing event ends there are two possible outcomes: the two stars merge into a single star or an initial binary transforms into an exotic short-period one,” said Ivanova. The event is believed to take anywhere from a dozen days to a few hundred years to complete—an extremely fast time frame in terms of celestial events, Ivanova says.

More than half of all stars in the universe are binary stars, but Ivanova says it was not known what a common envelope event would look like until now.

Full Story: http://www.news.ualberta.ca/article.aspx?id=37D4798A034F42F39CDC8080F7037942

Baffling Pulsar Leaves Astronomers In The Dark

February 6, 2013 Leave a comment

New observations of a highly variable pulsar using ESA’s XMM-Newton are perplexing astronomers. Monitoring this pulsar simultaneously in X-rays and radio waves, astronomers have revealed that this source, whose radio emission is known to ‘switch on and off’ periodically, exhibits the same behaviour, but in reverse, when observed at X-ray wavelengths. It is the first time that a switching X-ray emission has been detected from a pulsar, and the properties of this emission are unexpectedly puzzling. As no current model is able to explain this switching behaviour, which occurs within only a few seconds, these observations have reopened the debate about the physical mechanisms powering the emission from pulsars.

“There is a general agreement about the origin of the radio emission from pulsars: it is caused by highly energetic electrons, positrons and ions moving along the field lines of the pulsar’s magnetic field, and we see it pulsate because the rotation and magnetic axes are misaligned,” explains Wim Hermsen from SRON, the Netherlands Institute for Space Research in Utrecht, The Netherlands. “How exactly the particles are stripped off the neutron star’s surface and accelerated to such high energy, however, is still largely unclear,” he adds.

Full Story: http://sci.esa.int/science-e/www/object/index.cfm?fobjectid=51314
Also: http://www.astron.nl/about-astron/press-public/news/chameleon-pulsar-baffles-astronomers/chameleon-pulsar-baffles-astro-0