Archive for June 11, 2013

Ten Years At Mars: New Global Views Plot The Red Planet’s History

New global maps of Mars released on the 10th anniversary of the launch of ESA’s Mars Express trace the history of water and volcanic activity on the Red Planet, and identify sites of special interest for the next generation of Mars explorers.

The unique atlas comprises a series of maps showing the distribution of minerals formed in water, by volcanic activity, and by weathering to create the dust that makes Mars red. They create a global context for the dominant geological processes that sculpted the planet we see today.

The maps were built from ten years of data collected by the OMEGA mineralogical mapper on Mars Express, which determines the mineral composition of the martian surface by analysing the spectrum of reflected sunlight.

“The history of Mars is encoded in its minerals,” says Alvaro Giménez, ESA’s Director of Science and Robotic Exploration.

Full Story:


New Observations Of A “Dust Trap” Around A young Star Solve Long-Standing Planet Formation Mystery

ALMA image of dust trap around Oph IRS 48. Credit: ALMA (ESO/NAOJ/NRAO) / Nienke van der Marel

ALMA image of dust trap around Oph IRS 48. Credit: ALMA (ESO/NAOJ/NRAO) / Nienke van der Marel

Astronomers now know that planets around other stars are plentiful. But they do not fully understand how they form and there are many aspects of the formation of comets, planets and other rocky bodies that remain a mystery. However, new observations exploiting the power of ALMA are now answering one of the biggest questions: how do tiny grains of dust in the disc around a young star grow bigger and bigger — to eventually become rubble, and even boulders well beyond a metre in size?

Computer models suggest that dust grains grow when they collide and stick together. However, when these bigger grains collide again at high speed they are often smashed to pieces and sent back to square one. Even when this does not happen, the models show that the larger grains would quickly move inwards because of friction between the dust and gas and fall onto their parent star, leaving no chance that they could grow even further.

Somehow the dust needs a safe haven where the particles can continue growing until they are big enough to survive on their own [1]. Such “dust traps” have been proposed, but there was no observational proof of their existence up to now.

Full Story:

NASA’s Swift Produces Best Ultraviolet Maps Of The Nearest Galaxies

June 11, 2013 1 comment

UV image credit: NASA/Swift/S. Immler (Goddard) and M. Siegel (Penn State)

UV image credit: NASA/Swift/S. Immler (Goddard) and M. Siegel (Penn State)

Astronomers at NASA and Pennsylvania State University have used NASA’s Swift satellite to create the most detailed ultraviolet light surveys ever of the Large and Small Magellanic Clouds, the two closest major galaxies.

“We took thousands of images and assembled them into seamless portraits of the main body of each galaxy, resulting in the highest-resolution surveys of the Magellanic Clouds at ultraviolet wavelengths,” said Stefan Immler, who proposed the program and led NASA’s contribution from the agency’s Goddard Space Flight Center in Greenbelt, Md.

“Prior to these images, there were relatively few UV observations of these galaxies, and none at high resolution across such wide areas, so this project fills in a major missing piece of the scientific puzzle,” said Michael Siegel, lead scientist for Swift’s Ultraviolet/Optical Telescope (UVOT) at the Swift Mission Operations Center at the university in State College, Pa.

Full Story, Video and Images:

Hubble Maps 3-D Structure Of Ejected Material Around Erupting Star

A flash of light from a stellar outburst has been used to probe for the first time the 3-D structure of material ejected by an erupting nova.

Astronomers used NASA’s Hubble Space Telescope to observe the light emitted by the close double-star system T Pyxidis, or T Pyx, a recurrent nova, during its latest outburst in April 2011. Contrary to some predictions, the astronomers were somewhat surprised to find that the ejecta from earlier outbursts stayed in the vicinity of the star and formed a disk of debris around the nova. The discovery suggests that material continues expanding outward along the system’s orbital plane, but it does not escape the system.

“We fully expected this to be a spherical shell,” says Arlin Crotts of Columbia University in New York City, a member of the research team. “This observation shows that it is a disk, and it is populated with fast-moving ejecta from previous outbursts.”

Full Story:

Sun-Grazing Comet Flies Deep Into Solar Corona, Adding Fidelity To Existing Solar Magnetic Field Models

On December 15-16, 2011, a Sun-grazing comet, designated Lovejoy (C/2011 W3), passed deep within the hot solar atmosphere – the corona – effectively probing a region that could never be visited by spacecraft because of the intense heat radiating from the nearby solar surface. In a paper published today in the journal Science, researchers from several institutions – including the Solar & Astrophysics Lab at the Lockheed Martin [NYSE: LMT] Advanced Technology Center (ATC) in Palo Alto, Calif. – have analyzed extreme-ultraviolet observations (EUV) from three sun-watching spacecraft and identified characteristics of the embedded magnetic fields through which the comet passed.

“The corona shapes most of the space weather storms that impact Earth,” said Dr. Karel Schrijver of the Lockheed Martin ATC, co-author of the Science paper, and principal investigator of the Atmospheric Imaging Assembly (AIA) onboard NASA’s Solar Dynamics Observatory (SDO). “The only part of the corona that we can study with observatories is the part we can see.

“Comet Lovejoy flew through the corona down to a height of only 10% of the solar diameter, where there is almost nothing that we can image,” continued Schrijver. “It is essentially an ultra high vacuum with a density even lower than where the International Space Station orbits Earth. But when Lovejoy flew through, material from its warming surface evaporated, forming a tail that then lit up brightly enough to be observed. The wiggling of its direction and the changes in intensity and persistence of that tail allowed us to map the otherwise invisible magnetic field.

Full Story:

Stars Don’t Obliterate Their Planets (Very Often)

Stars have an alluring pull on planets, especially those in a class called hot Jupiters, which are gas giants that form farther from their stars before migrating inward and heating up.

Now, a new study using data from NASA’s Kepler Space Telescope shows that hot Jupiters, despite their close-in orbits, are not regularly consumed by their stars. Instead, the planets remain in fairly stable orbits for billions of years, until the day comes when they may ultimately get eaten.

“Eventually, all hot Jupiters get closer and closer to their stars, but in this study we are showing that this process stops before the stars get too close,” said Peter Plavchan of NASA’s Exoplanet Science Institute at the California Institute of Technology, Pasadena, Calif. “The planets mostly stabilize once their orbits become circular, whipping around their stars every few days.”

The study, published recently in the Astrophysical Journal, is the first to demonstrate how the hot Jupiter planets halt their inward march on stars. Gravitational, or tidal, forces of a star circularize and stabilize a planet’s orbit; when its orbit finally become circular, the migration ceases.

Full Story: