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Archive for February 23, 2013

Stellar Motions In Outer Halo Shed New Light On Milky Way Evolution

February 23, 2013 Leave a comment

Peering deep into the vast stellar halo that envelops our Milky Way galaxy, astronomers using NASA’s Hubble Space Telescope have uncovered tantalizing evidence for the possible existence of a shell of stars that are a relic of cannibalism by our Milky Way.

Hubble was used to precisely measure, for the first time ever, the sideways motions of a small sample of stars located far from the galaxy’s center. Their unusual lateral motion is circumstantial evidence that the stars may be the remnants of a shredded galaxy that was gravitationally ripped apart by the Milky Way billions of years ago. These stars support the idea that the Milky Way grew, in part, through the accretion of smaller galaxies.

“Hubble’s unique capabilities are allowing astronomers to uncover clues to the galaxy’s remote past. The more distant regions of the galaxy have evolved more slowly than the inner sections. Objects in the outer regions still bear the signatures of events that happened long ago,” said Roeland van der Marel of the Space Telescope Science Institute (STScI) in Baltimore, Md.

Full Story: http://hubblesite.org/newscenter/archive/releases/2013/07/full/

ESA Chooses Instruments For Its Jupiter Icy Moons Explorer

February 23, 2013 Leave a comment

The JUpiter ICy moons Explorer mission, JUICE, will carry a total of 11 scientific experiments to study the gas giant planet and its large ocean-bearing moons, ESA announced today.

JUICE is the first Large-class mission in ESA’s Cosmic Vision 2015–2025 programme. Planned for launch in 2022 and arrival at Jupiter in 2030, it will spend at least three years making detailed observations of the biggest planet in the Solar System and three of its largest moons, Ganymede, Callisto and Europa.

These moons are thought to harbour vast water oceans beneath their icy surfaces and JUICE will map their surfaces, sound their interiors and assess their potential for hosting life in their oceans.

Full Story: http://www.esa.int/Our_Activities/Space_Science/ESA_chooses_instruments_for_its_Jupiter_icy_moons_explorer
Also: http://www.bis.gov.uk/ukspaceagency/news-and-events/2013/Feb/uk-led-instrument-selected-for-europes-jupiter-mission
Also: http://www.nasa.gov/home/hqnews/2013/feb/HQ_13-060_JUICE_Instruments.html
Also: http://www.swri.org/9what/releases/2013/juice.htm

Mercury May Have Harbored An Ancient Magma Ocean

February 23, 2013 Leave a comment

Photo: United States Geological Survey

Photo: United States Geological Survey

By analyzing Mercury’s rocky surface, scientists have been able to partially reconstruct the planet’s history over billions of years. Now, drawing upon the chemical composition of rock features on the planet’s surface, scientists at MIT have proposed that Mercury may have harbored a large, roiling ocean of magma very early in its history, shortly after its formation about 4.5 billion years ago.

The scientists analyzed data gathered by MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging), a NASA probe that has orbited the planet since March 2011. Later that year, a group of scientists analyzed X-ray fluorescence data from the probe, and identified two distinct compositions of rocks on the planet’s surface. The discovery unearthed a planetary puzzle: What geological processes could have given rise to such distinct surface compositions?

To answer that question, the MIT team used the compositional data to recreate the two rock types in the lab, and subjected each synthetic rock to high temperatures and pressures to simulate various geological processes. From their experiments, the scientists came up with only one phenomenon to explain the two compositions: a vast magma ocean that created two different layers of crystals, solidified, then eventually remelted into magma that then erupted onto Mercury’s surface.

Full Story: http://web.mit.edu/newsoffice/2013/mercury-may-have-harbored-ancient-magma-ocean-0221.html

A Simple View Of Gravity Does Not Fully Explain The Distribution Of Stars In Crowded Clusters

February 23, 2013 Leave a comment

Gravity remains the dominant force on large astronomical scales, but when it comes to stars in young star clusters the dynamics in these crowded environments cannot be simply explained by the pull of gravity. After analyzing Hubble Space Telescope images of star cluster NGC 1818 in the Large Magellanic Cloud, a satellite galaxy of the Milky Way, researchers at the Kavli Institute for Astronomy and Astrophysics (KIAA) at Peking University in Beijing found more binary star systems toward the periphery of cluster than in the center – the opposite of what they expected. The surprising distribution of binaries is thought to result from complex interactions among stars within young clusters.

In the dynamic environment of a star cluster, high-mass stars are thought to gravitate toward the center of a cluster when they give a ‘kick’ to lower-mass stars and lose energy, explained KIAA Prof. Richard de Grijs, who led the study. This leads them to sink to the cluster center, while the lower-mass stars gain energy and might move to orbits at greater distances from the cluster core. Astronomers call this process “mass segregation.”

However, when the Kavli researchers looked closely at binary star systems within NGC 1818, they found a much more complex picture.

Full Story: http://www.kavlifoundation.org/kavli-news/KIAA-simple-view-gravity-crowded-clusters

Comet Will Be Visible In Northern Hemisphere In March

February 23, 2013 1 comment

Credit: Terry Lovejoy/ Austrailia

Credit: Terry Lovejoy/ Austrailia

Comet Pan-STARRS C/2011 L4, discovered by the Pan-STARRS 1 telescope on Haleakala in June 2011, is expected to become visible to the naked eye in the Northern Hemisphere in March. The comet is currently visible in the Southern Hemisphere.

From about March 7, it will appear above the horizon. To see it, you will need an unobstructed, cloudless view of the western horizon. It is best to pick a dark spot, away from streetlights. Look in the direction of the Sunset just after the Sun has gone down. The comet will be just above the horizon. The twilight sky will make the comet much harder to see than if it were high up in a dark sky, and moonlight will interfere with viewing the comet after March 13. To see the comet’s tails, you may need a pair of binoculars.

Although the brightness of comets is notoriously difficult to predict ahead of time, scientists expect this comet will have a brightness similar to that of the stars in the bowl of the Big Dipper or Orion’s belt (magnitude 2 to 3). March 13 may be the best time to take an interesting picture of the comet because on that evening, it will appear just below the thin crescent Moon.

Additional Info: http://www.ifa.hawaii.edu/info/press-releases/CometPANSTARRS/
Photo: http://www.ifa.hawaii.edu/info/press-releases/CometPANSTARRS/CometPANSTARRS_by_T.Lovejoy-Australia_HR.jpeg