Archive for March 26, 2013

LRO’s LAMP Ultraviolet Spectrograph Observes Mercury And Hydrogen In GRAIL Impact Plumes

When NASA’s twin GRAIL spacecraft made their final descent for impact onto the Moon’s surface last December, the Lunar Reconnaissance Orbiter’s sophisticated payload was in position to observe the effects. As plumes of gas rose from the impacts, the Lyman Alpha Mapping Project (LAMP) aboard LRO detected the presence of mercury and hydrogen and measured their time evolution as the gas rapidly expanded into the vacuum of space at near-escape velocities.

NASA intentionally crashed the GRAIL twins onto the Moon on Dec. 17, 2012, following successful prime and extended science missions. Both spacecraft hit a mountain near the lunar north pole, which was shrouded in shadow at the time. Developed by Southwest Research Institute (SwRI), LAMP uses a novel method to peer into the darkness of the Moon’s permanently shadowed regions, making it ideal for observations of the Moon’s night-side and its tenuous atmospheric constituents.

“While our results are still very new, our thinking is that the hydrogen detected from the GRAIL site might be related to an enhancement at the poles caused by hydrogen species migrating toward the colder polar regions,” says Dr. Kurt Retherford, LAMP principal investigator and a principal scientist at SwRI.

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NASA Scientists Find Moon, Asteroids Share History

NASA and international researchers have discovered that Earth’s moon has more in common than previously thought with large asteroids roaming our solar system.

Scientists from NASA’s Lunar Science Institute (NLSI) in Moffett Field, Calif., discovered that the same population of high-speed projectiles that impacted our lunar neighbor four billion years ago, also hit the giant asteroid Vesta and perhaps other large asteroids.

The research unveils an unexpected link between Vesta and the moon, and provides new means for studying the early bombardment history of terrestrial planets. The findings are published in the March issue of Nature Geoscience.

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Astronomers Discover A New Kind Of Supernova

Artist's conception. Credit: Christine Pulliam (CfA)

Artist’s conception. Credit: Christine Pulliam (CfA)

Until now, supernovas came in two main “flavors.” A core-collapse supernova is the explosion of a star about 10 to 100 times as massive as our sun, while a Type Ia supernova is the complete disruption of a tiny white dwarf. Today, astronomers are reporting their discovery of a new kind of supernova called Type Iax. This new class is fainter and less energetic than Type Ia. Although both varieties come from exploding white dwarfs, Type Iax supernovas may not completely destroy the white dwarf.

“A Type Iax supernova is essentially a mini supernova,” says lead author Ryan Foley, Clay Fellow at the Harvard-Smithsonian Center for Astrophysics (CfA). “It’s the runt of the supernova litter.”

Foley and his colleagues identified 25 examples of the new type of supernova. None of them appeared in elliptical galaxies, which are filled with old stars. This suggests that Type Iax supernovas come from young star systems.

Based on a variety of observational data, the team concluded that a Type Iax supernova comes from a binary star system containing a white dwarf and a companion star that has lost its outer hydrogen, leaving it helium dominated. The white dwarf collects helium from the normal star.

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Venus Vortices Go For Chaotic Multi-Storey Strolls Around The Poles

Credit: ESA/VIRTIS/INAF-IASF/Obs. de Paris-LESIA/Universidad del País Vasco (I. Garate-Lopez)

Credit: ESA/VIRTIS/INAF-IASF/Obs. de Paris-LESIA/Universidad del País Vasco (I. Garate-Lopez)

A detailed study of Venus’ South Polar Vortex shows a much more chaotic and unpredictable cyclone than previously thought. The analysis reveals that the center of rotation of the vortex wanders around the pole differently at different altitude levels in the clouds of Venus. In its stroll around the Pole, in layers separated by 20 km, the vortex experiences unpredictable changes in its morphology.

The results of this study are published online in Nature Geoscience today.

The study, entitled ‘A chaotic long-lived vortex at the southern pole of Venus’, used infrared images from VIRTIS instrument onboard the European Space Agency’s Venus Express spacecraft. VIRTIS provides spectral images at different levels of the atmosphere and allows the observation of the lower and upper clouds of Venus.

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‘Sideline Quasars’ Helped To Stifle Early Galaxy Formation, Says CU Study

Image courtesy NASA

Image courtesy NASA

University of Colorado Boulder astronomers targeting one of the brightest quasars glowing in the universe some 11 billion years ago say “sideline quasars” likely teamed up with it to heat abundant helium gas billions of years ago, preventing small galaxy formation.

CU-Boulder Professor Michael Shull and Research Associate David Syphers used the Hubble Space Telescope to look at the quasar — the brilliant core of an active galaxy that acted as a “lighthouse” for the observations — to better understand the conditions of the early universe. The scientists studied gaseous material between the telescope and the quasar with a $70 million ultraviolet spectrograph on Hubble designed by a team from CU-Boulder’s Center for Astrophysics and Space Astronomy.

During a time known as the “helium reionization era” some 11 billion years ago, blasts of ionizing radiation from black holes believed to be seated in the cores of quasars stripped electrons from primeval helium atoms, said Shull. The initial ionization that charged up the helium gas in the universe is thought to have occurred sometime shortly after the Big Bang.

“We think ‘sideline quasars’ located out of the telescope’s view reionized intergalactic helium gas from different directions, preventing it from gravitationally collapsing and forming new generations of stars,” he said.

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