Follow Friday & Weekly Stumbles For 2011-04-08

This week I recommend to follow @HUBBLE_space for interesting tweets from the Hubble Space Telescope, in collaboration between ESA and NASA. For more Twitter follow suggestions see our astronomy list @TheAstroBlog/astronomy

Weekly Stumbles:

In praise of Mercury
Like the Moon, Mercury is also airless. Once its bulk density was determined I became less scientifically interested in it. Density is an important piece of data for modeling the evolution of the solar system. I was deeply involved with early measurements of the mass of Mercury and did a lot of work on the first Mercury mission, Mariner 10, launched in 1973. In fact, on my first day of work at JPL, I was told to go to a Mercury meeting and introduce myself to some guy named Bruce Murray to work on the trajectory and navigation analysis of Mariner 10.

Astrophysicist: White Dwarfs Could Be Fertile Ground for Other Earths
Planet hunters have found hundreds of planets outside the solar system in the last decade, though it is unclear whether even one might be habitable. But it could be that the best place to look for planets that can support life is around dim, dying stars called white dwarfs. In a new paper published online March 29 in The Astrophysical Journal Letters, Eric Agol, a University of Washington associate professor of astronomy, suggests that potentially habitable planets orbiting white dwarfs could be much easier to find – if they exist – than other exoplanets located so far.

Space law and the new era of commercial spaceflight
Recent NASA policy sent a clear signal to the private sector, urging them to buckle up for a ride to the final frontier, and has been categorized as representing a “paradigm shift” by some commentators. But while there has been much spoken about the subcontracting of human spaceflight capability, little has been made of what happens when this journey encompasses activity that, in a terrestrial setting, would be regarded as criminal. This is one of many space-related areas in which sweeping legal reform and regulation, both national and international, is needed.

Black Hole Found in Binary Star System: More Than Five Times Greater in Mass Than Our Sun
Researchers from the Instituto de Astrofísica de Canarias (IAC) have discovered the existence of a black hole 5.4 times greater in mass than that of our Sun, located in the X-ray binary system XTE J1859+226. The observations carried out from the Gran Telescopio Canarias (GTC), managing to obtain the first spectroscopic data from this binary system to be published, have been determinant for the discovery. X-ray binaries are stellar systems composed by a compact object (which may be a neutron star or a black hole) and a ‘normal’ star.

NASA’s Venerable Comet Hunter Stardust Spacecraft Wraps Up Mission
At 33 minutes after 4 p.m. PDT March 24, 2011, NASA’s Stardust spacecraft finished its last transmission to Earth. The transmission came on the heels of the venerable spacecraft’s final rocket burn, which was designed to provide insight into how much fuel remained aboard after its encounter with comet Tempel 1 in February. “Stardust has been teaching us about our solar system since it was launched in 1999,” said Stardust-NExT project manager Tim Larson from NASA’s Jet Propulsion Laboratory in Pasadena, Calif. “It makes sense that its very last moments would be providing us with data we can use to plan deep space mission operations in the future.”

Picking sides in cislunar space
In debates about human space policy, the question of destinations looms over all the others. If human spaceflight is about going somewhere, where one goes determines the plan, the architecture, and the investment strategy. Destinations for exploration are historically defined as places where one can leave footprints or collect samples. Big rocks, like the Moon and Mars, and even smaller rocks like asteroids seem to fit that bill. But attached to this list of destinations for federal space policy are some very different places, the L1 and L2 Earth-Moon Lagrange (or libration) points.

When Is an Asteroid Not an Asteroid?
On March 29, 1807, German astronomer Heinrich Wilhelm Olbers spotted Vesta as a pinprick of light in the sky. Two hundred and four years later, as NASA’s Dawn spacecraft prepares to begin orbiting this intriguing world, scientists now know how special this world is, even if there has been some debate on how to classify it. Vesta is most commonly called an asteroid because it lies in the orbiting rubble patch known as the main asteroid belt between Mars and Jupiter. But the vast majority of objects in the main belt are lightweights, 100-kilometers-wide (about 60-miles wide) or smaller, compared with Vesta, which is about 530 kilometers (330 miles) across on average.

Salt-Seeking Spacecraft Arrives at Launch Site; NASA Instrument Will Measure Ocean Surface Salinity
An international spacecraft that will take NASA’s first space-based measurements of ocean surface salinity has arrived at its launch site at Vandenberg Air Force Base in California. The Aquarius/SAC-D mission will provide scientists with a key missing variable in satellite observations of Earth that links ocean circulation, the global balance of freshwater and climate. The Aquarius/SAC-D spacecraft left Sáo José dos Campos, Brazil, on March 29. Following final tests, the spacecraft will be attached to a Delta II rocket for a June 9 launch.

MESSENGER Sends Back First Image of Mercury from Orbit
On March 29, 2011, at 5:20 am EDT, MESSENGER captured a historic image of Mercury. The image is the first ever obtained from a spacecraft in orbit about the Solar System’s innermost planet. Over the subsequent six hours, MESSENGER acquired an additional 363 images before downlinking some of the data to Earth. The MESSENGER team is currently looking over the newly returned data, which are still continuing to come down. The dominant rayed crater in the upper portion of the image is Debussy. The smaller crater Matabei with its unusual dark rays is visible to the west of Debussy. The bottom portion of the image is near Mercury’s south pole and includes a region of Mercury’s surface not previously seen by spacecraft.

Space Will Make You Cranky and Euphoric
Think you have what it takes to endure a five-month stay in orbit? Be prepared to go through some psychological changes. According to nearly a decade of Russian observations and a 1993 report on human adaptation to long-duration space flight, it all breaks down like this: Stage One: Welcome to microgravity! You’ll spend the first phase of your journey adjusting to a cramped environment, an upset stomach, headaches and space motion sickness. According to NASA’s Johnson Space Center, you’ll also experience a 26 percent drop in sleep efficiency, with greatly reduced REM (rapid eye movement) time. In other words, you may experience dream deprivation. Expect to feel uncomfortable and sluggish with your work.

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