Archive for April 17, 2014

NOAO: A Sharp Eye On Southern Binary Stars

Unlike our sun, with its retinue of orbiting planets, many stars in the sky orbit around a second star. These binary stars, with orbital periods ranging from days to centuries, have long been the primary tool for measuring basic quantities like the star’s mass. While masses of normal stars are now well determined, some binaries present special interest because their stars are unusual (e.g. very young) or because they may contain planets, gas clouds, or other stars.

Now, astronomers at the Cerro Tololo Inter-American Observatory (CTIO) and at the US Naval Observatory (USNO) are making use of the latest technology, speckle imaging, to measure the separation of close binary stars. By observing them over a period of years, their obits have been determined with exquisite precision.

Using the new speckle camera at the 4.1-m Southern Astrophysical Research Telescope (SOAR) in Chile with its novel electron-multiplication CCD detector, the team is able to measure the angular separation of stars down to 25 milli arcseconds: this is equivalent to measuring the size of a quarter atop the Empire State building in New York – from Washington, DC. This is over 2000 times better than the human eye can resolve. As Dr. Andrei Tokovinin, the lead author on the paper, said: “This camera surpasses adaptive-optics instruments at the 8-m telescopes, which work in the infrared and can only resolve binaries wider than 50 milli arcseconds.“

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Meteorites Yield Clues To Red Planet’s Early Atmosphere

Geologists who analyzed 40 meteorites that fell to Earth from Mars unlocked secrets of the Martian atmosphere hidden in the chemical signatures of these ancient rocks. Their study, published April 17 in the journal Nature, shows that the atmospheres of Mars and Earth diverged in important ways very early in the 4.6 billion year evolution of our solar system.

Heather Franz, a former University of Maryland research associate who now works on the Curiosity rover science team at the NASA Goddard Space Flight Center, led the study with James Farquhar, co-author and UMD geology professor. The researchers measured the sulfur composition of 40 Mars meteorites—a much larger number than in previous analyses. Of more than 60,000 meteorites found on Earth, only 69 are believed to be pieces of rocks blasted off the Martian surface.

The meteorites are igneous rocks that formed on Mars, were ejected into space when an asteroid or comet slammed into the red planet, and landed on Earth. The oldest meteorite in the study is about 4.1 billion years old, formed when our solar system was in its infancy. The youngest are between 200 million and 500 million years old.

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