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NASA’s Chandra Suggests Rare Explosion Created Our Galaxy’s Youngest Black Hole

February 19, 2013 Leave a comment

Credit: X-ray: NASA/CXC/MIT/L.Lopez et al.; Infrared: Palomar; Radio: NSF/NRAO/VLA

Credit: X-ray: NASA/CXC/MIT/L.Lopez et al.; Infrared: Palomar; Radio: NSF/NRAO/VLA

New data from NASA’s Chandra X-ray Observatory suggest a highly distorted supernova remnant may contain the most recent black hole formed in the Milky Way galaxy. The remnant appears to be the product of a rare explosion in which matter is ejected at high speeds along the poles of a rotating star.

Usually when a massive star runs out of fuel, the central region of the star collapses, triggering a chain of events that quickly culminate in a supernova explosion. Most of these explosions are generally symmetrical, with the stellar material blasting away more or less evenly in all directions. However, in the W49B supernova, material near the poles of the doomed rotating star was ejected at a much higher speed than material emanating from its equator. Jets shooting away from the star’s poles mainly shaped the supernova explosion and its aftermath.

The remnant now glows brightly in X-rays and other wavelengths, offering the evidence for a peculiar explosion. By tracing the distribution and amounts of different elements in the stellar debris field, researchers were able to compare the Chandra data to theoretical models of how a star explodes. For example, they found iron in only half of the remnant while other elements such as sulfur and silicon were spread throughout. This matches predictions for an asymmetric explosion.

Full Story: http://chandra.si.edu/press/13_releases/press_021313.html

Gaia Will Reveal The Secrets Of Ultra-Cool Dwarfs

February 19, 2013 Leave a comment

Among the hundred billion stars which can be observed in the Milky Way, there is a group of stars, the so-named ultra-cool dwarfs, defined as stars with a temperature below 2500 K, which includes ultra-cool dwarfs and brown dwarfs. It is a really interesting group: they are the most ancient objects in our Galaxy and, therefore, they can provide information about its primitive chemical composition. This is one of the objectives of Gaia mission which will be launched at the end of 2013 by the European Space Agency.

When observing them, they seem quite similar, but there are clear differences between brown dwarfs and ultra-cool dwarfs: brown dwarfs do not reach the temperature they need to produce the nuclear reactions which characterize ultra-cool dwarfs. It could be said that brown dwarfs are failed stars because they lack mass.

A study published on the journal Astronomy & Astrophysics, led by the National University of Distance Education (UNED) and in which researchers from the Institute of Cosmos Sciences of the UB (ICCUB) participated, has developed a method that will allow Gaia to detect tens of ultra-cool dwarfs in the Milky Way. The method to estimate physical parameters of these objects, such as temperature or gravity, has also been validated. Researchers have used data mining techniques to make estimations taking into account the parameters that Gaia can measure and its design characteristics.

Full Story: http://www.ub.edu/web/ub/en/menu_eines/noticies/2013/02/026.html