* Astronomy

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Credit  NASA, ESA, and Q.D. Wang (University of Massachusetts, Amherst)

This composite colour infrared image of the center of our Milky Way galaxy reveals a new population of massive stars and new details in complex structures in the hot ionised gas swirling around the central 300 light-years. This sweeping panorama is the sharpest infrared picture ever made of the Galactic core. It offers a nearby laboratory for how massive stars form and influence their environment in the often violent nuclear regions of other galaxies. This view combines the sharp imaging of the Hubble Space Telescope's Near Infrared Camera and Multi-Object Spectrometer (NICMOS) with colour imagery from a previous Spitzer Space Telescope survey done with its Infrared Astronomy Camera (IRAC). The Galactic core is obscured in visible light by intervening dust clouds, but infrared light penetrates the dust. The spatial resolution of NICMOS corresponds to 0.025 light-years at the distance of the galactic core of 26,000 light-years. Hubble reveals details in objects as small as 20 times the size of our own solar system. The NICMOS images were taken between February 22 and June 5, 2008.

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The center of the Milky Way presents astronomers with a paradox: it holds young stars, but no one is sure how those stars got there. The galactic center is wracked with powerful gravitational tides stirred by a 4 million solar-mass black hole. Those tides should rip apart molecular clouds that act as stellar nurseries, preventing stars from forming in place. Yet the alternative - stars falling inward after forming elsewhere - should be a rare occurrence.
Using the Very Large Array of radio telescopes, astronomers from the Harvard-Smithsonian Center for Astrophysics and the Max Planck Institute for Radio Astronomy have identified two protostars located only a few light-years from the galactic center. Their discovery shows that stars can, in fact, form very close to the Milky Way's central black hole.

"We literally caught these stars in the act of forming" - Smithsonian astronomer Elizabeth Humphreys. She presented the finding today at a meeting of the American Astronomical Society in Long Beach, Calif.

Source  Harvard-Smithsonian Center for Astrophysics

Iowa State University's Martin Pohl is part of a research team that has developed the first complete map of the Milky Way galaxy's spiral arms.
The map shows the inner part of the Milky Way has two prominent, symmetric spiral arms, which extend into the outer galaxy where they branch into four spiral arms.

"For the first time these arms are mapped over the entire Milky Way. The branching of two of the arms may explain why previous studies - using mainly the inner or mainly the outer galaxy - have found conflicting numbers of spiral arms" - Martin Pohl , an Iowa State associate professor of physics and astronomy.

The new map was developed by Pohl, Peter Englmaier of the University of Zurich in Switzerland and Nicolai Bissantz of Ruhr-University in Bochum, Germany.
As the sun and other stars revolve around the center of the Milky Way, researchers cannot see the spiral arms directly, but have to rely on indirect evidence to find them. In the visible light, the Milky Way appears as an irregular, densely populated strip of stars. Dark clouds of dust obscure the galaxy's central region so it cannot be observed in visible light.
The National Aeronautics and Space Administration's Cosmic Background Explorer satellite was able to map the Milky Way in infrared light using an instrument called the Diffuse IR Background Experiment. The infrared light makes the dust clouds almost fully transparent.
Englmaier and Bissantz used the infrared data from the satellite to develop a kinematic model of gas flow in the inner galaxy. Pohl used the model to reconstruct the distribution of molecular gas in the galaxy. And that led to the researchers' map of the galaxy's spiral arms.

Source Iowa State University

Astronomers find proof that the galaxy has a hot corona
With the help of a new satellite capable of finding the telltale, superheated gas created by stars that exploded long ago, scientists have confirmed a four-decade-old theory that the Milky Way is swathed in a corona of hot gas.
The discovery is important because it provides strong evidence that supernovas continuously pump extremely hot gas atoms high into the galactic halo, a nebulous region far above the plane of the galaxy. It fleshes out astronomers' ideas of how the material that makes up all the stars in the galaxy is recycled and confirms a hypothesis that the galaxy has a hot corona or halo, an idea first postulated nearly 45 years ago by renowned astronomer Lyman Spitzer.

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