Space- News NASA's Fermi Telescope Finds Giant Structure in our Galaxy

WASHINGTON — NASA’s Fermi Gamma-ray Space Telescope has unveiled a previously unseen structure centered in the Milky Way. The feature spans 50,000 light-years and may be the remnant of an eruption from a supersized black hole at the center of our galaxy.

“What we see are two gamma-ray-emitting bubbles that extend 25,000 light-years north and south of the galactic center,” said Doug Finkbeiner, an astronomer at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass., who first recognized the feature. “We don’t fully understand their nature or origin.”

The structure spans more than half of the visible sky, from the constellation Virgo to the constellation Grus, and it may be millions of years old. A paper about the findings has been accepted for publication in The Astrophysical Journal.

Finkbeiner and his team discovered the bubbles by processing publicly available data from Fermi’s Large Area Telescope (LAT). The LAT is the most sensitive and highest-resolution gamma-ray detector ever launched. Gamma rays are the highest-energy form of light.

Other astronomers studying gamma rays hadn’t detected the bubbles partly because of a fog of gamma rays that appears throughout the sky. The fog happens when particles moving near the speed of light interact with light and interstellar gas in the Milky Way. The LAT team constantly refines models to uncover new gamma-ray sources obscured by this so-called diffuse emission. By using various estimates of the fog, Finkbeiner and his colleagues were able to isolate it from the LAT data and unveil the giant bubbles.

Scientists now are conducting more analyses to better understand how the never-before-seen structure was formed. The bubble emissions are much more energetic than the gamma-ray fog seen elsewhere in the Milky Way. The bubbles also appear to have well-defined edges. The structure’s shape and emissions suggest it was formed as a result of a large and relatively rapid energy release – the source of which remains a mystery.

One possibility includes a particle jet from the supermassive black hole at the galactic center. In many other galaxies, astronomers see fast particle jets powered by matter falling toward a central black hole. While there is no evidence the Milky Way’s black hole has such a jet today, it may have in the past. The bubbles also may have formed as a result of gas outflows from a burst of star formation, perhaps the one that produced many massive star clusters in the Milky Way’s center several million years ago.

“In other galaxies, we see that starbursts can drive enormous gas outflows,” said David Spergel, a scientist at Princeton University in New Jersey. “Whatever the energy source behind these huge bubbles may be, it is connected to many deep questions in astrophysics.”

Hints of the bubbles appear in earlier spacecraft data. X-ray observations from the German-led Roentgen Satellite suggested subtle evidence for bubble edges close to the galactic center, or in the same orientation as the Milky Way. NASA’s Wilkinson Microwave Anisotropy Probe detected an excess of radio signals at the position of the gamma-ray bubbles.

The Fermi LAT team also revealed Tuesday the instrument’s best picture of the gamma-ray sky, the result of two years of data collection.

“Fermi scans the entire sky every three hours, and as the mission continues and our exposure deepens, we see the extreme universe in progressively greater detail,” said Julie McEnery, Fermi project scientist at NASA’s Goddard Space Flight Center in Greenbelt, Md.

NASA’s Fermi is an astrophysics and particle physics partnership, developed in collaboration with the U.S. Department of Energy, with important contributions from academic institutions and partners in France, Germany, Italy, Japan, Sweden and the United States.

“Since its launch in June 2008, Fermi repeatedly has proven itself to be a frontier facility, giving us new insights ranging from the nature of space-time to the first observations of a gamma-ray nova,” said Jon Morse, Astrophysics Division director at NASA Headquarters in Washington. “These latest discoveries continue to demonstrate Fermi’s outstanding performance.”

Lisa Beightol — Space Stuff—The

NASA’s Chandra X-ray Observatory has found evidence of what could be the youngest black hole in our “neighborhood”. The object itself is only about thirty years old and appears to be a remnant of supernova SN 1979C in the galaxy M100, located about 50 million light-years away. According to NASA, data from Chandra, Swift, XMM-Newton and ROSAT have shown that a bright X-ray source in the region has been steady between 1995 and 2007, which suggests that the source is a black hole that is either receiving material from the supernova, or a binary companion. The hypothesis of the formation of SN 1979C is that a star about twenty times the mass of our sun collapsed.
Keep your eyes to the sky and enjoy the view!

Venus Express Update- from Lisa Beightol –

Hello, astro-nuts!
Venus Express, which was launched by ESA back in 2005, has been studying the atmosphere of Venus from different levels within it, as well as from its highly elliptical orbit. During a series of low passes in summer of 2008, October 2009 and just this past February and April, Venus Express found data suggesting that the atmosphere above the poles of Venus is much thinner than previously thought–60% thinner, in fact. Studying the density of the atmosphere is very important to the mission controllers, because they wish to take the craft lower into the atmosphere to continue observing. Given the destruction of so many other robotic explorers before this one, the team wants to be sure that they understand the density of the Venusian atmosphere so yet another spacecraft isn’t lost. To date, the closest Venus Express has been to the surface was about 108 miles. Next week, the craft will drop down to 102 miles. On average, its orbit takes it from 155 miles all the way out over 41,000 miles, yet it can complete an orbit in about 24 hours. However, at its farthest point, the sun’s gravity starts pulling the craft off course and its engines are fired to compensate. Unless its orbit can be lowered, Venus Express’ fuel will be used up by 2015. With constant study, this orbital lowering may be achieved by 2012.

Venus in Ultraviolet from Venus Express-ESA/MPS/DLR/IDA
Nice fall weather is finally returning to central PA, so I’m looking forward to getting my telescope out and hunting for Comet Hartley! Have any of you had the chance to look for it yet? Its not quite naked-eye visible yet, but I’ve seen reports that you can pick it up as a fuzzy blob with 10×50 binoculars, and most definitely a small telescope. Don’t forget that Hartley will be near the Double Cluster in Perseus tonight and Friday night. The Double Cluster in Perseus is just that, two star clusters that appear to be near one another–NGC 884 and NGC 869. The two are not actually that far apart in space, only about 800 light years (they are 7600 and 6800 light years from Earth, respectively). While Hartley may only look like a “fuzzy” from Earth without much of a tail, the WISE spacecraft with its incredible infrared detectors, has picked up a very long tail on Hartley that stretches over a million miles behind it.