Tag: galaxy

Marvels of the Universe

1 Comment

A site worth visiting week after week.

 
And if you need to back up and peruse a wider view of the comparative unimportance of our species – and the truly irrational crappola of True Believers – play and rewind this voyage through our nearest neighbor, Andromeda. Reflect upon this view of a less-than significant morsel less important than a mustard seed lost on the beach in Coney Island.

But – we think we’re important.

Fermi Bubbles are burps from our galaxy’s black hole eating stars

1 Comment

Last year, astronomers analysing data from NASA’s orbiting Fermi Gamma Ray Telescope made an extraordinary announcement. They said that Fermi had spotted two giant bubbles emanating from the centre of the galaxy, stretching some 20,000 light years above and below the galactic plane.

These bubbles are clearly some kind of shockwave in which high energy electrons interact with photons, giving up their energy in the form of gamma rays.

But what could have caused such a shockwave, which is many times bigger than astronomers would expect to see from a supernova?

Kwong Sang Chen at The University of Hong Kong and a few pals say think they know. They say the bubbles are the remnants of stars that have been eaten by the supermassive black hole at the centre of the galaxy. What this idea may also explain is the energy distribution of cosmic rays, which astronomers have puzzled over for decades.

Our galaxy’s supermassive black hole is, well, huge–some 4 million times more massive than the Sun. Chen and co assume that a star falls into it every 1000 years or so. When this happens, part of the star is devoured by the black hole, while the rest is burped back out into space in the form of high energy protons.

These protons heat up the gas and dust surrounding the black hole creating an expanding bubble of high energy electrons. This cannot expand far in the plane of the galaxy where it is absorbed.

But the electrons can travel far into the space above and below the galactic plane, creating the gamma ray bubbles seen by Fermi. This explains why the edge of the bubble is so well defined.

RTFA for notes of other questions in astrophysics resolved by this theory. Poisonally, the burp alone impresses the crap out of me.

Fermi Telescope finds giant structure in center of our galaxy

Leave a comment

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…

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…

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.

Click on the photo up above for the LAT team’s latest and best view of the gamma-ray feature. It took 2 years of data collection.

Thanks, WOK3