Mystery Gamma Ray Sources Coming from Milky Way Center



The Fermi Gamma-Ray Telescope has just picked up “crazy-energetic photons,” says Dave Thompson, an astrophysicist at NASA’s Goddard Space Flight Center. “And it’s detecting so many of them we’ve been able to produce the first all-sky map of the very high energy universe. About a third of the new sources can’t be clearly linked to any of the known types of objects that produce gamma rays,” Thompson says. “We have no idea what they are.”

Among them are super massive black holes called blazars (image above), the seething remnants of supernova explosions, and rapidly rotating neutron stars called pulsars. 

A blazar (image below) is a compact energy source fueled by supermassive black holes. They are considered one of the most dangerous phenomena in space. These objects were first seen and discovered around 1972, thanks to the technology of A Very Long Baseline Interferometry. The name was coined by astronomer Ed Spiegel in 1978. Blazars are usually divided into two, the BL Lacertae objects (BL Lac) and the Optically Violent Variable (OVV) quasars. There are also a few intermediate blazars, which have the properties of both the BL Lac and the OVV.



Blazars emit high-energy plasma jets so fast that it’s almost at the speed of light. A blazar is actually a compact type of quasar, which is a galaxy far from the Milky Way. This means that a blazar is a member of active galaxy out in the universe. Blazars are characterized by their high speed and high energy. They are also extremely powerful. A blazar is usually an exciting topic for scientists when it comes to extragalactic astronomy.

Because they are fueled by black holes, a blazar lives on the energy of the objects like dust and stars that the supermassive black holes suck in. This explains the enormous amount of energy that they have.
Some of the gamma rays seem to come from “Fermi bubbles” — giant structures just discovered two years ago that emanate from the Milky Way’s center. Exactly how these bubbles formed is another mystery, but they may be the remnant of an eruption from a supersized black hole at the center of our galaxy, astronomers say.



The source of the hour-glassed-shaped bubbles is a mystery, but an analysis of the Fermi data suggests that the gamma radiation traces out a pair of distinct bubbles that span some 65,000 light years from end to end – soaring above the disc of the galaxy.

The analysis of the data has ruled out dark matter, which you would expect to be smoothly distributed and produce a diffuse glow, from gamma rays produced after dark matter particles meet and annihilate each other rather than such a well-defined shape according to Douglas Finkbeiner of the Harvard-Smithsonian Center for Astrophysics 

The Harvard-Smithsonian team thinks the bubbles may have been blown out by the explosion of short-lived, massive stars born in a burst of new star formation about 10 million years or they may have been created about 100,000 years ago by high-speed jets of matter created when roughly 100 suns' worth of material fell into the Milky Way's black hole. 

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.

“We don’t fully understand their nature or origin,” said Harvard-Smithsonian Center for Astrophysics astronomer Doug Finkbeiner, who discovered the bubbles by processing publicly available data from Fermi’s Large Area Telescope (LAT) — 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.

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