VERITAS Fields Galactic Gamma Rays From Halfway Across The Visible Universe

VERITAS Fields Galactic Gamma Rays
An artist's rendering of a burst of gamma rays ejected from a blazar. Photo by M. Weiss/CfA

CAMBRIDGE, Mass., Dec. 15 (UPI) — VERITAS, the Very Energetic Radiation Imaging Telescope Array System, recently fielded a blast of gamma rays from half-way across the visible universe.

According to a new study, published this week in The Astrophysical Journal, the rays came from a galaxy named PKS 1441+25, located nearly seven billion light-years away. PKS 1441+25 is rare type of galaxy called a blazar.

Blazars are active elliptical galaxies with a supermassive black hole at their center and a corresponding compact quasar. Like quasars, blazars are characterized by high-powered relativistic jets, which spit out high-energy particles at nearly the speed of light.

One of the jets of the blazar is directed at Earth, offering astronomers a view straight into the center of compact quasar’s engine room.

“We’re looking down the barrel of this relativistic jet,” Wystan Benbow, an astronomer with the Harvard-Smithsonian Center for Astrophysics, explained in a press release. “That’s why we’re able to see the gamma rays at all.”

Until now, scientists hadn’t been able to pinpoint exactly where gamma rays blast off from within a blazar.

The new VERITAS data, when combined with observations by the Fermi Gamma-Ray Space Telescope, showed that the blazar’s gamma rays are shot out from within the relativistic jet but very far from the black hole itself.

Researchers measured a gamma-ray emission region roughly one-third of a light-year across, located five light years from the galaxy’s supermassive black hole.

“These jets tend to have clumps in them. It’s possible that two of those clumps may have collided and that’s what generated the burst of energy,” added astronomer Matteo Cerruti, also with the CfA.


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