Astronomers are extremely excited about a new burst of gamma ray radiation coming from a blazar galaxy known as PKS 1441+25 close to the constellation Bootes. These intense gamma rays began their journey toward Earth some 7.6 billion years ago, and are arguably the highest-energy light ever recorded coming from such a long distance away. NASA’s Fermi Gamma-ray Space Telescope recorded the gamma ray burst, and an Italian astronomer alerted the scientific community about the new anomaly in April.
NASA helps identify distant blazar galaxy as source of strong gamma rays
It is known that black holes generate gamma rays. Until now, the general assumption had been that light at different energies originally emanated from regions at various distances from the black hole. Therefore, given that gamma rays are the highest-energy form of light, they were generated the closest to the event horizon of the black hole. However, the new data suggest that light at all wavelengths emanates from one area around five light-years from the black hole (more than the distance between our sun and the nearest star).
The newly found gamma ray source is called PKS 1441+25, an active galaxy known as a blazar. Near to the constellation Boötes, the gamma rays have taken an amazing 7.6 billion years to reach the Earth. The galaxy contains a giant black hole with a mass 70 million times the sun’s and has a disk of hot gas and dust all around it. When matter from the disk falls toward the black hole, much of it is converted to dual particle jets that are ejected out of the disk in opposite directions at very close to the speed of light.
Blazar galaxies appear so bright in gamma rays because one “particle jet” is aimed almost directly toward our galaxy, allowing researchers a clear of the black hole’s dynamics.
Gamma rays reached Earth this April
PKS 1441+25 erupted spectacularly some 7.6 billion years ago and we are just finding out about it today. Luigi Pacciani at the Italian National Institute for Astrophysics in Rome was the head of a research project to identify early-stage blazar flares working with the Major Atmospheric Gamma-ray Imaging Cerenkov experiment (MAGIC), on La Palma in the Canary Islands. Pacciani discovered the new gamma ray burst when he examined the new data from NASA’s Fermi’s Large Area Telescope. The new NASA Fermi data showed gamma rays up to 33 billion electron volts had reached Earth, among the highest ever recorded. Visible light, for example, typically has around 2 or 3 electron volts.
The MAGIC team focused on the blazar, and they detected very intense gamma rays ranging from 40 to 250 GeV. Given the distance away, astronomers were very surprised to detect gamma rays with energies this high as they break into smaller particles (electrons and positrons) when they collide with lower energy light.
All of the light from stars shining throughout the history of the universe creates a remnant glow called the extragalactic background light, and this EBL serves as a kind of “cosmic gauntlet” that gamma rays must pass through to reach Earth. That means the farther away the blazar is, the less likely it is for its gamma rays to make it all the way to Earth.
Another gamma ray telescope, VERITAS (in southern Arizona), also confirmed the discovery, as it detected gamma rays approaching 200 GeV. PKS 1441+25 is only the second galaxy from which gamma rays with energies above 100 GeV have been detected.