June 18, 2013
Burst Of High-Energy Cosmic Events Keeping NuSTAR Observatory Busy
Brett Smith for redOrbit.com - Your Universe Online
NASA´s NuSTAR orbiting observatory is designed to investigate high-energy events throughout the universe, and the cosmos has been keeping it busy in recent months, producing one event after another.
In early April, the galaxy Markarian 421 produced a high-energy event that increased its brightness by more than 50 times its usual level. Markarian 421 is known as a blazer, a unique class of galaxies with supermassive "feeding" black holes at their centers.
As these central black holes feed, they often eject jets of material — lighting up the space around them in the process. When these jets are pointing toward Earth, they are described as blazars. By using specially calibrated telescopes, astrophysicists can often study a black hole´s feeding process and the physical conditions surrounding it.
According to a NASA statement, NuSTAR “got lucky” with respect to Markarian 421, because it just happened to be monitoring the blazar at the time of its flare-up, along with other NASA telescopes onboard the Fermi and Swift satellites. The eruption was so bright — the brightest ever observed for that galaxy — that NuSTAR and other telescopes were immediately recalibrated to spend more time examining Markarian 421. According to NASA, these observations are currently being analyzed, and their findings are expected to be published in the near future.
"These data will help us better understand the gentle giant at the heart of our galaxy and why it sometimes flares up for a few hours and then returns to slumber,” said Fiona Harrison, the mission's principal investigator at the California Institute of Technology (Caltech) in Pasadena.
Near the end of April, NASA's Swift satellite observed a region close to the center of our own Milky Way galaxy lighting up. Flares from our galaxy´s own black hole Sagittarius A* are fairly common and tend to last anywhere from few minutes to three hours. NuSTAR observed just such an event last July.
However, the newer Milky Way event lasted tens of hours — long enough to get the attention of the entire high-energy astrophysics community, NASA said. NuSTAR observations, which began 50 hours after the initial Swift discovery, showed the flare-up was actually due to a type of neutron star called a magnetar and not the black hole. The observations and findings are to be published soon in the Astrophysical Journal Letters.
Just several days after that event, Swift noticed an exceptionally brilliant gamma-ray burst, brighter than anything it had seen throughout its almost 10 years in orbit. Suspected to be the collapse of a massive star in a distant galaxy, NuSTAR and other observers quickly reacted to the event, providing the first focused high-quality imagery of a gamma-ray burst in high-energy X-rays.
Launched on June 13, 2013, NuStar is the only telescope capable of producing these types of highly focused images. The 772-pound orbiting observatory is expected to spend at least two years closely investigating high-energy cosmic X-rays. This type of radiation is beyond the scope of visible light and challenging to detect, NASA scientists say. Using two sets of 133 thin, nested shells of mirrors, NuStar captures the X-rays by bouncing them off the reflecting surfaces at various angles.