December 20, 2014

23.10.09:Fermi Pegs Gamma-Ray Pulsars.

the gamma-ray sky as seen by Fermi. (Credit: NASA/DOE/International LAT team).

The gamma-ray sky as seen by Fermi. the plane of our galaxy runs down the center, while pulsars dot the periphery. (Credit: NASA/DOE/International LAT team).

NASA’s Large Area Telescope aboard the orbiting Fermi gamma-ray observatory continues to turn out some amazing science, picking up where Compton left off in 2002 as it surveys the gamma-ray sky. Of particular interest are gamma-rays emitted from pulsars. Pulsars are the swiftly rotating remnants of massive stars that have gone supernova, leaving a superdense core in their wake. These are sometimes called “neutron stars” because the matter comprising them is packed so tightly the individual nuclei are literally stacked end to end, making a spoonful weigh as much as a mountain! After all, most ordinary matter is made of….nothing. A neutron star can be thought of as a large, singular atomic nucleus, again weird stuff. Most of the 1,800 pulsars thus detected are because of their copious radio emissions beaming from their poles. Thus, we have to be in the line of sight before we see their blinking radio pulsations. Enter Fermi, which has thus far spotted 16 new pulsars via their gamma-ray emissions alone. This promises to aid in identifying pulsars whose poles aren’t tipped to our line of sight, which are probably in the majority. But even the gamma-ray sky is relatively dim; for example, the Vela pulsar is one of the brightest in the sky, and it emits a mere 1 gamma-ray photon every 2 minutes! Initially dubbed “Little Green Men” (LGMs!) during their discovery in the 1960′s, pulsars were soon naturally explained, but still continue to amaze. Watch this space and the Fermi mission for news from the high energy end of the spectrum!

11.10.09: Zooming in on Blazars.

the VLBA Radio Telescope (1 of 10) in Hancock, New Hampshire. (Credit:NRAO / AUI / NSF).

The VLBA Radio Telescope (1 of 10) in Hancock, New Hampshire. (Credit:NRAO / AUI / NSF).

Astronomers have recently utilized an enormous radio telescope to examine some of the most exotic objects in the universe; active galactic nuclei. Sometimes called “Blazars”, these distant galaxies are spewing huge jets of particles at amazing relativistic speeds. These emit immense energy across the electromagnetic spectrum. NASA’s Fermi Gamma Ray Space Telescope has identified and monitored these sources since its launch in 2008 and now scientists at the Max Planck Institute for Radio Astronomy have used the National Science Foundation’s Very Long Baseline Array (VLBA) to map these jets with unprecedented accuracy. The VLBA is a series of 10 interlinked radio telescopes spanning an area from the Virgin Islands to Hawaii that utilize interferometry to produce an effective baseline of 5,300 miles and can resolve details less than 100 light years across at a distance of 7 billion light years. Fermi, the predecessor to the Compton Gamma Ray Observatory that was de-orbited in 2000, scans the entire sky once every three hours looking for gamma-ray bursts. First spotted in the early 70′s during global monitoring of nuclear weapons tests, pinning down gamma-ray bursts has been the name of the game in astrophysics over the past decades. The backup study proves the link between the gamma-ray emissions seen by Fermi and the energetic radio jets pinpointed by the VLBA… expect more high resolution radio maps to come!