Stunning Reindeer Migration Captured by Drone
Haven't you herd it's not Christmas anymore? It seems this bunch of reindeer have only just got the message after they were spotted staggering back to Santa's.
NASA | Best-Ever View of the High-Energy Gamma-ray Sky - 4K
This image, constructed from more than six years of observations by NASA's Fermi Gamma-ray Space Telescope, is the first to show how the entire sky appears at energies between 50 billion (GeV) and 2 trillion electron volts (TeV).
A diffuse glow fills the sky and is brightest in the middle of the map, along the central plane of our galaxy. The famous Fermi Bubbles, first detected in 2010, appear as red extensions north and south of the galactic center and are much more pronounced at these energies. Discrete gamma-ray sources include pulsar wind nebulae and supernova remnants within our galaxy, as well as distant galaxies called blazars powered by supermassive black holes. Labels show the highest-energy sources, all located within our galaxy and emitting gamma rays exceeding 1 TeV.
Major improvements to methods used to process observations from NASA's Fermi Gamma-ray Space Telescope have yielded an expanded, higher-quality set of data that allows astronomers to produce the most detailed census of the sky yet made at extreme energies. This new sky map reveals hundreds of these sources, including 12 that produce gamma rays with energies exceeding a trillion times the energy of visible light. The survey also discovered four dozen new sources that remain undetected at any other wavelength. The improved data, known as Pass 8, effectively sharpens the Large Area Telescope's (LAT) view while also significantly widening its useful energy range.
Using 61,000 Pass 8 gamma rays collected over 80 months, Marco Ajello and his colleagues constructed a map of the entire sky at energies ranging from 50 billion (GeV) to 2 trillion electron volts (TeV). For comparison, the energy of visible light ranges from about 2 to 3 electron volts.
The Fermi team cataloged 360 individual gamma-ray sources, about 75 percent of which are blazars -- distant galaxies sporting jets powered by supermassive black holes. The highest-energy sources, which are all located within our galaxy, are mostly the remnants of supernova explosions and pulsar wind nebulae, places where rapidly rotating neutron stars accelerate particles to near the speed of light.
A famous example, the Crab Nebula, tops the list of the highest-energy Fermi sources, producing a steady drizzle of gamma rays exceeding 1 TeV.
Astronomers think these very high-energy gamma rays are produced when lower-energy light collides with accelerated particles. This results in a small energy loss for the particle and a big gain for the light, transforming it into a gamma ray.
For the first time, Fermi data now extend to energies previously seen only by ground-based detectors. Because ground-based telescopes have much smaller fields of view than the LAT, which scans the whole sky every three hours, they have detected only about a quarter of the objects in the new catalog. This study provides ground facilities with more than 280 new targets for follow-up observations.
January 06, 2016
Lenovo Link First Look
The Lenovo Link bridges the gap between the Android smartphone and the computer - and we think it's pretty damn cool.