Yesterday, NASA released the first set of images from its newest space telescope, the Gamma-Ray Large Area Space Telescope, which has now been renamed Fermi in honor of the particle physicist Enrico Fermi. After less than three months of collecting data, the Fermi telescope produced a map of the sky showing the sources of powerful gamma rays as bright spots of light.
“I like to call it our extreme machine,” said Jon Morse, the director of astrophysics for NASA. “It will help us crack the mysteries of these enormously powerful emissions.” Gamma rays are powerful light rays invisible to the naked eye [Washington Post]. As the Earth’s atmosphere absorbs gamma rays, they can only be studied from an orbiting telescope.
The $700 million telescope will observe gamma rays emitted by black holes, neutron stars, and other cosmic eccentrics, and will also scan the skies for the mysterious gamma ray bursts that are of special interest to astronomers because they are among the brightest events ever observed. The intense flashes of gamma rays can release within seconds the same amount of energy that the sun will put out over its entire ten-billion-year lifetime—but no one is sure what causes them. The going theory is that the bursts are tied to the explosive deaths of massive stars, but exactly what types of stars and how the explosions are triggered remains a mystery [National Geographic News]. Already, the Fermi telescope has detected gamma ray bursts at a rate of about one a day.
The Fermi’s first map of steadier sources of gamma ray emissions also gives researchers plenty to feast their eyes on, showing a sky spangled with bright spots of light in an image that one scientist compared to a cosmic Fourth of July celebration. Bright spots in the map include the Crab Nebula, which hosts a radiation-spewing stellar corpse called a pulsar, and several blazars, violent active galaxies where colossal black holes accelerate particles to more than 99% the speed of light. But the maps’ main feature is a long swath of gamma rays emitted by the disc of our Milky Way galaxy. Most of the gamma rays come from cosmic rays hitting interstellar gas [New Scientist].
Scientists are also hoping the Fermi will find evidence of hypothetical particles sometimes known as WIMPs, for Weakly Interacting Massive Particles. These unseen particles, whatever they are, are thought by many scientists to make up the mysterious “dark matter” that has never been detected but is known from the unseen effects of its gravity and may make up most of the total mass of the universe – far more than the ordinary matter all around us [San Francisco Chronicle]. Astrophysicists have proposed that WIMPs may lurk in the heart of the Milky Way, and suggest that some of the gamma rays seen in our galaxy may be produced when two WIMPs collide and annihilate each other.
Image: NASA/DOE/International LAT Team
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