GBM will also view the entire sky—except for the pocket blocked by Earth. GLAST is slated to scan the heavens for gamma rays for five years, but researchers hope the satellite may peer across the universe for a full decade. With each pass of the sky, astronomers hope to gather more information about faraway, gamma-bright objects, watching them evolve as their gamma-ray emissions change over time.
JR Minkel was a news reporter for Scientific American. Already a subscriber? Sign in. Thanks for reading Scientific American. Create your free account or Sign in to continue. See Subscription Options. Go Paperless with Digital. This computer processed image shows the Crab Nebula pulsar below and right of center and the Geminga pulsar above and left of center in the "light" of gamma-rays.
The Crab nebula, shown also in the visible light image, was created by a supernova that brightened the night sky in A. In , astronomers detected the remnant core of that star; a rapidly rotating, magnetic pulsar flashing every 0. Perhaps the most spectacular discovery in gamma-ray astronomy came in the late s and early s.
Detectors on board the Vela satellite series, originally military satellites, began to record bursts of gamma-rays -- not from Earth, but from deep space! Today, these gamma-ray bursts, which happen at least once a day, are seen to last for fractions of a second to minutes, popping off like cosmic flashbulbs from unexpected directions, flickering, and then fading after briefly dominating the gamma-ray sky.
Gamma-ray bursts can release more energy in 10 seconds than the Sun will emit in its entire 10 billion-year lifetime!
So far, it appears that all of the bursts we have observed have come from outside the Milky Way Galaxy. Scientists believe that a gamma-ray burst will occur once every few million years here in the Milky Way, and in fact may occur once every several hundred million years within a few thousand light-years of Earth.
Gamma-rays are the most energetic form of electromagnetic radiation , with over 10, times more energy than visible light photons. If you could see gamma-rays, the night sky would look strange and unfamiliar. The familiar sights of constantly shining stars and galaxies would be replaced by something ever-changing. Your gamma-ray vision would peer into the hearts of solar flares , supernovae , neutron stars , black holes , and active galaxies. Gamma-ray astronomy presents unique opportunities to explore these exotic objects.
By exploring the universe at these high energies, scientists can search for new physics, testing theories and performing experiments which are not possible in earth-bound laboratories. Watch the video below to see a few of the highlights of Fermi's first five years in orbit for an idea of the types of objects gamma-ray astronomers study. Fermi at five years, a compilation video summarizing the wide range of science from the first five years of the Fermi Gamma-ray Telescope.
Credit: NASA. Astronomer's Toolbox. Gamma-ray Astronomy Long before experiments could detect gamma rays emitted by cosmic sources, scientists had known that the Universe should be producing such high energy photons. Artist's concept of Explorer 11 in orbit. The Vela 5B satellite in low-Earth orbit. Credit: LANL. An electronvolt is defined as how much energy a single electron gains when its electric potential increases by one volt, according to Encyclopedia Britannica.
Electric potential is the amount of work to move a unit charge from one spot to another against an electric field. Visible light has a photon energy of between 1. The scale for electronvolts continues as follows: kilo-electron volt keV, one thousand eV , mega-electron volt MeV, one million eV , giga-electron volt GeV, one thousand million eV , etc.
For a quick idea of how much energy we're talking about, a single nuclear fission event is measured at about MeV, according to the Lawrence Berkeley National Laboratory. Fermi can view objects at a wide range of scales — anywhere between 8 keV to GeV. The GBM can view the entire sky and is designed to spot about gamma-ray bursts every year, as well as events such as solar flares.
It detects X-rays and gamma-rays that have an energy range between 8 keV and 30 meV, Goddard says. The LAT can view 20 percent of the sky at once, and if it is left in its default "sky-survey" mode, it will move around the entire sky once every three hours. Researchers can also choose to swing the LAT to view interesting objects. Fermi discovered two massive bubbles of material emanating from the Milky Way's center in Follow-up observations have been performed in X-rays and radio wavelengths, including a Hubble Space Telescope study released in that clocked these bubbles moving at 2 million mph 3.
NASA periodically releases all-sky maps from Fermi taken over several years of observations, such as this version that had two years of data included. More than a third of the sources revealed in this particular map had never been detected before.
Also in , Fermi released a large scientific haul of results including nine newly discovered pulsars and spotted a mysterious burst near the Crab Nebula. An automatic report showed that Fermi was only a week away from a potentially devastating collision with Cosmos , a dead Soviet-era spy satellite that used to be operational during the Cold War in the s.
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