This four-page color brochure describes the science of NASA’s GLAST mission, as well as providing tables that summarize the instrumental parameters and the mission participants. Note: In 2008, the Gamma-ray Large Area Space Telescope (GLAST) was renamed Fermi, for the physicist Enrico Fermi. Educational levels: General public

Lynn cominsky

English

Digital Library for Earth System Education

National Aeronautics and Space Administration
Exploring the Extreme Universe: 
Under a Gamma-ray Sky
In distant regions of space, supermassive black 
holes eject streams of gamma-ray producing 
matter stretching many thousands of light-years. 
Gamma-ray bursts, the most energetic explosions 
in the universe, release more energy in 
a moment than our Sun 
emits in 10 billion years. 
Theory suggests that 
gamma rays are also produced 
when mysterious dark matter particles col-
lide and annihilate each other. Exotic and surreal 
though it may seem to some, this is the extreme 
universe of high-energy astrophysics. 
We are now peering into the heart of this cos-
mic landscape with the Fermi Gamma-ray Space 
Telescope. An advance in space-science explora-
tion technology, Fermi is probing the nature of 
the gamma-ray sky and shedding light on some 
of the most important mysteries of modern as-
trophysics. Exploring the most extreme environ-
ments in the universe, where nature harnesses 
energies far beyond anything possible on Earth, 
Fermi is answering long-standing questions 
across a broad range of topics and is searching 
for signs of new laws of physics. 
Fermi Mission Profile
Fermi is the first imaging gamma-ray observa-
tory to survey the entire sky every day and with 
high sensitivity. Orbiting Earth every 95 min-
utes, Fermi is giving scientists a unique oppor-
tunity to learn about the ever-changing universe 
at extreme energies. With improved resolution, 
Fermi’s scientists are identifying the celestial 
sources with objects that are recognizable at 
lower energies, such as distant quasars, pul-
sars, or supernova remnants. 
A network of ground-based 
and space-based telescopes are 
working together with Fermi as 
it opens the high-energy universe for explora-
tion. Fermi is a flexible observatory for inves-
tigating a wide range of extreme astrophysical 
phenomena.
General Spacecraft Information:
Lifetime 5-10 years
Height 2.9 m (9.2 feet)
Width 1.8 m (4.6 feet) across spacecraft bus
Mass 4,303 kg (9,487 lbs)
Download Link 40 megabits/second
Power  1,500 watts
Launch June 11, 2008
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The image above shows a map of the high-energy gamma-ray sky as seen by the Fermi Large Area Telescope in three months of observations. The map is in galactic coordinates, with 
the plane of the Milky Way galaxy stretching horizontally across the center of the map. Below are descriptions of a few of the notable sources within and beyond the Milky Way.
Five notable sources within our galaxy:
The Sun. Now near the minimum of its activ-
ity cycle, the Sun would not be a particularly 
notable source except for one thing: It’s the 
only one that moves across the sky. The Sun’s 
annual motion against the background sky is a 
reflection of Earth’s orbit around the Sun. 
The gamma rays Fermi now sees from the Sun 
actually come from high-speed particles col-
liding with the Sun’s gas and light. The Sun is 
only a gamma-ray source when there’s a solar 
flare. During the next few years, as solar activity 
increases, scientists expect the Sun to produce 
growing numbers of high-energy flares, and no 
other instrument will be able to observe them 
in the LAT’s energy range.
LSI +61 303. This is a high-mass X-ray binary 
located 6,500 light-years away in Cassiopeia. 
This unusual system contains a hot B-type star 
and a neutron star and produces radio out-
bursts that recur every 26.5 days. Astronomers 
cannot yet account for the energy that powers 
these emissions. 
PSR J1836+5925. This is a pulsar — a type of 
spinning neutron star that emits beams of radia-
tion — located in the constellation Draco. It’s 
one of the new breed of pulsars discovered by 
Fermi that pulse only in gamma rays.
47 Tucanae. Also known as NGC 104, this is a 
sphere of ancient stars called a globular cluster. It 
lies 15,000 light-years away in the southern con-
stellation Tucana.
Unidentified. More than 30 of the brightest 
gamma-ray sources Fermi sees have no obvious 
counterparts at other wavelengths. This one, 
designated 0FGL J1813.5-1248, was not seen 
by previous missions, and Fermi’s LAT sees it 
as variable. The source lies near the plane of the 
Milky Way in the constellation Serpens Cauda. 
As a result, it’s likely within our galaxy -- but 
right now, astronomers don’t know much more 
than that. 
Five notable sources beyond our galaxy:
NGC 1275. Also known as Perseus A, this gal-
axy at the heart of the Perseus Galaxy Cluster is 
known for its intense radio emissions. It lies 233 
million light-years away.
3C 454.3. This is a type of active galaxy called 
a “blazar.” Like many active galaxies, a blazar 
emits oppositely directed jets of particles trav-
eling near the speed of light as matter falls into 
a central supermassive black hole. For blazars, 
the galaxy happens to be oriented so that one 
jet is aimed right at us. Over the time period 
represented in this image, 3C 454.3 was the 
brightest blazar in the gamma-ray sky. It flares 
and fades, but for Fermi it’s never out of sight. 
The galaxy lies 7.2 billion light-years away in 
the constellation Pegasus. 
PKS 1502+106. This blazar is located 10.1 
billion light-years away in the constellation 
Boötes. It appeared suddenly, briefly outshone 
3C 454.3, and then faded away.
PKS 0727-115. This object’s location in the 
plane of the Milky Way would lead one to 
expect that it’s a member of our galaxy, but it 
isn’t. Astronomers believe this source is a type 
of active galaxy called a quasar. It’s located 9.6 
billion light-years away in the constellation 
Puppis.
GRB 080916C. The first gamma-ray burst 
to be seen in high-resolution by Fermi’s LAT 
is one for the record books. The blast had the 
greatest total energy, the fastest motions and 
the highest-energy initial emissions recorded 
to date. For a few moments, it was the brightest 
source in the universe.
National Aeronautics and Space Administration
Sonoma State University, NASA E/PO
1801 E Cotati Avenue
Rohnert Park, CA 94928
fermi.sonoma.edu
http://www.nasa.gov
FS-2008-4-103-GSFC
Gamma-ray Origins?
At the core of Fermi’s mission is finding out 
what gives birth to the diverse spectrum 
of gamma rays. There are many intriguing 
possibilities, including blazars, gamma-ray 
bursts, and pulsars.
Gamma rays permeate the cosmos. They are 
emitted from objects as nearby as our own Sun 
and Milky Way galaxy to those as far away as 
tremendous explosions in the early universe. 
Fermi, NASA’s new gamma-ray observatory, is 
opening a wide window on the extreme uni-
verse. With a huge leap in all key capabilities, 
Fermi is enabling scientists to answer deep and 
perplexing questions related to supermassive 
black-hole systems, gamma-ray bursts, pulsars, 
and the origins of cosmic rays. Fermi is also 
uncovering new sources of gamma rays and 
enabling searches for signals of new physics. 
NASA’s Fermi mission is an astrophysics and 
particle physics partnership, developed in col-
laboration with the U.S. Department of Ener-
gy, along with important contributions from 
academic institutions, laboratories, and part-
ners in France, Germany, Italy, Japan, Sweden, 
and the United States. 
Large Area Telescope (LAT)
The Large Area Telescope, the observatory’s 
primary instrument, is seeing an enormous 
20 percent of the sky at any given time and 
is detecting the arrival time and direction of 
gamma rays broadly ranging from 20 MeV (20 
million electron volts) to 300 GeV (300 bil-
lion electron volts). The LAT’s field-of-view 
is four times that of its predecessor instru-
ment, the Energetic Gamma-ray Experiment 
Telescope  (EGRET), which operated on 
board the Compton Gamma-ray Observatory 
(CGRO) from 1991-2000. The sensitivity of 
the LAT is 30 or more times that of EGRET, 
depending on energy. 
Gamma-ray Burst Monitor (GBM)
Gamma-ray bursts (GRBs) are elusive and 
short-lived. Although they are among the most 
energetic explosions in the universe, it is chal-
lenging to catch them even with a telescope 
having a field of view as large as the LAT’s. The 
Fermi Gamma-ray Burst Monitor solves this 
problem by providing all-sky coverage with an 
array of 12 low- and 2 medium-energy gamma-
ray detectors pointing in different directions 
from the spacecraft. These detectors are track-
ing the direction and time histories of GRBs 
and other rapidly flaring gamma-ray sources. 
The Gamma-ray Burst Monitor is detecting 
approximately 200 GRBs each year, as well as 
solar flares, and other short-lived, high-energy 
cosmic events.
Anatomy of a Space Telescope
LAT Instrument 
(Large Area Telescope under the Anticoincidence Detector)
Anticoincidence 
Detector
Ku-Band Antenna
LAT Radiator
15 m from tip to tip
Solar Panels
top view
side view4 x 4 Array of Towers
Calorimeter
Tracker
GBM Instrument 
(GLAST Burst Monitor)
2.9
 m
 hi
gh
1.8 m wide
Fermi
Gamma-ray Space Telescope
http://www.nasa.gov/fermi
Gamma-ray Mysteries
Dark Matter  - The origin of dark matter, 
which makes up as much as 80 percent of 
the mass of the universe, remains a mystery. 
If dark matter is made up of hypothetical 
particles called WIMPs (Weakly Interacting 
Massive Particles), as many scientists theo-
rize, then interactions of these WIMPs may 
produce gamma rays detectable by Fermi’s 
Large Area Telescope. If so, Fermi could pro-
vide scientists with data that shed critical new 
light on the mystery of dark matter. 
Unidentified Sources - It is likely there 
are many more types of gamma-ray sources 
among those presently unidentified and 
those to be discovered by Fermi. The supe-
rior angular resolution of Fermi’s Large Area 
Telescope is helping to unveil the nature of 
these mystery sources, providing new under-
standing of the origin of their gamma rays 
and possible new laws of physics.
Active Galaxies and Blazars: An active galaxy is a galaxy with an 
accreting super-massive central black hole. These black holes pro-
duce high-energy radiation from the swirling disks of matter falling 
into them. Some of these black holes also eject streams of matter 
thousands of light-years at very nearly the speed of light. Blazars 
are thought to be active galaxies whose jets happen to be pointing 
toward us, and we see gamma rays associated with the jets. 
Gamma-ray Bursts: Gamma-ray bursts are among  the most ener-
getic explosions in the universe. Recent observations have linked the 
origins of GRBs to the death throes of very massive stars, or to colli-
sions between two black holes and/or neutron stars – both events will 
lead to the birth of a new black hole. Fermi is providing new insights 
into these mysterious and exotic events by studying their gamma rays 
over a huge range of energies. 
Fermi
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Pulsars: When the core of a massive star undergoes gravitational collapse, 
it forms a very dense object known as a neutron star. These objects have 
densities on the order of 1018 kg/m3. (Imagine condensing Mount Everest 
down to the size of a sugar cube.) With magnetic fields trillions of times 
that of Earth, these objects work like high-energy particle accelerators, ex-
pelling jets of gamma rays which rotate through our line of sight, producing 
pulsations that we can observe. Other neutron stars – the so-called magne-
tars  –  may possess even stronger magnetic fields. Magnetar starquakes can 
unleash tremendous flares of gamma rays.
NASAfacts
Cosmic Rays and Supernova Remnants: Cosmic 
rays are subatomic particles that are accelerated to very 
near the speed of light by mechanisms that are still a 
mystery. One theory suggests that these particles are ac-
celerated by the shock waves of supernovae. The LAT 
is searching for the telltale gamma-ray signature of this 
acceleration. 


GLAST Launch Fact Sheet

http://glast.sonoma.edu/teachers/Fermifactsheet09pt1_508.pdf

GLAST Launch Fact Sheet

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