NASA’s Fermi telescope reveals best-ever view of the gamma-ray sky

National Aeronautics and Space Administration

Segue 1

CTA 1 Pulsar

Nova V407 Cygni

W44

Crab Nebula

3C454.3
GRB 090510A

2FGL0143.6-5844

Credit: NASA/DOE/Fermi/LAT Collaboration
The image above shows a map of the high-energy gamma-ray sky as seen by the Fermi Large Area Telescope in four years of observations. The map is in galactic coordinates, with theplane 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:Fermi Bubbles (dashed line): These huge, faintstructures stretch halfway across the sky aboveand below the center of the Milky Way. They may
be remnants of some powerful activity around theblack hole in the Galactic Center.
CTA 1 Pulsar: The first of many pulsars
discovered by Fermi LAT scientists using only
gamma-ray data was the one in supernova
remnant CTA 1. A pulsar is a neutron star whose
rapid rotation powers beams of radio, optical,
X-ray and gamma radiation. Although 10,000
years old, the CTA 1 pulsar still emits a thousand
times more energy than our sun.
Nova V407 Cygni: Fermi LAT scientists weresurprised and delighted in March 2010 when
gamma rays from a nova were detected for thefirst time. These stellar eruptions in a binary starsystem were not expected to be powerful enoughto produce gamma rays, the highest-energy formof light.
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.govFS-2008-4-103-GSFC

W44: Fermi’s LAT has spatially resolved GeV
gamma rays in the supernova remnant W44, thedebris left behind by a star that exploded about
20,000 years ago. The features clearly align withstructures detectable in X-rays, infrared, and radio.
The gamma-ray observations support the idea thathigh-energy cosmic-ray particles are produced insuch supernova remnants.
Crab Nebula: Fermi observations of the CrabNebula, a 1000-year-old supernova remnant
containing a pulsar, revealed gamma-ray flares
set off by the most energetic particles ever traced
to a specific astronomical object. To account forthe days-long flares, scientists say that electrons
near the pulsar must be accelerated to energies athousand trillion (1015) times greater than that ofvisible light.

Five notable sources beyond our galaxy:
3C454.3: In 2009 and 2010, Fermi’s LAT recordeda series of flares from the blazar 3C 454.3. In
November 2010, 3C454.3 briefly was the brightest
object in the gamma-ray sky. The source is a particle
jet powered by the galaxy’s supermassive blackhole. This blazar is 7 billion light-years away, but isespecially bright because its jet is directed toward
Earth.
Cen A: Fermi’s LAT resolved extended lobes ofhigh-energy gamma rays from a region aroundthe active galaxy Centaurus A. The emission
corresponds to million-light-year-wide radioemitting gas thrown out by the galaxy’s supersized
black hole. How the energy is conveyed the huge
distances out to the gamma-ray lobes remains apuzzle.
Segue 1: This dwarf spheroidal galaxy, a compan­
ion of our own Milky Way Galaxy, is not seen ingamma rays. The absence of gamma-ray signals
from any such dwarf galaxies is important because
they are thought to contain large amounts of dark
matter. Fermi observations are ruling out somemodels of dark matter that predicted gamma-ray
detections of these galaxies.
GRB 090510A: This short gamma-ray burst test­
ed Einstein’s idea that all light travels at the samespeed. Low-energy and high-energy gamma raysfrom this burst arrived within one second after
traveling 7 billion years, eliminating some theo­ries that challenged Einstein’s idea.
2FGL0143.6-5844: This gamma-ray source is
known by its name in the Second Fermi LAT
Catalog, because scientists still do not knowwhat it is. Its location far from the plane of theMilky Way suggests that it lies outside our Galaxy.
Searches with radio, X-ray, and optical telescopes
have not yet found a counterpart to the gammaray source. Like almost a third of the gamma-ray
sources, it remains a mystery waiting to be solved.

Exploring the Extreme Universe:
Under a Gamma-ray Sky
In distant regions of space, supermassive blackholes eject streams of gamma-ray producingmatter stretching many thousands of light-years.
Gamma-ray bursts, the most energetic explosions
in the universe, release more energy ina moment than our Sun
emits in 10 billion years.
Theory suggests that
gamma rays are also produced
when mysterious dark matter particles col­lide 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 explora­tion technology, Fermi is probing the nature of
the gamma-ray sky and shedding light on someof the most important mysteries of modern as­
trophysics. Exploring the most extreme environ­ments 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 searchingfor 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 withhigh sensitivity. Orbiting Earth every 95 min­utes, Fermi is giving scientists a unique oppor­
tunity to learn about the ever-changing universeat extreme energies. With improved resolution,
Fermi’s scientists are identifying the celestialsources with objects that are recognizable atlower energies, such as distant quasars, pul­sars, or supernova remnants.
A network of ground-based
and space-based telescopes areworking together with Fermi as
it opens the high-energy universe for explora­tion. Fermi is a flexible observatory for inves­tigating a wide range of extreme astrophysicalphenomena.

NASAfacts

Cen A

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

Power1,500 watts

LaunchJune 11, 2008

Active Galaxies and Blazars: An active galaxy is a galaxy with anaccreting 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.
FermiTracker
4 x 4 Array of Towers

Calorimeter
top view

Solar Panels

Gamma-ray Burst Monitor (GBM)
Gamma-ray bursts (GRBs) are elusive andshort-lived. Although they are among the mostenergetic explosions in the universe, it is chal­lenging 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 thisproblem by providing all-sky coverage with anarray of 12 low- and 2 medium-energy gamma­
ray detectors pointing in different directions
from the spacecraft. These detectors are track­ing 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.

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 hypotheticalparticles called WIMPs (Weakly Interacting
Massive Particles), as many scientists theo­rize, then interactions of these WIMPs may
produce gamma rays detectable by Fermi’s
Large Area Telescope. If so, Fermi could pro­vide scientists with data that shed critical newlight on the mystery of dark matter.

Anticoincidence
Detector

LAT Radiator

15 m

GBM Instrument(Gamma-ray Burst Monitor)

Gamma-ray Bursts: Gamma-ray bursts are among the most ener­
getic explosions in the universe. Recent observations have linked theorigins of GRBs to the death throes of very massive stars, or to colli­
sions between two black holes and/or neutron stars – both events willlead 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.

Gamma-ray Mysteriesside viewfromtip totip

Ku-Band Antenna

Fermi

Unidentified Sources - It is likely there
are many more types of gamma-ray sourcesamong those presently unidentified andthose to be discovered by Fermi. The supe­rior angular resolution of Fermi’s Large Area
Telescope is helping to unveil the nature ofthese mystery sources, providing new understanding of the origin of their gamma rays
and possible new laws of physics.

Gamma-ray Space Telescope
http://www.nasa.gov/fermi

Pulsars: When the core of a massive star undergoes gravitational collapse,
it forms a very dense object known as a neutron star. These objects havedensities 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, ex­pelling jets of gamma rays which rotate through our line of sight, producing
pulsations that we can observe. Other neutron stars – the so-called magne­tars – may possess even stronger magnetic fields. Magnetar starquakes canunleash tremendous flares of gamma rays.

NASA/CXC

Aurore Simonnet, SSU

NASA’s Fermi mission is an astrophysics andparticle physics partnership, developed in col­laboration with the U.S. Department of Ener­gy, along with important contributions fromacademic institutions, laboratories, and partners in France, Germany, Italy, Japan, Sweden,
and the United States.

LAT Instrument(Large Area Telescope under the Anticoincidence Detector)

2.9 m highGamma rays permeate the cosmos. They are
emitted from objects as nearby as our own Sun
and Milky Way galaxy to those as far away astremendous explosions in the early universe.
Fermi, NASA’s new gamma-ray observatory, isopening a wide window on the extreme uni­verse. With a huge leap in all key capabilities,Fermi is enabling scientists to answer deep andperplexing 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 andenabling searches for signals of new physics.

The Large Area Telescope, the observatory’s
primary instrument, is seeing an enormous
20 percent of the sky at any given time andis detecting the arrival time and direction of
gamma rays broadly ranging from 20 MeV (20million electron volts) to 300 GeV (300 bil­lion 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 ofthe LAT is 30 or more times that of EGRET,
depending on energy.

Casey Reed/Penn StateAt the core of Fermi’s mission is finding out
what gives birth to the diverse spectrumof gamma rays. There are many intriguing
possibilities, including blazars, gamma-ray
bursts, and pulsars.

Large Area Telescope (LAT)

Dana Berry/NASAGamma-ray Origins?

Anatomy of a Space TelescopeCosmic Rays and Supernova Remnants: Cosmic
rays are subatomic particles that are accelerated to very
near the speed of light by mechanisms that are still amystery. One theory suggests that these particles are ac­celerated by the shock waves of supernovae. The LAT
is searching for the telltale gamma-ray signature of thisacceleration.
NASAfacts