Mission Research

    What Will Fermi Study?

    GLAST satellite

    Image above: Image of the Fermi Satellite. Credit: NASA E/PO, Sonoma State University, Aurore Simonnet

    Here is a list of features that explain the different things Fermi will explore.

    Blazars and active galaxies
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    Gamma-ray bursts
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    Neutron stars
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    Cosmic rays and supernova remnants
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    The Milky Way galaxy
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    Gamma-ray background radiation
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    The early universe
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    Our solar system
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    Dark matter
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    Fundamental physics
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    The unknown!
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    Electromagnetic Spectrum Basics

    The electromagnetic spectrum is the basis for the observations Fermi undertakes.

    what are gamma rays

    Image above: Measuring wavelengths.

    + High resolution image

    To be able to understand how Fermi works, you need to understand the electromagnetic spectrum.

    What we call "light" is actually just a tiny fraction of the broad range of radiation on the electromagnetic radiation spectrum. The entire span stretches from very-low-energy radio waves through microwaves, infrared light, visible light, ultraviolet light, X rays, and finally to very-high-energy gamma rays. The processes producing photons (single particles of electromagnetic radiation) of each type of radiation differ, as do their energy, but all of the different forms of radiation are still just part of the electromagnetic spectrum's family. The only real difference between a gamma-ray photon and a visible-light photon is the energy. Gamma rays can have over a billion times the energy of the type of light visible to our eyes.

    In fact, gamma rays are so energetic that they are harmful to life on Earth. Luckily, Earth's atmosphere absorbs gamma rays, preventing them from affecting life on the ground. But this poses a problem if you want to observe the Universe in gamma-ray light. The very atmosphere that protects us from gamma rays prevents us from directly observing them from the ground. Astronomical observations of gamma-ray sources in the Fermi energy range are therefore done with high-altitude balloons or satellites, above the protective blanket of Earth's atmosphere.

    The high energy of gamma rays poses another problem: they can pass right through any lens or mirror, making it very difficult to focus them in a telescope. Astronomical observations, therefore, must rely on a different technology to view the gamma-ray universe. Scientists must make use of methods developed by particle physicists, who have long understood techniques for measuring high-energy particles. Fermi's specialized astronomical instruments will therefore employ detectors used and perfected by physicists interested in the interactions of subatomic particles.

Mission Factoids

    The atmosphere that protects us from gamma rays prevents us from directly observing them from the ground.

    A gamma ray is a photon more energetic than an X-ray (more than about 50 keV). Gamma rays are created from nuclear reactions or particle accelerations. Gamma rays are the most energetic photons of the electromagnetic spectrum.

    The GLAST Burst Monitor (GBM) is the instrument on Fermi that is specifically designed to detect gamma-ray bursts.

    Gravity is the attractive force of an object with mass on another object. The gravitational force between two objects depends on their masses and the distance between them.