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Fermi's Eye on the Universe

by Sandra Ning, Terra Linda HS

An image of the Milky Way Galaxy and its surroundings, by Fermi.

    Since their invention, telescopes have allowed humans to examine closely, and in more detail, the universe around them. Advances in optic technology have brought humans closer to understanding the microscopic world around us and the far-away mysteries above us. Telescopes like Hubble and Chandra directed into space have been sending back dazzling pictures of nebulae, galaxies and star clusters that are as beautiful as they are scientifically fascinating. Fermi joins the research team with new equipment: gamma- ray sensing technology.
    Dr. Lynn Cominsky, who is the Department Chair of Physics and Astronomy at Sonoma State University, stopped to answer a couple of questions about her upcoming presentation on NASA's Fermi Gamma-ray Space Telescope. She also lent her expertise to explaining the various, fascinating phenomena that occur out in the vast expanse of space.

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1. What is the goal of the Fermi Gamma-ray Telescope mission?

From http://fermi.gsfc.nasa.gov/science/

Mission Objectives:
  • Explore the most extreme environments in the Universe, where nature harnesses energies far beyond anything possible on Earth.
  • Search for signs of new laws of physics and what composes the mysterious Dark Matter.
  • Explain how black holes accelerate immense jets of material to nearly light speed.
  • Help crack the mysteries of the stupendously powerful explosions known as gamma-ray bursts.
  • Answer long-standing questions across a broad range of topics, including solar flares, pulsars and the origin of cosmic rays.
2. What sorts of cosmic substances/structures is Fermi looking for?

     Most of the objects that Fermi sees are Active Galaxies which are aiming jets of gamma rays towards Earth (also known as blazars).
     Fermi is also discovering many pulsars, gamma-ray bursts, solar flares, supernova remnants and a handful of other objects, such as high-mass binaries, novae and extended objects like the "Fermi bubbles."


Gamma-ray emissions around the Milky Way, detected by Fermi.

3. How are black holes formed? Why are supermassive ones, like Sagittarius A*, often (always?) at the center of galaxies?

     We don't know exactly how the supermassive black holes are formed. Current research indicates a correlation in size between the size of the galactic bulge and its black hole's mass. This would indicate that both the BH and the galaxy were formed together, when structure
began to form about a 500 million years after the Big Bang. Supermassive BHs are always at the centers of galaxies, as they are the most massive objects in the galaxy.

4. What about white holes and wormholes? Are they purely theoretical, 

     White holes and wormholes are theoretically allowed by Einstein's theory of General Relativity. However, we know of no earthly-substance that could go into a BH and come out a WH without being destroyed.
or even fictional?

     White holes and wormholes are theoretically allowed by Einstein's theory of General Relativity. However, we know of no earthly-substance that could go into a BH and come out a WH without being destroyed.

5. What are pulsars?

     Pulsars are rotating cores of dead stars - about the size of a large city. They are formed when regular, massive stars end their lives in supernova explosion. The outer layers of the star are ejected out, while the inner layers collapse down to form the pulsar. They also have very strong magnetic fields, which channel the particles and gamma-rays  in opposite directions.

6. And why are all of these high-energy phenomena of interest to researchers? How much (or perhaps, how little) do we know about these cosmic events that Fermi is looking for?

     Researchers are excited to study the most exotic and energetic phenomena in the Universe - we cannot duplicate the extreme conditions on Earth that naturally occur in space. Extreme magnetic fields, strong field gravity, high temperatures - all are of interest to scientists, as we can test our laws of physics at these extremes.


The Fermi satellite.


7. How does gamma-ray detection help Fermi in its mission? Is Fermi the only telescope with gamma-ray detection at the moment?

     Fermi is a gamma-ray telescope. So it must detect gamma rays in order to accomplish its mission. AGILE is a smaller telescope that was built and launched by the Italians, a few months before Fermi.

8. Aren't gamma rays without mass? How exactly does Fermi detect gamma rays?

     Gamma rays are the highest-energy form of light, and all forms of light are massless. Fermi has two instruments: the Large Area Telescope and the Gamma-ray Burst Monitor. Each detects the gamma ray light in a different manner.

You can read about the LAT here:
http://fermi.gsfc.nasa.gov/science/instruments/lat.html

You can read about the GBM here:
http://fermi.gsfc.nasa.gov/science/instruments/gbm.html

9. As part of the public outreach program for Fermi, why do you believe its important for the public to know about projects
like Fermi?

     Everyone is curious about the Universe - where we came from, where we are going, and are we alone? Fermi provides answers to some of these important questions. It is our job to explain Fermi's amazing discoveries to the public.

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Come see Dr. Cominsky present "Exploring the Extreme Universe with Fermi" on Wednesday, March 6th, in Terra Linda High School's room 207. This month is Astronomy Month for the Marin Science Seminar. Check out our Facebook for more updates!

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Sandra Ning
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