Mysterious Objects at the Edge of the Electromagnetic Spectrum
- URL to an article from NASA
This is a wonderful time to be alive
First few paragraphs
"March 16, 2012: The human eye is crucial to astronomy. Without the
ability to see, the luminous universe of stars, planets and galaxies would be
closed to us, unknown forever. Nevertheless, astronomers cannot shake their
fascination with the invisible.
Outside the realm of human vision is an entire electromagnetic spectrum of
wonders. Each type of light--from radio waves to gamma-rays--reveals
something unique about the universe. Some wavelengths are best for studying
black holes; others reveal newborn stars and planets; while others
illuminate the earliest years of cosmic history.
NASA has many telescopes "working the wavelengths" up and down the
electromagnetic spectrum. One of them, the Fermi Gamma-Ray Telescope orbiting
Earth, has just crossed a new electromagnetic frontier.
A new ScienceCast video takes viewers on a trip to the edge of the
electromagnetic spectrum, where mysterious objects are puzzling astronomers.
[_Play it_ (http://www.youtube.com/watch?v=1hIF36ty1Eo) ]
"Fermi is picking up crazy-energetic photons," says Dave Thompson, an
astrophysicist at NASA's Goddard Space Flight Center. "And it's detecting so
many of them we've been able to produce the first all-sky map of the very high
is what the sky looks like near the very edge of the electromagnetic
spectrum, between 10 billion and 100 billion electron volts.”
The light we see with human eyes consists of photons with energies in the
range 2 to 3 electron volts. The gamma-rays Fermi detects are billions of
times more energetic, from 20 million to more than 300 billion electron
volts. These gamma-ray photons are so energetic, they cannot be guided by the
mirrors and lenses found in ordinary telescopes. Instead Fermi uses a sensor
that is more like a Geiger counter than a telescope. If we could wear
Fermi's gamma ray "glasses," we'd witness powerful bullets of energy –
individual gamma rays – from cosmic phenomena such as supermassive black holes and
hypernova explosions. The sky would be a frenzy of activity.
Before Fermi was launched in June 2008, there were only four known
celestial sources of photons in this energy range. "In 3 years Fermi has found
almost 500 more,” says Thompson.
What lies within this new realm?
"Mystery, for one thing," says Thompson. "About a third of the new sources
can't be clearly linked to any of the known types of objects that produce
gamma rays. We have no idea what they are."
The rest have one thing in common: prodigious energy.
An artist's concept of giant 'Fermi bubbles' emerging from the heart of
the Milky Way. [_more_
"Among them are super massive black holes called blazars; the seething
remnants of supernova explosions; and rapidly rotating neutron stars called
And some of the gamma rays seem to come from the 'Fermi bubbles' – giant
structures emanating from the Milky Way's center and spanning some 20,000
light years above and below the galactic plane.
Exactly how these bubbles formed is another mystery.
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