Explanation: What shines in the gamma-ray sky? The most complete answer yet to that question is offered by the Fermi Gamma-ray Space Telescope's first all-sky catalog. Fermi's sources of cosmic gamma-rays feature nature's most energetic particle accelerators, ultimately producing 100 MeV to 100 GeV photons, photons with more than 50 million to 50 billion times the energy of visible light. Distilled from 11 months of sky survey data using Fermi's Large Area Telescope (LAT), the 1,451 cataloged sources include energetic star burst galaxies and active galactic nuclei (AGN) far beyond the Milky Way. But within our own galaxy are many pulsars (PSR) and pulsar wind nebulae (PWN), supernova remnants (SNR), x-ray binary stars (HXB) and micro-quasars (MQO). Fermi's all sky map is shown centered on the Milky Way with the diffuse gamma-ray emission from the Galactic plane running horizontally through the frame. To locate the cataloged gamma-ray sources, just slide your cursor over the map. For now, 630 of the sources cataloged at gamma-ray energies remain otherwise unidentified, not associated with sources detected at lower energeries.
Why does there appear to be a hole in the "mapped" view vs the unmapped view just to the right and slightly below what seems to be galactic center (or @ least image center), of an extremely bright source (in the unmapped view?)?
Whoops. My bad. It appears that my loss of the source was just due to the "crush" of the signal by a label. I guess it just goes to prove that how you look at something, is just as important as just looking @ it.
With the milky way being more prominent in the southern hemisphere, I wonder if all those gamma ray have a little to do with the ozone depletion. What about cancer rates in the southern hemisphere vs. the northern hemisphere?
I think APOD just might be responsible for 80% of my Googling...
From Wikipedia (because of course I had to look up blazar):
A blazar (blazing quasi-stellar object) is a very compact quasar (quasi-stellar object) associated with a presumed supermassive black hole at the center of an active, giant elliptical galaxy. Blazars are among the most violent phenomena in the universe and are an important topic in extragalactic astronomy.
Blazars are members of a larger group of active galaxies, also termed active galactic nuclei (AGN). A few rare objects may be "intermediate blazars" that appear to have a mixture of properties from both OVV quasars and BL Lac objects. The name "blazar" was originally coined in 1978 by astronomer Edward Spiegel to denote the combination of these two classes.
When I read through the various links in today's APOD description and try to get an understanding of those many vast sources of such immense energy scattered through out the universe, it is easier to understand the forces that might have been behind the "Big Bang" when all those energy sources were possibly compressed into one tiny space and then released.
But the impossible question -- how could all that energy have been so compressed initially and what was there before it? It's hard to believe that we will ever really know ....
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.
"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 energy universe."
“This 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."
Click to play embedded YouTube video.
The rest have one thing in common: prodigious energy.
"Among them are super massive black holes called blazars; the seething remnants of supernova explosions; and rapidly rotating neutron stars called pulsars.”
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.
Now that the first sky map is complete, Fermi is working on another, more sensitive and detailed survey.
"In the next few years, Fermi should reveal something new about all of these phenomena, what makes them tick, and why they generate such 'unearthly' levels of energy," says David Paneque, a leader in this work from the Max Planck Institute in Germany.
For now, though, there are more unknowns than knowns about "Fermi's world."
Says Thompson: "It's pretty exciting!"
Know the quiet place within your heart and touch the rainbow of possibility; be
alive to the gentle breeze of communication, and please stop being such a jerk. — Garrison Keillor
Fermi Catalogs the Gamma ray Sky
