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1000 Fermi Bursts!
 Posted on Sep 21, 2012 05:36:05 PM | Julie McEnery
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The gamma-ray burst monitor (GBM) instrument on Fermi detected its 1000th gamma-ray burst today! This figure from Valerie Connaughton shows the location on the sky of these 1000 cosmic explosions.


The 1000th burst was detected at 21:03 UT on September 21. It lasted for around 3 seconds, and consisted of a single large pulse of gamma-rays. It was automatically detected on board the observatory by the GBM and an alert was sent to the ground, that was then relayed to a worldwide team of astronomers in less than 15 seconds.

Originally, predictions indicated that we would need to wait for around 5 years before getting to the 1000th burst.  However, due to excellent search routines implemented by the team of scientists who developed GBM, the rate of GRB detections has been significantly higher.

GRBs allow Fermi to see farther than any other class of object it detects and  each GRB is a probe of the oldest and most violent explosions in the Universe. Every new one helps us better understand these interesting events.

The Sound of a Fermi Gamma-ray Burst
 Posted on Jun 21, 2012 01:58:32 PM | Julie McEnery
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What does the universe look like at high energies? Thanks to the Fermi Large Area Telescope (LAT), we can extend our sense of sight to "see" the universe in gamma rays. But humans not only have a sense of sight, we also have a sense of sound. If we could listen to the high-energy universe, what would we hear? What does the universe sound like?


A gamma-ray burst, the most energetic explosions in the universe, converted to music. Made by Sylvia Zhu (music) and Judy Racusin (animation)

Every photon has its own energy and frequency; the higher the energy, the higher the frequency. Some photons have just the right frequencies for us to see them as different colors, while others -- such as the gamma rays studied by the Fermi LAT -- are much too energetic to be seen with our eyes. Sound waves have frequencies too, and similarly, we can hear some of them as musical notes. So what happens if we convert high-energy photons into musical notes?

Gamma-ray bursts (GRBs) are some of the most powerful explosions in the universe. GRB 080916C was a particularly energetic burst that occurred in September of 2008. The brightest part of it lasted less than a minute, during which the LAT detected hundreds of gamma rays from the extremely-distant explosion; when we converted the data to music, we slowed the rates down by a factor of five times to hear the individual gamma rays better.

In translating the gamma-ray measurements into musical notes we assigned the photons to be "played" by different instruments (harp, cello, or piano) based on the probabilities that they came from the burst. This particular conversion is a fairly simple one; We built this on work done by other members of the LAT team (Luca Baldini and Alex Drlica-Wagner) who explored converting our data into music in different ways.

In the beginning of the song, before the burst starts, the harp plucks out a few lonely notes. After about half a minute, the piano joins in on top of the harp background, and the notes begin to pile on more and more rapidly. The cello enters the scene as the burst begins in earnest.

We created an accompanying animation to help see what is happening. The top panel shows each individual gamma-ray. The colors refer to low (red), medium (blue) and high (green) quality gamma-rays (played by harp, cello and piano respectively). The energy of the gamma-ray is on the y-axis (higher energy gamma-rays are towards the top of the plot) and the arrival time of the gamma-rays are on the x-axis (later arriving gamma-rays are further to the right). The vertical white line tells you where the music is currently playing. The bottom panel shows the number of gamma-rays (which is the number of notes played) in each time slice.

By converting gamma rays into musical notes, we have a new way of representing the data and listening to the universe.

Happy Birthday Fermi
 Posted on Jun 11, 2012 10:26:12 PM | Julie McEnery
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The cake features a (hand drawn) Fermi gamma-ray skymap, showing the bright band produced by diffuse emission from the disk of our Galaxy, the Fermi bubbles (in black) - huge lobes of gamma-rays extending above and below the Galactic disk, and many point sources of gamma-rays (active galaxies, pulsars and much more).

The Fermi observatory, sculpted here from fondant, shows the Large Area Telescope (grey box) and a 3-d representation of the NaI (black/yellow) and BGO (orange) detectors of the gamma-ray burst monitor. Combined these instruments provide observations over an extraordinarily large swath of the electromagnetic spectrum (from 8keV to over 300 GeV).

A pen is included to show the scale - this was a monstrous cake! The 70 or so of us at the launch anniversary celebration only got through half the cake, despite being a delicious combination of chocolate and vanilla. This is fortunate for our waistlines given the following ingredient list:
7 lbs flour
9 lbs sugar
30 eggs
6 lbs butter
3 lbs marshmallow
1 lb corn starch
8 cups of buttermilk

Fermi on the go! Fermi iPhone App now available
 Posted on May 07, 2011 01:12:48 PM | Julie McEnery
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You can now keep up to date with Fermi activities via a new iphone/ipad app developed by my Italian colleagues. This is available from iTunes  (search for "fermi" to find it). Some screenshots are shown below:



The timing of this release is not accidental - the world-wide community of Fermi-users are meeting in Rome next week for the 3rd Fermi Symposium (the first was in Palo Alto, California in 2007 and the second was in Washington, DC in 2009). Over 400 scientists are meeting to discuss the implications of the exciting observations we have made with Fermi over the past 3 years, and to announce new discoveries. These meetings occur roughly every 18 months, and are a major highlight in the Fermi scientific calendar. Keep your eye out for announcements of new Fermi results next week!

Fermi and solar eclipses
 Posted on Jan 03, 2011 10:33:16 PM | Julie McEnery
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A solar eclipse occurs when the moon comes between the Sun and the Earth and thus casts a shadow on Earth. The shadow can be quite large - as you can see from the excellent image in the January 2, APOD.

There will be a partial solar eclipse tomorrow (January 4). Fermi orbits the Earth every 96 minutes: for two of those orbits tomorrow Fermi will pass through the shadow of the eclipse. This won't cause any problems - each orbit, we pass through the nighttime and thus dark side of the Earth. Passing through the eclipse means that we will spend a little more time recharging the spacecrafts battery from the solar panels than we would ordinarily need.

The Fermi flight operations team closely monitors the performance of the observatory,  they need to know if we will pass through an eclipse so that we won't interpret the change in battery charging performance as a potential problem on the spacecraft.

It's neat to think that a observatory designed to detect gamma-rays from the Universe can notice more classical local phenomena on Earth.

Fermi's Spectacular Second Year
 Posted on Jun 11, 2010 11:13:29 PM | Elizabeth Hays
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Happy Launch Anniversary to Fermi!!
Only two short years ago we watched Fermi take a perfect ride into orbit.

It turns out that the only thing better than Fermi's fantastic first year is its spectacular second year. The data from both instruments are now being analyzed by scientists around the world. The Large Area Telescope team released a first catalog, which was based on 11 months of observations and contains 1451 gamma-ray sources (this is 5x larger than previous catalogs at similar energies).  One of the great things about Fermi is that even though we have been observing for almost 2 years that is not the end of the story. The gamma-ray sky changes every day. Because Fermi sees so much much of the sky for so much of the time, we not only see things we expect to be interesting, but also get to watch the unscripted reality show that is the gamma-ray universe. Here are some of the highlights from the past year.
  • the active galaxy 3C 454.3 briefly became the brightest persistent object ever seen in the gamma-ray sky in December -- link
  • the microquasar Cygnus X-3 (a compact object and massive star binary system) flared and was definitively detected in gamma rays for the first time -- link
  • the gamma-ray bursts burst (and gave us some insight into properties of space-time) -- link
As Fermi continues to watch the sky, we will continue to catch gamma-rays sources doing amazing things. It has been a wonderful two years, and I am looking forward to the next one.

Fermi in Cambodia
 Posted on Apr 13, 2010 11:36:28 AM | Julie McEnery
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Last March, I spent an afternoon talking about Fermi to the children at Aziza's place in Phnom Penh, Cambodia.  Aziza's place is a home and learning center for impoverished children. I was in Cambodia to visit my sister. She lived in an apartment next door to Aziza's place and and had come to know the people at Aziza's place. She suggested that I might like to visit and talk with the children about Astronomy, NASA and Fermi. It was a remarkable experience. The children had several astronomy lessons and activities in anticipation of my visit and were extremely enthusiastic and friendly. The discussion started with Fermi and astronomy and rapidly expanded to include rockets, spaceflight and the nature of the moon.

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