Subscribe free to our newsletters via your
. 24/7 Space News .

Fermi's Motion Produces a Study in Spirograph
by Francis Reddy for Goddard Space Flight Center
Greenbelt, MD (SPX) Feb 28, 2013

This image compresses the Vela movie sequence into a single snapshot by merging pie-slice sections from eight individual frames. Credit: NASA/DOE/Fermi LAT Collaboration.

NASA's Fermi Gamma-ray Space Telescope orbits our planet every 95 minutes, building up increasingly deeper views of the universe with every circuit. Its wide-eyed Large Area Telescope (LAT) sweeps across the entire sky every three hours, capturing the highest-energy form of light -- gamma rays -- from sources across the universe. These range from supermassive black holes billions of light-years away to intriguing objects in our own galaxy, such as X-ray binaries, supernova remnants and pulsars.

Now a Fermi scientist has transformed LAT data of a famous pulsar into a mesmerizing movie that visually encapsulates the spacecraft's complex motion.

Pulsars are neutron stars, the crushed cores of massive suns that destroyed themselves when they ran out of fuel, collapsed and exploded. The blast simultaneously shattered the star and compressed its core into a body as small as a city yet more massive than the sun.

The result is an object of incredible density, where a spoonful of matter weighs as much as a mountain on Earth. Equally incredible is a pulsar's rapid spin, with typical rotation periods ranging from once every few seconds up to hundreds of times a second. Fermi sees gamma rays from more than a hundred pulsars scattered across the sky.

One pulsar shines especially bright for Fermi. Called Vela, it spins 11 times a second and is the brightest persistent source of gamma rays the LAT sees. Although gamma-ray bursts and flares from distant black holes occasionally outshine the pulsar, they don't have Vela's staying power.

Because pulsars emit beams of energy, scientists often compare them to lighthouses, a connection that in a broader sense works especially well for Vela, which is both a brilliant beacon and a familiar landmark in the gamma-ray sky.

Most telescopes focus on a very small region of the sky, but the LAT is a wide-field instrument that can detect gamma rays across a large portion of the sky at once. The LAT is, however, much more sensitive to gamma rays near the center of its field of view than at the edges. Scientists can use observations of a bright source like Vela to track how this sensitivity varies across the instrument's field of view.

With this in mind, LAT team member Eric Charles, a physicist at the Kavli Institute for Particle Astrophysics and Cosmology and the SLAC National Accelerator Laboratory at Stanford University in California, used the famous pulsar to produce a novel movie. He tracked both Vela's position relative to the center of the LAT's field of view and the instrument's exposure of the pulsar during the first 51 months of Fermi's mission, from Aug. 4, 2008, to Nov. 15, 2012.

The movie renders Vela's position in a fisheye perspective, where the middle of the pattern corresponds to the central and most sensitive portion of the LAT's field of view. The edge of the pattern is 90 degrees away from the center and well beyond what scientists regard as the effective limit of the LAT's vision.

The pulsar traces out a loopy, hypnotic pattern reminiscent of art produced by the colored pens and spinning gears of a Spirograph, a children's toy that produces geometric patterns.

The pattern created in the Vela movie reflects numerous motions of the spacecraft. The first is Fermi's 95-minute orbit around Earth, but there's another, subtler motion related to it. The orbit itself also rotates, a phenomenon called precession. Similar to the wobble of an unsteady top, Fermi's orbital plane makes a slow circuit around Earth every 54 days.

In order to capture the entire sky every two orbits, scientists deliberately nod the LAT in a repeating pattern from one orbit to the next. It first looks north on one orbit, south on the next, and then north again.

Every few weeks, the LAT deviates from this pattern to concentrate on particularly interesting targets, such as eruptions on the sun, brief but brilliant gamma-ray bursts associated with the birth of stellar-mass black holes, and outbursts from supermassive black holes in distant galaxies.

The Vela movie captures one other Fermi motion. The spacecraft rolls to keep the sun from shining on and warming up the LAT's radiators, which regulate its temperature by bleeding excess heat into space.

The braided loops and convoluted curves drawn by Vela hint at the complexity of removing these effects from the torrent of data Fermi returns, but that's a challenge LAT scientists long ago proved they could meet.

Still going strong after more than four years on the job, Fermi continues its mission to map the high-energy sky, which is now something everyone can envision as a celestial Spriograph traced by a pulsar pen.


Related Links
Fermi Gamma-ray Space Telescope
Stellar Chemistry, The Universe And All Within It

Comment on this article via your Facebook, Yahoo, AOL, Hotmail login.

Share this article via these popular social media networks DiggDigg RedditReddit GoogleGoogle

Memory Foam Mattress Review
Newsletters :: SpaceDaily :: SpaceWar :: TerraDaily :: Energy Daily
XML Feeds :: Space News :: Earth News :: War News :: Solar Energy News

Sweeping the Dust from a Cosmic Lobster
Munich, Germany (SPX) Feb 25, 2013
A new image from ESO's VISTA telescope captures a celestial landscape of glowing clouds of gas and tendrils of dust surrounding hot young stars. This infrared view reveals the stellar nursery known as NGC 6357 in a surprising new light. It was taken as part of a VISTA survey that is currently scanning the Milky Way in a bid to map our galaxy's structure and explain how it formed. Located a ... read more

Water On The Moon: It's Been There All Along

Building a lunar base with 3D printing

US, Europe team up for moon fly-by

Russia to Launch Lunar Mission in 2015

Lab Instruments Inside Curiosity Eat Mars Rock Powder

First-ever space tourist plans mission to Mars

Mars rover ingests rock powder for tests

Opportunity Is On A Rock Hunt

Stanford scientist closes in on a mystery that impedes space exploration

U.S. research to be free online

NASA Creates Space Technology Mission Directorate

Educator Teams Fly On NASA Sofia Airborne Observatory

Welcome Aboard Shenzhou 10

Reshuffle for Tiangong

China to launch 20 spacecrafts in 2013

Mr Xi in Space

Record Number of Students Control ISS Camera

NASA briefly loses contact with space station

Temporary Comm Loss Interrupts Crew's Day

Low-Gravity Flights Will Aid ISS Fluids and Combustion Experiments

'Faulty Ukrainian Parts' Blamed for Zenit Launch Failure

The light-lift member of Arianespace's launcher family is readied for its second mission

SpaceX 2 Launch Set for March 1

NASA Releases Glory Taurus XL Launch Failure Report Summary

Scientists spot birth of giant planet

NASA's Kepler Mission Discovers Tiny Planet System

Kepler helps astronomers find tiny exo planet

Searching for a Pale Blue SPHERE in the Universe

Ancient Egyptian pigment points to new security ink technology

Laser mastery narrows down sources of superconductivity

In probing mysteries of glass, researchers find a key to toughness turns heads with 3-D iPad app

The content herein, unless otherwise known to be public domain, are Copyright 1995-2014 - Space Media Network. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA Portal Reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement,agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. Privacy Statement