An international team of scientists using NASA's Fermi Gamma-ray Space Telescope has discovered a surprisingly powerful millisecond pulsar that challenges existing theories about how these objects form. At the same time, another team has exploited improved analytical techniques to locate nine new gamma-ray pulsars in Fermi data.A pulsar, also called a neutron star, is the closest thing to a black hole astronomers can observe directly, crushing half a million times more mass than Earth into a sphere no larger than a city. This matter is so compressed that even a teaspoonful weighs as much as Mount Everest.Typically, millisecond pulsars are a billion years or more old, ages commensurate with a stellar lifetime. But in the Nov. 3 issue of Science, the Fermi team reveals a bright, energetic millisecond pulsar only 25 million years old.The object, named PSR J1823—3021A, lies within NGC 6624, a spherical assemblage of ancient stars called a globular cluster, one of about 160 similar objects that orbit our galaxy. The cluster is about 10 billion years old and lies about 27,000 light-years away toward the constellation Sagittarius."With this new batch of pulsars, Fermi now has detected more than 100, which is an exciting milestone when you consider that before Fermi's launch only seven of them were known to emit gamma rays," said Pablo Saz Parkinson, an astrophysicist at the Santa Cruz Institute for Particle Physics, University of California Santa Cruz. ||

In this illustration, one photon (purple) carries a million times the energy of another (yellow). Some theorists predict travel delays for higher-energy photons, which interact more strongly with the proposed frothy nature of space-time. Yet Fermi data on two photons from a gamma-ray burst fail to show this effect, eliminating some approaches to a new theory of gravity. ||

In its first year, NASA's Fermi Gamma-ray Space Telescope discovered GeV (billions of electron volts) intensity variations revealing orbital motion in high-mass X-ray binaries (HMXBs). These are systems where a compact companion, such as a neutron star or a black hole, rapidly orbits a hot, young, massive star. The first examples include LSI +61 303, which sports a 26-day orbital period, and LS 5039 (3.9 days). This animation shows such a system. When the compact object lies far from its host star, TeV (trillions of electron volts) gamma-rays (white) are seen by ground-based gamma-ray observatories. But, as the object plunges closer to the star, the TeV emission is quenched and GeV emission turns on. Interactions by accelerated particles from the compact source with gas encircling the star — or in some systems, the star's light itself — is thought to be responsible for this change. ||

In the simplest and most common interaction, a cosmic-ray proton strikes another proton. The protons survive the collision, but their interaction creates an unstable particle — a pion — with only 14 percent the mass of a proton. In 10 millionths of a billionth of a second, the pion decays into a pair of gamma-ray photons. More complex scenarios occur when cosmic-ray protons strike nuclei containing greater numbers of particles. ||

Gamma rays are the highest-energy forms of light in the electromagnetic spectrum and they can have over a billion times the energy of the type of light visible to the human eye. Gamma rays can be created in several different ways: a high-energy particle can collide with another particle, a particle can collide and annihilate with its anti-particle, an element can undergo radioactive decay, or a charged particle can be accelerated. In this animation, we see a high-energy photon collide with a free electron, which causes the creation of a gamma-ray. ||

GLAST will be launched into a circular orbit around the Earth at an altitude of about 560 km (350 miles). At that altitude, the observatory will circle Earth every 90 minutes. In sky-survey mode, GLAST will be able to view the entire sky in just two orbits, or about 3 hours. Because gamma rays in the GLAST's energy band are unable to penetrate the Earth's atmostphere, it is essential that GLAST perform its observations from space. ||

GLAST will carry two instruments: the Large Area Telescope (LAT) and the GLAST Burst Monitor (GBM). The LAT is GLAST's primary instrument and consists of four components: the Tracker, the Calorimeter, the Anticoincidence Detector (ACD), and the Data Acquisition System (DAQ). These instrument components working together will detect gamma rays by using Einstein's famous equation (E=mc(squared) in a technique known as pair production. The GLAST Burst Monitor is a complementary instrument and consists of low-energy detectors, high-energy detectors, and data processing unit. The GBM can see all directions at once, except for the area where Earth blocks its view. When the GBM detects a bright gamma-ray burst, it immediately sends a signal to the LAT to observe that area of the sky. ||

The Universe is home to numerous extoic and beautiful phenomena, some of which can generate inconceiveable amounts of energy. GLAST (Gamma-ray Large Area Telescope) will open this high-energy world as the first imaging gamma-ray observatory to survey the entire sky every day and with high sensitivity. Astronomers will gain a superior tool to study how black holes, notorious for pulling matter in, can accelerate jets of gas outward at fantastic speeds. Physicists will be able to search for signals of new fundamental processes that are inaccessable in ground-based accelerators and observatories. And scientists will have a unique opportunity to learn about the every-changing Universe at extreme energies. ||

Fermi's Large Area Telescope (LAT) detects particles produced in a physical process known as pair production that epitomizes Einstein's famous equation, E=mc2. When a gamma ray, which is pure energy (E), slams into a layer of tungsten in one of the tracking towers that compose the LAT, it creates mass (m) in the form of a pair of subatomic particles, an electron and its antimatter counterpart, a positron. Several layers of high-precision silicon detectors track the particles as they move through the instrument. The direction of the incoming gamma ray is determined by projecting the particle paths backward. The particles travel through the trackers until they reach a separate detector called a calorimeter, which absorbs and measures their energies. The LAT produces gamma-ray images of astronomical objects, while also determining the energy of each detected gamma ray. ||

GLAST's launch is scheduled for early 2008 from Cape Canaveral Air Station on Florida's eastern coast. GLAST will be carried on a Delta II Heavy launch vehicle, with 9 solid rocket boosters. The solids are actually from the Delta III series (hence the term 'heavy'), mounted on a Delta II. It has a 10-foot fairing and two stages. Stowed in the launch vehicle, the spacecraft is 9.2 feet (2.8 meters) high by 8.2 feet (2.5 meters) in diameter. Once deployed, GLAST becomes a little bit taller and much wider (15 meters) with the Ku-band antenna deployed and the solar arrays extended. ||