Apr 7 2011

From The Space Library

RELEASE: 11-103 BREAKTHROUGH STUDY CONFIRMS CAUSE OF SHORT GAMMA-RAY BURSTS

WASHINGTON -- A new supercomputer simulation shows the collision of two neutron stars can naturally produce the magnetic structures thought to power the high-speed particle jets associated with short gamma-ray bursts (GRBs). The study provides the most detailed glimpse of the forces driving some of the universe's most energetic explosions. The state-of-the-art simulation ran for nearly seven weeks on the Damiana computer cluster at the Albert Einstein Institute (AEI) in Potsdam, Germany. It traces events that unfold over 35 milliseconds -- about three times faster than the blink of an eye. GRBs are among the brightest events known, emitting as much energy in a few seconds as our entire galaxy does in a year. Most of this emission comes in the form of gamma rays, the highest-energy form of light. "For the first time, we've managed to run the simulation well past the merger and the formation of the black hole," said Chryssa Kouveliotou, a co-author of the study at NASA's Marshall Space Flight Center in Huntsville, Ala. "This is by far the longest simulation of this process, and only on sufficiently long timescales does the magnetic field grow and reorganize itself from a chaotic structure into something resembling a jet." GRBs longer than two seconds are the most common type and are widely thought to be triggered by the collapse of a massive star into a black hole. As matter falls toward the black hole, some of it forms jets in the opposite direction that move near the speed of light. These jets bore through the collapsing star along its rotational axis and produce a blast of gamma rays after they emerge. Understanding short GRBs, which fade quickly, proved more elusive. Astronomers had difficulty obtaining precise positions for follow-up studies. That began to change in 2004, when NASA's Swift satellite began rapidly locating bursts and alerting astronomers where to look. "For more than two decades, the leading model of short GRBs was the merger of two neutron stars," said co-author Bruno Giacomazzo at the University of Maryland and NASA's Goddard Space Flight Center in Greenbelt, Md. "Only now can we show that the merger of neutron stars actually produces an ultrastrong magnetic field structured like the jets needed for a GRB." A neutron star is the compressed core left behind when a star weighing less than about 30 times the sun's mass explodes as a supernova. Its matter reaches densities that cannot be reproduced on Earth -- a single spoonful outweighs the Himalayan Mountains. The simulation began with a pair of magnetized neutron stars orbiting just 11 miles apart. Each star packed 1.5 times the mass of the sun into a sphere just 17 miles across and generated a magnetic field about a trillion times stronger than the sun's. In 15 milliseconds, the two neutron stars crashed, merged and transformed into a rapidly spinning black hole weighing 2.9 suns. The edge of the black hole, known as its event horizon, spanned less than six miles. A swirling chaos of superdense matter with temperatures exceeding 18 billion degrees Fahrenheit surrounded the newborn black hole. The merger amplified the strength of the combined magnetic field, but it also scrambled it into disarray. Over the next 11 milliseconds, gas swirling close to the speed of light continued to amplify the magnetic field, which ultimately became a thousand times stronger than the neutron stars' original fields. At the same time, the field became more organized and gradually formed a pair of outwardly directed funnels along the black hole's rotational axis. This is exactly the configuration needed to power the jets of ultrafast particles that produce a short gamma-ray burst. Neither of the magnetic funnels was filled with high-speed matter when the simulation ended, but earlier studies have shown that jet formation can occur under these conditions. "By solving Einstein's relativity equations as never before and letting nature take its course, we've lifted the veil on short GRBs and revealed what could be their central engine," said Luciano Rezzolla, the study's lead author at AEI. "This is a long-awaited result. Now it appears that neutron star mergers inevitably produce aligned jet-like structures in an ultrastrong magnetic field." The study is available online and will appear in the May 1 edition of The Astrophysical Journal Letters. The authors note the ultimate proof of the merger model will have to await the detection of gravitational waves -- ripples in the fabric of space-time predicted by relativity. Merging neutron stars are expected to be prominent sources, so the researchers also computed what the model's gravitational-wave signal would look like. Observatories around the world are searching for gravitational waves, so far without success because the signals are so faint. STS-134 was the 134th shuttle flight and the 36th shuttle mission dedicated to station assembly and maintenance. With Endeavour and its crew safely home, the stage is set for the launch of shuttle Atlantis on its STS-135 mission, targeted to begin July 8. Four veteran astronauts will deliver supplies and spare parts to the space station. The 12-day mission also will install an experiment designed to demonstrate and test the tools, technologies and techniques needed to refuel satellites in space robotically -- even satellites not designed to be serviced. Chris Ferguson, a veteran of two previous shuttle missions, will command the flight. Doug Hurley will be the pilot, a role he filled on the STS-127 mission in 2009. Sandy Magnus and Rex Walheim will be the mission specialists. Magnus spent four and a half months aboard the station beginning in November 2008. Walheim flew on the STS-110 mission in 2002 and the STS-122 mission in 2008. STS-135 will be Atlantis' 33rd mission and the 37th shuttle flight dedicated to station assembly and maintenance. It will be the 135th and final mission of NASA's Space Shuttle Program.

RELEASE: 11-104 SOFIA COMPLETES FIRST FLIGHT OF GERMAN SCIENCE INSTRUMENT

WASHINGTON -- The Stratospheric Observatory for Infrared Astronomy, or SOFIA, completed its first science flight Wednesday, April 6, using the German Receiver for Astronomy at Terahertz Frequencies (GREAT) scientific instrument. GREAT is a high-resolution far-infrared spectrometer that finely divides and sorts light into component colors for detailed analysis. SOFIA is the only operational airborne observatory. It is a joint program between NASA and the German Aerospace Center (DLR). The observatory is a heavily modified Boeing 747SP aircraft carrying a reflecting telescope with an effective diameter of 100 inches. Flying at altitudes between 39,000 and 45,000 feet, above the water vapor in Earth's lower atmosphere that blocks most infrared radiation from celestial sources, SOFIA conducts astronomy research not possible with ground-based telescopes. "SOFIA's onboard crew seamlessly combined scientists, engineers and technicians from the U.S. and Germany, working together on an observatory developed in the U.S., using a telescope and instrument built in Germany, to gather data of great interest to the entire world's scientific community," said Bob Meyer, NASA's SOFIA Program manager at the agency's Dryden Flight Research Center in Edwards, Calif. GREAT Principal Investigator Rolf Guesten of the Max Planck Institute for Radio Astronomy in Bonn, Germany, and his team conducted observations high above the central and western United States beginning the night of April 5 with their instrument installed on SOFIA's telescope. Among their targets were IC 342, a spiral galaxy located 11 million light-years from Earth in the constellation Camelopardalis ("The Giraffe"), and the Omega Nebula (known as M17), 5,000 light-years away in Sagittarius. The team captured and analyzed radiation from ionized carbon atoms and carbon monoxide molecules to probe the chemical reactions, motions of matter and flows of energy occurring in interstellar clouds. Astronomers have evidence such clouds in both IC 342 and M17 are forming numerous massive stars. "These first spectra are the reward for the many years of work creating this technology, and underline the scientific potential of airborne far-infrared spectroscopy," Guesten said. GREAT focused on strong far-infrared emissions from interstellar clouds that cool the clouds. The balance between heating and cooling processes regulates the temperature of the interstellar material and controls initial conditions for the formation of new stars. "These observations give us unique information about the physical processes and chemical conditions in the stellar nurseries," said Juergen Stutzki, a co-investigator on the GREAT team. "SOFIA will give us new and deep insight into how stars form." GREAT, one of two German first-generation SOFIA scientific instruments, was developed by the Max Planck Institute for Radio Astronomy and the University of Cologne in collaboration with the Max Planck Institute for Solar System Research and the DLR Institute of Planetary Research. "This first science flight with a German instrument is a huge milestone for the SOFIA observatory," said John Gagosian, SOFIA program executive at NASA Headquarters in Washington. "GREAT, in combination with SOFIA's other German and U.S.-developed instruments, demonstrates SOFIA's extraordinary versatility, allowing it to play a unique and essential role alongside the Spitzer and Herschel spacecraft." NASA's Ames Research Center in Moffett Field, Calif., manages the SOFIA science and mission operations in cooperation with the Universities Space Research Association headquartered in Columbia, Md., and the German SOFIA Institute at the University of Stuttgart, Germany. SOFIA is based and managed at Dryden's Aircraft Operations Facility in Palmdale, Calif.

RELEASE: 11-105 COMMUNITY COLLEGE SCHOLARS SELECTED TO DESIGN ROBOTIC ROVERS

HOUSTON --Eighty students from community colleges in 28 states and Puerto Rico have been selected to travel to a NASA center to develop robotic rovers. The National Community College Aerospace Scholars program encourages students to pursue careers in science, technology, engineering and mathematics (STEM) disciplines. The students will visit either NASA's Jet Propulsion Laboratory in Pasadena, Calif., April 27-29 or the Johnson Space Center in Houston May 12-14. Participants were selected based on completion of Web-based assignments during the school year. The students will establish teams and form fictitious companies pursuing Mars exploration. Each team will shape a company infrastructure to develop and design a prototype rover. The on-site experience includes a tour of NASA facilities and briefings from agency scientists, engineers and astronauts. "This innovative experience allows students to take what they’ve learned in the classroom and apply it to technical questions in the real world, simulating what NASA engineers and scientists do every day," said Leland Melvin, NASA associate administrator for education. "It will help them develop the skills they need to be the problem solving explorers of tomorrow." The program is based on the state of Texas' Aerospace Scholars, originally created in partnership with NASA and the Lone Star state's educational community. The programs are designed to encourage community and junior college students to enter careers in science and engineering and ultimately join the nation's highly technical workforce. Through this program, NASA continues the agency's investment in educational programs that attract and retain students in STEM disciplines critical to NASA's future missions.