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Integral identifies supernova rate for Milky Way EUROPEAN SPACE AGENCY NEWS RELEASE Posted: January 4, 2006 Using ESA's Integral observatory, an international team of researchers has been able to confirm the production of radioactive aluminium (Al 26) in massive stars and supernovae throughout our galaxy and determine the rate of supernovae - one of its key parameters. The team, led by Roland Diehl of the Max Planck Institute for Extraterrestrial Physics in Garching, Germany, determined that gamma rays from the decay of Al 26 originate from the central regions of our galaxy, implying that production of new atomic nuclei is an ongoing process and occurs in star-forming regions galaxy-wide. Our environment is composed of chemical elements formed long ago by nuclear fusion reactions in stellar interiors and supernovae. This process of Œnucleosynthesis' leads to the emission of gamma rays, which easily reach us from all regions of our galaxy. ESA's Integral observatory has been measuring such gamma rays since October 2002. Roland Diehl and his colleagues were able to measure the Al 26 gamma-ray emissions along the plane of the inner galaxy. However, because the disc of the galaxy rotates about its central axis, with the inner regions orbiting faster, gamma rays from decaying Al 26 observed from these regions should be moderated by the Doppler effect in a characteristic way. It is this characteristic pattern that has been found by Integral. From this measurement, the team found that Al 26 decay gamma rays do indeed reach us from the inner regions of the galaxy, rather than from foreground regions along the same line of sight possibly caused by local and peculiar Al 26 production. These regions would not have the observed high relative velocity. From these new observations, it is possible to estimate the total amount of radioactive Al 26 in our galaxy as is equivalent to three solar masses. This is a lot, given that Al 26 is an extremely rare isotope; the fraction estimated for the early Solar System is 5/100 000 of Al 26, in proportion to its stable aluminium isotope (Al 27). Because astrophysicists had inferred that the likely sources are mainly massive stars, which end their lives as supernovae, they could estimate the rate of such supernova events. They obtained a rate of one supernova every 50 years - consistent with what had been indirectly found from observations of other galaxies and their comparison to the Milky Way. Integral's study of gamma rays will continue to operate for several more years. Astrophysicists hope to increase the precision of such measurements. Project leader Roland Diehl said, "These gamma-ray observations provide insights about our home galaxy, which are difficult to obtain at other wavelengths due to interstellar absorption." Notes to editors: Gamma rays from decaying Al 26 were first detected in space in 1978. Because of its known half-life of 720 000 years, this provided direct proof of currently ongoing nucleosynthesis in recently-formed stars. In the mid-1990s, Roland Diehl and his colleagues were able to show that this relatively long-lived radioactivity is present over large regions along the plane of the galaxy. Hence, production of new atomic nuclei was found to be common in our galaxy. Many scientists were surprised, because at the end of the 1970s, traces of Al 26 decay had only been found in meteorite samples originating from the early Solar System. This was interpreted as evidence that the Al 26 radioactivity was a key ingredient in the formation of planetary bodies (radioactive heat is a necessary to melt cometary material to form rocks), and that Al 26 radioactivity was intimately related to the early Solar System. From the theories of the 1950s that all chemical elements were produced inside stars, novae, and supernovae, two competing scenarios emerged that are still debated. Al 26 in the early Solar System could be the result of such stellar processing, occurring, with some enhancement, near the formation site of our Solar System 4500 million years ago. Alternatively, special conditions during the formation of the Solar System could have caused high-energy particle collisions, producing Al 26 locally. Although gamma rays clearly show widespread cosmic nucleosynthesis, it remains to be understood if only this, or additional local high-energy reactions, has produced the amount of Al 26 inferred for the early Solar System. One way to answer this question is the determination of the total Al 26 content of our galaxy. These Integral based studies appear in the 439th issue of the scientific journal Nature, in an article titled: ŒRadioactive 26Al and massive stars in the Galaxy', by R. Diehl, lead author, H. Halloin, K. Kretschmer, G.G. Lichti, V. Schönfelder, A.W. Strong, A. von Kienlin and W. Wang, (Max Planck Institute for Extraterrestrial Physics, Garching, Germany), P. Jean, J. Knödlseder, J.P.Roques, G.Weidenspointner (Centre d'Etude Spatiale des Rayonnements and Université Paul Sabatier, Toulouse, France), S. Schanne (DSM/DAPNIA/Service d'Astrophysique, CEA Saclay, Gif-Sur-Yvette, France), D.H.Hartmann (Clemson University, USA), C. Winkler (ESA, Noordwijk, the Netherlands), and C. Wunderer (Space Sciences Lab., Berkeley, USA) |
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The space shuttle program was grounded for 32 months in the painful wake of the 1986 Challenger accident. Americans finally returned to space in September 1988 when shuttle Discovery safely launched for its mission to deploy a NASA communications satellite. Enjoy this post-flight presentation narrated by the astronauts as they show movies and tell the story of the STS-26 mission.
Imagine a space shuttle mission in which the astronaut crew launched two commercial and one military communications spacecraft, then conducted a pair of incredible spacewalks to recover, fix and redeploy a satellite that malfunctioned just four months earlier. The rescue mission was a success, starting with an astronaut making a catch of the spinning satellite with just his gloved-hand. Enjoy this post-flight presentation narrated by the astronauts as they tell the story of shuttle Discovery's August 1985 mission known as STS-51I.
In our continuing look back at the classic days of the space shuttle program, today we show the STS-41D post-flight presentation by the mission's astronauts. The crew narrates this film of home movies and mission highlights from space shuttle Discovery's maiden voyage in August 1984. STS-41D deployed a remarkable three communications satellites -- a new record high -- from Discovery's payload bay, extended and tested a 100-foot solar array wing and even knocked free an icicle from the shuttle's side using the robot arm.
As the title aptly describes, this movie straps you aboard the flight deck for the thunderous liftoff, the re-entry and safe landing of a space shuttle mission. The movie features the rarely heard intercom communications between the crewmembers, including pilot Jim Halsell assisting commander Bob Cabana during the landing.
On Christmas Eve in 1968, a live television broadcast from Apollo 8 offered this message of hope to the people of Earth. The famous transmission occurred as the astronauts orbited the Moon.
The International Space Station receives its 20th Russian Progress cargo ship, bringing the outpost's two-man Expedition 12 crew a delivery of fresh food, clothes, equipment and special holiday gifts just in time for Christmas.
This movie features highlights of the December 23 rendezvous between the Russian Progress 20P vessel and the International Space Station. The footage comes from a camera mounted on the supply ship's nose.
NASA's Stardust spacecraft encountered Comet Wild 2 two years ago, gathering samples of cometary dust for return to Earth. In this Dec. 21 news conference, mission officials and scientists detail the probe's homecoming and planned landing in Utah scheduled for January 15, 2006.
The first robotic space mission to visit the distant planet Pluto and frozen objects in the Kuiper Belt is explained by the project's managers and scientists in this NASA news conference from the agency's Washington headquarters on Dec. 19.
Scientists marvel at the achievements made by the orbiting Hubble Space Telescope in this produced movie looking at the crown jewel observatory that has served as our window on the universe.