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Planetary System Formation Around Binary Stars
"We tend to focus on looking for other solar systems around stars just like our Sun," Boss says. "But we are learning that planetary systems can be found around all sorts of stars, from pulsars to M dwarfs with only one third the mass of our Sun". Two out of every three stars in the Milky Way is a member of a binary or multiple star system, in which the stars orbit around each other with separations that can range from being nearly in contact (close binaries) to thousands of light-years or more (wide binaries). Most binaries have separations similar to the distance from the Sun to Neptune (~30 AU, where 1 AU = 1 astronomical unit = 150 million kilometers--the distance from the Earth to the Sun)......... Posted by: Brooke Permalink January 13, 2006, 0:33 AM CT Radioactivity from the Inner Part of Our Galaxy
This implies that production of new atomic nuclei is an on-going process and occurs in star forming regions galaxy-wide. From those new observations, the astronomers estimate that the total amount of radioactive 26Al in the Galaxy is equivalent to three solar masses. This amount of production corresponds to a galactic rate of supernovae from gravitational collapse of about one every 50 years. We are familiar with radioactive isotopes from medical radiology tests and therapys. Astrophysicists use penetrating gamma rays emitted during radioactive decay to obtain direct messages from cosmic nuclear fusion reactions, through special telescopes operated in near-Earth space. Gamma-rays from decaying 26Al were detected in 1978, and because of its known half life of 720, 000 years, this provided direct proof of currently-ongoing nucleosynthesis. Supernova 1987 in the Large Magellanic Cloud galaxy was then observed through short-lived radioactive gamma rays. This led researchers to think that these nuclei had been produced within this supernova event......... Posted by: Brooke Permalink January 11, 2006, 8:52 PM CT Space Propulsion Breakthrough
Ion engines are a form of electric propulsion and work by accelerating a beam of positively charged particles (or ions) away from the spacecraft using an electric field. ESA is currently using electric propulsion on its Moon mission, SMART-1. The new engine is over ten times more fuel efficient than the one used on SMART-1. "Using a similar amount of propellant as SMART-1, with the right power supply, a future spacecraft using our new engine design wouldn't just reach the Moon, it would be able to leave the Solar System entirely," says Dr Roger Walker of ESA's Advanced Concepts Team, Research Fellow in Advanced Propulsion and Technical Manager of the project. The new experimental engine, called the Dual-Stage 4-Grid (DS4G) ion thruster, was designed and built under a contract with ESA in the extremely short time of four months by a dedicated team at the Australian National University. "The success of the DS4G prototype shows what can be achieved with the passion and drive of a capable and committed team. It was an incredible experience to work with ESA to transform such an elegant idea into a record-breaking reality", says Dr. Orson Sutherland, the engine's designer and head of the development team at the ANU. During November 2005, the DS4G engine was tested for the first time in ESA's Electric Propulsion Laboratory at ESTEC in the Netherlands, with support from Dr Sutherland and ESA test engineers......... Posted by: Brooke Permalink January 8, 2006, 9:09 AM CT Era of Rapid Galaxy Formation
The findings, each of which was obtained at facilities supported in whole or in part by the NSF, include the following: Evidence from the Sloan Digital Sky Survey (SDSS) that at least a few ultra-massive black holes had come into existence less than a billion years after the universe began in the Big Bang, some 13.7 billion years ago. Each of these black holes is several billion times more massive than stars like our own Sun, and is sitting in the middle of an otherwise normal galaxy, swallowing up the surrounding gas and dust; the thermonuclear energy released in that process is visible to the SDSS astronomers as a brilliant, but very distant, point of light known as a quasar. The puzzle is that the SDSS black holes are as large as any ever seen, including those observed in nearby quasars that are much older. So how did they manage to form and grow to such a size before the universe was a tenth its present age? "The formation should have taken time," says Michael A. Strauss of Princeton University, who is the scientific spokesperson for the SDSS project and a co-principal investigator on this study. A formal report would be published in the Astronomical Journal in March 2004. A press release is available online at http://www.sdss.org/news/releases/20031217.lensing.html......... Posted by: Brooke Permalink December 30, 2005, 4:52 PM CT Most detailed image of the Crab Nebula
The Crab Nebula is one of the most intricately structured and highly dynamical objects ever observed. The new Hubble image of the Crab was assembled from 24 individual exposures taken with the NASA/ESA Hubble Space Telescope's Wide Field and Planetary Camera 2 (WPFC2) and is the highest resolution image of the entire Crab Nebula ever made. The Crab Nebula is a six-light-year-wide expanding remnant of a star's supernova explosion. Japanese and Chinese astronomers witnessed this violent event nearly 1,000 years ago in 1054. The filaments are the tattered remains of the star and consist mostly of hydrogen. The rapidly spinning neutron star embedded in the centre of the nebula, only barely visible in this Hubble image, is the dynamo powering the nebula's eerie interior bluish glow. The blue light comes from electrons whirling at nearly the speed of light around magnetic field lines from the neutron star. The neutron star, like a lighthouse, ejects twin beams of radiation that appear to pulse 30 times a second due to the neutron star's rotation. A neutron star is the crushed ultra-dense core of the exploded star......... Posted by: Brooke Permalink December 29, 2005, 0:02 AM CT Black Hole Swallowing Neutron Star
This rare event, seen on 24 July 2005, created a gamma-ray burst that lasted only for a few milliseconds. Observations of the lingering afterglow, however, provided evidence of what could have been the bizarre demise of a neutron star orbiting a black hole. The black hole may have first stretched the dense neutron star into a crescent, breaking off crumbs in the process. The black hole then could have swallowed the star largely in one gulp, feeding on the crumbs in the minutes and hours that followed. Such a black hole would grow more massive, like a python that downs a wild boar. "For billions of years this black hole and neutron star orbited each other in a gravitational tug-of-war," said Scott Barthelmy of NASA Goddard Space Flight Center in Greenbelt, Maryland, lead author on one of three the Nature articles on the subject. "The neutron star lost." In recent months the Swift team has reported that "short" gamma-ray bursts arise from a merger either between two neutron stars or a neutron star and black hole. The specific scenario was not clear. This latest analysis of a July burst, although not definitive, is the best evidence of a black hole-neutron star merger, Barthelmy said......... Posted by: Brooke Permalink December 27, 2005, 9:38 PM CT Reionization With A Radio Telescope
It has long been known (e.g. Field 1959) that neutral hydrogen in the IGM may be directly detectable at frequencies that fall in the radio band (in the range 70-170 MHz) and measurements at different frequencies should allow us to probe accurately the structure and the evolution of the reionizing gas. This experiment is especially attractive as a new generation of radio telescope (e.g. LOFAR, PAST, SKA) is under construction. LOFAR, which is being built in the Netherlands, will use almost 40000 antennas grouped into roughly 100 "stations", distributed over an area of about 400 kilometers across. The possible configuration for station layout is shown in Fig. 1......... Posted by: Brooke Permalink December 27, 2005, 9:21 PM CT View Chaotic Star Birth
The young stars in NGC 1333 do not form a single cluster, but are split between two sub-groups. One group is to the north near the nebula shown as red in the image. The other group is south, where the features shown in yellow and green abound in the densest part of the natal gas cloud. With the sharp infrared eyes of Spitzer, researchers can detect and characterize the warm and dusty disks of material that surround forming stars. By looking for differences in the disk properties between the two subgroups, they hope to find hints of the star- and planet-formation history of this region. The knotty yellow-green features located in the lower portion of the image are glowing shock fronts where jets of material, spewed from extremely young embryonic stars, are plowing into the cold, dense gas nearby. The sheer number of separate jets that appear in this region is unprecedented. This leads researchers to think that by stirring up the cold gas, the jets may contribute to the eventual dispersal of the gas cloud, preventing more stars from forming in NGC 1333......... Posted by: Brooke Permalink December 27, 2005, 9:18 PM CT Meet the First Woman to Drive on Mars!
Right before the Mars Exploration Rovers made history, Stroupe joined JPL, and what a time to join the ranks. Holiday excursions were cut short or non-existent and the lab simmered over from the heat of anticipation. Last-minute meetings to ensure all was well filled restless hours as the world prepared to focus on the dramatic rover landings. While the rovers were getting their "land legs," Stroupe was getting used to working in an oversized sandbox. Deep in the corners of an aging building that was part of the original bones of JPL, toddler robots train for possible future missions. Intended to precede humans to Mars, these petite teams carry and integrate structural components, simulating remote habitat building. "We want to send robots ahead of astronauts to build a safe habitat that's already there when they arrive," said Stroupe. "Particularly for Mars, if you have to wait six months for a rescue, you want to make sure it's safe when you go."........ Posted by: Brooke Permalink December 26, 2005, 10:30 PM CT First Gamma-ray Bursts Detected By New Nasa Satellite
"I'm thrilled," said Berger. "We've shown that we can chase the Swift bursts at a moment's notice, even right before Christmas! This is a great sign of exciting advances down the road." The discoveries herald a new era in the study of gamma-ray bursts, hundreds of which are expected to be discovered and scrutinized in the next several years. The Swift satellite detected the first of the four bursts on December 23, 2004, in the constellation Puppis, and Carnegie astronomers used telescopes at the Las Campanas Observatory in Chile to pinpoint the visual afterglow within several hours. This was the first burst detected solely by the new Swift satellite to be pinpointed with sufficient accuracy to study the remains. The next three bursts came in quick succession between January 17 and 26 and were immediately pinpointed by a team of Carnegie and Caltech astronomers using the Palomar Mountain 200-inch Hale telescope in California and the Keck Observatory 10-meter telescopes in Hawaii......... Posted by: Brooke Permalink |
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