July 1, 2005Far-out Einstein ring
Using the European Southern Observatory's Very Large Telescope, Remi Cabanac of Chile's Pontifical Catholic University in Santiago, Chile, and his European colleagues have found the most distant Einstein ring known.
An Einstein ring is a kind of cosmic mirage in which gravity from a foreground galaxy distorts light from a background galaxy into an arc. If the alignment is precise enough, the distant galaxy's image warps into a complete ring. The new cosmic ring, dubbed FOR J0332-3557, arcs through 75 percent of a circle and lies in the southern constellation Fornax.
Such gravitational lensing allows astronomers to "weigh" the galaxy responsible for the mirage, and serves as a cosmic magnifying glass that lets astronomers see details in objects otherwise beyond the reach of current telescopes.
In the case of FOR J0332-3557, Cabanac's team reports
in the June III Astronomy & Astrophysics
, the lensing galaxy seems to be an isolated, inactive elliptical perhaps 40,000 light-years across with a mass of 1 trillion Suns. The more distant object is a compact galaxy less than 1/6 this size, brimming with bright clusters from a recent burst of star formation.
The lensing galaxy lies about 8 billion light-years away and magnifies the background galaxy, which is 12 billion light-years away, almost 13 times. Thanks to the objects' close alignment, astronomers can glimpse a galaxy as it was when the universe was only 12 percent of its present age. — Francis ReddyAstro-E2 feels X-ray heat
When Japan's new Astro-E2 X-ray observatory blasts into space this month, it will carry a pioneering detector. The satellite's primary instrument is a high-resolution X-ray Spectrometer (XRS) developed jointly by NASA's Goddard Space Flight Center in Greenbelt, Maryland, and the Japan Aerospace Exploration Agency's (JAXA) Institute of Space and Astronautical Science (ISAS).
"Astro-E2 will showcase an entirely new technology," says Anne Kinney, director of the Universe Division in NASA's Science Mission Directorate. "This is the highly anticipated complement to NASA's Chandra X-ray Observatory and Europe's XMM-Newton. Scientists around the world eagerly await the launch."
The XRS, which is cooled to approximately –460º Fahrenheit (–273º Celsius) measures heat released by the individual X-ray photons it absorbs. Each particle will raise the device's temperature by just thousandths of a degree. This new technique lets the XRS measure high X-ray energies with a precision about 10 times greater than that of previous sensors.
Astro E-2 carries five other X-ray detecting instruments, built in collaboration between Japanese institutions and the Massachusetts Institute of Technology. The spacecraft is scheduled for launch into Earth orbit July 6 from Japan's Uchinoura Space Center in Kagoshima. It's expected to return data for 5 years. — Francis ReddyOlivine from a supernova
Scientists have discovered pristine grains of the mineral olivine they say formed in an ancient supernova explosion. Scott Messenger and Lindsay Keller NASA's Johnson Space Center in Houston, and Dante Lauretta of the University of Arizona's Lunar and Planetary Laboratory, Tucson, found the grains among extraterrestrial dust snatched from Earth's upper atmosphere by a high-flying NASA research aircraft.
Scientists have found evidence a supernova produced radioactive atoms a few million years before our Sun formed, although no one knows if the explosion helped kick-start our solar system. Messenger's team used a new type of ion microprobe to measure oxygen isotopes in these unusual grains. The researchers then used well-known models of supernova structure to see if the grain could have condensed directly from a supernova's cooling gaseous envelope.
"The supernova grains have oxygen isotopic ratios that have never been seen before in meteorites or comet dust, but are predicted in astrophysical models of supernova explosions," Messenger says. The team published its results in this week's Science
According to Lauretta, his chemical analysis matched the grain's actual composition "dead on," while Messenger's isotope ratios enabled the team to detail the grain's natural history.
The scientists say the mineral comes from magnesium, iron, and silicon mixed when a star about 15 times the Sun's mass collapsed and exploded. The olivine crystallized when the supernova's expanding gas shell cooled enough to form dust. Many olivine grains stuck together to form a submicron-size rock.
The microscopic rock floated through the interstellar medium for millions of years. It was swept eventually into a cold, dust cloud, and coated with a veneer of organic matter. When this cloud collapsed to form our solar system 4.5 billion years ago, the grain found its way into a comet or asteroid. There the tiny rock remained until a comet jet or collision ejected it into space, where Earth could sweep it up for scientists to collect. — Francis Reddy