When theories aren't borne out by observation, the problem just may be the size of the dataset. As witness recent work on gravitational lensing, that phenomenon where light is distorted and magnified by the gravitational pull of galaxies and other matter as it makes its immense journey from distant quasars to the Earth. Such lensing has been observed for over a decade, but just how the light is magnified, and on what scale, has until now been an elusive question. And answers to it haven't seemed to fit the standard model of cosmology, one in which visible galaxies represent only a small part of the mass of a universe seemingly filled with dark matter. Now researchers from the Sloan Digital Sky Survey (SDSS) have been able to perform a large-scale study of such magnification, and their theories do gibe with the standard model. The team was able to measure the brightness of some 200,000 quasar sources and determine the precise magnification caused by gravitational lensing. The new...

Hard to believe that it was fully fifteen years ago today that the Hubble Space Telescope was placed into orbit from the Space Shuttle Discovery. Hubble's list of achievements has been outstanding, from detecting proto-galaxies whose light was emitted less than a billion years after the Big Bang to providing data that helped astronomers confirm the age of the universe, now calculated at some 13.7 billion years. And don't forget the extraordinary moments closer to home, such as the space telescope's views of comet Shoemaker-Levy 9, the famous 'string of pearls,' hitting Jupiter in 1994. Hubble's 700,000 images have provided views up to ten times sharper than any previous telescope could offer. The image above, a part of the Eagle Nebula, shows a tower of cold gas and dust being shaped by the light of hot new stars. It was taken with Hubble's Advanced Camera for Surveys (ACS), providing a picture so sharp that, at full resolution, the image could be blown up to the size of a billboard...

More on the 'fine structure constant,' that fundamental number that seems to be crucial to our understanding of electromagnetism, and therefore the way the universe works. Our recent story on Michael Murphy and his Cambridge team discussed findings from the Keck I telescope on Mauna Kea that suggested subtle changes to the value of the fine structure constant since the earliest era of the universe. But those findings remain highly controversial, as was apparent on Monday the 18th. That was the day that astronomer Jeffrey Newman (Lawrence Berkeley National Laboratory) presented data from the DEEP2 redshift project, a five-year survey of galaxies more than seven light years away. Speaking at the annual meeting of the American Physical Society (APS) in Tampa, Newman said his team's results showed no change to the constant within one part in 30,000. "The fine structure constant sets the strength of the electromagnetic force, which affects how atoms hold together and the energy levels...

Michael Murphy has been studying the fundamental constants of nature -- numbers that are key to any given theory of how the universe works -- for the past five years. His work at the Institute of Astronomy at Cambridge University has particularly foused on possible changes to the fine structure constant, a number central to electromagnetism, and therefore crucial to the interaction between light and matter. If its value were slightly different, life could not exist, although tiny changes over time could be tolerated. Normally denoted by the Greek letter α (alpha), the fine structure constant can be worked out through experiment to great precision. According to Murphy, the numbers come to 1/alpha = 137.03599958, with an experimental uncertainty of a mere 0.00000052. But as the astronomer told the Physics 2005 conference at the University of Warwick (UK) today, the fine structure constant may have had a slightly different value in the early universe. Murphy bases his conclusion...

"It's a near certainty that black holes don't exist," says George Chapline. A physicist at the Lawrence Livermore National Laboratory, Chapline has an alternative explanation: when a massive star collapses, what remains is not a black hole but a star that's filled with dark energy. Some 70 percent of the universe seems to be composed of dark energy, though no one knows precisely what it is. Chapline's work may lead to new insights into the stuff. A preprint of Chapline's paper "Dark Energy Stars" appears at the ArXiv site, where the author lays down the gauntlet early on: In the 1950s a consensus was reached, partly as a result of meetings such as a famous meeting at Chapel Hill in 1957, that although quantum effects might be important below some very small distance, on any macroscopic scale the predictions of classical general relativity (GR) should be taken seriously. In the summer of 2000 Bob Laughlin and I realized that this cannot possibly be correct. Indeed I am sure it will be...

Centauri Dreams continues to maintain that a major justification for interstellar research is the need of our species to protect itself. The record of life on earth is studded with extinction-level events evidently caused by asteroid or cometary impacts, and as technology matures, the danger of a man-made catastrophe cannot be ruled out. We know that life is fragile, as is underscored by the following story. According to a new study from NASA and the University of Kansas, working with 'what if' scenarios and a finely-tuned model of Earth's atmosphere, a gamma-ray burst from the explosion of a relatively nearby star could destroy up to half the atmosphere's ozone layer. Remarkably, a burst that hit the Earth for only ten seconds could do the trick, damaging Earth's only shield against powerful ultraviolet radiation from the Sun. With recovery time of no less than five years, that could have catastrophic effect on all surface species and destroy the food chain. "A gamma-ray burst...

The central part of the Milky Way has never been surveyed in gamma ray wavelengths with the sensitivity offered by HESS, the High Energy Stereoscopic System. And as announced in the March 25th issue of Science, the HESS team has not only found eight new very high energy (VHE) gamma ray sources in the galactic disk, thus doubling the number of known sources, but has also discovered two 'dark accelerators,' objects that emit energetic particles but have no known optical or x-ray counterpart. It takes a particle accelerator of cosmic proportions to produce gamma rays, such as the explosion of a supernova. But such sources should be visible in other wavelengths. Says Dr. Paula Chadwick of the University of Durham (UK): "Many of the new objects seem to be known categories of sources, such as supernova remnants and pulsar wind nebulae. Data on these objects will help us to understand particle acceleration in our galaxy in more detail; but finding these 'dark accelerators' was a surprise....

We always thought that the real impetus to the theory of 'dark energy' came from the discovery that the expansion of the universe seems to be accelerating. But an article in New Scientist points out that Allan Sandage (Carnegie Observatories, Pasadena) had studied evidence that might have led to the theory of dark energy way back in 1972. Sandage was working with 'peculiar velocities,' deviations in the normal rate of cosmic expansion caused by the gravitational pull between groups and clusters of galaxies. And he had seen that galaxies just outside the Local Group showed velocities that were below what was expected. Fabio Governato of the University of Washington has now plugged dark energy into a computer model of galaxy formation and finds that this force matches nicely with the peculiar velocities for galaxies in regions like the Local Group. The Sandage data plus the new computer model, it can be argued, point to dark energy. You can find an abstract of Governato's study, "The...

Ordinary (or baryonic) matter -- the stuff that you and I and Procyon are made of -- is outnumbered five to one by so-called 'dark matter,' mysterious stuff whose presence can only be inferred from the way galaxies rotate. Some galaxies rotate so fast that, if they were made only of ordinary matter, they would fly apart. So some stronger gravitational force must be involved, even though we can't see what's causing it. Now an international team of astronomers has found a valuable clue in the form of a galaxy that is all but invisible. VIRGOHI21 was found in the Virgo cluster of galaxies some 50 million light years from Earth, and is the first galaxy ever detected that is made up almost entirely of dark matter. Observed by radio telescopes at the University of Manchester and Arecibo (and later studied at the Isaac Newton Telescope in the Canary Islands), the galaxy contains a mass of hydrogen atoms a hundred million times larger than the Sun. The mass rotates, just like a galaxy, but...

Construction of the world's largest scientific instrument is proceeding in the frigid wastes of Antarctica. The initial deployment of what will become the IceCube neutrino telescope involved drilling a 1.5-mile deep hole into Antarctic ice, then installing 60 optical detectors in it that will detect the elusive particles. But that's just the beginning: IceCube demands 70 such holes and 4200 of the volley-ball sized optical detectors. The final telescope will take up a cubic kilometer of ice and capture particles from the edge of the visible universe. What makes neutrinos so interesting is their ability to travel vast distances without deflection or absorption; they seem to pass ghost-like through ordinary matter, and are unaffected by magnetic fields. "Neutrinos travel like bullets through a rainstorm," Francis Halzen, a University of Wisconsin-Madison professor of physics and the principal investigator for the project explains. "Immense instruments are required to find neutrinos in...

A star that apparently had a close encounter with the black hole at the center of the Milky Way is now speeding out of the galaxy at some 1.5 million miles per hour. That's the conclusion of astronomers at the Harvard-Smithsonian Center for Astrophysics (CfA), who say the star is moving fast enough to have achieved galactic escape velocity. "We have never before seen a star moving fast enough to completely escape the confines of our galaxy," said co-discoverer Warren Brown (CfA). "We're tempted to call it the outcast star because it was forcefully tossed from its home." The star is catalogued as SDSS J090745.0+24507; it was apparently a member of a binary system before its close brush with the black hole. According to the scientists' scenario, the companion star was pulled into orbit around the black hole while the outcast star was flung on a trajectory that will take it out of the galaxy entirely. Image: Astronomers at the Smithsonian Astrophysical Observatory have discovered the...

When you hear the word 'baryon,' you can think of neutrons and protons, though the term really covers any subatomic particles that use the strong nuclear force for their interactions. We know a surprising amount about baryons in the early universe, including the fact that a large fraction of their number -- almost half -- cannot be accounted for by current theory. What happened to the missing baryons? A paper in the February 2005 issue of Nature may shed some light on the matter. Using computer simulations of galaxy formation, Fabrizio Nicastro of the Harvard-Smithsonian Center for Astrophysics and colleagues write that the baryons could well be contained in 'warm-hot intergalactic matter' (WHIM), clouds of gas out of which galaxies and galactic clusters first formed. This work was based on observations made by the Chandra X-ray satellite on the quasar Markarian 421 (located in Ursa Major, the Big Dipper). A key player in these investigations was Ohio State associate professor of...

In Blazing Speed: The Fastest Stuff in the Universe, Robert Roy Britt looks at recent studies of a form of matter that moves remarkably close to the speed of light. The material comes in the form of huge jets of hot gas that are ejected from a kind of galaxy called a blazar. Some of these jets attain speeds of 99.9 percent of the speed of light, according to a study presented at the recent AAS meeting by Glenn Piner of Whittier College in Whittier, California. Britt's article gives an overview of Piner's work, but dig deeper at Piner's Web site Quasar Research at Whittier College, where he explains the study's methodology, which used Very Long Baseline Interferometry. The technique combines data from widely separated telescopes to achieve the same angular resolution as a single telescope with a size equal to the maximum separation between the individual dishes. From a news release from Whittier: Blazars are active galactic nuclei -- energetic regions surrounding massive black holes...