Fog lifted on dark gamma-ray bursts across the universe

Gamma-ray bursts, with their ability to pierce through gas and dust to shine brightly across the universe, are revealing areas of intense star formation and stellar death where astronomers have been unable to look -- the dusty corners of otherwise dust-free galaxies.

The conclusion comes from a survey of "dark" gamma-ray bursts -- bright in gamma- and X-ray emissions, but with little or no visible light -- reported today at a meeting of the American Astronomical Society in Pasadena.

Star formation occurs in dense clouds that quickly fill with dust as the most massive stars rapidly age and explode, spewing newly created elements into the interstellar medium to seed new star formation. Hence, astronomers presume that a large amount of star formation is occurring in dust-filled galaxies, although actually measuring how much dust this process has built up in the most distant galaxies has proved extremely challenging.

Long-duration gamma-ray bursts, the most brilliant flashes of light in the universe, are thought to originate from the explosion of massive stars. These events create two pencil-like beams of light, akin to lighthouse beacons, bright enough to be seen from as far away as 13 billion light years, near the limits of the observable universe.

While most gamma-ray bursts continue to shine brightly in optical light for many hours after the gamma-ray emission subsides -- a phenomenon known as an Œafterglow' -- those with little or no detectable afterglow, dubbed "dark GRBs," have puzzled astronomers. Some have speculated that most were so far away, and thus at such high redshift, that their optical afterglow shifted out of the wavelength region that optical telescopes can detect

Herschel and Planck gear up for 14 May launch

ESA's two missions to probe the far reaches of the Universe are gearing up to launch from the Guiana Space Center in French Guiana on 14 May.

The two satellites, Herschel and Planck, will share a ride aboard the same Ariane 5 rocket. Shortly after launch they will separate and follow different trajectories to the second Lagrangian point of our Solar System, 1.5 million kilometres from Earth.

Both missions’ instruments have completed their final checkouts, and the spacecrafts’ thruster tanks have been fueled.

Planck will be dedicated to answering fundamental questions about the origin and evolution of the Universe by peering back to just 400,000 years after the Big Bang gave birth to existence. It will spend at least 15 months mapping the cosmic microwave background, light from the primordial soup of particles that eventually evolved to become our modern-day Universe.

Gamma-ray burst smashes cosmic distance record

WASHINGTON -- NASA's Swift satellite and an international team of astronomers have found a gamma-ray burst from a star that died when the universe was only 630 million years old, or less than five percent of its present age. The event, dubbed GRB 090423, is the most distant cosmic explosion ever seen.

At 3:55 a.m. EDT on April 23, Swift detected a ten-second-long gamma-ray burst of modest brightness. It quickly pivoted to bring its ultraviolet/optical and X-ray telescopes to observe the burst location. Swift saw a fading X-ray afterglow but none in visible light.