Sunday, April 27, 2008
Plethora of interacting galaxies on Hubble's birthday
NASA Releases Largest Collection of Hubble Images
In celebration of the 18th anniversary of Hubble’s launch, NASA released a series of 59 new images of colliding galaxies. Astronomy textbooks typically present galaxies as staid, solitary, and majestic island worlds of glittering stars.
But galaxies have a wild side. They have flirtatious close encounters that sometimes end in grand mergers and overflowing “maternity wards” of new star birth as the colliding galaxies morph into wondrous new shapes.
As this astonishing Hubble atlas of interacting galaxies illustrates, galaxy collisions produce a remarkable variety of intricate structures.
Interactions are slow stately affairs, despite the typically high relative speeds of the interacting galaxies, taking hundreds of millions of years to complete. The interactions usually follow the same progression, and are driven by the tidal pull of gravity. Actual collisions between stars are rare as so much of a galaxy is simply empty space, but as the gravitational webs linking the stars in each galaxy begin to mesh, strong tidal effects disrupt and distort the old patterns leading to new structures, and finally to a new stable configuration.
Most of the 59 new Hubble images are part of a large investigation of luminous and ultraluminous infrared galaxies called the GOALS project (Great Observatories All-sky LIRG Survey). This survey combines observations from Hubble, the NASA Spitzer Space Observatory, the NASA Chandra X-Ray Observatory and NASA Galaxy Explorer. The Hubble observations are led by Professor Aaron S. Evans from the University of Virginia and the National Radio Astronomy Observatory (USA). The images released today can be seen here.
The Hubble Space Telescope (HST) will be repaired and overhauled in August. Seven astronauts who will fly the Atlantis space shuttle to rendezvous with Hubble will carry out the revamping mission. Their mission has already been labeled STS-125. The goal of the mission is to repair the orbiting telescope until a replacement will be manufactured in 2013.
The U.S. astronauts selected for the next servicing mission to the Hubble Space Telescope had begun already their training in February last year.
NASA had intended to mothball the Hubble before the new telescope was in place, a decision that was met with protests among astronomers who have been able to look into space 2.2 billion light years and more because they don't have to peer through Earth's atmosphere.
Missions to the space station are easier because ISS crew is on hand to help inspect the shuttle. The ISS also offers up to three months refuge for visiting crew in case of an emergency. The Hubble, which orbits 580 kilometers above Earth, offers neither. That means the shuttle would have to survive on its own for up to 25 days, with the second shuttle on stand-by at a separate launch pad for a rescue mission.
A year ago, the Hubble telescope's most far-seeing camera shut down due to a possible power failure and other problems, prompting NASA engineers to put the entire telescope on temporary standby. The Advanced Camera for Surveys (ACS) was installed in 2002 in a special shuttle mission to replace the old space camera - in orbit since 1990 - and was hailed as the gateway to some of humankind's most spectacular views of the universe.
The August STS-125 mission aims to install a cosmic origins spectrograph and to replace a wide field camera in operation since 1993 with a Wide Field Camera 3. This latest camera will be the first on the Hubble that can cover everything from the ultraviolet to the infrared spectrum.
Theoretically, the James Webb observatory will replace Hubble in 2013 the earliest. The Hubble Space Telescope (HST) was first conceived in 1946 by astronomer Lyman Spitzer, constructed since 1979 and launched in 1990.
Astronomy textbooks typically present galaxies as staid, solitary, and majestic island worlds of glittering stars.
But galaxies have a wild side. They have flirtatious close encounters that sometimes end in grand mergers and overflowing "maternity wards" of new star birth as the colliding galaxies morph into wondrous new shapes.
Today, in celebration of the Hubble Space Telescope's 18th launch anniversary, 59 views of colliding galaxies constitute the largest collection of Hubble images ever released to the public. This new Hubble atlas dramatically illustrates how galaxy collisions produce a remarkable variety of intricate structures in never-before-seen detail.
Astronomers observe only one out of a million galaxies in the nearby universe in the act of colliding. However, galaxy mergers were much more common long ago when they were closer together, because the expanding universe was smaller. Astronomers study how gravity choreographs their motions in the game of celestial bumper cars and try to observe them in action.
For all their violence, galactic smash-ups take place at a glacial rate by human standards - timescales on the order of several hundred million years. The images in the Hubble atlas capture snapshots of the various merging galaxies at various stages in their collision.
Most of the 59 new Hubble images are part of a large investigation of luminous and ultra-luminous infrared galaxies called the GOALS project (Great Observatories All-sky LIRG Survey). This survey combines observations from Hubble, NASA's Spitzer Space Telescope, NASA's Chandra X-ray Observatory, and NASA's Galaxy Evolution Explorer. The majority of the Hubble observations are led by Aaron S. Evans of University of Virginia, Charlottesville/NRAO/Stony Brook University.
Posted by SANJIDA AFROJ at 5:45 PM