Galaxies Begin to Age Gracefully
Our Milky Way galaxy is not alone. Edwin Hubble made that amazing revelation in the early 1900’s and named the many galaxies “island univeras swimming in the sea of space”. Today, NASA’s Galaxy Evolution Explorer is working at piecing together the evolution of these cosmic species.
Tens of thousands of galaxies in ultraviolet light across nine billion years of time have been surveyed since the mission was launched in 2003. The findings supply new, comprehensive evidence for the “nurture” theory of galaxy evolution, which shows that the galaxies that Hubble first described - elegant spirals and blob - like ellipticals - are evolutionarily linked.
Known as the “nurture” theory, a typical young galaxy begins life as a spiral that is churning out stars. Eventually, the spiral might join another spiral or an irregular - shaped galaxy, and with a few bursts produce newly minted stars. After a time, the galaxy’s production slows down and becomes an elliptical. “Our data confirms that all galaxies begin life forming stars”, said Chris Martin, principal investigator for the Galaxy Evolution Explorer at the California Institute of Technology in Pasadena CA. “Then through a combination of mergers, fuel exhaustion, and perhaps suppression by black holes, the galaxies eventually stop producing stars.”
Astronomers often refer to galaxies by their color, blue or red rather than by their shape. Though there are some exceptions, most blue galaxies are smaller spirals or irregular, while most red galaxies are larger ellipticals. About half of all galaxies are blue and half are red. By using a color code, it can be determined how. Actively the galaxies are making new stars. The younger stars are ultraviolet or blue light so these blue galaxies are busy producing stars. Older stars give off infrared or red light and have shut down their star - making factories.
According to scientists the blue galaxies grow up to become red. But something happens to the blue galaxies to cause them to run out of gas or star-making material and mature into passive red ones. There should be a population of “teenage” galaxies when changing from blue to red, young to old if the “nuture” theory is true. However a cosmic metamorphosis like this could take billions of years. How can astronomers study a process in a short lifetime?
By looking through hundreds of pictures of galaxies such as those provided by the Galaxy Evolution Explorer provides the data needed to allow scientists to find teenage galaxies , which will grow into elderly red or eliptical galaxies. The Sloan Digital Sky Survey provided visible light data to help establish the age of the teenage galaxies and how fast they run out of star-making fuel. Results suggested that young galaxies can ripen into old age quickly while others age gradually.
This entry was posted on Tuesday, February 26th, 2008 at 9:04 am and is filed under Mars News, Public Relations. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.
