Monday, May 23, 2011

Hubble views the star that changed the universe

NASA's Hubble Space Telescope has been trained on a single variable star that in 1923 altered the course of modern astronomy. 
V1 is a special class of pulsating star called a Cepheid variable that can be used to make reliable measurements of large cosmic distances.
 Credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA)

( -- Though the universe is filled with billions upon billions of stars, the discovery of a single variable star in 1923 altered the course of modern astronomy. And, at least one famous astronomer of the time lamented that the discovery had shattered his world view.
The star goes by the inauspicious name of Hubble variable number one, or V1, and resides in the outer regions of the neighboring , or M31. But in the early 1900s, most astronomers considered the Milky Way a single "island universe" of stars, with nothing observable beyond its boundaries. Andromeda was cataloged as just one of many faint, fuzzy patches of light astronomers called "spiral nebulae."
Were these spiral nebulae part of the Milky Way or were they independent island universes lying outside our galaxy? Astronomers didn't know for sure, until  found a star in Andromeda that brightened and faded in a predictable pattern, like a lighthouse beacon, and identified it as V1, a Cepheid variable. This special type of star had already been proven to be a reliable distance marker within our galaxy.
The star helped Hubble show that Andromeda was beyond our galaxy and settled the debate over the status of the spiral nebulae. The universe became a much bigger place after Hubble's discovery, much to the dismay of astronomer Harlow Shapley, who believed the fuzzy nebulae were part of our Milky Way.
Nearly 90 years later, V1 is in the spotlight again. Astronomers pointed Edwin Hubble's namesake, NASA's , at the star once again, in a symbolic tribute to the legendary astronomer's milestone observation.

"It's a landmark discovery that proved the universe is bigger and chock full of galaxies. I thought it would be nice for the Hubble telescope to look at this special star discovered by Hubble, the man."
But Hubble Heritage team member Max Mutchler of the STScI says that this observation is more than just a ceremonial nod to a famous astronomer.
"This observation is a reminder that Cepheids are still relevant today," he explains. "Astronomers are using them to measure distances to galaxies much farther away than Andromeda. They are the first rung on the cosmic distance ladder."
The Hubble and AAVSO observations of V1 will be presented at a press conference May 23 at the American Astronomical Society meeting in Boston, Mass. 

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