HONOLULU — Astronomers working with telescopes atop Hawaii's Mauna Kea Volcano are studying a galaxy they said is the biggest, brightest, hottest and one of the most ancient star-forming regions yet viewed in the universe.
The explosive galaxy of more than one million hot stars normally could not be examined because its stars were born so long ago and so far away. But a combination of powerful telescopes and natural "gravitational lensing" that enhances Earth's view of the object are credited for the scientific advance.
Discovery of the Lynx Arc cluster, one million times brighter than the somewhat similar Milky Way cluster known as the Orion Nebula and eight million light years farther away, was announced Thursday by the W. M. Keck Observatories and reported in the latest issue of the Astrophysical Journal.
Stars in the galaxy are bigger than stars much older and closer, scientists said. Twelve million light years from Earth, the spectacular growth spurt of stars is believed to have occurred when the universe was just two billion years old, or about 15 per cent of its current age.
The cluster is not unique, said astronomer Bradford Holden of the University of California's Lick Observatory at Santa Cruz, but the clear view of it is.
Gravitational pull of the light coming from a nearer galaxy, called "gravitational lensing," naturally stretches and magnifies the image scientists see of the star cluster, creating a sort of natural telescope that has made the Lynx Arc brighter and more visible than other similar clusters, Holden said in a telephone interview.
Originally, the Lynz Arc appeared as a "puzzling red arc" behind the nearer galaxy, he said.
"The potentially cool thing for me is that because it has certain gross properties that make it like a whole lot of other objects, it could be that every galaxy goes through a phase like this, including our own Milky Way," he said.
He described the view of the cluster aided by gravitational lensing as "a lucky coincidence."
Discovery of the ancient star cluster is credited to an international team of astronomers and scientific researchers including Holden and led by Bob Fosbury of the European Space Agency's Space Telescope-Eurolean Co-ordinating Facility in Germany. The German agency used the dual Keck telescopes atop Mauna Kea for part of its research.
Fosbury said, in a release from the observatory, the discovery of the cluster takes scientists a step closer to seeing the earliest, or primordial, stars believed to have formed after creation of the Universe, as much as 1.8 billion years earlier than the Lynx Arc itself.
"This remarkable object is the closest we have come so far to seeing what such primordial objects might look like when our telescopes become powerful enough to see them," Fosbury said.
In contrast to the Orion Nebula, which is powered by only four hot and bright blue stars, the super-cluster contains more than a million stars that are twice as hot as stars in the Milky Way galaxy, Fosbury said.
The scientists used the twin 10-metre Keck telescopes and other major X-ray, optical and infrared telescopes in a systematic study of distant clusters to make the discovery, he said.
Attaching the Keck Observatory's Echellette Spectrograph and Imager to the telescopes, researchers were able to determine the number of stars in the super-cluster and their temperatures, the scientists said. |
