NASA's Hubble Space Telescope has found the farthest supernova so far of the type used to measure cosmic distances. Supernova UDS10Wil, nicknamed SN Wilson after American President Woodrow Wilson, exploded more than 10 billion years ago. SN Wilson belongs to a special class called Type Ia supernovae. These bright beacons¹（指向标） are prized by astronomers³ because they provide a consistent level of brightness that can be used to measure the expansion of space. They also yield clues to the nature of dark energy, the mysterious force accelerating the rate of expansion.

 

"This new distance record holder⁴ opens a window into the early universe, offering important new insights into how these stars explode," said David O. Jones of Johns Hopkins University in Baltimore, Md., an astronomer² and lead author on the paper detailing the discovery. "We can test theories about how reliable these detonations⁵ are for understanding the evolution of the universe and its expansion."

 

The discovery was part of a three-year Hubble program, begun in 2010, to survey faraway Type Ia supernovae and determine whether they have changed during the 13.8 billion years since the explosive birth of the universe. Astronomers took advantage of the sharpness and versatility⁶ of Hubble's Wide Field Camera 3 to search for supernovae in near-infrared light and verify their distance with spectroscopy. Leading the work is Adam Riess of the Space Telescope Science Institute in Baltimore, Md., and Johns Hopkins University.

 

Finding remote supernovae provides a powerful method to measure the universe's accelerating expansion. So far, Riess's team has uncovered more than 100 supernovae of all types and distances, looking back in time from 2.4 billion years to more than 10 billion years. Of those new discoveries, the team has identified eight Type Ia supernovae, including SN Wilson, that exploded more than 9 billion years ago.

 

"The Type Ia supernovae give us the most precise yardstick⁷（码尺） ever built, but we're not quite sure if it always measures exactly a yard," said team member Steve Rodney of Johns Hopkins University. "The more we understand these supernovae, the more precise our cosmic yardstick will become."

 

Although SN Wilson is only 4 percent more distant than the previous record holder, it pushes roughly 350 million years farther back in time. A separate team led by David Rubin of the U.S. Energy Department's Lawrence Berkeley National Laboratory in California announced the previous record just three months ago.

 

Astronomers still have much to learn about the nature of dark energy and how Type Ia supernovae explode.

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