NASA's Hubble Telescope has discovered a new supernova, detecting the feeble glow of a star that exploded more than nine billion years ago.
Nicknamed SN Primo, the stellar explosion belongs to a special class called Type Ia supernovae, which are bright beacons used as distance markers for studying the expansion rate of the universe. Astronomers believe Type Ia supernovae likely arise when white dwarf stars, the burned-out cores of normal stars, siphon too much material from their companion stars and explode.
Spectroscopic observations were used to confirm the distance of SN Primo, which is the farthest Type Ia supernova. In these observations, a spectrum splits the light from a supernova into its constituent colors. By analyzing those colors, astronomers can confirm its distance by measuring how much the supernova's light has been stretched, or red-shifted, into near-infrared wavelengths because of the expansion of the universe.
The discovery was part of a three-year Hubble program to survey faraway Type Ia entities.
Remote supernovae can help astronomers determine whether exploding stars remain dependable cosmic yardsticks across vast distances of space in an epoch when the cosmos was only one-third its current age of 13.7 billion years, said Adam Riess of the Space Telescope Science Institute and The Johns Hopkins University in Baltimore.
Astronomers hope to determine the frequency of Type Ia supernovae during the early universe and glean insights into the mechanisms that detonated them.
"In our search for supernovae, we had gone as far as we could go in optical light," said Riess. "But it's only the beginning of what we can do in infrared light. This discovery demonstrates that we can use [Hubble's] Wide Field Camera 3 to search for supernovae in the distant universe."
Added team member Steve Rodney of The Johns Hopkins University: "If we look into the early universe and measure a drop in the number of supernovae, then it could be that it takes a long time to make a Type Ia supernova.
"Like corn kernels in a pan waiting for the oil to heat up, the stars haven't had enough time at that epoch to evolve to the point of explosion. However, if supernovae form very quickly, like microwave popcorn, then they will be immediately visible, and we'll find many of them, even when the universe was very young. Each supernova is unique, so it's possible that there are multiple ways to make a supernova."