SN Wilson is in a special class of exploding stars known as “Type Ia supernovae,” which have been long valued by astronomers because they provide a reliable level of brightness that can be used to measure the expansion of space.
These bright celestial objects can also provide clues to the nature of the mysterious force known as dark energy, which scientists theorize is responsible for accelerating the expansion rate of the universe.
“This new distance record holder opens a window into the early universe, offering important new insights into how these stars explode,” said David O. Jones of Johns Hopkins University, an astronomer and lead author on the paper detailing the discovery. “We can test theories about how reliable these detonations are for understanding the evolution of the universe and its expansion.”
SN Wilson was found by scientists participating in a three-year Hubble program that surveyed the skies for distant Type Ia supernovae to determine whether they had changed in the billions of years since our Universe began in the Big Bang. Since the program began in 2010, Hubble has found more than 100 supernovae and eight of the special Type Ia supernovae, including the SN Wilson.
“The Type Ia supernovae give us the most precise yardstick ever built, but we’re not quite sure if it always measures exactly a yard,” said Steve Rodney of Johns Hopkins University and a member of Hubble’s supernovae survey team. “The more we understand these supernovae, the more precise our cosmic yardstick will become.”
Astronomers still have much to learn about the nature of dark energy and how Type Ia supernovae explode.
Finding Type Ia supernovae created so early in the history of the Universe will also provide astronomers with a way to compare two competing supernovae explosion models. One model specifies that the explosions are caused when two white dwarf compact stars merge. The other model indicates that a white dwarf that’s slowly feeding off a neighboring normal star explodes when it gathers too much mass.
Evidence gathered by the team so far seems to favor the white dwarf merger model because it predicts that most stars existing in the early Universe are much too young to become Type Ia supernovae.
“If supernovae were popcorn, the question is how long before they start popping?” said team leader Adam Riess of the Space Telescope Science Institute in Baltimore, Md., and Johns Hopkins University. “You may have different theories about what is going on in the kernel. If you see when the first kernels popped and how often they popped, it tells you something important about the process of popping corn.”
By knowing what sets off the Type Ia supernovae, scientists are also hoping to determine just how quickly the Universe became enriched with heavier elements such as iron. Through a process called supernova nucleosynthesis, these exploding stars produce about half of the iron in the universe, some of the raw material used for building planets, and life itself.