Improvements to the ways in which scientists are able to measure distances are always improving and old methods are being retired. The best Type Ia supernovae were rated by astronomers in the March 27 issue of the journal Science.
Archived data from NASA's Galaxy Evolution Explorer (GALEX) identified a class of Type Ia supernovae that occur near younger stars. Using those particular supernovae can improve the measurements times two.
"We have discovered a population of Type Ia supernovae whose light output depends very precisely on how quickly they fade, making it possible to measure very exact distances to them," said lead author Patrick Kelly of the University of California, Berkeley, according to the press release. "These supernovae are found close to populations of bright, hot young stars."
The new information will also help shed some light on dark energy, the "leading culprit behind the baffling acceleration of our cosmos, a phenomenon discovered in 1998," according to the press release. The acceleration refers to the way galaxies are pulling away from each other at escalating speeds.
Type Ia supernovae are like a string of cosmic light bulbs and the key to measuring the spread of galaxies - and dark matter. Knowing how bright a bulb is means you can gauge its distance by the amount of dimming noted.
Type Ia supernovae are also called "standard candles," according to the press release, and they consistently shine with the same amount of light. The process leading up to the explosions is still unknown, but the detonation occurs when a white dwarf erupts and lights up the host galaxy for a brief moment.
The problem is, the explosions aren't always uniform in the light they emit. According to the press release, "They can differ considerably depending on various factors, which appear to be connected to the environments and histories of the exploding stars. It's as if our 60-watt bulbs sometimes give off 55 watts of light, skewing distance measurements."
Nearly 100 previous Type Ia supernovae were analyzed by Kelly and his team using data from GALEX, which detects ultraviolet light, thus distinguishing between old and young star neighborhoods. The team discovered that Type Ia supernovae near young, hot stars were more reliable as instruments of measurement than those in an older community.
"These explosions are likely the result of youthful white dwarfs," Kelly said, according to the press release.
"GALEX surveyed the entire sky, allowing past and future eruptions of these high-quality standard candles to be identified easily," said Don Neill, a member of the GALEX team at the California Institute of Technology in Pasadena, not affiliated with the study. "Any improvement in the standard candles will have a direct impact on theories of dark energy, allowing us to home in on this mysterious force propelling the acceleration of the universe."
From the press release: "Caltech led the galaxy Evolution Explorer mission and was responsible for science operations and data analysis. The mission ended in 2013 after more than a decade of scanning the skies in ultraviolet light. NASA's Jet Propulsion Laboratory in Pasadena, California, managed the mission and built the science instrument. The mission was developed under NASA's Explorers Program managed by the Goddard Space Flight Center, Greenbelt, Md. Researchers sponsored by Yonsei University in South Korea and the Center National d'Etudes Spatiales (CNES) in France collaborated on this mission."
