White Dwarf Bursts into a Supernova Type 1a

Images from the Hubble Space Telescope reveal the birth of a Type 1a supernova, a "standard candle" for measuring the expansion of the universe. Nicknamed SN Primo, this supernova is the most distant of its type ever discovered. Image: NASA, ESA, A. Riess (Space Telescope Science Institute and The Johns Hopkins University), and S. Rodney (The Johns Hopkins University)

Astronomers have found the most distant Type 1a supernova, a kind of star explosion that should help scientists better understand the ever-expanding universe and the nature of dark energy, the strange force accelerating that expansion.

Bursting into existence 9 billion years ago, the supernova (nicknamed SN Primo) was born from the violent death of a shrunken, super-dense star called a white dwarf. 

Light from such explosions falls within a very narrow range, which is why astronomers call them "standard candles." As the light travels toward Earth, astronomers can measure how it is stretched by the expansion of the universe.

"If we look into the early universe and measure a drop in the supernovae, then it could be that it takes a long time to make Type 1a supernovae," said Steve Rodney, also of Johns Hopkins. more here