Lawrence Berkeley National Laboratory | 2015 Nov 05
Less than 20 years ago the world learned that the universe is expanding ever faster, propelled by dark energy. The discovery was made possible by Type Ia supernovae; extraordinarily bright and remarkably similar in brightness, they serve as “standard candles” essential for probing the universe’s history.
In fact, Type Ia supernovae are far from standard. Intervening dust can redden and dim them, and the physics of their thermonuclear explosions differs — a single white dwarf (an Earth-sized star as massive as our sun) may explode after borrowing mass from a companion star, or two orbiting white dwarfs may collide and explode. These “normal” Type Ia’s can vary in brightness by as much as 40 percent. Brightness dispersion can be reduced by well-proven methods, but cosmology continues to be done with catalogues of supernovae that may differ in brightness by as much as 15 percent.
Now members of the international Nearby Supernova Factory (SNfactory), based at the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab), have dramatically reduced the scatter in supernova brightnesses. Using a sample of almost 50 nearby supernovae, they identified supernova twins — pairs whose spectra are closely matched — which reduced their brightness dispersion to a mere eight percent. The distance to these supernovae can be measured about twice as accurately as before. ...
Improving Cosmological Distance Measurements Using Twin Type Ia Supernovae - H. K. Fakhouri et al
- arXiv.org > astro-ph > arXiv:1511.01102 > 03 Nov 2015