Carnegie Institution for Science | 2018 Dec 11
New work from the Carnegie Supernova Project provides the best-yet calibrations for using type Ia supernovae to measure cosmic distances, which has implications for our understanding of how fast the universe is expanding and the role dark energy may play in driving this process. ...
Type Ia supernovae are fantastically bright stellar phenomena. They are violent explosions of a white dwarf—the crystalline remnant of a star that has exhausted its nuclear fuel—which is part of a binary system with another star.
In addition to being exciting to observe in their own right, type Ia supernovae are also a vital tool that astronomers use as a kind of cosmic mile marker to infer the distances of celestial objects.
While the precise details of the explosion are still unknown, it is believed that they are triggered when the white dwarf approaches a critical mass, so the brightness of the phenomenon is predictable from the energy of the explosion. The difference between the predicted brightness and the brightness observed from Earth tells us the distance to the supernova.
Astronomers employ these precise distance measurements, along with the speed at which their host galaxies are receding, to determine the rate at which the universe is expanding. Thanks to the finite speed of light, not only can we measure how quickly the universe is expanding right now, but by looking farther and farther out into space, we see further back in time and can measure how fast the universe was expanding in the distant past. This led to the astonishing discovery in the late-1990s that the universe’s expansion is currently speeding up due to the repulsive effect of a mysterious “dark” energy. Improving the distance estimates made using type Ia supernovae will help astronomers better understand the role that dark energy plays in this cosmic expansion. ...
The Carnegie Supernova Project: Absolute Calibration and the Hubble Constant ~ Christopher. R. Burns et al
- Astrophysical Journal 869(1):56 (10 Dec 2018) DOI: 10.3847/1538-4357/aae51c
arXiv.org > astro-ph > arXiv:1809.06381 > 17 Sep 2018 (v1), 19 Sep 2018 (v2)