Supernovae Twins Open Up New Possibilities for Precision Cosmology

Type Ia supernovae are some of the most powerful tools for testing different theories of gravity. These supernovae are explosions of massive stars that all look remarkably similar. By measuring how bright a supernova is, we can figure out how far away it is. Type Ia supernovae were used to make the initial discovery of dark energy in 1998. We have since used supernovae to measure the properties of dark energy with better and better precision with the goal of determining what it really is. In our new work, we developed a technique that uses the spectra of Type Ia supernovae to improve how well we can measure the distances to them. Our new technique can measure these distances around twice as well as previous techniques, and our results will be very important for measurements of dark energy with upcoming surveys such as the Legacy Survey of Space and Time (LSST) at the Rubin Observatory, or for the Nancy Grace Roman Space Telescope.

The upper left figure shows the spectra — brightness versus wavelength — for two supernovae. One is nearby and one is very distant. To measure dark energy, scientists need to measure the distance between them very accurately, but how do they know whether they are the same? The lower right figure compares the spectra — showing that they are indeed “twins.” This means their relative distances can be measured to an accuracy of 3 percent. The bright spot in the upper-middle is a Hubble Space Telescope image of supernova 1994D (SN1994D) in galaxy NGC 4526. (Graphic credit: Zosia Rostomian/Berkeley Lab; photo credit: NASA/ESA)

Kyle Boone is a lead author on two papers published in The Astrophysical Journal that report these findings. Currently a postdoctoral fellow at the University of Washington, his research focuses on developing novel statistical methods for astronomy and cosmology. He is particularly interested in using Type Ia supernovae to probe the accelerated expansion of the universe that we believe is due to some form of “dark energy”. Dr. Boone is a former graduate student of Nobel laureate Saul Perlmutter, the Berkeley Lab senior scientist and UC Berkeley professor who led one of the teams that originally discovered dark energy. Dr. Perlmutter was also a co-author on both studies.

The Twins Embedding of Type Ia Supernovae. II. Improving Cosmological Distance Estimates

The Twins Embedding of Type Ia Supernovae. I. The Diversity of Spectra at Maximum Light