Using star-shattering explosions to measure the universe.
An multinational team of 23 scientists, led by Maria Dainotti, Assistant Professor at the National Astronomical Observatory of Japan (NAOJ), has analyzed archival data for massive cosmic explosions produced by star deaths and discovered a new method to measure distances in the furthest reaches of the Universe.
It is difficult to gain a sense of depth in space since there are no landmarks. One method used by astronomers is to search for “standard candles,” objects or events whose absolute brightness (what you would see if you were right next to it) is determined by the underlying physics to be constant.
This allows it to be possible to estimate the distance to the standard candle and, by extension, other objects in the same region by comparing the predicted absolute brightness to the apparent brightness (what is really viewed from Earth). The scarcity of standard candles bright enough to be seen from more than 11 billion light-years distant has hampered research into the distant Universe. Gamma-Ray bursts (GRBs), radiation bursts caused by the demise of huge stars, are visible, although their brightness is dependent on the characteristics of the explosion.
Taking on the challenge of using these bright events as standard candles, the team examined archive data for visible light observations of 500 GRBs taken by world-class telescopes such as the Subaru Telescope (owned and operated by NAOJ), RATIR, and satellites such as the Neil Gehrels Swift Observatory.
The scientists found a class of 179 GRBs with common traits and likely caused by similar events by studying the light curve’s pattern of how the GRB brightens and dims over time. The team was able to determine a unique brightness and distance for each GRB based on the characteristics of the light curves, which could be utilized as a cosmological tool.
These findings will provide new insights into the mechanics behind this class of GRBs, and provide a new standard candle for observing the distant Universe. Lead author Dainotti had previously found a similar pattern in X-ray observations of GRBs, but visible light observations have been revealed to be more accurate in determining cosmological parameters.
Reference: “The Optical Two- and Three-dimensional Fundamental Plane Correlations for Nearly 180 Gamma-Ray Burst Afterglows with Swift/UVOT, RATIR, and the Subaru Telescope” by M. G. Dainotti, S. Young, L. Li, D. Levine, K. K. Kalinowski, D. A. Kann, B. Tran, L. Zambrano-Tapia, A. Zambrano-Tapia, S. B. Cenko, M. Fuentes, E. G. Sánchez-Vázquez, S. R. Oates, N. Fraija, R. L. Becerra, A. M. Watson, N. R. Butler, J. J. González, A. S. Kutyrev, W. H. Lee, J. X. Prochaska, E. Ramirez-Ruiz, M. G. Richer and S. Zola, 21 July 2022, The Astrophysical Journal Supplement Series.