Measuring the universe with star-shattering explosions

An international team of 23 researchers led by Maria Dainotti, an assistant professor at the National Astronomical Observatory of Japan (NAOJ), analyzed archival data from powerful cosmic bursts of star death and found a new way to measure distances in the distant universe.

Without landmarks in space, it is very difficult to get a sense of depth. One technique astronomers use is to look for “standard candles“objects or events where the underlying physics dictate that the absolute brightness (what you would see if you were right next to it) is always the same. When comparing this calculated absolute brightness to the apparent brightness (what is actually observed from Earth), it is possible to determine the distance to the standard sail and, by extension, to other objects in the same area.

The lack of standard candles bright enough to be seen over 11 billion light-years away has made research into the distant universe difficult. Gamma-ray bursts (GRBs), bursts of radiation produced by the death of massive stars, are bright enough, but their brightness depends on the characteristics of the explosion.

Accepting the challenge of trying to use these bright events as standard candles, the team analyzed archival data for the 500 GRB visible-light observations taken by world-leading telescopes such as the Subaru Telescope (owned and operated by NAOJ), RATIR and satellites. . like the Neil Gehrels Swift Observatory.

By studying the light curve pattern of how the GRB brightens and dims over time, the team identified a class of 179 GRBs that have common features and are likely to have been caused by similar phenomena. From the characteristics of the light curves, the team was able to calculate a single brightness Y distance for each GRB it can be used as a cosmological tool.

These findings will provide new insights into the mechanics behind this class of GRBs and provide a new standard sail 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.

These results appeared in The Astrophysical Journal Supplement Series on July 21, 2022.