Measuring the universe with stellar explosions

(ORDO NEWS) — An international team of 23 researchers led by Maria Dinotti, associate professor at the National Astronomical Observatory of Japan (NAOJ), has analyzed archived data on powerful cosmic explosions resulting from star death and found a new way to measure distances in the distant universe.

There are no landmarks in space, so it’s very difficult to get a sense of depth. One method used by astronomers is to look for “standard candles” – objects or events for which physics dictates that the absolute brightness (what you see if you get close to them) is always the same.

By comparing the calculated absolute brightness with the apparent brightness (what is actually observed from the Earth), it is possible to determine the distance to the standard candle and, accordingly, to other objects in the same area.

The lack of standard candles bright enough to be seen more than 11 billion light-years away has hampered exploration of the distant universe. Gamma rays (GRBs), bursts of radiation produced when massive stars die, are quite bright, but their brightness depends on the characteristics of the explosion.

Faced with the challenge of trying to use these bright events as standard candles, the team analyzed archived 500 GRB visible-light observations made by the world’s leading telescopes such as the Subaru Telescope (owned and operated by NAOJ), RATIR, and satellites such as the Observatory Neil Gerels Swift.

By studying the light curve, a picture of how GRB brightens and dimmers over time, the team identified a class of 179 GRBs that share common features and were likely caused by similar phenomena.

Based on the characteristics of the light curves, the team was able to calculate a unique brightness and distance for each GRB, which can be used as a cosmological tool.

These results 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 Dinotti had previously found a similar pattern in X-ray observations of GRBs, but visible-light observations proved to be more accurate in determining cosmological parameters.

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