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Astronomical Observatory of the Jagiellonian University


Astronomy Object of the Month: 2023, September

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Rewriting the Past and Future of the Universe

New research has improved the accuracy of the parameters governing the expansion of the Universe. More accurate parameters will help astronomers determine how the Universe grew to its current state and how it will evolve in the future.

Illustration: ΩM and its uncertainty vs. the number of Quasars (N). The color bar shows the probability density function (PDF), indicating the most probable value, thus the smallest uncertainty on ΩM. Credit: Dainotti et al. 2023, ApJ Volume 950, 45.

It is well established that the Universe is expanding. But with no landmarks in space, it is difficult to measure how fast it is expanding accurately. So, astronomers search for reliable landmarks. In the same way, a candle looks fainter as it gets farther away. Even though the candle itself hasn’t changed, distant objects in the Universe look fainter. If we know the intrinsic (initial) brightness of an object, we can calculate its distance based on its observed brightness. Objects of known brightness in the Universe that allow us to calculate the distance are called standard candles.

An international team led by Maria Giovanna Dainotti, an Assistant Professor at the National Astronomical Observatory of Japan, collaborating with, among others, Aleksander Lenart, OA UJ student, conducted a novel research endeavor using the NAOJ institute's supercomputers. They employed advanced statistical methods to analyze data related to standard candles like Supernovae, Quasars, and Gamma Ray Bursts. Developing new statistical tools was crucial for accurately estimating astronomical parameters, considering the varied statistical distributions of measurements from different sources. Each standard candle provided insights within specific distant ranges. By combining data from these sources, the team successfully mapped larger areas of the Universe, shedding light on new aspects of our cosmos.

The new results reduce the uncertainty of key parameters by up to 35%. More accurate parameters will help determine whether the Universe will continue expanding forever or eventually fall back in on itself.

Illustration: A conceptual diagram of the Gamma-Ray Bursts, Quasars, and Supernovae to measure cosmological parameters shown in a pie chart. Credit: The Authors.

Original publications:

M. G. Dainotti et al., Reducing the uncertainty on the Hubble constant up to 35% with an improved statistical analysis: different best-fit likelihoods for Supernovae Ia, Baryon Acoustic Oscillations, Quasars, and Gamma-Ray Bursts, Astrophysical Journal, 951, 63 (2023)

M. G. Dainotti et al., Quasars: Standard Candles up to z=7.5 with the Precision of Supernovae Ia, Astrophysical Journal, 950, 45 (2023)

The research was conducted at the Department of High Energy Astrophysics of the Jagiellonian University’s Astronomical Observatory (OA UJ). The Authors acknowledge the National Astronomical Observatory of Japan and RIKEN for their support in realising this work.


Aleksander Lenart
Astronomical Observatory
Jagiellonian University
Aleksander.Lenart [@] student.uj.edu.pl