Quasars will be used to measure distances close to the beginning of the universe

To measure the distances of cosmic objects, astronomers have several methods. One of the most basic is parallax, but it only works for relatively short measurements. For more distant things, it is necessary to find luminous bodies known as the “standard candle”. detected

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  • The type of object to be used as a standard sail depends on the distance you want to measure. For closer distances, Cepheid stars are used, which pulsate in a way related to their luminosity, revealing the distance from the galaxy where it is located. At a farther level, Type IA supernovae are used, dating back to about three billion years after the Big Bang.

    To go even further into space—and therefore , more distant in the past — the new study proposes to use the luminosity of quasars as standard candles, because these objects would allow to reach 660 millions of years after the Big Bang. This would be an impressive advance over measurements made with Type IA supernovae.

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    Artistic concept of jet from a distant quasar (Image: Reproduction/NASA/CXC/ M.Weiss)

    The authors of the study argue that they found a correlation between the analyzed X-ray light of 2.700 quasars and their respective emissions from ultraviolet radiation. They also explain how this relationship is not altered with redshift (a phenomenon that “stretches” light waves due to the expansion of the universe, making them more reddish) and therefore can be used to calculate the distance of objects.

    Fortunately, quasars are one of the most energetic and luminous objects in the entire universe. They are the result of the activity of supermassive black holes at the center of their respective galaxies, feeding on matter and emitting huge amounts of radiation through the plasma in their accretion disks and relativistic jets. This type of object is one of several (and the most powerful) classes of active galactic centers.

    With such luminosity, quasars located more than ten billion light-years away are detected by instruments such as the Hubble telescope. In fact, some of them are among the most distant objects ever seen by mankind — the ULAS J700+

    quasar , for example, has a redshift of 7,54, which gives it an comoveable distance (that is, in constant variation due to the expansion of the universe) estimated at about billions of light years. This brings quasar formation close to the era of the universe’s reionization.

    Artistic representation of the quasar Pōniuāena (Image: Reproduction/International Gemini Observatory /NOIRLab/NSF/AURA/P. Marenfeld)430140 Speaking of universe expansion, perhaps the use of quasars for measurements, proposed by the new study, accepted for publication in Astronomy & Astrophysics, may also be useful for attempts to calculate the rate of this expansion. This calculation has been a matter of debate in astronomy because the different approaches to solving the problem result in different numbers.

    Upcoming scientific instruments, such as the Vera Rubin Observatory, and X-ray observatories like NuSTAR and Chandra, already in operation, will certainly add to the catalog of quasars already discovered early in the universe and collect ever better data, especially X-rays, to refine distance measurements. With this, the use of these objects as standard candles can be put to the test.

    Source: Harvard & Smithsonian, Universe Today

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