Description: The redshift of quasars is a measure of how much the light from a quasar has been stretched due to the expansion of the universe. This phenomenon is observed when the light emitted by a quasar, which is an extremely luminous and distant astronomical object, shifts towards longer wavelengths, that is, towards the red end of the electromagnetic spectrum. This redshift indicates that the quasar is moving away from us, which is interpreted as evidence of the universe’s expansion. The greater the redshift, the farther away the quasar is, and thus the older the observed object. This concept is fundamental in modern cosmology, as it allows astronomers to calculate the speed at which celestial objects are receding and, therefore, better understand the history and evolution of the universe. Redshift applies not only to quasars but also to galaxies and other celestial bodies, becoming an essential tool for measuring astronomical distances and understanding the structure of the cosmos.
History: The concept of redshift was introduced in the context of astronomy in the 1920s when Edwin Hubble observed that galaxies were moving away from Earth, leading to the formulation of Hubble’s law. However, the specific study of quasars began in the 1960s when they were identified as extremely luminous and distant objects. The first quasar, 3C 273, was discovered in 1963 by Maarten Schmidt, who also measured its redshift, confirming that it was billions of light-years away. This discovery revolutionized the understanding of the structure of the universe and the evolution of astronomical objects.
Uses: The redshift of quasars is primarily used in cosmology to determine the distance and recession velocity of quasars and other celestial objects. By measuring redshift, astronomers can infer the expansion of the universe and study the distribution of matter in the cosmos. Additionally, it is used to investigate the formation and evolution of galaxies, as well as to understand phenomena such as dark energy and dark matter.
Examples: A notable example of the use of redshift is the quasar 3C 273, which has a redshift of approximately 0.158, indicating that it is located about 2.5 billion light-years away. Another example is the quasar APM 08279+5255, which has a redshift of 3.9, making it one of the most distant known quasars, located over 12 billion light-years from Earth.
