A team of astronomers recently focused on GN-z11, considered for several years to be the oldest galaxy detected. From our point of view, researchers confirm that this galaxy is the most distant ever observed.
Measure the distance of galaxies
From its discovery about four years ago, GN-z11, found in the constellation Ursa Major, has been considered the most distant and oldest known galaxy in the observable universe. And for good reason, according to the observations of Hubble, astronomers had estimated that this object was formed more or less 13.4 billion years ago. That is only around 400,000 years after the Big Bang.
In a new study, a team of astronomers led by Nobunari Kashikawa of the University of Tokyo have sought to clarify these measurements. To do this, they relied on the technique of redshift, widely used in cosmology.
Concretely, as light travels immense distances in the universe, its wavelengths stretch as it expands, drawing more red. In other words, the longer a photon travels in expanding space, the more its wavelength stretches because of that expansion. By measuring a galaxy’s redshift, researchers can then determine precisely how far away it is.
According to the research paper, published in Nature Astronomy, the team targeted certain chemical signatures, called emission lines, known to imprint distinct patterns in the light of distant objects. By measuring how stretched these telltale signatures are, astronomers were then able to deduce the distance the light traveled from the targeted galaxy, revealing the distance to the galaxy itself.
“We focused on ultraviolet light specifically, because it is in this area of the electromagnetic spectrum where we expected to find the red-shifted chemical signatures,” Nobunari Kashikawa explains.
By employing near infrared spectroscopic observations using the MOSFIRE spectrograph, available at the WM Keck Observatory in Hawaii, Kashikawa and his team specified the value of his “redshift” (z = 10.957) by a factor of 100 These measurements confirmed that GN-z11 is indeed the most distant object ever observed by mankind, formed 13.4 billion years ago. At the time, the Universe was only 3% of its current age.
In collaboration with a team led by Linhua Jiang of Peking University, the astronomers also explain that these photons, which made it possible to determine the distance of GN-z11, were originally those of a very flash of light. fleeting. During these observations, the galaxy appeared hundreds of times brighter for a little less than three minutes.
According to the researchers, this was probably the tip of a long, GRB-like gamma-ray burst generated by a star explosion.