Not long ago, the Hubble Space Telescope took an image of a star 12.9 billion light years away from Earth. This star emitted the light that we now see at a time when the universe was 900 million years old. The newly discovered star is named Earendel, meaning 'morning star' or 'dawn' in Old English, and by all accounts it holds the record for the most distant known star, displacing the blue giant Icarus, which is four billion light-years closer.
Nevertheless, the numbers quoted above may throw us off a little. The 12.9 billion light years to Earendel and 9 billion light years to Icarus is the so called "lookback time", with the present time as the reference point. However, if the expansion of the Universe is taken into account, the star Earendel must be 28 billion light years away now, or, to be more precise, it should be, because it most likely completed its life cycle a long time ago.
Gravitational lens
The rate of expansion of the universe is the tool with which astronomers measure such vast distances. When light flies through space, the expansion of the Universe seems to stretch the wavelength of this light, shifting it towards the red region. Calculating the so-called red shift can show us how far away the source was. In this case, the redshift of the light from the star Earendel is 6.2 and that from Icarus is only 1.5 by comparison.
Of course, no existing astronomical instrument is capable of directly detecting a single star at such a vast distance. However, astronomers have 'received' help from a single massive galaxy located between Earth and the star Earendel. This galaxy has gravitationally warped the space-time continuum, forming what is known as a gravitational lens. This lens, in turn, through a lucky mutual arrangement of all the "participants" in the process, has focused and intensified the light from the star by a thousand times, which allowed the Hubble telescope to see it quite clearly.
By correcting for distortions from the gravitational lens, astronomers determined that the Earendel star had a mass 50 times that of the Sun. There is also some chance that the star Earendel is not a single lone star but in fact a binary system of two stars. But even this variant in no way detracts from the current achievement, which holds the record for the longest detection range of a star or stars.
Unfortunately, due to Hubble's limited capabilities, astronomers were unable to measure other parameters of the Earendel star, such as light spectrum, surface temperature, etc. But do not despair, all this will be able to the new space telescope James Webb Space Telescope, which will begin making astronomical observations in a few months.
