Shortly after the Big Bang, the Universe was completely dark. Stars and galaxies, which offer deep space with light, had not yet formed, and deep space consisted of a primitive soup of neutral hydrogen and helium atoms and invisible ‘dark matter’. During these cosmic dark ages, which lasted for a number of hundred million years, the very first stars and galaxies emerged. Sadly, observations of this period are challenging due to the fact that dark-age galaxies are remarkably faint 1 Composing in Nature, Willis et al. 2 supply a look of what happened throughout the dark ages by doing some stellar archaeology. By measuring the ages of stars in one of the most remote clusters of galaxies understood, the authors situated galaxies that formed stars in the dark ages, close to the earliest possible time that stars could emerge.
A galaxy cluster is a group of thousands of galaxies that orbit each other at speeds 3 of about 1,000 kilometres per second. They are prevented from flying apart by the gravitational pull of the accompanying dark matter, which has the comparable total mass of about one hundred trillion Suns 4 Astronomers utilize these clusters as laboratories for lots of experiments in astrophysics, such as measuring the structure of the Universe, testing theories of gravity and determining how galaxies form. Willis et al. utilized among the most distant clusters known to study when the most huge galaxies in deep space started to produce stars.
Although close-by clusters, such as the Coma cluster, are simpler to observe than those further away, we can not measure their ages precisely since the galaxies are very old. It is hard to distinguish between, for example, a galaxy that is 7 billion years of ages and one that is 13 billion years old 5 Therefore, to obtain an exact date for when clusters initially formed their stars, Willis and colleagues utilized NASA’s Hubble Area Telescope to look at among the most remote clusters they might discover.
Due to the fact that light travels at a limited speed, the most remote clusters we can see are also those in the earliest stages of the Universe that we can see. The light from the cluster analyzed by Willis et al. has been taking a trip for 10.4 billion years prior to it reaches Earth, which suggests that we are taking a look at a cluster as it was simply 3.3 billion years after the Big Bang. As a result, this cluster functions as a keyhole through which we can peer into the early Universe (Fig. 1).
Willis and colleagues found that the cluster consists of numerous galaxies that have comparable red colours. The colour of a galaxy can be used to estimate its age because more youthful stars are bluer than their older, redder counterparts. As a result, galaxies that have red colours formed their stars a very long time ago 5 By comparing the colours of the cluster galaxies with those of designs, the authors estimated that the stars of these galaxies started to emerge when deep space was only 370 million years of ages. This epoch is when we anticipate the very first stars to have actually formed in the cosmic dark ages 6
One especially intriguing point is that Willis et al. determined a minimum of 19 galaxies in the cluster that have similar colours, which suggests that the galaxies have comparable ages. At the time when these galaxies formed their stars, they would have been well expanded, so it is a conundrum as to why they all began producing stars at approximately the very same time. Were they affected by their environment? Additionally, did the star formation in one galaxy somehow set off a chain reaction, causing star development in nearby gas clouds? We do not presently have the response, but what is clear from the authors’ work is that these distant clusters have lots of the oldest galaxies in deep space.
In my viewpoint, Willis and colleagues’ age quotes are the very best ones possible, provided the restricted information that the authors have from the Hubble telescope. Nevertheless, identifying ages from the colours of galaxies is a relatively crude technique that undergoes big uncertainties. For instance, a young galaxy that contains a lot of astronomical dust can have the same colour as an old galaxy containing little dust. For that reason, although the authors’ outcomes are tantalizing, they should be treated with care until NASA’s James Webb Space Telescope (JWST) is introduced in the next couple of years.
The JWST will determine spectra of the light produced by these galaxies. A comparison of the spectra with designs will be a much more precise method to determine the ages of the stars than using the colours of galaxies. In addition, since it is much easier to determine the ages of earlier galaxies than those of more recent ones 5, it makes sense to target galaxies in the progenitors of these galaxy clusters in the early Universe. Willis and colleagues’ outcomes make a strong case for these remote clusters being some of the first targets that the JWST ought to observe.