The James Webb telescope detects complex organic molecules near the Big Bang

2023-06-05 21:01:06

The James Webb telescope has opened up a new way of looking into what happened shortly after the Big Bang and the birth of the first galaxies. Now, thanks to their observations, an international team of astrophysicists led by the University of Texas has just detected the most distant galaxy with the presence of complex organic molecules, an impressive finding published by the journal Nature .

These are polycyclic aromatic hydrocarbons (PAH, for its acronym in English), tiny dust molecules widely known on our planet. These are generated as by-products of incomplete combustion, such as in coffee roasting, and are believed to play a crucial role in the more complex organic components. essentials for life.

False color image using data from James Webb. The lens galaxy is shown in blue, while the magnified galaxy (or target galaxy) is shown in red.
J. Spilker / S. Doyle, NASA, ESA, CSA

Alert: stars being born

PAH molecules arouse a great interest in astronomy due to its ability to trace the regions of formation of new stars in the universe. When PAHs are illuminated by light from young “suns”, they emit extremely bright bands in the infrared range that can be detected with proper instrumentation. This characteristic makes them an essential tool for investigating the formation of new stars both in nearby galaxies like distant.

Until now, the study of PAH molecules in galaxies has been limited to relatively close locations due to the limited sensitivity of the available instruments. However, the James Webb is drastically changing this perspective. Specially designed to observe the infrared range of the electromagnetic spectrum, it is the largest and most complex telescope ever launched into space, it has an exceptional ability to collect light. Much larger than its predecessors.

Its launch is revolutionizing the field of extragalactic astrophysics by allowing us to study extremely distant galaxies, even close to the Big Bang. Furthermore, it provides us with a unique opportunity to investigate in detail the innermost regions of nearby galaxies.

The James Webb has already demonstrated its ability to characterize the properties of PAH molecules. near supermassive black holes in local galaxiesand now allows us to detect them in the very early stages of the universe.

A glimpse into the infancy of the universe

In this new study, astronomer Justin S. Spilker and his team have detected PAHs in a galaxy more than 12 billion light-years away; that is, when our cosmos was only a tenth of its present age.

In particular, this work shows the detection of the 3.3 micron band, which is related to the smallest PAHs (less than 100 carbons) and neutrals, thus ruling out the presence of a strong radiation field in that galaxy.

This scientific breakthrough has been possible thanks to an exceptional combination. On the one hand, the excellent sensitivity of James Webb and, on the other, the decisive help of a phenomenon called gravitational lensing.

The galaxy observed by James Webb shows an Einstein ring formed by a phenomenon called gravitational lensing. This occurs when two galaxies are perfectly aligned with our perspective from Earth. The gravity of the lensing galaxy produces a magnification in the light we observe from the background galaxy (target galaxy). This magnification makes it possible to study galaxies much more distant thanks to these ‘cosmic magnifying glasses’.
S. Doyle / J. Spilker

Predicted by Albert Einstein, this phenomenon occurs when two galaxies align so that, from the observer’s perspective, the background galaxy (or target galaxy) is magnified due to the gravitational influence of the lensing galaxy. In other words, the latter acts as a “cosmic magnifying glass”, amplifying the light that we observe and forming a characteristic ring shape.

Gravitational lenses allow us to see very distant galaxies in detail that would not be possible to study without them. In this case, the amplification factor is 30.

Smoke was found, but is there a fire?

PAHs, very common in space, are exceptional “detectors” of stellar birth. The speed with which an active galaxy creates new stars, as well as the number and distribution of these, allow us to know how galaxies consume their main fuel to grow: gas. This gas is mostly consumed by stars and, when present, supermassive black holes.

It is important to note that the PAHs may also be affected by such black holes.. This presents certain limitations in the use of these molecules to accurately measure the rate of star formation in a galaxy. However, Spilker and his collaborators were able to rule out the presence of a dominant black hole in this galaxy, since its PAHs are not affected by strong radiation fields.

One of the most significant results is that the distribution of PAH molecules and the regions forming new stars are not the same. That is, regions were observed where there are PAHs but no recent star creation, and vice versa. This finding suggests that the interstellar medium in the early stages of the universe may differ significantly from what we observe in a more mature cosmos, such as the one we see today.

In Spilker’s own words, “now that we know that we have detected these molecules at great distances, the next step is to understand if it is true that where we have smoke (PAH molecules) there is fire (star formation)”.

Their results point to the importance of further studies in distant galaxies. This will help us understand to what extent PAHs can be used as indicators of new star formation in the early Universe, where the physical and chemical processes may be different from what we see in local galaxies.