Free Astronomy Magazine November-December 2023

10 NOVEMBER-DECEMBER 2023 ASTRO PUBLISHING A stronomers using ALMA, in which the ESO is a partner, have revealed an ex- tremely distant galaxy that looks surprisingly like our Milky Way. The gal- axy, SPT0418-47, is gravitationally lensed by a nearby galaxy, appearing in the sky as a near-perfect ring of light (left). The research team reconstructed the dis- tant galaxy’s true shape (right) and the motion of its gas from the ALMA data using a new computer modelling technique. [ALMA (ESO/NAOJ/NRAO), Rizzo et al.] lar cloud of these large organics. As the name implies, polycyclic aro- matic hydrocarbons (PAHs) are com- posed of carbon and hydrogen, contain two more rings in their frame (the most famous aromatic molecule, benzene, is not considered a PAH. Naphthalene, containing two ben- zene rings fused on a side, is the smallest member containing only six-member rings), and are aro- matic , a term that originated from their often-fragrant smell but which was even- tually reduced to a chemically-defined state of these mole- cules sharing elec- trons among their carbon rings in a way that adds to their sta- on Earth broadly interesting and meaningful across disciplines. Two recent discoveries by the James Webb Space Telescope (JWST) reveal the extent to which the element carbon was both an active presence in the early universe and continues to be driven into forms ready for complex chemistry to occur in mo- lecular clouds within our own cos- mic neighborhood. The first study, pub- lished in the June 5 th issue of the presti- gious journal Na- ture , reports the detection of the most ancient organic molecules yet de- tected – polycyclic aromatic hydrocar- bons in the galaxy SPT0418-47, 12.3 bil- lion light years away. This galaxy was first detected in 2020 by the ground-based South Pole Telescope of the U.S. National Science Foundation (NSF) and was only observable at all through the phe- nomenon of gravita- tional lensing that T his schematic animation shows how light from a distant galaxy is dis- torted by the gravitational effects of a foreground galaxy, which acts like a lens and makes the distant source appear distorted, but magnified, forming characteristic rings of light, known as Einstein rings. This effect has allowed astronomers to see the distant galaxy SPT0418-47 (which ap- pears as a golden ring in the ALMA images) in finer detail than would have been possible otherwise. The foreground galaxy is not visible in the ALMA images of SPT0418-47 because it is too faint at the wavelengths used. The blue colour used in this schematic to represent this foreground galaxy is artificial. [ALMA (NRAO/ESO/NAOJ)/Luis Calçada (ESO)] made it appear 30 times brighter. Recent JWST observations collected the diagnostic spectra of a molecu-