Free Astronomy Magazine November-December 2023

12 NOVEMBER-DECEMBER 2023 ASTRO PUBLISHING that spectrum is identical to a sam- ple of that same molecule here on Earth because electrons, protons, and neutrons all share the same fundamental properties and com- bine to form molecules in the same fundamental ways. When that same spectrum is obtained from a mole- cule in a distant galaxy, the only dif- ference we find is the redshifting of that spectrum due to the expansion of space itself. When that redshift is accounted for in the spectrum, that ancient molecule “way over there” is identical in all ways to that same molecule here on Earth. We take this as one of the many signs that the physics and chemistry of the early and distant universe, based on fundamental constants like the charge of the electron, Planck’s con- stant, and the speed of light itself, are not different in a detectable way from the same physics and chemistry that drives everything here on Earth today. The detection of PAHs in SPT0418- 47 by Prof. Joaquin Vieira and Kedar Phadke of the University of Illinois Urbana-Champaign and an international team of collaborators were interesting for three signifi- cant reasons. First, they were de- tectable at all at 12.3 billion light years and, thanks to the high-qual- ity and well-investigated diagnostic fingerprints of these molecules here on present-day Earth, their assign- ment was only complicated by the many different molecular structures that make up this branch of the or- ganic family tree. The second rea- son has less to do with organic chemistry and more to do with as- trophysics – there is an established connection between star formation and the presence of PAHs. These large aromatic molecules absorb strongly in the UV and radiate in the infrared, so much so that 20% of the infrared light we detect from star forming regions are attributa- T he universe is expanding, and that expansion stretches light traveling through space in a phenomenon known as cosmological redshift. The greater the redshift, the greater the distance the light has traveled. As a result, tele- scopes with infrared detectors are needed to see light from the first, most dis- tant galaxies. [NASA, ESA, Leah Hustak (STScI)] ble to PAH emissions. Some modern perspectives even directly link the presence of PAHs with stellar forma- tion – a hypothesis that is chal- lenged with these SPT0418-47 measurements by the confirmed ab- sence of PAHs in some of the ob- served star-forming regions. The