Free Astronomy Magazine November-December 2024

27 NOVEMBER-DECEMBER 2024 ASTRO PUBLISHING presenting the Webb results. While this region has been observed pre- viously with NASA’s Hubble Space Telescope, the dusty red gal- axy that forms the intriguing question-mark shape only came into view with Webb. This is a result of the wave- lengths of light that Hubble detects getting trapped in cosmic dust, while longer wavelengths of infrared light are able to pass through and be detected by Webb’s in- struments. Astronomers used both tele- scopes to observe the galaxy cluster MACS-J0417.5-1154, which acts like a magnifying glass because the cluster is so massive it warps the fabric of space-time. This allows astronomers to see enhanced detail in much more distant galaxies behind the cluster. However, the same gravitational effects that mag- nify the galaxies also cause distor- tion, resulting in galaxies that ap- pear smeared across the sky in arcs and even appear multiple times. These optical illusions in space are called gravitational lensing. The red galaxy revealed by Webb, along with a spiral galaxy it is in- teracting with that was previously detected by Hubble, are being mag- nified and distorted in an unusual way, which requires a particular, rare alignment between the distant galaxies, the lens, and the observer — something astronomers call a hy- perbolic umbilic gravitational lens. This accounts for the five images of the galaxy pair seen in Webb’s im- age, four of which trace the top of the question mark. The dot of the question mark is an unrelated galaxy that happens to be in the right place and space-time, from our perspective. In addition to producing a case study of the Webb NIRISS (Near-In- frared Imager and Slitless Spectro- graph) instrument’s ability to detect star formation locations within a galaxy billions of light-years away, the research team also couldn’t re- sist highlighting the question mark shape. “This is just cool looking. Amazing images like this are why I got into astronomy when I was young,” said astronomer Marcin Sawicki of Saint Mary’s University, one of the lead researchers on the team. “Knowing when, where, and how star formation occurs within galax- ies is crucial to understanding how galaxies have evolved over the his- tory of the universe,” said as- tronomer Vicente Estrada-Carpen- ter of Saint Mary’s University, who used both Hubble’s ultraviolet and Webb’s infrared data to show where new stars are forming in the galax- ies. The results show that star for- mation is widespread in both. The spectral data also confirmed that the newfound dusty galaxy is lo- cated at the same distance as the face-on spiral galaxy, and they are likely beginning to interact. “Both galaxies in the Question Mark Pair show active star formation in several compact regions, likely a re- sult of gas from the two galaxies colliding,” said Estrada-Carpenter. “However, neither galaxy’s shape appears too disrupted, so we are probably seeing the beginning of their interaction with each other.” “These galaxies, seen billions of years ago when star formation was at its peak, are similar to the mass that the Milky Way galaxy would have been at that time. Webb is al- lowing us to study what the teenage years of our own galaxy would have been like,” said Sawicki. ! P revious page: The galaxy cluster MACS-J0417.5-1154 is so massive it is warping the fabric of space-time and distorting the appearance of galaxies behind it, an effect known as gravitational lensing. This natural phenomenon magnifies distant gal- axies and can also make them ap- pear in an image multiple times, as NASA’s James Webb Space Telescope saw here. Two distant, interacting galaxies — a face-on spiral and a dusty red galaxy seen from the side — appear multiple times, tracing a familiar shape across the sky. Active star formation, and the face-on galaxy’s remarkably intact spiral shape, indicate that these galaxies’ interaction is just beginning. [NASA, ESA, CSA, STScI, Vicente Estrada-Car- penter (Saint Mary’s University)] A side-by-side comparison of how the Hubble Space Telescope and Webb each viewed this same re- gion of space. [NASA, ESA, CSA, STScI, Vicente Estrada-Carpenter (Saint Mary’s University)]