It’s 7 billion years in the past, and star formation in the universe is starting to dwindle. What could our Milky Way galaxy have looked like during this period? Astronomers have discovered hints in the shape of a cosmic question mark, arising from a rare alignment across vast distances in space.
Considered 7 billion years ago, the universe’s prime phase of star creation is starting to decline. How might the Milky Way galaxy have appeared back then? Scientists using NASA’s James Webb Space Telescope have uncovered significant clues in the form of a cosmic question mark, which is the result of a unique alignment stretched across light-years.
According to astronomer Guillaume Desprez from Saint Mary’s University in Halifax, Nova Scotia, “There are only three or four known gravitational lens configurations like this in the observable universe, making this discovery thrilling. It showcases Webb’s capabilities and suggests we might uncover more similar phenomena in the future.”
Although this area has been previously observed using NASA’s Hubble Space Telescope, the dusty red galaxy that creates the captivating question mark shape was only visible through Webb’s advanced technology. This is because Hubble captures shorter wavelengths of light, which can get trapped in cosmic dust, while Webb’s instruments detect longer infrared wavelengths that are able to penetrate this dust.
Researchers studied the galaxy cluster MACS-J0417.5-1154 with both telescopes, as the enormity of the cluster warps space-time, acting like a cosmic magnifying glass. This allows scientists to observe distant galaxies in greater detail. However, this magnification also causes distortion, making galaxies appear smeared in arcs or even seen multiple times, creating what are known as gravitational lensing effects.
The red galaxy identified by Webb, along with a spiral galaxy it is in contact with—previously discovered by Hubble—exhibit a strange magnification and distortion that occur only under a rare alignment of the galaxies, the lensing mass, and the observer. This phenomenon is referred to as a hyperbolic umbilic gravitational lens. Consequently, Webb’s images show five versions of the galaxy pair, with four outlining the top of the question mark. The dot of the question mark is an unrelated galaxy positioned perfectly from our viewpoint.
Besides providing a fascinating example of the Webb NIRISS (Near-Infrared Imager and Slitless Spectrograph) instrument’s capability to pinpoint star formation sites in a galaxy billions of light-years away, the research team couldn’t overlook the striking question mark shape. “This is just visually stunning. Incredible images like these fueled my passion for astronomy as a young person,” remarked Marcin Sawicki of Saint Mary’s University, who is among the lead researchers on the project.
“Understanding when, where, and how stars form in galaxies is vital for grasping how galaxies have evolved throughout the universe’s history,” added astronomer Vicente Estrada-Carpenter from Saint Mary’s University, who combined both Hubble’s ultraviolet and Webb’s infrared data to map out where new stars are emerging in the galaxies. The findings indicate extensive star formation in both galaxies. Additionally, spectral data confirmed that the newly discovered dusty galaxy shares the same distance as the spiral galaxy seen face-on, suggesting they are likely beginning to merge.
“Both galaxies in the Question Mark Pair exhibit evident active star formation in multiple compact areas, likely due to gas interaction from the two colliding galaxies,” Estrada-Carpenter noted. “However, neither galaxy appears drastically deformed, so we are likely witnessing the initial stages of their interaction.”
“These galaxies, which we view billions of years ago during the peak of star formation, resemble the mass the Milky Way would have possessed at that time. Webb is enabling us to explore what the adolescent years of our galaxy might have entailed,” Sawicki explained.
The images and spectral data from this study were derived from the Canadian NIRISS Unbiased Cluster Survey (CANUCS). The findings have been published in the Monthly Notices of the Royal Astronomical Society.
