Ever since the James Webb Space Telescope first spotted compact, bright red objects in the early universe in 2022, dubbed "little red dots," astronomers have been trying to figure out what they are. These sources of light existed when the cosmos was only a few hundred million years old. They looked unusual: dense, red, numerous at high redshifts, and nearly vanishing closer to our time. One popular idea linked them to active supermassive black holes at the centers of galaxies, but the details did not add up. The main question remained open: what do they turn into as the universe matures?
The answer began to be sought in an object that is much closer. The spiral galaxy WISEA J123635.56+621424.2, nicknamed "Saguaro" for its long arms resembling those of a cactus from the Sonoran Desert, existed about 3,3 billion years after the Big Bang. At its center, scientists discovered a compact red core strikingly similar to those distant dots. A team led by Pierluigi Rinaldi (University of Arizona, now at the Space Telescope Science Institute) studied "Saguaro" using archival data from Webb and Hubble. The core turned out to be brighter in ultraviolet and infrared than in visible light—just like classic little red dots. The Chandra X-ray Observatory detected faint emission indicating an active but heavily obscured galactic nucleus.
To test the hypothesis, the researchers "moved" Saguaro in a virtual experiment to a much higher redshift—where the early red dots lived. The surrounding spiral structure disappeared from view, leaving only the bright compact core. This, the scientists believe, is what creates the observational effect: at large distances, we simply do not see the faint outer parts of galaxies, but only their active centers.
The results, published on 29 July 2026 in The Astrophysical Journal, offer one possible evolutionary path. Little red dots may not be a separate class of objects but a temporary phase in the life of supermassive black holes actively interacting with surrounding matter. "Everything that emerged in the early universe must evolve into something we see around us. Now we have a way to search for their descendants," notes co-author George Rieke.
The work continues: the scientists plan to revisit Webb's archives to compile a more complete census of such objects and understand how the environment influences their development. For now, Saguaro is just one example, but it already shows how closely connected the epochs are. Light traveling to us for billions of years carries not just a snapshot of the past, but a hint at a unified chain of processes where compact red dots of the early cosmos become familiar galaxies with active nuclei. The universe turns out to be arranged so that even its most distant and mysterious corners gradually fit into a comprehensible, albeit grand, picture.
