Beyond Pluto: The Surprising Discovery of Gas on Distant Makemake
In a groundbreaking astronomical revelation, scientists have detected gas on Makemake, a frigid world located more than 2 billion kilometers farther from the Sun than Pluto. This discovery pushes the boundaries of our understanding of the outer solar system and establishes a new record for the most distant gas ever observed in our cosmic neighborhood. The finding, submitted to arXiv.org on September 8 by planetary scientist Silvia Protopapa of the Southwest Research Institute and her colleagues, challenges previous assumptions about the conditions necessary for gas to exist in the far reaches of our solar system.
The detection is particularly remarkable given Makemake’s extreme remoteness. This distant world takes a staggering 306 years to complete a single orbit around the Sun—significantly longer than Pluto’s already lengthy 248-year journey. Prior to this discovery, Pluto held the record for the most distant world with a detectable atmosphere since 1988, when observations of it passing in front of a star revealed the presence of gas. Scientists had not expected to find any gas around Makemake, especially after previous stellar occultation observations showed no evidence of an atmosphere. However, the James Webb Space Telescope (JWST), with its unprecedented sensitivity and infrared capabilities, managed to detect what appears to be an extremely tenuous presence of gas.
The gas detected on Makemake is remarkably sparse. If it constitutes an atmosphere, the surface pressure would be approximately one hundred billionth of Earth’s atmospheric pressure, or about one millionth of Pluto’s. William McKinnon, a planetary scientist at Washington University in St. Louis who wasn’t involved in the discovery, emphasized the significance of the Webb telescope’s role, stating that it has “blown the doors off the outer solar system in terms of figuring out what’s on the surfaces of all these mysterious worlds.” This detection demonstrates JWST’s extraordinary capability to uncover previously undetectable features of distant celestial bodies.
Makemake’s surface is dominated by methane ice, which gives it high reflectivity—bouncing back about 80 percent of the sunlight that reaches it. The gas detected may originate from this methane ice vaporizing in the weak sunlight, creating a barely-there atmosphere. However, Protopapa suggests a more intriguing possibility: the gas might be erupting from Makemake’s interior through plumes similar to the water geysers observed on Saturn’s moon Enceladus. While Enceladus is energized by Saturn’s gravitational influence, Makemake’s potential activity would stem from its considerable size. At approximately 1,430 kilometers in diameter (about 60 percent of Pluto’s width), it ranks as the fourth largest known object beyond Neptune’s orbit.
Both Makemake and Pluto share an orange coloration, likely resulting from sunlight and cosmic rays transforming methane into more complex compounds. However, a key difference between the two worlds is their nitrogen content. Unlike Pluto, which has abundant nitrogen in both ice and gas forms, JWST detected no nitrogen signature on Makemake. Researchers hypothesize that Makemake’s smaller size and correspondingly weaker gravity may have been insufficient to retain nitrogen over cosmic timescales, as nitrogen becomes more volatile than methane at Makemake’s frigid surface temperatures. It remains possible, though, that nitrogen ice could still exist beneath Makemake’s methane-dominated surface.
This remarkable discovery raises intriguing questions about other distant worlds in our solar system. Eris, which orbits almost twice as far from the Sun as Makemake and is nearly as large as Pluto, has both methane and nitrogen ice on its surface. Yet observations from a 2010 stellar occultation and current JWST data have not revealed any gas. For now, Makemake stands unique in exhibiting methane emission at such an extreme distance from the Sun. However, as JWST continues its exploration of the outer solar system with its unprecedented infrared vision, more surprises may await in the depths of our cosmic backyard, potentially reshaping our understanding of these distant, mysterious worlds.
