Employing the formidable observational capabilities of the NASA/ESA/CSA James Webb Space Telescope, stellar cartographers have uncovered compelling indications of gaseous methane adorning the distant dwarf planet Makemake. This groundbreaking revelation, detailed in a scientific publication within the prestigious Astrophysical Journal Letters, necessitates a re-evaluation of Makemake’s previously held characterization as a placid, frozen celestial entity. It establishes Makemake as only the second trans-Neptunian object, following in the footsteps of Pluto, for which the existence of atmospheric gas has been definitively ascertained.
Protopapa et al. utilized Webb observations (represented in white) to ascertain the presence of methane gas on Makemake. Distinctive emission spikes in proximity to 3.3 microns unequivocally signify methane in its gaseous state above Makemake’s surface. A continuum model (depicted in cyan) is superimposed for comparative analysis; the aforementioned gas emission peaks are precisely located where the registered spectrum surpasses the established continuum. Image attribution: S. Protopapa / I. Wong / SwRI / STScI / NASA / ESA / CSA / Webb.
Makemake, also cataloged as 2005 FY9 and designated (136472), was initially identified in 2005 by a cohort of astronomers affiliated with the California Institute of Technology, under the leadership of Mike Brown.
Situated within a spatial domain extending beyond Neptune, this dwarf planet resides in a region populated by numerous smaller celestial bodies of the Solar System.
Its radial dimension is estimated at approximately 715 kilometers (444 miles), a measurement that renders it marginally smaller and less luminous than Pluto.
Completing a single orbital circuit around the Sun requires approximately 305 Earth years for this dwarf planet.
Prior observations of stellar occultations had suggested that Makemake possessed no substantial global atmosphere, though the possibility of a tenuous one could not be entirely dismissed.
Concurrently, infrared data acquired from the dwarf planet hinted at perplexing thermal anomalies and unusual characteristics associated with its methane ice, thereby raising the prospect of geographically localized heated regions on its surface and potential atmospheric emission.
Dr. Silvia Protopapa, an astronomer associated with the Southwest Research Institute, stated, “Makemake stands as one of the most substantial and luminous icy bodies situated beyond Neptune, with its surface predominantly composed of frozen methane.”
“The Webb telescope has now revealed that methane also exists in a gaseous state in the vicinity of its surface, a finding that imbues Makemake with even greater intrigue.”
“This discovery underscores that Makemake is not merely an inert relic of the outer Solar System, but rather a dynamically active body where methane ice continues to undergo transformations.”
The observed emission spectrum of methane is interpreted as a consequence of solar-excited fluorescence, which entails the re-emission of solar radiation that has been absorbed by methane molecules.
According to the research team’s analysis, this phenomenon could signify either the presence of a highly tenuous atmosphere in equilibrium with surface ices—akin to Pluto—or more episodic activity, such as sublimation characteristic of comets or the eruption of cryovolcanic plumes.
Both hypothetical scenarios are deemed physically plausible and align with the extant observational data, taking into account the inherent noise levels and limited spectral resolution of the measurements.
Dr. Ian Wong, an astronomer based at the Space Telescope Science Institute, commented, “While the inclination to connect Makemake’s diverse spectral and thermal anomalies is considerable, establishing the precise mechanism driving this volatile activity remains an essential prerequisite for interpreting these observations within a cohesive framework.”
“Subsequent Webb observations, conducted at a superior spectral resolution, will be instrumental in discerning whether the methane originates from a thinly bound atmosphere or from plume-like outgassing events.”
Dr. Emmanuel Lellouch, an astronomer at the Paris Observatory, posited, “This recent discovery introduces the possibility that Makemake supports an exceptionally tenuous atmosphere sustained by the sublimation of methane.”
“Our most refined models suggest a gas temperature in the vicinity of 40 Kelvin (equivalent to minus 233 degrees Celsius) and a surface pressure of merely around 10 picobars—a pressure that is 100 billion times lower than Earth’s atmospheric pressure and a million times more attenuated than that of Pluto.”
“Should this hypothesis be validated, Makemake would join a select group of outer Solar System bodies where active surface-atmosphere exchanges are still occurring in the present epoch.”
Dr. Protopapa further elaborated, “An alternative hypothesis posits that the methane is being liberated through explosive, plume-like outbursts.”
“Within this framework, our modeling indicates that methane could be expelled at a rate approaching several hundred kilograms per second, a volume comparable to the vigorous water plumes emanating from Saturn’s moon Enceladus and significantly exceeding the faint vapor observed at Ceres.”
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Silvia Protopapa et al. 2025. JWST Detection of Hydrocarbon Ices and Methane Gas on Makemake. ApJL, in press; arXiv: 2509.06772
