NASA’s Telescópio Espacial James Webb has detected methane on the interstellar comet 3I/ATLAS. The observation marks the first direct detection of this gas in an interstellar visitor. The measurements took place last December, as the object moved away from Sol after its closest pass.
The data comes from the MIRI instrument, which captured chemical signatures in the mid-infrared. Comet 3I/ATLAS was traveling back out of the solar system. The observations took place on two different dates.
Methane Detecção reveals deep comet material
Methane appeared late in 3I/ATLAS emissions. Esse compound is highly volatile and sublimates easily. The presence suggests that the gas was protected in deeper layers of the icy core. The heat from passing through Sol reached these internal regions.
Cientistas observed the comet at distances of about 329 million kilometers and then 379 million kilometers from Sol. The first data collection took place between December 15th and 16th. The second measurement was on December 27th. Nesses moments, the object had already completed perihelion.
- Methane emerged after solar heating removed surface layers
- The relative amount of water vapor is greater than in comets in the solar system
- The gas indicates a different chemical composition than most local objects
- Observações confirms volatile activity even when moving away from Sol
The proportion of methane in relation to water surprised the researchers. Poucos comets from our solar system show a similar pattern.
Rico in carbon dioxide, 3I/ATLAS differentiates itself from local comets
Comet 3I/ATLAS releases much more carbon dioxide compared to water. Essa characteristic had already been noticed in previous observations. New measurements with MIRI reinforced the pattern. The object maintains high CO2 production even after passing through Sol.
Essa abundance points to a different training environment. The comet came from another star system. Sua chemistry does not follow the patterns dominant among comets born near Sol.
Carbon dioxide appears more concentrated near the nucleus. Já water vapor spreads over a larger region in the coma. The methane is also closer to the comet’s center. Imagens from MIRI show this spatial distribution of gases.
Produção of gas falls as comet moves away
3I/ATLAS activity decreased between the two December observations. Overall gas production fell sharply. O vapor de água apresentou a redução mais forte. Esse behavior follows that expected for comets. Menos solar heat means less ice vaporized on the surface.
Methane and carbon dioxide maintained stable relative proportions. Water, less volatile than these two, stopped being released more quickly. The comet continued to be active, but at a slower pace.
Instrumento MIRI enabled detailed composition analysis
MIRI’s Espectrômetro decomposed infrared light. The tool simultaneously measured several gases around the nucleus. Cada point in the sky generated a complete spectrum. Essa capability helped map the distribution of the compounds.
Cientistas identified clear spectral lines of methane, carbon dioxide and water. Nickel also appeared in the measurements. The results were published in the journal The Astrophysical Journal Letters.
Implicações for origin of interstellar objects
The composition of 3I/ATLAS suggests formation in a region rich in volatiles. The high carbon dioxide content and the presence of deep methane indicate conditions different from those in our solar system. The object preserves material from its source system.
Essa is the third confirmed interstellar visit to the solar system. The previous two allowed less detailed chemical data. James Webb has opened a new observation window for these rare visitors.
Comet 3I/ATLAS makes its way out of the solar system. Ele não retornará. Post-perihelion observations captured the innermost material. Future Estudos can compare this data with other interstellar objects.
