Astronomers using the NASA/ESA/CSA James Webb Space Telescope detected methane emissions from the. CWISEP J193518.59-154620.3 (W1935 for short) is an isolated brown dwarf star with a temperature of about 482 K. Their findings also suggest that W1935 could produce auroras similar to those seen on our planet, Jupiter, and Saturn.
W1935 is located about 47 light-years away in the constellation Sagittarius.
This brown dwarf was co-discovered by Backyard Worlds: Planet 9 citizen science volunteer Dan Caselden and NASA's CatWISE team.
W1935's mass is not well known, but it is probably in the range of 6 to 35 times the mass of Jupiter.
After observing numerous brown dwarfs observed by Webb, Dr. Jackie Faherty Researchers at the American Museum of Natural History found W1935 to be similar, with one notable exception. It was emitting methane, which had never been seen before in brown dwarfs.
“Methane gas is expected to be present in giant planets and brown dwarfs, but we typically see it absorbing light rather than absorbing it,” Faherty said.
“At first we were confused by what we were seeing, but eventually it turned into pure excitement when it was discovered.”
Computer modeling provided another surprise. W1935 may have a temperature inversion, a phenomenon in which the atmosphere becomes warmer as altitude increases.
Temperature inversions easily occur in planets orbiting stars, but brown dwarfs are isolated and have no obvious external heat source.
“We were pleasantly shocked when the model clearly predicted a temperature inversion,” said Dr Ben Burningham, an astronomer at the University of Hertfordshire.
“But we also needed to figure out where that extra upper atmosphere heat was coming from.”
To find out, astronomers turned to our solar system. In particular, they focused on the study of Jupiter and Saturn. Both show methane release and temperature inversions.
Since the aurora is likely the cause of this feature on the solar system's giants, the researchers speculated that they had discovered the same phenomenon in W1935.
Planetary scientists know that one of the main drivers of Jupiter and Saturn's auroras are high-energy particles from the sun that interact with the planets' magnetic fields and atmospheres, heating the upper layers.
This is also the reason for the aurora borealis we see on Earth. Auroras are most unusual near the poles, so they are commonly referred to as aurora borealis or southern lights.
However, W1935 does not have a host star, so solar wind cannot contribute to the explanation.
There's another fascinating reason why auroras occur in our solar system.
Both Jupiter and Saturn have active moons that occasionally eject material into space, interacting with the planets and enhancing the auroral footprints of those worlds.
Jupiter's moon Io is the most volcanically active world in the solar system, spewing fountains of lava tens of miles high. Also, Saturn's moon Encereadus spews water vapor from geysers that freeze and boil as soon as they reach space.
Although more observations are needed, researchers speculate that one explanation for W1935's aurora may be an active moon that has yet to be discovered.
“Every time astronomers point an object at the Webb, new and surprising discoveries can occur,” Dr. Faherty said.
“When we started this project, we weren't concerned about methane emissions, but now that we know that methane emissions can exist and the explanations are very attractive, we're always paying attention. That's part of how science moves forward.”
a paper The survey results were published in a magazine Nature.
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JK Faherty other. 2024. Methane emission from cool brown dwarfs. Nature 628, 511-514; doi: 10.1038/s41586-024-07190-w
Source: www.sci.news
