Gases gushing from the lava-covered surface of the super-Earth exoplanet 55 Cancri may provide an atmosphere rich in carbon dioxide or carbon monoxide, according to a new study.
55 Cancri e is one of five planets orbiting the Sun-like star 55 Cancri A, located 40 light-years away in the constellation Cancer.
Discovered in 2004, the planet is twice the radius and eight times more massive than Earth, making it a so-called super-Earth.
55 Cancri orbits 0.015 astronomical units from its host star (about 25 times closer than Mercury to the Sun) every 18 hours.
The planet is also tidally fixed and does not rotate like Earth, instead having a permanent “day” and “night” side.
Previous studies of 55 Cancri using data from NASA's Spitzer Space Telescope suggested the presence of an atmosphere rich in volatile substances such as oxygen, nitrogen, and carbon dioxide.
However, astronomers could not rule out another possibility. It's possible that the planet is bare except for a thin cover of evaporated rock rich in elements such as silicon, iron, aluminum, and calcium.
“Earth is so hot that some of the molten rock should evaporate,” says Renyu Hu, an astronomer at NASA's Jet Propulsion Laboratory.
To distinguish between the two possibilities, Dr. Hu and colleagues used: Webb's NIRCam (near infrared camera) and mm (Mid-infrared measuring instrument) An instrument that measures infrared rays from 4 to 12 microns coming from 55 Cancer.
Although Webb cannot capture direct images of the planet, it can measure subtle changes in light from the entire system as the planet orbits the star.
By subtracting the brightness during a secondary solar eclipse, when the planet is behind the star, from the brightness when the planet is directly next to the star, astronomers can estimate the different wavelengths coming from the dayside of the planet. We were able to calculate the amount of infrared radiation. .
This method, known as secondary eclipse spectroscopy, is similar to the method used by other research teams to search for the atmospheres of other rocky exoplanets, such as TRAPPIST-1b.
The first indication that 55 Cancri may have a significant atmosphere came from temperature measurements based on thermal radiation, which is thermal energy emitted in the form of infrared radiation.
If the planet were covered in dark lava with a thin veil of evaporated rock, or had no atmosphere at all, the daytime temperature would be about 2,200 degrees Celsius.
“Instead, the MIRI data showed a relatively low temperature of about 1,540 degrees Celsius,” Dr. Hu said.
“This is a very strong indication that energy is being distributed from the day side to the night side, probably by an atmosphere rich in volatiles.”
Although lava flows can transport some heat to the night side, they cannot transfer heat efficiently enough to account for cooling effects.
When the researchers looked at the NIRCam data, they saw a pattern consistent with a volatile-rich atmosphere.
Thermal emission spectra captured by Webb's NIRCam instrument in November 2022 and by the MIRI instrument in March 2023 show a variety of infrared (x-axis) emissions from the super-Earth exoplanet 55 Cancri. shows the brightness (y-axis) at different wavelengths. Image credits: NASA / ESA / CSA / J. Olmsted, STScI / R. Hu, JPL / A. Bello-Arufe, JPL / M. Zhang, University of Chicago / M. Zilinskas, SRON Netherlands Institute for Space Research.
“We're seeing evidence that the spectrum is dropping between 4 and 5 microns. Less light is reaching the telescope,” said Dr. Aaron Belloalfe, also of NASA's Jet Propulsion Laboratory.
“This suggests the presence of an atmosphere containing carbon monoxide or carbon dioxide, both of which absorb light at these wavelengths.”
“Planets without atmospheres or with only evaporated rock in their atmospheres would not have these unique spectral features.”
“This is exciting news,” said Dr Yamira Miguel, an astronomer at the Leiden Observatory and the Netherlands Institute for Space Research.
“We've spent the past decade modeling different scenarios and imagining what this world could be like. It's invaluable to finally have our work confirmed.”
The authors believe that the gas enveloping 55 Cancri has not been present since the planet's formation, but may be coming from within.
“Due to the high temperatures and intense radiation from this star, the primary atmosphere would have long since disappeared,” Dr. Bello Alfe said.
“This is probably a secondary atmosphere that is continually replenished by the magma ocean. Magma is not only crystals and liquid rock, but also contains many dissolved gases.”
Most likely, the atmosphere surrounding the Earth will become more complex and highly variable as a result of interactions with the magma ocean.
In addition to carbon monoxide and carbon dioxide, gases such as nitrogen, water vapor, sulfur dioxide, evaporated rock, and even short-lived clouds of small droplets of lava condensing from the air can be present.
Although 55 Cancri is too hot to be habitable, it provides a unique window into studying interactions between the atmospheres, surfaces, and interiors of rocky planets, perhaps providing insights into early Earth, Venus, and Mars. Scientists think there is a possibility. It is believed that it was once covered by a sea of ​​magma.
“Ultimately, we want to understand the conditions under which rocky planets can maintain gas-rich atmospheres, which is a key ingredient for habitable planets,” Dr. Hu said.
of findings It was published in the magazine Nature.
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R. Hu other. Secondary atmosphere of the rocky exoplanet 55 Cancri e. Nature, published online on April 15, 2024. doi: 10.1038/s41586-024-07432-x
Source: www.sci.news
