Diagram of HAT-P-18 b. (Image credit: NASA/Eyes on Exoplanets).
HAT-P-18 b is an exoplanet about 500 light-years away with a mass comparable to Saturn but comparable in size to Jupiter. This is because as the gas giant planet orbits around its host star, its atmosphere expands like a hot air balloon. Depending on how close an exoplanet is to its host star, it is a good candidate for observation using the transit method, a phenomenon in which a world passes in front of its star from a vantage point on Earth. Astronomers can carefully examine the light passing through an exoplanet’s atmosphere to determine its characteristics.
However, its host star, HAT-P-18, is not uniform; like the Sun, there are bright areas and dark areas. In a new study, astronomers observed a transit phenomenon in which hot Saturn passes over an active region, or sunspot, of its host star. To determine the atmosphere’s composition, the researchers also needed to model the host star’s peculiarities. Researchers were able to detect the presence of water and carbon dioxide on hot Saturn, which is not unusual for such a world. The researchers were also able to conclude that the host star contains many star spots, which can have a big impact on how the data is interpreted.
A paper explaining the findings Published in Monthly Notices of the Royal Astronomical Society (MNRAS).Marie-Lou Fournier-Tondreau, lead author of the study To tell“We found that accounting for stellar contamination implied the presence of spots and clouds rather than haze, and recovered almost an order of magnitude lower water vapor content.” Indeed, Canada’s NIRISS (Near Infrared Imager and Slitless Imager) This is the first time that we have been able to unambiguously disentangle the characteristics of haze and star spots thanks to a spectrometer, which provides a wider wavelength range extending into the visible light range.” Taking singularities into account will be essential in interpreting future exoplanet observation data.
