Temperament stars are distorting our view of distant planets

Most of the information we have about planets outside the solar system (exoplanets) comes from submerging in starlight as these planets pass in front of their host stars.

This technology can provide clues to the size of the Earth (by seeing how many stars are blocked) and what its atmosphere is composed of (by seeing how the planet changes the pattern of the stars passing through it).

But a new study, published in Astrophysics Journal Supplementary Seriesit concluded that due to the hotter and colder areas on the star surface, the fluctuations of starlight may distort our interpretation of planets than previously thought.

The researchers studied the atmosphere of 20 planets the size of Jupiter and Neptune and found that the variability of the host star distorted the data by about half of the data.

If researchers cannot correctly interpret these changes, they may misunderstand a range of characteristics such as the size of the planet, temperature and atmospheric composition. The team added that if researchers look at a range of light rays, including in the optical areas where the impact of star pollution is most noticeable, the risk of misunderstanding is manageable.

Lead author Dr. Arianna Saba (UCL Physics & Surtonomy) who is part of her PhD at UCL, said: “These results are surprising – we found that the data has more stellar pollution to the data than we expected. This is for us. Said it is important. By refining our understanding of how variability of stars affects our interpretation of exoplanets, we can improve the model and make more wise use of James Webb, Ariel, and Te Twinkle’s tasks include larger datasets.”

Second author Alex Thompson is a current PhD student in Physics and Astronomy in UCL, whose research focuses on external host stars. Things coming from the stars and planets.

“Some stars may be described as ‘spots’ – they are in darker, hotter areas on the surface, and they have a deeper proportion and are hotter. This is due to stronger magnetic activity.

“Hotter, brighter areas (faculae) emit more light, for example, if planets pass through the hottest places of the star, this could cause researchers to overestimate the size of the Earth to block more stars’ light, or they It may be inferred that the Earth is hotter than the stars, or that it has a strong atmosphere. If the planet passes in front of the cold star point, the opposite is correct, making the Earth look “small”.

“On the other hand, the reduction of light emitted from the star point can even mimic the effects of the planets transmitted in front of the star, which makes you think there may be a planet when there are no stars. That’s why following up observations for confirming exoplanet detection Such an important reason.

“For example, these changes in these stars can also distort the estimated estimates, such as how much water vapor is in the planet’s atmosphere. That’s because at different wavelengths reaching the telescope, the changes can mimic or mask the characteristics of water vapor.”

In the study, the researchers used 20-year observations from the Hubble Space Telescope, combining data from two telescope instruments, namely the Space Telescope Imaging Spectrometer (STIS) and the Wide Field Camera 3 (WFC3).

They processed and analyzed the data for each planet in the same way to ensure they were compared like this to minimize the bias that occurs when using different methods to process the data set.

The team then looked at which combination of atmospheric and stellar models best suited their data, comparing the models that caused stellar variability with the simpler models. They found that of the 20 analyses analyzed, the data for six planets were better than models adjusted for star variability, while the other six planets could be slightly contaminated by their host stars.

They analyzed the visible, near-infrared and near-powder wavelengths by the fact that in the near-UV and visible (optical) regions, the distortion of star activity is more pronounced than the longer wavelengths of infrared.

The team described two ways to tell whether excellent variability may affect planetary data.

Dr. Saba explained: “One is to look at the overall shape of the spectrum, i.e., the light patterns at different wavelengths through the planet – to see if this is explained only by planets requires star activity. The other is to be different in different Two observations of the same planet are made in the spectral region of time. If these observations are very different, the possible explanation is variable stellar activity.”

Alex Thompson added: “With the correct wavelength coverage, the risk of misunderstanding is manageable. Shorter wavelengths, optical observations (such as those used in this study) are particularly useful because this It is the most obvious place for the stellar pollution effect.”