by A new study has shown that temperamental stars that can be brightened up and dimming in the course of just a few hours can distort the position of astronomers over thousands of planets outside the solar system.
The team behind this study came to this conclusion by studying 20 extrasolar planets or “exoplanets” while crossing the faces of their elder, or “passages” using the Hubble Space Telescope. This revealed that star light fluctuations caused by hotter and colder areas on the surfaces of the stars were more responsible for deforming interpretations of exoplanet -atmospheres than previously thought.
To their surprise, the team discovered that the information about about half of the 20 planets they studied, which varied from Neptune-like worlds to blown hot Jupiter planets, were influenced by the changeability of their host stars. This is a worrying development, because if these variations in stellar brightness are not justified, scientists can get a number of things about exoplanets wrong, including their size, temperature and the composition of their atmospheres.
“These results were a surprise – we found more excellent contamination of our data than we expected. This is important for us to know,” said team leader and researcher at the University College of London (UCL) Arianna Saba in a statement to the space was sent. com. “By refining our understanding of how the variability of stars can influence our interpretations of exoplanets, we can improve our models and make smarter use of the much larger datasets that come from missions, including the James Webb Space Telescope (JWST), Ariel and Twinkle. “
Some stars blow hot and cold
Transits are a vital important element of exoplanet science.
While planets pass for their old stars as seen from the earth, they cause a small dive in the amount of starlight that we receive from those stars. These dips can be used to detect a groundbreaking planet, and the timing between dips in light can be used to help scientists determine how long the new discovered world takes to turn its star.
Moreover, analyzing the starlight that goes through the atmosphere of a planet can tell researchers the composition of that atmosphere. This is possible because elements slightly absorb with different characteristic wavelengths. So when star light goes through a planetary atmosphere, the elements in that atmosphere leave their fingerprints in that light.
Scientists read these chemical fingerprints using a method called “Spectroscopy”.
But if scientists read Starlight incorrectly, data on planetary atmospheres and even some exoplanet detections that are made with the transit method can be threatened.
“We learn about exoplanets from the light of their host stars and it is sometimes difficult to discharge what a signal is from the star and what comes from the planet,” said team member and UCL researcher Alexandra Thompson. “Some stars can be described as ‘fragmentary’ – they have a larger part of colder areas that are darker, and hot areas that are brighter on their surface. This is due to a stronger magnetic activity.”
She explained that these brighter regions, or ‘faculae’ radiate more light, which means that if a planet passes for the hottest part of the star, this researchers can cause how large the planet is. This is because the planet will seem to block more of the light of the star, whether the scientists can conclude that the planet is hotter than it actually is or that it has a denser atmosphere than it actually has.
Thompson added that the opposite is also true: if the planet passes for the cold spot of a star, it can lead to the world seems smaller than it actually is.
“The reduction of the broadcast light of a star spot can even imitate the effect of a planet that passes in front of a star, so you think there can be a planet if there is none,” said Thompson. “This is the reason why follow-up observations are so important to confirm exoplanet detections. These variations of the star can also deform estimates from how much water vapor, for example, is in the atmosphere of a planet.
“That’s because the variations can simulate or hide the signature of water vapor in the light pattern at different wavelengths that reach our telescopes.”
What help from Hubble
To investigate this potential effect, Saba, Thompson and colleagues turned up to 20 years from Hubble observations with the help of the Long-Serving Space Telescope’s Space Telescope Imaging Spectrograph (Stis) and wide field camera 3 (WFC3) instruments.
The team analyzed visible, near-infrared and near-cultviolet wavelength data from 20 exoplanet systems in the same way to minimize bias that can be inherent to other studies.
Consider models that take into account stellar variability and models that do not do, the researchers looked at combinations of star light and atmospheric models that best match the data they have recovered.
This revealed that 6 out of 20 exoplanets were better characterized using models that take into account variations in the light of their elder stars. They also discovered that data around 6 other planets may have been somewhat corrupted by slight contamination of their guest stars.
About the electromagnetic spectrum that the team considered, the distortions caused by stellar variability were much clearer in visible light and in near-UV radiation than in the infrared.
The findings of the team have revealed two ways in which the variability of starlich can influence exoplanet observations.
“People are to look at the overall form of the spectrum – that is, the light pattern at different wavelengths that have gone the planet of the star – to see if this can only be explained by the planet or whether stellar activity is needed, “Saba concluded. “The other is to have two observations of the same planet in the optical area of the spectrum that are taken at different times.
“If these observations are very different, the likely explanation is variable stellar activity.”
The results of the team will be published in the Astrophysical Journal Supplement Series and are available as a preprint on the Arxiv site of the research repository.
