Researchers observe iron in an exoplanet atmosphere

US, WASHINGTON (ORDO NEWS) — An international team of researchers led by astronomers from the University of Amsterdam first demonstrated the presence of iron in the atmosphere of an exoplanet. Researchers have discovered emission lines of uncharged iron atoms in the light spectrum of the KELT-9b exoplanet.

The observation was difficult because the exoplanet is obscured by its bright host star.

The exoplanet KELT-9b revolves around its star KELT-9 in 36 hours. A star and a planet are located about 620 light-years from Earth in the constellation Cygnus. A star has a temperature of more than 10,000 degrees, almost twice as hot as the sun. The planet KELT-9b is larger than Jupiter. It is close to its star, about thirty times closer than the Earth to the Sun.

Researchers already knew that there should be iron in the planet’s atmosphere. A few years ago, they already saw signs of this when studying starlight when a planet passed in front of its star.

In new observations, the researchers looked directly at the light of the planet. This is difficult because the planet is illuminated by the light of its star. In addition, due to its proximity to the star, one year on the planet lasts about a day and a half. For half of this very short “year,” the night side of the planet faces the Earth, but at this time it is too dark to be seen.

Thus, the researchers had to observe the planet for a short 8 hours before the planet was hiding behind the star in order to observe its hot, bright day side.

Lorenzo Pino (University of Amsterdam), lead author of the study, compares the search for light from an exoplanet in the bright light of her star with the search for a firefly near a lamppost: “A few years ago we saw a shadow of a firefly or, in our case, the shadow of an exoplanet. Now we looked at the exoplanet directly. ”

Researchers made their observations on the Spanish island of La Palma on the night of July 22, 2018 using the Italian telescope Telescopio Nazionale Galileo. This telescope is equipped with HARPS-N, a spectrograph that can split the light and detect the presence of certain atoms and molecules: Researchers have extracted the emission lines of atoms using a technique called cross-correlation.

“The star is motionless, but the planet is moving. Cross-correlation is a kind of filter that moves with the planet. This allows us to isolate the light of the planet. ”

Based on the data, the researchers now believe that iron in the KELT-9b exoplanet atmosphere heats the upper atmosphere, making it warmer than the lower. The idea is that iron absorbs the light of the star, thereby heating the atmosphere. On Earth, a similar process takes place in the atmosphere. However, in this case, not iron, but ozone heats the upper layers.

In the future, researchers hope to conduct a deeper study by accurately measuring the iron content in the planet’s atmosphere. For example, this can be done using the Hubble Space Telescope, in which time for observation has already been set for Lorenzo Pino.

Ultimately, the researchers hope to uncover the mystery of how hot gaseous giant exoplanets such as KELT-9b arise, and why there are no comparable examples in our solar system.

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