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Astronomers have a rare direct view of an exoplanet thanks to the new telescope technology



Artistic concept of HR8799e.
Illustration: ESO / L. Calçada

Scientists have directly observed an exoplanet in an entirely new way thanks to an instrument of the Very Large Telescope Interferometer of the Southern Observatory.

Telescopes are more than just lenses and mirrors – they are sophisticated electromagnetic radiation detectors to overcome the many challenges of observing very distant objects. Exoplanets are especially hard to spot because they are thousands of times weaker than the stars that surround them. The new way of observing with optical interferometry with the GRAVITY instrument is another important tool because it can directly measure the light of exoplanets and not how they orbit the light from the stars they orbit.

"It's a technical achievement for us," said study's first author, Sylvestre Lacour, team leader and researcher at the CNRS Observatoire de Paris – PSL, to Gizmodo. "We did something that no one else could do before."

Researchers observed HR 8799e, a young Jupiter-like exoplanet, orbiting a bright star named HR 8799, 39.4 parsecs (128.5 light-years). It is not a newly discovered exoplanet, but it was the first time that scientists were able to observe an exoplanet with optical interferometry. Their results will be published in Astronomy and Astrophysics.

HR 8799, which was imaged directly from the VLT (but does not use optical interferometry).

Optical interferometry is similar to other forms of interferometry that we occasionally write about. The researchers performed simultaneous observations with visible light using the four 8-meter Very Large Telescope units in Chile and later added the observations. It's like building a larger mirror to collect light from a central camera, but instead of mirrors reflecting the light in one place, it brings light from four different telescopes thanks to the GRAVITY instrument.

This is a typical tool of the Radio Astronomy Toolbox, but if you perform these measurements in the optical spectrum, researchers can get more information. "It brings more accurate measurements to the planet's position and brings a better understanding of the planet's spectra," says the colors of the emitted light, which help researchers determine what materials are in the planet's atmosphere, Lacour said.

The results brought some surprises: HR 8799e contains more carbon monoxide than methane, which was unexpected due to chemical calculations. Lacour told Gizmodo that vertical winds on the planet might prevent the formation of methane-forming chemical reactions.

Some comments: No, this does not mean that we can now directly map the optical light of an exoplanet, as this method does not work. They produce pretty pictures, but record data in a kind of mathematically transformed spectrum. "It's not nice to show," Lacour said. In addition, we do not yet have the observational ability to look for biosignatures, signs that life has changed the atmosphere of a planet, although it is unlikely that a Jupiter-like planet contains such signatures.

Still, it's an exciting observation for the team – a new tool for observing exoplanets, which could potentially lead to important new discoveries.


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