Breaking New Ground in Exoplanet Imaging

The GRAVITY instrument on the ESO (European Southern Observatory) Very Large Telescope Interferometer has made the first direct observation of an exoplanet using a method known as optical interferometry. The observations revealed that the exoplanet, a gas giant called HR 8799 e, has a complex exoplanet atmosphere with clouds of iron and silicates swirling in a planet-wide storm.

The result was announced today in a letter in the journal Astronomy & Astrophysics by the GRAVITY Collaboration. HR 8799 e was first spotted in 2010 orbiting the young star HR 8799, which is around 129 light-years from Earth in the constellation of Pegasus.

The GRAVITY instrument combines data from the Very Large Telescope's four telescopes to mimic a single larger telescope using a technique known as interferometry. This creates a super-telescope—the Very Large Telescope Interferometer or VLTI—that collects and precisely disentangles the light from an exoplanet's atmosphere and the light from its parent star.

"Optical interferometry allows us to combine 8-meter telescopes, some of the largest telescopes in the world currently, to achieve the resolution of a 100-meter telescope, which is far bigger than the 30- to 40-meter telescopes that are planned in the next decade," says study co-author Jason Wang, a 51 Pegasi b Postdoctoral Scholar in Astronomy at Caltech. "In the far future, if we can use this technique on telescopes separated by 10 kilometers, we could even map out the surfaces of Jupiter-like exoplanets."

The new observations of HR 8799 e's atmosphere, which are 10 times more detailed than previous measurements by other instruments, led to some unexpected findings.

"Our analysis showed that HR 8799 e has an atmosphere containing far more carbon monoxide than methane—something not expected from equilibrium chemistry," explains team leader Sylvestre Lacour of LESIA (Laboratory of Spatial Studies and Instrumentation in Astrophysics) at the Observatoire de Paris, Paris Science and Letters Research University, and the Max Planck Institute for Extraterrestrial Physics. "We can best explain this surprising result with high vertical winds within the atmosphere preventing the carbon monoxide from reacting with hydrogen to form methane."

The team also found that the atmosphere contains clouds of iron and silicate dust. When combined with the excess of carbon monoxide, this suggests that HR 8799 e's atmosphere is engaged in an enormous and violent storm.

Read the full story from ESO at https://www.eso.org/public/news/eso1905/.