Astronomers use a bevy of different methods to analyze distant exoplanets, but the GRAVITY instrument attached to the European Space Observatory’s Very Large Telescope Interferometer (VLTI) recently set a precedent when it became the first to make a direct observation of a world from another stellar system using a technique known as optical interferometry.
Image Credit: ESO/L. Calçada
Optical interferometry utilizes signals from two or more telescopes to gather more information at a glance. Naturally, this results in a higher-resolution dataset than what can be achieved with a single telescope. GRAVITY’s accomplishment was no different; it took advantage of all four of the ESO’s Very Large Telescope units at the time that it made its groundbreaking observation.
The results, which have been published in the journal Astronomy and Astrophysics, describe what the astronomers found after using the VLTI’s GRAVITY instrument to peer at a ‘super-Jupiter’-like exoplanet called HR8799e. The world was originally discovered in 2010, and it purportedly resides about 129 light-years away in the constellation Pegasus where it orbits its host star HR8799.
HR8799e is particularly young at just 30 million years of age, and while that might seem like a long time to you and I, that’s only the blink of an eye in cosmic terms. The circumstances are ideal for astronomers because it means they can study a world not long after its formation and seize an unprecedented opportunity to gather more clues about how planets are made.
GRAVITY’s high-resolution capabilities made it possible for astronomers to distinguish the unique characteristics of HR8799e’s atmosphere from the Earth’s surface, a feat that is traditionally accomplished from outer space with the help of observatories such as NASA’s Hubble Space Telescope. Their findings were captivating.
"Our analysis showed that HR8799e has an atmosphere containing far more carbon monoxide than methane—something not expected from equilibrium chemistry," elucidated study lead author Sylvestre Lacour. "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."
HR8799e’s atmosphere appears to be a scorching-hot mess of carbon monoxide, iron, and silicate dust. With temperatures reaching that of 1,000 degrees Celsius, the astronomers concluded that the exoplanet’s atmosphere is currently ‘engaged in a violent storm.’
"Our observations suggest a ball of gas illuminated from the interior, with rays of warm light swirling through stormy patches of dark clouds," Lacour added. "Convection moves around the clouds of silicate and iron particles, which disaggregate and rain down into the interior. This paints a picture of a dynamic atmosphere of a giant exoplanet at birth, undergoing complex physical and chemical processes."
Albeit impressive, this is just the tip of the iceberg involving GRAVITY’s capabilities. As you might come to expect, astronomers are foaming at the mouth for an opportunity to use it for a multitude of future observations. It ought to be interesting to see what they’ll find.