Exoplanet with heavy metal atmosphere discovered

A hot gas giant whose atmosphere is made up of iron and titanium vapours has been discovered 650 light years away from Earth.¹

Located in 2016 in the Cygnus (swan) constellation, the exoplanet Kelt-9b is a gas giant, not unlike Jupiter. But while the average temperature on Jupiter is a chilly –145°C, Kelt-9b’s atmosphere gets heated to more than 3700°C as it orbits a star twice as hot as the sun. Viewed from the planet’s surface, its blue star would appear 70 times the size of the sun in the Earth’s sky.

Indeed, Kelt-9b is so hot that heavy metals get vaporised into individual atoms. Iron molecules, iron cations and titanium cations form a haze around the exoplanet, scientists have discovered. Using a spectrograph at the Galileo National Telescope on the island of La Palma, Spain, they recorded the metals’ telltale spectral lines as Kelt-9b passed in front of its star.

This is the first time iron has been found on an exoplanet. With a boiling point of 2862°C, it is usually confined to solid or liquid states and therefore hard to detect by absorption spectroscopy.

Just a few months ago, Kelt-9b’s atmosphere was found to be made mostly of hydrogen.² The researchers behind the new study now hope to search for carbon monoxide and water.