It takes some serious heat to turn titanium into vapor – temperatures upward of 3,200 °C (5,800 °CF), to be precise. It appears KELT-9b, which we crowned the exoplanet Least Likely To Host Life last year, is up for the job. Its broiling surface temperatures make it hotter than many stars – and, according to a new discovery, hot enough to vaporize heavy metals, with researchers detecting iron and titanium vapor in its atmosphere.
Sitting about 650 light-years from Earth, this utterly uninhabitable exoplanet orbits the star KELT-9 so closely that its "year" lasts only 36 hours. Being that close to a star that burns almost twice as hot as the Sun, it's no wonder KELT-9b is known as an "ultra-hot Jupiter" – a class that was invented specially for this planet with its surface temperatures of up to 4,327° C (7,820° F).
While it won't be of much interest to those hunting for extraterrestrial life, KELT-9b still has plenty to teach us. No other exoplanet has an atmosphere quite like this one, so to investigate, Swiss researchers ran simulations to see what they could expect to find in the air around KELT-9b. Among the molecules floating around out there, the simulation predicted that iron vapor would be detectable.
"The results of these simulations show that most of the molecules found there should be in atomic form, because the bonds that hold them together are broken by collisions between particles that occur at these extremely high temperatures," says Kevin Heng, an author of the study.
The next step was to check how accurate those predictions were. The researchers used the HARPS-North spectrograph on the Galileo National Telescope to examine the spectrum of the planet as it passes in front of its host star. And as hoped, the spectrum returned the clear signature of iron vapor. But that wasn't the only heavy metal found in the atmosphere – a titanium vapor signature was spotted as well.
"With the theoretical predictions in hand, it was like following a treasure map," says Jens Hoeijmakers, lead author of the study. "And when we dug deeper into the data, we found even more."
The research sheds more light on these unfortunate exoplanets, which could potentially evaporate completely under these extreme conditions. KELT-9b is in fact showing signs of evaporation, leaving a comet-like tail in its wake, but the team believes it should be able to avoid that fate. That's thanks to its massive size – almost three times that of Jupiter.
"This planet is a unique laboratory to analyze how atmospheres can evolve under intense stellar radiation," says David Ehrenreich, principal investigator on the study.
The research was published in the journal Nature.
Source: University of Geneva