Atmosphere of ultrahot Jupiter found to contain iron and titanium

Discovery marks first detection of atomic iron and hydrogen in the atmosphere of an exoplanet.

Scientists have discovered iron and titanium in the atmosphere of a ultrahot Jupiter KELT-9b, the hottest known exoplanet. The finding marks the first discovery of these elements in a planet outside our solar system.

Located 620 light years away in the constellation Cygnus, KELT-9b is twice the diameter of Jupiter in our solar system and has three times its mass.

Ultrahot Jupiters are the hottest gas giants in close orbits around their parent stars, with temperatures greater than 3,100 degrees Fahrenheit (1,700 degrees Celsius). These extreme temperatures give them some characteristics of stars.

Temperatures on KELT-9b can reach 7,800 degrees Fahrenheit (4,300 degrees Celsius), making it far too hot to be habitable.

The planet’s extreme heat made it possible for researchers to detect the iron and titanium in KELT-9b’s atmosphere. At such high temperatures, clouds do not condense, meaning individual atoms of various metals travel in the atmosphere on their own.

By studying the light spectrum of objects in space, scientists can detect specific elements, as each element has its own unique “fingerprint,” which is detectable in high resolution.

Kevin Heng of the University of Bern in Switzerland noted that molecular titanium dioxide, molecules that have one titanium atom and two oxygen atoms, was found in the atmosphere of another exoplanet, Kepler-13A, last September by scientists using the Hubble Space Telescope (HST).

Atomic, as opposed to molecular titanium dioxide, has never been seen in an exoplanet’s atmosphere until now.

After conducting a theoretical study of KELT-9b that indicated its atmosphere should contain iron and titanium, the research team analyzed spectral data already collected for the planet by the High Accuracy Radial Velocity Planet Searcher (HARPS) spectrograph during a four-hour transit, when it passed directly in front of its parent star.

Through “a combination of high-performance computing know-how, a careful curation of the spectroscopic databases, and meticulous attention to detail,” the researchers confirmed the fingerprints of atomic iron and titanium in KELT-9b’s atmosphere, Heng reported.

The technique the scientists used to find these fingerprints is the same one that researchers will use to search the atmospheres of cooler exoplanets for biosignatures, or signs of life.

As a next step, the science team hopes to obtain time on the Hubble Space Telescope to look for evidence of possible water on KELT-9b, search for signs of violent storms likely to be occurring there, and obtain “a complete chemical inventory of the planet,” Heng said.

A paper on the findings has been published in the journal Nature.


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