Hydroxyl Molecule Common on Earth Detected for the First Time in Ultra-Hot Exoplanet's Atmosphere

An international team of astronomers led by Dr. Stevanus Nugroho from the Astrobiology Center and Queen's University Belfast, and researchers from Trinity College Dublin, have detected the molecule hydroxyl (HO) in the atmosphere of an exoplanet.

Although hydroxyl may be common on Earth, astronomers have not yet determined how abundant it could be in other planets beyond the Solar System. The discovery of the molecule in the ultra-hot Jupiter planet called WASP-33b is the first time, according to ScienceAlert.

Wasp-33b: The Ultra-Hot Jupiter

The bizarre exoplanet WASP-33b is found 400 light-years away from Earth, the Universe Today reported. Like Jupiter, it is a gas giant that orbits around its host star but closer than Mercury's location next to the Sun.

Due to that, it has an atmosphere that reaches a temperature of more than 4,500 degrees Fahrenheit (2,500 degrees Celsius), hot enough to melt almost any type of metal.

Astronomers were able to discover WASP-33b as the radiation emitted by the chemicals when the planet is orbiting its star periodically redshifts and blueshifts. This enabled the team to detect signatures of chemicals within the exoplanet's atmosphere.

This chemical is known as hydroxyl, a molecule common on Earth that is made up of one atom of oxygen and one atom of hydrogen. Astronomers believe that the chemical likely plays a significant role in the chemical mixture of the atmosphere of WASP-33b.

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First Evidence of Hydroxyl Molecule Outside the Solar System

"This is the first direct evidence of OH in the atmosphere of a planet beyond the Solar System," Dr. Nugroho said in a news release published in EurekAlert! "It shows not only that astronomers can detect this molecule in exoplanet atmospheres, but also that they can begin to understand the detailed chemistry of this planetary population."

Hydroxyl on earth is typically formed in the atmosphere when water vapor interacts with oxygen. But in the atmosphere of WASP-33b, it likely formed due to the intense heat from the stars that blasts water vapor.

Study co-author Dr. Ernst de Mooij from queen's University Belfast said that they could only see a tentative and weak signal from the water vapor, which supports the idea that it is broken to form hydroxyl in the atmosphere of WASP-33b.

According to the news release, the team used the InfraRed Doppler (IRD) instrument at the 8.2-meter diameter Subaru Telescope in Mauna Kea in Hawaii. This instrument detected atoms and molecules through the distinct spectral fingerprints of WASP-33b.

Its unique capabilities have enabled astronomers to detect even tiny signals of hydroxyl molecules in the exoplanet's atmosphere. The team noted that it is the best instrument to study such phenomenon in the infrared.

They pointed out that the importance of detecting hydroxyl molecules in exoplanets adds to the knowledge of modern astronomy especially in exploring the atmospheres of these planets in detail which eventually is crucial for the search of Earth-like exoplanets.