Aluminium oxide found in an ultra-hot Jupiter

November 7, 2018, Instituto de Astrofísica de Canarias
Credit: CC0 Public Domain

An international team led by the astrophysicist Carolina von Essen, has used the OSIRIS spectrograph on the Gran Telescopio Canarias (GTC) to study the chemical composition of a planet whose equilibrium temperature is around 3,200 °C.

WASP-33, the planet-star system that is the subject of this research work, lies some 380 light years away from Earth. The host star is the first Delta Scuti star known to be orbited by a hot Jupiter. The pronounced stellar pulsations, showing periods comparable to the primary transit duration, interfere with transit modeling. Thus, it is extremely challenging to carry out a proper characterization of the physical properties of the exoplanet without addressing the variability of the star.

WASP-33b is very interesting on its own: its temperature is around 3,200 °C, which places it among the few ultra-hot Jupiter exoplanets known to date. Its orbital period is as short as 29 hours, and its orbit is almost perpendicular to the equatorial plane of the star. Among other collection of peculiarities, its sense of motion is contrary to that of the rotation of the star.

The study, published in the journal Astronomy & Astrophysics, analyses the chemical composition of its atmosphere. This is important because "The current models of exoplanetary atmospheres predict that the ultra-hot Jupiters should be free of clouds, and present a range of oxides in the visible spectrum, such as vanadium , titanium oxide, and ," explains Carolina von Essen, of the University of Aarhus (Denmark), the principal investigator of this study. "But there is a limited number of exoplanets for which these molecules have been detected with a high significance, which makes us question the models."

A detailed determination of the chemical composition of ultra-hot Jupiters has the potential to challenge current models of exoplanet atmospheres. There is a close symbiosis between models and observations, of which this study is a good example, as it unveils the first sign of aluminium oxide in the atmosphere of WASP-33b, as theory predicted.

Ultra hot Jupiter simulation. Credit: Instituto de Astrofísica de Canarias
"GTC and OSIRIS sensitivity and performances have been key to the success of these challenging observations," says Herve Bouy, co-author of this article. "This combination has made of the GTC, in recent years, a key telescope in the study of exoplanetary atmospheres," adds Antonio Cabrera Lavers, GTC Head of Science Operations.

The high-precision data collected by GTC/OSIRIS allowed this team to construct a physically motivated model of the intrinsic variability of the . Here, the pulsations of WASP-33 and their amplitude changes with wavelength were taken into consideration while determining the chromatic variability of the planetary size. "Using modern methods for determining the of WASP-33b, we find that the feature observed in the transmission spectrum of WASP-33b between 450 and 550 nm can best be explained by aluminium oxide in its ," says von Essen. The team has not encountered significant evidence of other molecules, but a rather high abundance of aluminium oxide. Thus, new observations from ground-based and space-based instruments will be necessary to confirm this detection.

Explore further: Multiple metals – and possible signs of water – found in unique exoplanet

More information: C. von Essen et al. An optical transmission spectrum of the ultra-hot Jupiter WASP-33b. First indication of aluminum oxide in an exoplanet, Astronomy & Astrophysics (2018). DOI: 10.1051/0004-6361/201833837

Related Stories

Eight new 'hot Jupiters' discovered by astronomers

March 14, 2018

European astronomers have detected eight new "hot Jupiter" exoplanets as part of the WASP-South transit survey. The newly discovered gas giants have short orbital periods and masses ranging from 0.42 to 5.2 Jupiter masses. ...

Hubble captures blistering pitch-black planet

September 14, 2017

Astronomers have discovered that the well-studied exoplanet WASP-12b reflects almost no light, making it appear essentially pitch black. This discovery sheds new light on the atmospheric composition of the planet and also ...

VLT makes first detection of titanium oxide in an exoplanet

September 13, 2017

A team of astronomers led by Elyar Sedaghati, an ESO fellow and recent graduate of TU Berlin, has examined the atmosphere of the exoplanet [WASP-19b] in greater detail than ever before. This remarkable planet has about the ...

Iron and titanium in the atmosphere of an exoplanet

August 15, 2018

Exoplanets, planets in other solar systems, can orbit very close to their host stars. When the host star is much hotter than the sun, the exoplanet becomes as hot as a star. The hottest "ultra-hot" planet was discovered last ...

Recommended for you

Fish-inspired material changes color using nanocolumns

March 20, 2019

Inspired by the flashing colors of the neon tetra fish, researchers have developed a technique for changing the color of a material by manipulating the orientation of nanostructured columns in the material.

1 comment

Adjust slider to filter visible comments by rank

Display comments: newest first

not rated yet Nov 07, 2018
Sounds like a 'Three Body Problem' in their past...

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.