Extreme exoplanet has a complex and exotic atmosphere


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An international team including researchers from the University of Bern and the University of Geneva as well as the National Center of Competence in Research (NCCR) PlanetS analyzed the atmosphere on one of the most extreme known planets in detail. The results from this warm, Jupiter-like planet, first characterized by the CHEOPS space telescope, can help astronomers understand the complexity of many other exoplanets – including Earth-like planets.

The Earth’s atmosphere is not a uniform shell, but consists of different layers, each with characteristic properties. The lowest layer that stretches from the sea surface beyond the highest mountain peaks, for example – the troposphere – contains most of the water vapor and is thus the layer in which most weather phenomena occur. The layer above it – the stratosphere – is what contains the famous ozone layer that shields us from the Sun’s harmful ultraviolet radiation.

In a new study published in Nature astronomy, an international team of scientists led by the University of Lund shows for the first time that the atmosphere on one of the most extreme known planets can also have similar distinct layers – but with very different properties.

An exotic cocktail for an atmosphere

WASP-189b is a planet outside our own solar system, located 322 light-years from Earth. Extensive observations with the CHEOPS space telescope in 2020 revealed, among other things, that the planet is 20 times closer to its host star than the Earth is on the Sun and has a daytime temperature of 3200 degrees Celsius. Recent studies with the HARPS spectrograph at the La Silla Observatory in Chile have now, for the first time, enabled scientists to take a closer look at the atmosphere on this Jupiter-like planet.

“We measured the light that comes from the planet’s host star and passes through the planet’s atmosphere. The gases in its atmosphere absorb some of the starlight, just as ozone absorbs some of the sunlight in the Earth’s atmosphere, leaving their characteristic ‘fingerprints’.” Using HARPS, we were able to identify the corresponding substances, “explains lead author of the study and doctoral student at Lund University, Bibiana Prinoth. According to the researchers, the gases that left their fingerprints in the atmosphere of WASP-189b included iron, chromium, vanadium, magnesium and manganese.

An “ozone layer” on a windy hot planet?

A particularly interesting substance the team found is a gas containing titanium: titanium oxide. While titanium oxide is very rare on Earth, it can play an important role in the atmosphere of WASP-189b – similar to that of ozone in Earth’s atmosphere. “Titanium oxide absorbs shortwave radiation, such as ultraviolet radiation. Its detection could therefore indicate a layer in the atmosphere of WASP-189b that interacts with stellar radiation in the same way as the ozone layer on Earth,” co-author Kevin Heng of the study. , a professor of astrophysics at the University of Bern and a member of the NCCR PlanetS, explains.

In fact, scientists found hints of such a layer and other layers on the ultra-hot Jupiter-like planet. “In our analysis, we saw that the ‘fingerprints’ of the different gases were changed a bit in relation to our expectation. We believe that strong winds and other processes could generate these changes. And because the fingerprints from different gases were changed on different ways, and because the fingerprints of the different gases were changed in different ways, we have seen in our analysis that the ‘fingerprints’ of the different gases were changed slightly in relation to our expectation.We think this indicates that they exist in different layers – in the same way that fingerprints of water vapor and ozone on Earth would look different changed at a distance because they mostly occur in different atmospheric layers, “Prinoth explains. These results may change the way astronomers study exoplanets.

A different way of looking at exoplanets

“In the past, astronomers often assumed that the atmosphere on exoplanets existed as a uniform layer and tried to understand it as such. But our results show that even the atmosphere on intensely irradiated giant gas planets has complex three-dimensional structures,” points out author and associate professor at Lund Jens Hoeijmakers University.

“We are convinced that in order to fully understand these and other types of planets – including those similar to Earth, we need to appreciate the three-dimensional nature of their atmospheres. This requires innovations in data analysis techniques, computer modeling and basic atmospheric theory, “concludes Kevin Heng.

Water vapor detected on a ‘super Neptune’

More information:
Bibiana Prinoth et al., Titanium oxide and chemical inhomogeneity in the atmosphere of the exoplanet WASP-189 b, Nature astronomy (2022). DOI: 10.1038 / s41550-021-01581-z

Provided by the University of Bern

Citation: Extreme exoplanet has a complex and exotic atmosphere (2022, 28 January) retrieved 29 January 2022 from https://phys.org/news/2022-01-extreme-exoplanet-complex-exotic-atmosphere.html

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