Gemini North detects several rock-forming elements in the atmosphere a

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WASP-76b is a strange world. Located 634 light years from Earth towards the constellation Pisces, a Jupiter-like exoplanet orbits its host star at a very close distance — roughly 12 times closer than Mercury is to the Sun — which heats its atmosphere to 2000 °C. Such extreme temperatures have “inflated” the planet, increasing its volume to almost six times that of Jupiter.

Credit: Gemini International Observatory/NOIRLab/NSF/AURA/J. da Silva/Space machine/M. age

At such extreme temperatures, mineral and rock-forming elements, which would otherwise remain hidden in the atmospheres of cooler gas giant planets, can manifest themselves.

Using the Gemini North telescope, half of the Gemini International Observatory operated by NSF’s NOIRLab, an international team of astronomers has detected 11 of these rock-forming elements in WASP-76b’s atmosphere. The presence and relative amounts of these elements can provide important insight into how exactly gas giant planets formed — something that remains uncertain even in our own Solar System. The results are published in a journal Natural.

Since its discovery in 2013 during the Wide Angle Search for Planets (WASP) program, many astronomers have studied the enigmatic WASP-76b. These studies have led to the identification of various elements present in the atmospheres of hot exoplanets. Notably, in a study published in March 2020, a team concluded that there could be iron rain on the planet.

Aware of these existing studies, Stefan Pelletier, a PhD student with the Trottier Institute for Research on Exoplanets at Université de Montréal and lead author on the paper, was inspired to explore the mysteries of this strange exoplanet and the chemistry of its searing atmosphere.

In 2020 and 2021, using MAROON-X Gemini North (a new instrument specially designed for detecting and studying exoplanets), Pelletier and his team observed the planet as it passed in front of its host star on three separate occasions. The new observations reveal a number of rock-forming elements in WASP-76b’s atmosphere, including sodium, potassium, lithium, nickel, manganese, chromium, magnesium, vanadium, barium, calcium and, as previously detected, iron.

Due to the extreme temperature of WASP-76b’s atmosphere, the elements detected by the researchers, which normally form rocks on Earth, instead evaporate and are present in the atmosphere in their gaseous form. Although these elements contribute to the composition of the gas giants in our Solar System, the planets are too cold to evaporate them into the atmosphere to be nearly undetectable.

“It’s truly rare when an exoplanet hundreds of light years away can teach us something that might otherwise be impossible to know about our own Solar System.” said Pelletier. “That’s the case with this study.”

The abundance of many of these elements closely matches the abundances found in our Sun and the exoplanet host stars. This may not be a coincidence and provides additional evidence that gas giant planets, such as Jupiter and Saturn, formed in a manner more akin to star formation — coalescing from the gas and dust of a protoplanetary disk — than the gradual accretion and collision of dust, rock, and planetesimals, which in turn formed rocky planets, such as Mercury, Venus, and Earth.

Another important result of this research is the first unambiguous detection of vanadium oxide on an exoplanet. “This molecule is of great interest to astronomers because it can have a profound impact on the atmospheric structure of hot giant planets.” said Pelletier. “This molecule plays a role similar to ozone which is very efficient at heating the Earth’s upper atmosphere.”

Pelletier and his team are motivated to learn more about WASP-76b and other ultra-hot planets. They also hope other researchers will take what they learn from this giant exoplanet and apply it to better understand the planets of our own solar system and how they formed.

“Available to astronomers around the world, the International Gemini Observatory continues to provide new insights that drive our understanding of the physical and chemical structures of other worlds. Through such observing programs, we develop a clearer picture of the wider universe and our own place within itsaid NSF Gemini Observatory program director Martin Still.

“Generations of researchers have used Jupiter, Saturn, Uranus and Neptune to measure the abundance of hydrogen and helium as a yardstick for theories of gas planet formation,” said Université de Montréal professor Björn Benneke, a co-author of the study. “Likewise, measurements of heavier elements such as calcium or magnesium on WASP-76b will help further understanding gas planet formation.”

Further information

References: Pelletier, S, Benneke, B, and Ali-Dib, M, et al. (2023). “Vanadium oxide and a sharp cold strike on a giant exoplanet.” Natural.

NOIRLab NSF, the US center for ground-based optical-infrared astronomy, operates the Gemini International Observatory (NSF facilities, NRC–Canada, ANID–Chile, MCTIC–Brasil, MINCyT–Argentina and KASI–Republic of Korea), Kitt Peak National Observatory (KPNO ), the Cerro Tololo Inter-American Observatory (CTIO), the Community Science and Data Center (CSDC), and the Vera C. Rubin Observatory (operated in collaboration with the Department of Energy’s SLAC National Accelerator Laboratory). It is administered by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with NSF and is headquartered in Tucson, Arizona. The astronomical community is honored to have the opportunity to conduct astronomical research at Iolkam Du’ag (Kitt Peak) in Arizona, on Maunakea in Hawai’i, and at Cerro Tololo and Cerro Pachón in Chile. We recognize and acknowledge the highly significant cultural role and respect that these sites have for the Tohono O’odham Nation, the Indigenous Hawaiian community, and the local community in Chile, respectively.