Extreme exoplanet – An ultra-hot Jupiter raining iron – Even more exotic than originally thought

The fiery exoplanet WASP-76b – a hot Jupiter, raining iron – could be hotter than previously thought. Credit: ESO / M. Kornmesser

Considered an ultra-hot Jupiter – a place where iron vaporizes, condenses on the night side and then falls from the sky like rain – the fiery and hellish WASP-76b exoplanet perhaps even more sizzling than scientists had imagined.

An international team, led by scientists from Cornell University, the University of Toronto and Queen’s University in Belfast, reports the discovery of ionized calcium on the planet – suggesting an atmospheric temperature higher than expected thought, or strong winds in the upper atmosphere.

The discovery was made in high resolution spectra obtained with Gemini North near the summit of Mauna Kea in Hawaii.

Hot Jupiters are named for their high temperatures, due to the proximity of their stars. WASP-76b, discovered in 2016, is about 640 light years from Earth, but so close to its F-type star, which is slightly hotter than the sun, that the giant planet orbits every 1, 8 earth days.

The research results are the first of a multi-year project led by Cornell, Exoplanets with Gemini Spectroscopy survey, or ExoGemS, which explores the diversity of planetary atmospheres.

“As we remotely sense dozens of exoplanets, spanning a range of masses and temperatures, we will develop a more complete picture of the true diversity of alien worlds – from those warm enough to harbor iron rains to others. with more moderate climates, from those heavier than Jupiter to others not much bigger than Earth, ”said co-author Ray Jayawardhana, Harold Tanner Dean of the College of Arts and Sciences at Cornell University and professor of astronomy.

“It is remarkable that with today’s telescopes and instruments, we can already learn a lot about atmospheres – their constituents, their physical properties, the presence of clouds and even large-scale winds – from planets orbiting stars hundreds of light years away, ”Jayawardhana said.

The group spotted a rare trio of spectral lines in highly sensitive observations of the atmosphere of exoplanet WASP-76b, published in the Letters from astrophysical journals on September 28 and presented on October 5 at the annual meeting of the Division for Planetary Sciences of the American Astronomical Society.

“We see so much calcium; that’s a really strong characteristic, ”said first author Emily Deibert, a doctoral student at the University of Toronto, whose advisor is Jayawardhana.

“This spectral signature of the ionized calcium could indicate that the exoplanet has very strong winds in the upper atmosphere,” Deibert said. “Or the atmospheric temperature on the exoplanet is much higher than we thought.”

Since WASP-76b is locked in by the tides – in which one side always faces the star – it has a permanent night side that sports a relatively cool temperature of 2,400 degrees. Fahrenheit mean temperature. Its day side, facing the star, has an average temperature of 4,400 degrees F.

Deibert and his colleagues examined the zone of moderate temperature on the planet’s limb between day and night. “The exoplanet is moving quickly in its orbit and this is how we were able to separate its signal from the starlight,” she said. “You can see the calcium imprint on the spectra is moving rapidly with the planet.”

The ExoGemS survey – intended to study 30 or more planets – is led by Jake Turner, a Carl Sagan scholar in NasaHubble Fellowship program, which is part of Cornell’s Department of Astronomy (A&S) and is also advised by Jayawardhana.

Astronomers continue to deepen their understanding of exoplanets, considered a dream twenty years ago. “Our work, and that of other researchers, paves the way for the exploration of the atmospheres of terrestrial worlds beyond our solar system,” said Turner.

Reference: “Detection of Ionized Calcium in the Atmosphere of Ultra-Hot Jupiter WASP-76b” by Emily K. Deibert, Ernst JW de Mooij, Ray Jayawardhana, Jake D. Turner, Andrew Ridden-Harper, Luca Fossati, Callie E. Hood, Jonathan J. Fortney, Laura Flagg, Ryan MacDonald, Romain Allart and David K. Sing, September 28, 2021, Letters from the astrophysical journal.
DOI: 10.3847 / 2041-8213 / ac2513

Other authors of the article include Ernst JW de Mooij of Queen’s University Belfast; Luca Fossati from the Austrian Academy of Sciences; Callie E. Hood and Jonathan J. Fortney, both of the University of California, Santa Cruz; Romain Allart from the University of Montreal; and David K. Sing of Johns Hopkins University. The Cornellians included researchers Andrew Ridden-Harper and Laura Flagg, both of Jayawardhana’s group, and Ryan MacDonald. Part of this research was funded by NASA.

Gemini North is part of the Gemini International Observatory, a program of the National Science Foundation’s NOIRLab.