Detection of Chromium Hydride in WASP-31b: A Significant Advancement in Exoplanetary Science

by Amir Hussein
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Chromium Hydride in Exoplanet Atmospheres

Astronomers have verified the existence of chromium hydride in the atmosphere of the hot Jupiter WASP-31b through high-resolution spectral data. This molecule, which is primarily present between temperatures of 1,200-2,000 degrees Kelvin, could serve as a temperature indicator for exoplanets.

Chromium hydride has been identified in the atmosphere of the hot Jupiter WASP-31b, occurring within the temperature spectrum of 1,200-2,000 degrees Kelvin. This groundbreaking revelation sets the stage for the molecule’s application as an exoplanetary “thermometer.”

According to Laura Flagg, an astronomer, chromium hydride (CrH) is a relatively uncommon molecule highly sensitive to temperature fluctuations, making it a suitable “stellar thermometer.” Its prevalence is notably confined to a narrow temperature band of 1,200-2,000 degrees Kelvin.

Flagg, who is a research associate at the College of Arts and Sciences in Cornell University, has utilized this molecule, among other metal hydrides, to ascertain the temperatures of cool stars and brown dwarfs. Hypothetically, she mentioned, chromium hydride could perform a similar function for hot Jupiter exoplanets, which are temperature-wise similar to brown dwarfs, provided these specific molecules are present in the atmosphere of these exoplanets. Previous low-resolution studies have provided inklings of such a presence.

Noteworthy Observations on Hot Jupiter WASP-31b

Flagg and a research team led by Cornell have definitively confirmed chromium hydride’s presence in the atmosphere of the hot Jupiter WASP-31b. This opens the possibility of utilizing this temperature-sensitive molecular species as a “thermometer” to examine the temperature and other attributes of exoplanets.

The publication, titled “ExoGemS Detection of a Metal Hydride in an Exoplanet Atmosphere at High Spectral Resolution,” was released on August 16 in The Astrophysical Journal Letters. The research team comprises Ray Jayawardhana, Jake D. Turner, Ryan J. MacDonald, and Adam Langeveld, among others.

This research constitutes the inaugural confirmation of a metal hydride in a high-resolution exoplanet spectrum, the authors note.

Implications of the Finding

The unambiguous identification of metal hydrides in WASP-31b marks a significant milestone in comprehending the atmospheres of hot giant planets, states Flagg, although it does not furnish new insights about the specific planet. Discovered in 2011, WASP-31b orbits an F5 star every 3.4 days and has an extraordinarily low density, even for a giant planet. The study further confirms its equilibrium temperature at 1,400 Kelvin, suitable for the existence of chromium hydride.

Flagg explained that chromium hydride molecules are highly sensitive to temperature changes. “At higher temperatures, only chromium exists, and at cooler temperatures, it transforms into other compounds. Consequently, chromium hydride is abundant only within a limited temperature range of approximately 1,200 to 2,200 Kelvin.”

In our solar system, the solitary detected instance of chromium hydride is in sunspots, as the sun’s surface temperature is too elevated, around 6,000 K, and all other celestial objects are too cool.

Methodologies Employed

Flagg uses high-resolution spectroscopy for the study of exoplanet atmospheres, contrasting the comprehensive light emission when the planet is alongside the star versus when it occludes part of the star’s light. Specific elements block more light at distinct wavelengths, revealing their presence in the planetary atmosphere.

Flagg stated, “High spectral resolution enables extremely accurate wavelength data. We compile thousands of different spectral lines using statistical techniques and templates. A match between the template and data signifies a signal. In this instance, the chromium hydride template produced a signal.”

Owing to its rarity, even under suitable temperature conditions, highly sensitive instruments and telescopes are required, says Flagg.

For the study of WASP-31b, the research team used high-resolution spectra from an observation in March 2022 as part of the Exoplanets with Gemini Spectroscopy survey from Hawaii’s Maunakea, using the Gemini Remote Access to CFHT ESPaDOnS Spectrograph (GRACES). They also utilized archival data from 2017, initially not aimed to look for metal hydrides.

Future Directions

Flagg indicated that some of the data utilized was previously archived and would typically not have been searched. She is currently seeking chromium hydride and other metal hydrides in additional exoplanets, speculating that the evidence may already be present.

“I anticipate that this publication will spur other scientists to scour their data for chromium hydride and other metal hydrides. We believe these should be extant. Hopefully, more suitable data will emerge, enabling the construction of a larger sample size to discern trends,” said Flagg.

Reference: “ExoGemS Detection of a Metal Hydride in an Exoplanet Atmosphere at High Spectral Resolution” by Laura Flagg, Jake D. Turner, Emily Deibert, Andrew Ridden-Harper, Ernst de Mooij, Ryan J. MacDonald, Ray Jayawardhana, Neale Gibson, Adam Langeveld and David Sing, 16 August 2023, The Astrophysical Journal Letters. DOI: 10.3847/2041-8213/ace529.

Frequently Asked Questions (FAQs) about Chromium Hydride in Exoplanet Atmospheres

What is the significance of detecting chromium hydride in the atmosphere of WASP-31b?

The detection of chromium hydride in WASP-31b’s atmosphere is groundbreaking in exoplanetary science. This molecule could potentially serve as a precise “thermometer” for evaluating the temperatures and other attributes of exoplanets.

Who led the research on this discovery?

The research was led by Laura Flagg, a research associate at the College of Arts and Sciences in Cornell University. She collaborated with a team of scientists from Cornell and other institutions.

What was the method used for this research?

High-resolution spectral observations were employed to confirm the presence of chromium hydride in WASP-31b’s atmosphere. Researchers compared the overall light emission from the planetary system when the planet was alongside its star to when it was in front of the star.

Where was the research published?

The research findings were published in “The Astrophysical Journal Letters” on August 16, under the title “ExoGemS Detection of a Metal Hydride in an Exoplanet Atmosphere at High Spectral Resolution.”

What are the temperature conditions for the presence of chromium hydride?

Chromium hydride is primarily present in a narrow temperature range of 1,200-2,000 degrees Kelvin. It is highly sensitive to temperature changes, being abundant only within this specific range.

Are there any previous instances of detecting chromium hydride in other exoplanets?

No, this is the first instance of detecting a metal hydride, specifically chromium hydride, from a high-resolution exoplanet spectrum.

What instruments were used for this research?

High-resolution spectra were obtained using the Gemini Remote Access to CFHT ESPaDOnS Spectrograph (GRACES) as part of the Exoplanets with Gemini Spectroscopy survey from Hawaii’s Maunakea.

What does this discovery mean for future exoplanet research?

The discovery sets the stage for utilizing chromium hydride as a temperature-sensitive molecule to evaluate the characteristics of other exoplanets. It will likely encourage further research to look for chromium hydride in other celestial bodies.

How is chromium hydride relevant to our solar system?

In our solar system, chromium hydride has only been detected in sunspots. The sun’s surface temperature is too high (around 6,000 K), and all other objects are too cool for the molecule’s existence.

Is this molecule relevant for stars other than exoplanets?

Yes, Laura Flagg has used chromium hydride, among other metal hydrides, to ascertain the temperatures of cool stars and brown dwarfs. It is considered a suitable “stellar thermometer” due to its temperature sensitivity.

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7 comments

Jenny L. August 30, 2023 - 10:25 am

I had to read this twice to get it all but wow, what an amazing discovery. Makes me wonder what else is out there in the universe waiting to be discovered.

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Sarah T. August 30, 2023 - 11:49 am

Wow, this is mind-blowing! Using chromium hydride as a ‘thermometer’ for exoplanets? The future of space research looks so promising.

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Mike D. August 30, 2023 - 11:59 am

So were basically playing cosmic detective with molecules? Thats just awesome. A big hat tip to Laura Flagg and team.

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Tim R. August 30, 2023 - 4:57 pm

can’t wait to see what else comes out of this research. Keep pushing the boundaries ppl!

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Brian H. August 30, 2023 - 8:52 pm

I’m not a scientist, but this is insane! Who would’ve thought a single molecule could be so crucial for understanding entire planets?

Reply
Andy M. August 30, 2023 - 8:55 pm

This article’s a bit heavy on the jargon but the implications are incredible. Truly groundbreaking stuff happening in astronomy these days.

Reply
Nina S. August 30, 2023 - 10:17 pm

I feel like this could be a big game changer in how we understand exoplanets and maybe even our own solar system? Hats off to the researchers.

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