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Exoplanet Spectroscopy

planets and stars of different sizes and colors
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Brown dwarfs are mysterious astronomical objects that possibly link planets and stars.

They are often called “failed stars” because their masses are just below the critical values necessary to sustain fusion, which leaves trace amounts of “un-burned” alkali metals in their H2/He-dominated atmospheres. The alkali resonance doublets, such as potassium around 0.77 µm, lead to “fingerprint” absorption features in the spectral flux measured by space telescopes, and such distinctive observations can provide insight into the physical properties of their stellar atmospheres.

Laboratory characterizations of the potassium absorption line shapes are crucial to explain spectral observations, yet they are difficult to obtain because of the dangers and difficulties associated with alkali metal handling and disposal. We have demonstrated the use of potassium chloride as a safe and effective precursor of atomic potassium via a shock wave-assisted processes of sublimation, dissociation, and deionization.

As the very first step of the Hanson Group in the field of exoplanetary science, we have successfully characterized the potassium lines broadened by multiple collisional partners, at selected temperatures (1100–1900 K) to approximate the effective surface conditions of brown dwarfs [1].

a graph showing relative wavenumber against residual and absorbance
Near-infrared absorption line shapes of atomic potassium measured in a shock tube at 1595 K and 1.33 atm [1]

To learn more, check out some of our publications:

[1] Y. Ding, J. A. Vandervort, C. L. Strand, R. K. Hanson, “Shock tube measurements of high-temperature argon broadening and shift parameters for the potassium D1 and D2 resonance transitions,” Journal of Quantitative Spectroscopy and Radiative Transfer, Vol. 275 (2021), 107895. DOI: 10.1016/j.jqsrt.2021.107895