Results of the summarizing process for the arXiv paper: 2001.04532v1

K2-18 b is a mini-Neptune exoplanet that orbits a nearby cool M3 dwarf star located within its region of temperate irradiation. Researchers used Lyman-alpha transit spectroscopy with the Space Telescope Imaging Spectrograph (STIS) instrument on the Hubble Space Telescope (HST) to search for hydrogen escape from K2-18 b's atmosphere. Analysis of the time-series of fluxes revealed that during one partial transit, the average blueshifted emission decreased by 67% ± 18%, tentatively indicating vigorous hydrogen atom escape being blown away by radiation pressure. Reconstructed Lyman-alpha emission data estimated an EUV irradiation between $10^1$-$10^2$ erg s$^{-1}$ cm$^{-2}$ and a total escape rate around $10^8$ g s$^{-1}$. This suggests that K2-18 b will lose only a small fraction (<1%) of its mass and retain its volatile-rich atmosphere during its lifetime. Further observations are necessary to confirm in-transit absorption and gain a more comprehensive understanding of K2-18 b's high energy environment.

• K2-18 b is a mini-Neptune exoplanet that orbits a nearby cool M3 dwarf star
• Researchers used Lyman-alpha transit spectroscopy with the STIS instrument on the HST to search for hydrogen escape from K2-18 b's atmosphere
• During one partial transit, the average blueshifted emission decreased by 67% ± 18%, tentatively indicating vigorous hydrogen atom escape being blown away by radiation pressure
• Reconstructed Lyman-alpha emission data estimated an EUV irradiation between $10^1$-$10^2$ erg s$^{-1}$ cm$^{-2}$ and a total escape rate around $10^8$ g s$^{-1}$
• K2-18 b will lose only a small fraction (<1%) of its mass and retain its volatile-rich atmosphere during its lifetime
• Further observations are necessary to confirm in-transit absorption and gain a more comprehensive understanding of K2-18 b's high energy environment

Exploring the Atmosphere of K2-18 b: A Mini-Neptune Exoplanet

In recent years, exoplanets have become an increasingly popular topic in astronomy. These distant worlds are often studied to gain a better understanding of our own solar system and its planets. One such exoplanet is K2-18 b, a mini-Neptune located within its region of temperate irradiation that orbits a nearby cool M3 dwarf star.

Recently, researchers used Lyman-alpha transit spectroscopy with the Space Telescope Imaging Spectrograph (STIS) instrument on the Hubble Space Telescope (HST) to search for hydrogen escape from K2-18 b's atmosphere. Analysis of the time-series of fluxes revealed that during one partial transit, the average blueshifted emission decreased by 67% ± 18%, tentatively indicating vigorous hydrogen atom escape being blown away by radiation pressure.

EUV Irradiation and Escape Rate

The reconstructed Lyman-alpha emission data estimated an EUV irradiation between $10^1$-$10^2$ erg s$^{-1}$ cm$^{-2}$, which is comparable to Earth’s EUV irradiance at solar maximum. Additionally, it was determined that there was a total escape rate around $10^8$ g s$^{-1}$. This suggests that K2-18 b will lose only a small fraction (<1%) of its mass and retain its volatile rich atmosphere during its lifetime.

Further Observations Necessary

Although this research provides insight into K2–18b’s high energy environment, further observations are necessary to confirm in–transit absorption and gain a more comprehensive understanding about this exoplanet’s atmosphere. By studying these distant worlds we can learn more about our own solar system and how other planets may be similar or different from those in our own backyard.