Title: Astronomers Detect Helium Outflow from Nearby Exoplanet TOI-2134 b
Subtitle: Findings Could Provide Valuable Insights into Atmospheric Escape in Alien Worlds
By Tomasz Nowakowski, Phys.org
August 3, 2023
Astronomers from the University of Chicago and other institutions have made a significant discovery regarding atmospheric escape in exoplanets. In a research paper published on August 3 on the pre-print server arXiv, the team reported the detection of outflowing helium from the atmosphere of a nearby mini-Neptune exoplanet called TOI-2134 b.
Atmospheric escape plays a pivotal role in shaping the characteristics of exoplanets. Observations have previously indicated that atmospheric escape occurs in several nearby exoplanet systems, ranging from hot Jupiters to lower-mass super-Earths and mini-Neptunes. However, while the mass-loss rates for hot Jupiters are not significant enough to affect their evolution, lower mass planets are impacted and influenced by atmospheric escape processes.
Exoplanets with hydrogen or helium-rich atmospheres experience hydrodynamic atmospheric escape due to extreme levels of irradiation. This mechanism leads to the escape of heavier atoms in a planetary atmosphere through collisions with lighter atoms.
Led by Michael Zhang, the team of astronomers successfully detected the atmospheric escape of helium from TOI-2134 b, a mini-Neptune located approximately 73.8 light years away from Earth. The discovery was made using the Near Infrared Spectrometer (NIRSPEC) mounted on the Keck II Telescope in Mauna Kea, Hawaii.
In their research paper, the team stated, “In this paper, we present the first detection of escaping helium from TOI-2134 b, a warm mini-Neptune orbiting a nearby X-ray-quiet K dwarf.”
The team found that TOI-2134 b exhibited the smallest helium signal amongst exoplanets with detected helium. The helium signal was found to have an equivalent width of only 3.3 mÅ. In the absorption spectrum, the peak value of the helium signal was measured at 0.37% and occurred at a redshift of 7 km/s. Additionally, a secondary peak with a redshift of 10 km/s and a peak absorption of 0.13% was observed.
The study highlighted a strong correlation between the energy-limited mass loss rate and the observationally inferred mass loss rate in TOI-2134 b. Furthermore, TOI-2134 b was found to have the lowest extreme ultraviolet (XUV) flux among known exoplanets with helium in their atmospheres.
Based on their analysis, the astronomers concluded that the atmospheric escape of helium in TOI-2134 b is most likely due to photoevaporation caused by stellar XUV, disfavoring the core-powered mass loss mechanism. The study also suggests a mass loss timescale on the order of billions of years.
Encouraging further observations of TOI-2134 b and other mini-Neptunes with helium outflows orbiting mature stars, the researchers hope that such studies will contribute to a better understanding of atmospheric escape mechanisms in alien worlds.
The research paper, titled “Outflowing helium from a mature mini-Neptune” by Michael Zhang et al., provides more information on the discovery and can be accessed on arXiv with the DOI: 10.48550/arxiv.2308.02002.
As scientists continue to explore exoplanets, their findings shed light on the diversity and complexity of these distant worlds and their atmospheres. Further research into atmospheric escape mechanisms will contribute to our understanding of planetary evolution and the conditions required for habitability.
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