Importantly, according to the research paper, which is available on the pre-print website arXiv.org, “the density of HD 21749b indicates it is likely surrounded by a substantial atmosphere.” Unfortunately, the authors also point out the HD 21749b likely is not an ideal target for future atmospheric follow-up observations with the upcoming James Webb Space Telescope (JWST).
Finally, HD 21749b is also pretty cool for a planet its size. The world sports temperatures that hover around 300 degrees Fahrenheit (150 Celsius), which is just a bit too hot for liquid water to exist on its surface.
A Boiling Earth-sized World
In addition to finding HD 21749b, TESS also recently discovered an Earth-sized world orbiting the same system’s host star. However, since the planet has yet to be confirmed, it still holds the moniker TOI 186.02, which stands for “TESS Object of Interest 186.02.”
At roughly 80 percent the mass and 90 percent the size of Earth, if confirmed, TOI 186.02 would be the very first Earth-sized planet discovered by TESS.
However, just because a planet is about the same size and mass as Earth, it doesn’t mean it’s truly a fitting Earth analog. For example, TOI 186.02 has a very short orbital period of just 7.8 days and little is known about its composition or potential atmosphere. Furthermore, the world experiences temperatures of around 800 degrees Fahrenheit (430 Celsius), making it more akin to Venus than Earth.
No matter whether TOI 186.02 is truly a fitting Earth-like exoplanet or not, these new discoveries show that the multi-planet system HD 21749 is ripe for future study and exploration, so be sure to stay tuned.
The newly discovered planets were announced during this week’s 233rd annual meeting of the American Astronomical Society, held in Seattle, Washington.