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Merged from the "BREAKING: New potentially habitable exoplanet found around Teegarden's star" topic
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The exoplanet found, called Teegarden b, has a
minimum mass almost identical to Earth.
I hate to dim the excitement, but I think that this part is important to emphasize. When detecting an exoplanet by radial velocity measurements, the strength of the signal (how much it tugs its host star along our line of sight) depends on the inclination of the orbit, which is unknown (unless the planet also transits). So the mass is reported as a minimum possible value.
If the true orbit is edge on, then the reported mass is the true mass. But if it's closer to face on, then the true mass can be several times larger, because we only see a small portion of the star's induced wobble. It's statistically inevitable that some "potentially habitable planets" reported by radial velocity measurements are not planets at all, but brown dwarfs.
I think the excited announcements of potentially habitable exoplanets should be more limited to planets found by combination of both radial velocity and transit method, since then we get not only the true mass, but also the planets radius, and thus density and a good idea of its bulk composition.
The other big unknown is its atmosphere. This world could be much more like Venus than Earth, baked under a tremendous greenhouse atmosphere. Hopefully with next generation telescopes we can get much better data on atmospheric compositions, and look for evidence that they are not only potentially habitable, but actually inhabited.