Astronomers find 2nd Earth- planet in intriguing alien solar system

"Now, Gilbert and her colleagues say that TOI 700 d has a third sibling, and an intriguing one. This planet, dubbed TOI 700 e, isn't quite in the region astronomers have typically dubbed the habitable zone, but that definition is in flux. In particular, since astronomers have realized that Venus and Mars likely both once held water on their surfaces, some have proposed an "optimistic" habitable zone, which TOI 700 e resides in. Gilbert and her colleagues estimate that TOI 700 e is about 95% the size of Earth, so it's likely rocky and orbits about once every 28 Earth days — putting it in between TOI 700 c and d. The newly discovered world is also likely tidally locked, always showing the same side to its star. "That's most of what we know at this time from TESS data alone, but we do have some other campaigns currently underway to characterize this more," Gilbert said. "No results yet, but exciting things are coming."

Currently, the exoplanet sites show 3 confirmed for TOI 700.

The Extrasolar Planet Encyclopaedia — TOI-700 d (

TOI-700 | NASA Exoplanet Archive (

The .eu site indicates 700 d is 2.26 earth mass and 1.19 earth radii size. The mean density could be a bit more than 7 g cm^-3. Surface gravity compared to earth about 1.6 g so 100 lbs on earth would weigh 160 lbs on 700 d. Escape velocity 15.4 km/s, higher than earth escape velocity so our present rocket programs since 1957 would not work on 700 d. None of the TOI-700 exoplanets are confirmed with an atmosphere at present. Exoplanet atmospheres (

*that matches Earth's*, small differences above I note should be clearly pointed out when reporting. 700 e will need more follow up work to confirm and provide properties it seems.
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Nov 19, 2021
Tidally locked planet, with high surface gravity, an atmosphere and close to a star is going to have some incredible winds. Daytime side heats up, rises, flows to the back side at high altitude where it cools, descends and returns across the surface. The terminator area would be scoured with deep erosion features. Anywhere on the planet would either be too hot, too cold or too windy for comfortable living. It could be that the atmosphere will freeze out on the back side. A better example might be a 3:2 resonance like Venus where the back side ice was constantly moved onto the hot side.
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Another observation about earth size exoplanet reports like TOI-700 e. At the site, 272 are listed with radii 1.1 or less earth. Some or many are larger in mass than earth. GJ 143 c is 3.69 earth masses with radius 0.89 earth radii. K2-239 is 1.3984 earth masses and radius 1.1 earth radii. Kepler-131 is 8.2633 earth masses and 0.84 earth radii. Simply finding an earth size exoplanet does not mean it will be earthlike. While astronomers define the abiogenesis zone now, habitable zone, some of these earth size exoplanets could be in the twilight zone :)
Only TOI-700 d makes the HZ list for Earth but not 700 e, which is just a little too hot.

Neither make the other list that uses about 24 coefficients to address atmosphere thermal blanketing.

Both lists are updated in the Exoplanet Stats thread for your viewing pleasure. :)

It's worth mentioning that 700 e is closer than 700 d to the star, which is why it is hotter, of course.
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This is a new earth size exoplanet listed at the .eu site now. The Extrasolar Planet Encyclopaedia — LHS 475 b (

The title has "2nd Earth- planet" and "2nd Earth-size".

The earth-size list reported now needs a good review. At the site, 274 show up with radii 1.1 or less earth size. Masses range 0.0603858 earth mass up to 651.531 earth masses and mean 19.0716452681633 earth masses. The NASA exoplanet archive site is similar, NASA Exoplanet Archive (

That shows 262 exoplanets in the size range 1.1 or less earth radii. Radii range 0.3 to 1.1 earth radii size, mean mass = 10.2583689147287 earth masses with max mass = 158.915 earth masses.

Looking at our solar system, planets Mercury to Mars have sizes, that fall within 0.3825 earth radii up to 1.0 for earth. The mass range in our solar system is very different than what is shown for a number of the exoplanets with published masses listed. The exoplanets with earth-sizes can run into very large gravity wells, high surface gravities, and high escape velocities compared to Mercury-Mars in our solar system, some have much more mass than Earth, thus the *twilight zone* exoplanet list :)
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LHS 475 b is earth size but likely very hot. JWST finds its first exoplanet :)

James Webb Space Telescope confirms its first exoplanet,

"Researchers have confirmed the presence of an exoplanet, a planet that orbits another star, using the NASA/ESA/CSA James Webb Space Telescope for the first time. Formally classified as LHS 475 b, the planet is almost exactly the same size as our own, clocking in at 99% of Earth's diameter."
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