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Who_DaFuc_Asked t1_j6j5fow wrote

TLDR from the article:

  • TOI-700e is about 101 light years away, it's in the habitable zone of a red dwarf star (so it'll be tidally locked)

  • orbital period is 27.8 days

  • it is around the same diameter as the Earth, slightly more massive

  • "87% chance" that it's a rocky planet

  • it is pretty much on the very inner edge of the habitable zone, like it's possibly slightly too close

IMO seems unlikely to be habitable. I think a gas giant in the habitable zone of a red dwarf would be more likely if it has a possibly habitable rocky moon around the size of one of Jupiter's moons. If it has multiple moons, maybe two of them will be habitable.

The moon wouldn't be tidally locked to the star, it would be orbiting the gas giant, so it should get more evenly distributed sunlight


ye_olde_astronaut OP t1_j6jzlyh wrote

> it's in the habitable zone of a red dwarf star (so it'll be tidally locked)

So? Taken directly from the linked article: "Increasingly detailed climate modeling over the last quarter century has shown that synchronous rotation is not the impediment to global habitability as it was once thought. In fact, it has been predicted that slow or synchronous rotation can actually result in an increase of the Seff corresponding to the inner edge of the HZ owing to feedback mechanisms which result in the formation of a reflective cloud layer on the perpetually daylit side of the planet."

> it is around the same diameter as the Earth, slightly more massive

No, according to the linked article the mass of TOI-700e is unknown. But, according to the linked article: "based on a statistical analysis by Chen & Kipping of the mass-radius relationship for exoplanets with known radii and masses, the estimated mass of TOI-700e is about 0.85 +0.67/-0.34 times that of the Earth"

So the most probable mass of TOI-700e is 0.85 times that of the Earth (not "slightly more massive" as you claim).

> it is pretty much on the very inner edge of the habitable zone

So? According to one of the references used in the linked article and by the discovery team of TOI-700e (R. K. Kopparapu et al. 2013), the inner edge of the habitable zone for the Sun is at about 0.97 AU. Earth, at a distance of 1.00 AU, is right at the inner edge of the habitable zone and is still habitable.


QuasarMaster t1_j6mexnq wrote

Planets around red dwarfs are less likely to be habitable. Red dwarfs are far more temperamental than Sun-like stars, flaring often which irradiates nearby planets (which need to be very close in to be in the habitable zone).


ye_olde_astronaut OP t1_j6nglnq wrote

This is certainly true for smaller red dwarf stars, however there are other predictions that claim that it is not as big a problem as the more dire predictions would lead us to believe (never mind that there is a growing database of exoplanets orbiting red dwarfs that have low densities indicating that they have held onto their atmospheres and volatiles). More data is needed... which is why the linked paper (and other sources) refer to potential habitability.

That being said, TOI-700 is a larger and less active M2.5V red dwarf that would not have the same level of activity as smaller red dwarfs. Again, TOI-700e is potentially habitable and is a perfect target for future studies about the limits of planetary habitability.


sintos-compa t1_j6kc1ah wrote

So is it better or worse chance to be habitable than Mars/Venus would have if discovered elsewhere with its current orbital patterns and size?


Visual_Conference421 t1_j6kpbof wrote

I am not 100% sure I understand what you were asking, so I will give the simple things as to this planet. It is approximately the right size and mass to have the potential of a stable atmosphere (near earth size) and also in the habitable zone of its star. While a lot of factors can play into these things, having an atmosphere without being massive and super heavy, while also having a temperature range that allows for constant liquid water, are two big check marks on habitability.


sintos-compa t1_j6ktvw7 wrote

If we found an exact copy of our solar system 100 Ly away, what odds would we give mars and Venus for having life with the observational techniques we possess today


ye_olde_astronaut OP t1_j6kysjr wrote

Not good and zero. Mars, with an 1.52 AU orbit, is just within the 1.70 AU outer limits of the habitable zone as defined by the "maximum greenhouse" limit. But its mass is too small to hold onto an atmosphere and sustain the geologic activity support the carbonate-silicate cycle that acts as a thermostat on rocky planets. Studies suggest that a planet needs to be twice the mass of Mars to do that. The inner edge of the conservatively defined habitable zone is 0.97 AU. Venus, with an 0.72 AU orbit, is too close to the Sun to be habitable by this definition (contrary to claims frequently found in the popular press).


sintos-compa t1_j6l1jql wrote

Are those conclusions we could draw from what we could observe at 100 ly?


ye_olde_astronaut OP t1_j6l3ssf wrote

For TOI-700, we know the properties of the star, the radii of the planets and the characteristics of their orbits. My quick assessment is based on the same info for Venus and Mars in our solar system.