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Two potentially life-friendly planets found orbiting a nearby star

nationalgeographic.com

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Re: Two potentially life-friendly planets found orbiting a nearby star

#11

Post by Robotbeat »

skribbj wrote: post #2

How common are "life-friendly" planets (Let's say: on a ratio of Life-Friendly Planet:Non Life-Friendly Planet)? And is there any way to check if life-friendly planets contain life without actually going there?

I don't know that exact ratio, but the number of stars that you can see that probably have planets in their "habitable zone" is pretty high... One in 5.

https://www.popsci.com/article/science/one-five-sun-stars-ha...

In our solar system, 2-3 of the 8-9 planets are in the "habitable zone". So let's just say it's maybe one in 20 or so.

Re: Two potentially life-friendly planets found orbiting a nearby star

#12

Post by wongarsu »

TwoNineA wrote: post #4

I was under the impression that planets to be life-friendly have to be close to their red dwarf star to a point they'll be tidally locked (one side always light other night), meaning their atmosphere would freeze on the dark side and planet would end up without an atmostphere.

Atmospheres are useful, but are they a requirement for calling a planet life-friendly? Life on earth first developed in liquid oceans, not in the atmosphere.

Re: Two potentially life-friendly planets found orbiting a nearby star

#13

Post by sushibowl »

TwoNineA wrote: post #4

I was under the impression that planets to be life-friendly have to be close to their red dwarf star to a point they'll be tidally locked (one side always light other night), meaning their atmosphere would freeze on the dark side and planet would end up without an atmostphere.

This was indeed the prevailing wisdom for some time. However, more recent research is somewhat more optimistic. Even an atmosphere 10% as dense as that of earth can circulate heat to the dark side efficiently enough, given the right composition. The night side temperature could be within the parameters required to sustain some form of life.

Furthermore, tidal locking is dependent on oceans and atmosphere, and can take many billions of years to occur, or even never. Mercury has plenty of time to tidally lock but is in a 3:2 resonance with the sun. There are even other options; for example, moons of gas giants within the habitable zone would be tidally locked to their primary and thus have a day-night cycle.

Re: Two potentially life-friendly planets found orbiting a nearby star

#14

Post by yellowflash »

TwoNineA wrote: post #4

I was under the impression that planets to be life-friendly have to be close to their red dwarf star to a point they'll be tidally locked (one side always light other night), meaning their atmosphere would freeze on the dark side and planet would end up without an atmostphere.

I always visualized that the tidal locking to be sort of like meshed gears, such that the one revolution around itself is same as a rotation around the star/planet if its a satellite.

But that shouldn't affect the day/night in this case right? Since we are talking about planets not satellites of planets and they are light sources not just reflecting light from the star. Can you please correct where I am wrong?

Re: Two potentially life-friendly planets found orbiting a nearby star

#15

Post by consp »

wongarsu wrote: post #12
TwoNineA wrote: post #4

I was under the impression that planets to be life-friendly have to be close to their red dwarf star to a point they'll be tidally locked (one side always light other night), meaning their atmosphere would freeze on the dark side and planet would end up without an atmostphere.

Atmospheres are useful, but are they a requirement for calling a planet life-friendly? Life on earth first developed in liquid oceans, not in the atmosphere.

Wouldn't an ocean vaporise somewhat automatically to create an atmosphere of there wasn't one already?

Re: Two potentially life-friendly planets found orbiting a nearby star

#16

Post by titzer »

TwoNineA wrote: post #4

I was under the impression that planets to be life-friendly have to be close to their red dwarf star to a point they'll be tidally locked (one side always light other night), meaning their atmosphere would freeze on the dark side and planet would end up without an atmostphere.

Such planets might also have moons.

Re: Two potentially life-friendly planets found orbiting a nearby star

#17

Post by jerf »

sushibowl wrote: post #13
TwoNineA wrote: post #4

I was under the impression that planets to be life-friendly have to be close to their red dwarf star to a point they'll be tidally locked (one side always light other night), meaning their atmosphere would freeze on the dark side and planet would end up without an atmostphere.

This was indeed the prevailing wisdom for some time. However, more recent research is somewhat more optimistic. Even an atmosphere 10% as dense as that of earth can circulate heat to the dark side efficiently enough, given the right composition. The night side temperature could be within the parameters required to sustain some form of life. Furthermore, tidal locking is dependent on oceans and atmosphere, and can tak…

"However, more recent research is somewhat more optimistic."

I am deeply skeptical of that "recent research", which AFAIK is "computer models, where we have zero capability to verify the computer models against even a single data point".

The incentives to keep kicking the computer model until it provides something publishable, with no countervailing force provided by real data to be explained by the model, are just too strong for me to take that too seriously.

Re: Two potentially life-friendly planets found orbiting a nearby star

#18

Post by kybernetikos »

yellowflash wrote: post #14
TwoNineA wrote: post #4

I was under the impression that planets to be life-friendly have to be close to their red dwarf star to a point they'll be tidally locked (one side always light other night), meaning their atmosphere would freeze on the dark side and planet would end up without an atmostphere.

I always visualized that the tidal locking to be sort of like meshed gears, such that the one revolution around itself is same as a rotation around the star/planet if its a satellite. But that shouldn't affect the day/night in this case right? Since we are talking about planets not satellites of planets and they are light sources not just reflecting light from the star. Can you please correct where I am wrong?

It follows from "one revolution around itself is same as a rotation around the star" that a planet tidally locked to its star presents the same face to the star at all times, so you have a 'Day' side and a 'Night' side. Neither side of which is likely to be particularly life friendly. Perhaps there might be some 'twilight zone' that could be though...

Re: Two potentially life-friendly planets found orbiting a nearby star

#19

Post by __MatrixMan__ »

yellowflash wrote: post #14
TwoNineA wrote: post #4

I was under the impression that planets to be life-friendly have to be close to their red dwarf star to a point they'll be tidally locked (one side always light other night), meaning their atmosphere would freeze on the dark side and planet would end up without an atmostphere.

I always visualized that the tidal locking to be sort of like meshed gears, such that the one revolution around itself is same as a rotation around the star/planet if its a satellite. But that shouldn't affect the day/night in this case right? Since we are talking about planets not satellites of planets and they are light sources not just reflecting light from the star. Can you please correct where I am wrong?

Tidal locking means that the denser side of the lighter body always faces the heavier body, and the less-dense side of the lighter body already faces away from the heavier one.

The moon is tidally locked to the Earth, which is why it has a dark side.

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