Wolf 1061 - The closest known habitable exoplanet?

While most of Kepler’s finds are hundreds or even thousands of light years away, there have also been on going searches for exoplanets among the nearby stars. By the end of 2015 the announcement came of the discovery of three planets orbiting the nearby red dwarf known as Wolf 1061 including one that was claimed to be potentially habitable - Wolf 1061, also known as GJ 628.

http://www.drewexmachina.com/2015/12/19/habitable-planet-reality-check-wolf-1061/

 

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Planet b c d
Mass (Earth=1) ≥1.4 ≥4.3 ≥5.2
Orbit Period (days) 4.89 17.87 67.3
Orbit Radius (AU) 0.0355 0.0843 0.204
Seff (Earth=1) 6.2 1.10 0.19

As a hobby project I once worked on a computer program to generate solar systems procedurally, and this program also determined a few physical properties of the planets. One surprising finding was, that planets with a multiple mass of earth do not have a much higher surface gravity, unless the density also changes. So these planets are particularly interesting since they have a surface gravity a bit higher than earth, but not drastically higher, even the 4 and 5 times as heavy planets should have below 2g if I remember some examples from my simulation correctly (and if I had programmed that correctly).

This is a nice gravity range as it helps to keep gases and fluids to the planets (they won't dry out as easy as Mars) without putting too much pressure on organic cells (if such should exist).

But even assuming they are rocky planets similar to earth, without knowing anything about their atmospheres, it's hard to predict surface temperatures.

I strill struggle with the "habitable zone". The current idea depends on what we know about life on earth - it needs liquid water. So the habitable zone is usually limited by surface temperatures (or other conditions) that allows liquid water on the planets.

Ammonium NH3 is a nice polar fluid, too, and exists in liquid form from -77°C to -33°C (at normal pressure)
Sulfur Dioxide SO2 is an intersting polar fluid as well, and exists in liquid from from -71°C to -10°C (at normal pressure)

If we accept such fluids to support life, too, we can expand the habitable zone towards lower temperatures. NH3 is plenty in the universe. SO2 isn't as plenty, but also was confirmed to exist on other planets.

For temperatures above the boiling point of water, silicone oils were suggested. I don't know any research though about the frequency of silicone oils on other planets, but if they exist, they could boost the habitable zone up to 200 or even 300°C. These fluids are very heat resistant.

Looking at the results of my simulation and the findings about Wolf 1061, this seems to be a very promising solar system.

 

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