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Extraterrestrial

ET 'habitable zone' is smaller than thought

By T.K. Randall
June 12, 2019 · Comment icon 28 comments



The habitable zone is not quite as habitable as previously believed. Image Credit: ESO/L. Calcada
According to a new study, many planets in the so-called habitable zone can only support single-celled organisms.
Up until now, the habitable (or 'Goldilocks') zone of a star has been defined as the region in that star's orbit in which the temperature is sufficient for liquid water to exist on a planet's surface.

In practice however, while this might be sufficient for single-celled microbes, the actual conditions required for complex life forms to develop are actually much more specific and harder to come by.

The main problem is that many 'habitable' worlds have high levels of toxic gas, especially those that exist nearer to the edge of the zone traditionally considered to support life.
"To sustain liquid water at the outer edge of the conventional habitable zone, a planet would need tens of thousands of times more carbon dioxide than Earth has today," said study lead researcher Edward Schwieterman.

"That's far beyond the levels known to be toxic to human and animal life on Earth."

Taking this in to account, the size of the habitable zone around a star shrinks to half the size for simple animal life and a mere third of the size for complex life forms such as humans.

Based on these new figures, potentially habitable worlds around some of our nearest stellar neighbors such as Proxima Centauri can no longer be considered capable of hosting complex life.

Source: Live Science | Comments (28)


Recent comments on this story
Comment icon #19 Posted by XenoFish 4 years ago
I've always had this weird idea about organic space craft that were grown. I blame the works of H.R. Giger for that.
Comment icon #20 Posted by Piney 4 years ago
I did too but I blame Frank Herbert, the X-Men and being Native. We grew our fences, bows, and building material. I always wondered if we would've advanced in that direction. In the X-men the Brood grew living starships.  
Comment icon #21 Posted by XenoFish 4 years ago
I often wonder what a species that focused solely on genetic engineering would be able to do. 
Comment icon #22 Posted by Earl.Of.Trumps 4 years ago
hmmmph…  all I can grow is lint in my bellybutton  
Comment icon #23 Posted by Piney 4 years ago
Well, that would take a few million years after the initial "spark" of the idea. We could do it far in the future. If we survive as a species, which I doubt. 
Comment icon #24 Posted by godnodog 4 years ago
I have no problem admitting that technological advanced species may be rare by % within the already (also probable) small % of planets with life, but I find hard to understand why people consider life to be rare, with this I mean that there is a good chance that in the grand scheme although life may be rare, its simultaneously abundant, it may not be everywhere but where it is is abundant in concentrated locations like....Earth (this is a belief not making or trying to make a factual statement).
Comment icon #25 Posted by Earl.Of.Trumps 4 years ago
Yes, their desire to believe this  really is an emotional problem for people, not anything based in logic and science, to wit, 200 billion stars in the milky way galaxy, with at least one planet in the goldie locks zone gives 200 billion planets with the chance of having life. If we choose some low probability like one in a thousand to have life on those planets, that's 200 million planets that have life on them, yet *nobody* would give that figure the slightest chance of being accurate, while at the same time, cannot come up with a real reason as to why:-) And just think, there are only anoth... [More]
Comment icon #26 Posted by Golden Duck 4 years ago
Twice its mass as in volume? 
Comment icon #27 Posted by Piney 4 years ago
Pretty much.  It's got a iron nickle core about twice the size of Earth's so it lost some serious surface area. I think it still has as much mass as our ball of dirt. 
Comment icon #28 Posted by Golden Duck 4 years ago
I was thinking twice the advertiser distance or diameter was a bit much 


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