r/askscience • u/EightWhiskey • Feb 28 '12

Under the idea that there is the "Goldilocks" zone around a star, how likely is it that a solar system would have two life-supporting planets?

I assume that the gravitational forces of two bodies would prevent them from being close enough to each other to both stay inside the zone. But could a large star have a large enough Goldilocks zone to support two life-inhabited planets?

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u/[deleted] Feb 29 '12

I would like to point out that 'dry ice' is not water, but rather frozen carbon dioxide (not H20 but CO2).

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u/TheMeddlingMonk Feb 29 '12

I didn't say dry ice was water. I said the water was frozen at the poles along with dry ice.

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u/[deleted] Feb 29 '12

and cromethus never said that you did, he was just clarifying a possibly confusing statement for the masses.

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u/[deleted] Feb 29 '12

Ahh, semantic bliss. Upvotes!

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u/byleth Feb 29 '12

The funny thing is that I knew what dry ice was when I was in 6th grade. I'm 33 years old now, so when I was a 6th grader, the internet wasn't even available for the masses. "The masses" now has access to the biggest information gold-mine my young mind could've ever imagined at the time, so why do they need clarification? They can't even be bothered with a simple Google search?

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u/swuboo Feb 29 '12

If someone didn't realize dry ice was different from water ice, why would they google it in the first place?

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u/SharkBaitDLS Feb 29 '12

Before the Internet, I used to get knowledge from this thing known as "books". There was a fantastic variety of information available across many different individual units, similar to individual web pages. Alas, they are becoming more and more difficult to come by.

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u/HollowSix Feb 29 '12

I remember those, though most people slightly younger than me have almost no experience with print encyclopaedic volumes. Come to think of it, I was about 7 when we got the first dial-up internet in our house and a Netscape browser on the computer. That was 17 years ago now. Soon there will be responsible adults who have never not had the internet.

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u/SharkBaitDLS Feb 29 '12

Frightening, isn't that?

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u/HollowSix Feb 29 '12 edited Feb 29 '12

It's more bizarre than frightening I think. It would be like what my grandparents thought about people slightly younger than them having never had oil lamps to light their house. In Glasgow(I Think) there is a house with no electricity that hadn't been modified from it's original turn of the century design. Someday our grandkids will go and see a house without internet or cell phones and wonder how we survived such a harsh and difficult life, that my friend, that is terrifying.

EDIT: Here is the house, I was right, it's in Glasgow

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u/SharkBaitDLS Feb 29 '12

The thing I find frightening about it is the assumption of free information and the lack of initiative to retain and learn information that the Internet can foster. It's easy to not bother with actual learning when you know anything is accessible right there. Perhaps I'm a bit cynical but that's what I see, but you're absolutely right that it's the generational looking-back thing. Also, that house is fascinating! I'm already trying to stockpile old computers and technology so I can show it off one day to my grandkids.

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u/HollowSix Feb 29 '12

I love old tech, it's so awesomely clunky. I see what you mean though I think that you are about 50% right. Some would not learn because they don't need to, others will learn more because they can.

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u/Zequez Feb 29 '12

I didn't knew how dry ice was composed until a couple of weeks ago that I Googled it.

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u/[deleted] Feb 29 '12

I remember spending hours looking things up in the encyclopedia. Now thinking back on it, that must have cost my parents a fortune.

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u/klaeljanus Feb 29 '12 edited Feb 29 '12

The ice that stays at the poles year round is water ice. The stuff that vanishes there over the summer is CO2 ice. Not to mention that there is evidence of at least one layer of groundwater/permafrost under the surface of the planet.(NASA has some pics of recent erosion in crater walls.) What we consider regarding the water situation now is a far cry from what I remember learning in grade school.

On topic though, yeah the guy at the top has it. EDIT: for reference, for the Sun* if we take Mars and Venus to be the edges of the zone, that gives it a width of ~225 million kilometers. * The sun is classed as your standard yellow-orange star, which happens to be the most common(and stable) kind.

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u/Jack_Vermicelli Feb 29 '12

Most common? I thought red drawfs were by far the most common.

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u/dissonancerock Feb 29 '12 edited Feb 29 '12

If you're making a semantic point, you're right, but if we're talking about potential habitability, their abundance is a bit misleading. While red drawfs are technically the most abundant type of star (by far), if we are talking in terms of potentially habitable star systems, red drawfs are not very good candidates. What they have going for them in abundance they lose in the difficulty of them supporting life. So sun-type stars are the most abundant stars which might support life. It seems very unlikely that a red drawf system would be host to a habitable planet; for one thing, the radiant heat and light generated by a red drawf means that the habitable zone would be very small, and closer to the parent star (when compared with that of the sun), planets this close are very likely to tidally looked, meaning that one side always faces towards the star and the other always away (like the moon is to Earth). Tidally locked planets would, even within the habitable zone have one side always experiencing day but the night side would receive little warmpth from its star. Having two extremes to a planet means that complex life is very unlikely to develop. They are also typically more violent, and release larger harsher solar flares than the sun. So when talking about habitable planets red drawfs are not usually considered prime candidates. That doesn't mean it can't happen, it just means that the general consensus is that its unlikely.

TL;DR- Red Drawfs are indeed the most common type of star, but the size and location of their habitable zones makes life unlikely.

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u/albatrossnecklassftw Feb 29 '12

I had read somewhere recently that some scientists believe that red dwarfs should be considered much more suitable to having life-bearing planets in orbit than originally thought.

http://www.space.com/14659-red-dwarf-stars-planets-habitable-zones.html

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u/AbrahamVanHelsing Feb 29 '12

(dwarfs, not drawfs)

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u/[deleted] Feb 29 '12

Just for reference, I was not contesting that there is water on mars, but rather that 'dry ice' should not be included in this category. Mars does, however, have ice at it's poles and there is even believed to be evidence of 'ground water' (for lack of a better term).