[ExI] Gaian Bottleneck

John Clark johnkclark at gmail.com
Mon Feb 1 07:33:23 UTC 2016

On Sat, Jan 30, 2016 at 11:48 PM, Stuart LaForge <avant at sollegro.com> wrote:

> ​> ​
> the authors are 99% confident that KIC 8462852 has a small companion star.
> The original article can be found here:
> http://arxiv.org/pdf/1509.03622v2.pdf
> They say it is a class M3 red dwarf of about 0.4 solar masses

​The luminosity of a star is proportional to its mass cubed so a star of
0.4 solar mass would only be .064 as luminous as the sun. So to be in the
habitable zone a planet would have to be 4 times closer to its sun than the
Earth is. A planet that close would be gravitationally locked with one side
in perpetual day and the other in perpetual night; that might not be an
impossible burden for life but it certainly wouldn't help.

​Even worse with stars that small radiation is not important and convection
is the only energy transport mechanism of any ​significance, and that would
cause solar flares that are much larger and much more common than those
found on our sun; and that could be deadly to life on a planet closer than
Mercury is from our star.


​> ​
> Red dwarfs are some of the longest lived stars in the universe with
> lifespans of trillions of years, therefore the companion star could be
> older than our sun.

​Possible but very very unlikely. Double stars are almost always born at
the same time. If the big star is less than 2 billion years old, and it
must be, then its small companion is almost certainly no older.   ​

> ​I​
> f they exist, why would they have pointed their transmitters at us?

​Because our sun is only ​
1,480 light
​ years away and they must know the the sun is an ideal candidate star to
have a life producing planet and have probably even observed Earth in their
telescopes. And it's not like it would be a big deal for them to make such
a transmitter, for goodness sake they're capable of building a Dyson
sphere! Hell even we could make such a transmitter with little difficulty. ​

 John K Clark
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