[ExI] Gaian Bottleneck

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.

http://scienceillustrated.com.au/blog/science/red-dwarf-stars-are-prone-to-powerful-eruptions/

> 
> 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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