ASTROBIOLOGY 11notice an abnormal abundance of oxygen
and methane compared to atmospheric
models for planets like ours in systems like
ours. Although fluctuating, the disequilib-
rium has protracted long enough to be the-
oretically detectable from any point in the
galaxy and beyond. If, somewhere out there,
there is someone with adequate technology,
he will already know that life forms exist on
our planet.
We said above that, in the absence of a re-
plenishing supply of oxygen and methane,
the two molecules would soon disappear:
the Sun, with the help of oxygen, would
eliminate methane from the atmosphere in
just ten years; an M dwarf would take a cou-
ple of centuries instead.
Not knowing in what concentrations biosig-
natures can be present in the atmosphere of
another planet, searching for them around a
star less efficient than the Sun at eliminating
them could offer more chances for success.
As we have seen, however, M dwarfs are not
the ideal solution. Therefore, K dwarfs re-
main.
All the advantages of choosing this last spec-
tral class have been treated in a theoretical
study by Giada Arney of NASA’s Goddard
Space Flight Center in Greenbelt, Maryland,A
n artist’s ren-
dering of the
future Thirty
Meter Telescope
and a diagram
that shows how
new technology
developed at Cal-
tech will work: a
coronagraph
blocks a star’s
light, making or-
biting planets
easier to see and
study.[NAOJ, Cal-
tech/IPAC-TMT]
A similar process
is represented in
the animation
of the previous
page. [NASA/JPL]SEPTEMBER-OCTK type star EN_l'Astrofilo 29/08/2019 15:46 Page 11