Late For Party

[Wade Hampton III]

Did We Arrive Early To The Universe’s Life Party?
by Matt Williams


The Fermi Paradox essentially states that given the age of
the Universe, and the sheer number of stars in it, there
really ought to be evidence of intelligent life out there.
This argument is based in part on the fact that there is
a large gap between the age of the Universe (13.8 billion
years) and the age of our Solar System (4.5 billion years
ago). Surely, in that intervening 9.3 billion years, life
has had plenty of time to evolve in other star system!

However, new theoretical work performed by researchers from
the Harvard-Smithsonian Center for Astrophysics (CfA) offers
a different take on Fermi's Paradox. According to their study,
which will appear soon in the Journal of Cosmology and
Astrophysics, they argue that life as we know it may have
been a bit premature to the whole "intelligence party", at
least from a cosmological perspective.

For the sake of their study, titled "Relative Likelihood for
Life as a Function of Cosmic Time", the team calculated the
likelihood of Earth-like planets forming within our Universe,
starting from when the first stars formed (30 million years
ago) and continuing into the distant future. What they found
was, barring any unforeseen restrictions, life as we know
is determined by the mass of a star.

"If you ask, 'When is life most likely to emerge?' you might
naively say, 'Now'. But we find that the chance of life grows
much higher in the distant future. So then you may ask, why
aren't we living in the future next to a low-mass star? One
possibility is we're premature. Another possibility is that
the environment around a low-mass star is hazardous to life."

Essentially, higher-mass stars - i.e. those that have three
or more times the mass of our Sun - have a shorter life-span,
which means that they will likely die before life has a
chance to form on a planet orbiting them. Lower mass stars,
which are a class of red dwarfs that have 0.1 Solar masses,
have much longer lifespans, with some astrophysical models
indicating that they may stay in their main sequence phase
for six to twelve trillion years.

In other words, the probability of life existing in our
Universe grows over time. For the sake of their study, some
have concluded that certain red dwarfs that are in their
main sequence today could likely live for another 10 trillion
years. By this time, the probability that life will have
developed on some of their planets increased by a factor of
1000 over what it is today.

Hence, we could say that life as we know it - i.e. carbon-
based organisms that evolved on Earth over the course of
billions of years - emerged early in terms of cosmic history,
rather than late. This might explain why it is that we haven't
found any evidence of intelligent life yet - maybe it just
hasn't had enough time to emerge. It's certainly a better
prospect than the possibility that they were killed off
during the early phases of their star's evolution (as
other researchers have suggested).

However, a determination that there was an alternative to
this hypothesis, which has to do with the particular risks
faced by plants that form around low-mass stars. For instance,
low-mass stars emit strong flares of UV radiation in their
early life, which could adversely effect any planet orbiting
it by stripping away its atmosphere.

So, in addition to life being premature on Earth, its possible
that life on other planets is being wiped out before they have
a chance to reach maturity. Ultimately, the only way to know
for sure which possibility is correct is to continue hunting
for Earth-like exoplanets and conducting spectroscopic searches
of their atmospheres for biosignatures.

The Harvard-Smithsonian Center for Astrophysics, located in
Cambridge, Massachusetts, is a joint collaboration between
the Smithsonian Astrophysical Observatory and the Harvard
College Observatory. It's scientists are dedicating to studying
the origin, evolution and future of the universe.