A common assumption when dealing with habitable
zones is that they must necessarily exist
around main sequence stars, particularly dwarf
or sun like stars.
But this is not necessarily the case, other
kinds of habitable zones might exist around
other objects that under the right conditions
could allow life to arise.
One such alternative zone is hypothesized
to be possible around pulsars.
This all goes back to the idea of superhability,
that super earth planets may be better at
hosting life than our own planet is, see my
video on this channel on that subject.
But that doesn't just mean that there are
better earths out there, it also means that
there's more breathing room for super earths
that aren't in ideal conditions to harbor
life.
At first glance, it's hard to think of anything
less ideal than a pulsar.
Such an object would create an environment
where any planets orbiting it would be subjected
to extremely high levels of X-ray radiation.
But it doesn't stop there, pulsars emit a
wind of charged particles that would erode
a planet's atmosphere very rapidly, and in
the process produce gamma rays.
All of this would be deadly to life on an
earth sized planet in such a system.
But that may not be the case for a super earth.
In a 2017 paper by A. Patruno and M. Kama,
link below, they detail a way for a super
earth with a very thick atmosphere, many times
thicker than earth's, to weather the environment
of a pulsar and hold that atmosphere for hundreds
of millions, or even billions of years; long
enough for some sort of life to arise, at
least for a time.
And the fact that the planet's atmosphere
is absorbing so much radiation, that could
be enough to keep the surface warm enough
for liquid water.
But the atmospheric pressure on such a world
would be astonishing, again, this would be
an atmosphere thousands of times thicker than
earth's at the start.
But in the deep ocean of our own planet, under
immense pressure, life still exists.
But the problems facing any potential life
on a super earth orbiting a pulsar don't just
stop at the harsh conditions and the generally
shorter period of habitability.
There are also several other factors stacked
against this kind of habitable zone.
One would be that while planets around pulsars
are known to exist, they seem rather scarce.
There is an intuitive reason for this.
A pulsar is the remnant of a supernova and
during that event any planets that were previously
present in the system would have been destroyed
or otherwise ejected.
As a result, pulsar planets would need to
either be captured by the pulsar after the
supernova, or form from the materials created
in the supernova.
While captured planets would be a wildcard,
this would mean that any planets that formed
in pulsar systems would likely be rich in
heavier elements, but weak in lighter elements
such as hydrogen meaning it might be difficult
to gather the thick atmosphere needed for
life.
Given that pulsar planets are probably scarce,
and atmospheres around them rare, this type
of habitable zone is probably not going to
be one we encounter too often.
But it is possible, though marginally so,
and just maybe, given that this is a huge
universe with a correspondingly huge number
of pulsars, there exists a pulsar planet with
life, though probably only microbial and barely
eking out a living in the total blackness
of an immensely thick atmosphere, at least
for a while.
Thanks for listening!
I am futurist and science fiction author John
Michael Godier currently feeling sorry for
the pulsar planet microbes, they never had
a chance and be sure to check out my books
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