This is Exoplanet Radio, I'm Tony Darnell.
Based on our experience here on Earth, we know life to be tenacious and ubiquitous.
Even in the harshest climates, if we look
hard enough, we can usually find some sort
of life there.
We are hoping the same is true on worlds
around other stars and recent research has begun
looking into the question of whether life on
other worlds could exist in the most inhospitable
environments, the Terminator Zone of Tidally Locked Planets.
All planets that orbit a star have a Terminator Zone.
This is the band of shadow that marks the night side of a planet and the day side.
On most planets, the Terminator moves along the surface as it rotates.
But on a tidally locked planet, the
Terminator stays over the same spot all the time.
Tidally locking is a phenomenon that occurs
when a planet rotates at the same speed as
it orbits its star, so it always shows the same face to it.
This happens when the gravitational pull of
the star is stronger than the rotational force
of the planet and it causes the planet to
slow down until it reaches a stable state.
We might be familiar with this effect from
our own moon, which is tidally locked to Earth
and always shows us the same side.
But what if a planet was tidally locked to its star?
Well, that would create a huge contrast in
temperatures between the two sides of the planet
The day side would be constantly exposed to
the star's heat and light, while the night
side would be in perpetual darkness and cold.
Depending on how close the planet is to
its star, the day side could be hot enough to
melt rocks, while the night side could be cold enough to freeze water.
But there is a region in between called the
Terminator Zone, where things get more interesting.
The Terminator Zone is a band that
separates the day from the night, where temperatures
are more moderate and could allow liquid water to exist.
And where there is water, there could be life, right?
Well, maybe.
It depends on a lot of factors, such as the
type and size of the star, the amount of water
on the planet, and the presence of an atmosphere.
Some scientists have been studying these
Terminator Zones on exoplanets, especially those that
orbit dim red dwarf stars, which are very common in our galaxy.
Red dwarf stars are smaller and cooler than
our sun, but they can still emit powerful
flares and radiation that could harm life on nearby planets.
However, some of these planets could have
habitable climates in their Terminator Zones,
if they have enough water but not too much,
and if they have rocky surfaces instead of
global oceans.
Why does water and surface matter?
Well, water is essential for life as we know
it, but too much water could create a runaway
greenhouse effect that would make the planet too hot.
On the other hand, too little water could make the planet too dry and barren.
A rocky surface could help regulate the
temperature and provide nutrients for life, while an
ocean-covered surface could make the planet more uniform and, well, boring.
While this is an interesting idea, there
are still a lot of unknowns and challenges for
life to survive on these extreme worlds.
For example, how would life cope with the constant light or darkness?
How would it deal with the strong winds
and storms that could occur in the Terminator
Zone itself?
How would it adapt to any possible
volcanic activity on the day side or ice formation
on the night side?
How would it communicate and evolve in such diverse environments?
These are some of the questions that
astronomers hope to answer in the future as they search
for signs of life on these exotic planets.
Using telescopes like the James Webb Space
Telescope and the Future Habitable Worlds
Telescope, maybe one day we will find out
we are not alone in this vast universe and
that life can thrive in places we never imagined.