The world's oceans contain approximately 350 quintillion gallons of water which is an astonishing
amount.
When we cast a bucket into the ocean, even if it comes up with just water, it doesn’t
indicate the absence of the flourishing ecosystems concealed beneath the waves.
It’s a reminder of the limitless wonders that lie within the vast cosmic realm.
In the grand scheme of the universe, our explorations represent a mere fragment, and yet they have
already unveiled dozens of potentially habitable exoplanets.
Today, we're delving into the mystery of the most promising Kepler worlds, imagining life
on utterly alien planets.
[LOGO]
In the quest for potentially habitable planets, scientists seek out "twin Earths" – planets
that closely resemble our own.
A twin Earth is characterized by a size similar to that of Earth, which increases the probability
of having a rocky surface.
Additionally, it is essential for the planet to orbit a star akin in size and radiation
output to our Sun, while maintaining an optimal distance within the habitable or "Goldilocks
Zone."
[Kepler 452b]
Kepler 452b was the first Earth-like planet found orbiting around a star like the Sun,
and it might just be a perfect candidate as a habitable world.
Back in 2015, scientists considered it the most Earth-like planet ever discovered, and
there’s a reason for that.
Like the Sun, Kepler 452 is also a G-type star of about the same temperature, but 1.5
billion years older [6 billion years old].
Even though the star is brighter [120% x Sun’s brightness], and slightly larger in diameter
than the Sun [110% x Sun’s diameter], solar energy that reaches the exoplanet is just
about 10% more than what Earth receives.
At 1.6 times our planet’s size, there’s more than a 50% chance this super-Earth is
a rocky world.
Even the orbits of the two planets are similar [Kepler 452b Orbital Period: 385 days Earth
Orbital Period: 365 days].
Kepler 452b is located in the habitable zone of its star, about 5% farther compared to
Earth and the Sun distance.
Scientists believe that the planet had a valuable head start in the development of life compared
to Earth, as it spent 6 billion years in the star's habitable zone.
Of course, this is only if Kepler 452b had all the right conditions for life to emerge
on its surface in the first place.
However, we’ve recently discovered that Kepler meets some of those conditions.
One study shows that if the exoplanet’s CO2 concentrations in the atmosphere are similar
to the atmospheric amounts of the gas observed on Earth, the exoplanet is habitable.
So what would it be like to live in this alien world?
Because the planet is more massive than Earth, it would also likely have a stronger surface
gravity.
In the new environment, people would need to to their altered weight, experiencing a
sensation of being approximately twice as heavy as they are on our planet.
Initially, humans would encounter mobility challenges, but over time, we would undergo
adaptation, paving the way for the natural course of evolution to unfold.
Former NASA’s astronaut believes that just like firefighters carrying heavy loads, our
bodies would adapt to the new environment, gradually growing stronger.
Through heightened physical activity, our bones would develop resilience, countering
a potent gravitational force pulling us towards the ground.
Over generations, kids would be born with inherently robust physiques surpassing the
physical resilience of Earth-born infants.
Not everything, however, would be different.
Thanks to its current proximity to the star, Kepler 452b would feel much like home when
it comes to sunshine and surface temperature.
Plants would still rely on photosynthesis as their primary source of energy, maintaining
a growth pace and intensity akin to that observed on Earth.
Scientists also speculate the exoplanet might have a thick atmosphere, water on its surface,
and active volcanoes.
If most predictions are correct, Kepler 452b is a very promising candidate for Earth 2.0,
but it might not stay like that for long.
Researchers think the planet might experience a runaway greenhouse effect in about 500 million
years - the same phenomenon that made Venus a scorching world by trapping high amounts
of carbon dioxide in the planet’s atmosphere, making it 90 times as thick as Earth’s.
Still, that’s 500 million years, plenty enough time for the human race to colonize
it, and call it a homeworld.
Kepler 452b seems exciting, but it’s not the only Kepler world that shows promise,
and it’s a really distant one at that.
Even light would take 1,800 years to reach this exoplanet.
But what if we take the fastest man-made object ever created?
Breaking its own speed records as it approaches our Sun, the Parker Solar Probe is soaring
at a speed of 120 miles per second [190 km/s].
This is a striking achievement, and yet, it’s still only 0.063% of the speed of light.
If we imagine a direct journey from Earth to the exoplanet Kepler 452b, the probe would
still require an astonishing 2.8 million years to traverse the vast expanse of 1,800 light-years.
[Kepler 186f]
500 light-years away from Earth, within the constellation Cygnus, lies Kepler 186 — a
red dwarf star.
It is this celestial location where scientists discovered the first Earth-sized exoplanet
orbiting a distant star in the habitable zone.
Since then, astronomers are confident there are multiple worlds in the universe similar
to Earth in diameter, and could they have conditions that would allow for the existence
of liquid water on their surface.
Kepler 186f only exceeds the size of our planet by less than ten percent.
With an orbital period of 130 days, this alien world resides towards the outer boundaries
of the habitable zone.
Because of this, Kepler 186f receives approximately one-third of the heat energy the Earth receives
from the Sun, rendering its conditions more akin to those on Mars.
However, rather than being a misfortune, this disparity offers a unique advantage.
Red dwarfs are known to have powerful solar flares, increasing their brightness twice
within minutes.
But Kepler 186 star is smaller, less massive, cooler, and nowhere near as bright as the
Sun.
So even if the M type star experiences frequent outbursts of radiation, the exoplanet might
be far enough to avoid the deadly consequences.
The potential for liquid water and the existence of life on Kepler 186f are not solely determined
by the planet's distance from its star, but also by its atmospheric conditions.
The exoplanet's current position could indicate frozen water on the surface.
However, its larger size allows for a denser atmosphere compared to the Earth that can
retain and distribute heat, potentially warming the water.
The four other planets within the system [Kepler 186b, Kepler 186c, Kepler 186d, Kepler 186e]
are only about half the size of our planet, and all of them have short orbital periods
[4 days, 7 days, 13 days, 22 days], which makes the inner star companions extremely
hot worlds unsuitable for life as we currently understand it.
Today, it would take a 780,000-year journey to reach Kepler 186f.
But imagine that, sometime in the distant future, we invent a spacecraft with a speed
limit of 90% the speed of light.
In about 550 years, our descendants would step foot on Kepler 186f.
What would their experience be like?
The red dwarf star Kepler 186 is smaller, and about 25 times fainter than our Sun.
If you were standing on the exoplanet's surface at midday, the star's brightness would be
similar to our Sun's about an hour before sunset.
Scientists say the planet maintains a stable axial tilt, enabling it to have regular seasons
and a consistent climate, just like here on Earth.
Based on calculations, scientists have determined that the axial tilt of Kepler 186f has remained
stable for an extensive period of tens of millions of years.
Such stability is crucial as an erratic tilt can have catastrophic consequences, transforming
a potentially habitable planet into a barren and inhospitable world.
Think of Mars, where an unstable tilt might have played a key role in shaping its current
unfavorable conditions.
The search for the perfect ‘Goldilocks planet’ continues, and some of the best candidates
are often found by chance.
[Kepler 1649c]
In 2020, Kepler 1649c was accidentally discovered during a review of past observations, after
initially being misclassified as a false-positive exoplanet.
Scientists still don’t know much about this world, including what its atmosphere could
be.
But since Kepler 1649c, receives 75% of starlight compared to Earth and because of its much
shorter orbital period of just 19.5 days, it might have temperatures similar to those
we experience here on our planet.
If Kepler 186f lacked a heat-trapping atmosphere, its surface temperatures would be around -38°F
[-39°C].
Although this may not seem favorable, Earth's temperatures without greenhouse gasses would
also be lower, around 0°F [-18°C].
Even if the atmospheres of the two planets were similar, Kepler 186f would still require
more greenhouse gasses to compensate for this difference.
Many other worlds in the cosmos bear resemblances to Earth in terms of temperature or size,
like TRAPPIST 1f, TRAPPIST 1d, Teegarden c, and TOI 700d.
And these exoplanets are located much closer to us.
So far, Kepler 1649c seems unattainable — the vast expanse of 470,000 years of travel time
lies between us.
But when time comes, it would be a worthwhile journey as none of these nearby planets can
match the unique combination found in Kepler 1649c.
This extraordinary exoplanet not only potentially shares our planet's temperature and size characteristics
but also resides comfortably within the habitable zone of its star, making it a truly exceptional
discovery.
The star system has a second planet called Kepler 1649b that is roughly eight percent
larger than Earth but located much closer to the red dwarf.
Because of the quite unusual 4 to 9 orbit-period ratio between the two worlds, there’s potentially
a third planet hiding in the system.
Soon enough, next generation observatories will give us more clues on the habitability
of these worlds.
Meanwhile, we’ll explore yet another impressive celestial body lurking 1,100 light-years away
in the constellation of Lyra.
[Kepler 442b]
Every 112 days, Kepler 442b orbits a K-type star at about half the Earth-Sun distance.
Such a close proximity might lead to multiple issues for the well-being of any potential
life forms present on the exoplanet.
Typically, planets that orbit close to their host stars become tidally locked, resulting
in a potentially harsh environment on their surfaces.
However, Kepler 442b is situated just outside the range where the star's gravitational forces
could cause tidal locking.
K-type stars are generally dimmer compared to the Sun.
Additionally, Kepler 442 itself is a smaller and cooler star.
So the exoplanet around it finds itself in an optimal position, approximately 0.4 astronomical
units away from its relatively tranquil host star.
Scientists consider K-type stars a ‘sweet spot’ in the search for habitable worlds.
Although they aren’t as bright as G-type stars, and not as long-living as M-type red
dwarfs, they offer a favorable combination of properties.
Only within 100 light-years of our Sun lie at least 1,000 K stars.
These orange dwarfs can exist between 15 to 45 billion years.
And throughout the entire lifespan of our Sun, which is about 10 billion years, orange
dwarfs only gain approximately 10-15% in their brightness.
All the while our Sun can make the Earth uninhabitable in a mere 1-2 billion years.
So how promising is Kepler 442b?
Astronomers like to categorize planets based on their potential habitability.
The updated scale called the Comparative Habitability Index improves upon previous methods by considering
multiple factors.
It takes into account the planet's composition, favoring rocky planets, as well as the eccentricity
of its orbit, which affects the stability of light and heat received from the star.
Additionally, the scale considers the albedo, which measures the amount of solar energy
reflected by the planet's atmosphere.
These combined factors play a crucial role in determining habitability, even in cases
where the orbit is irregular.
Just like the Earth Similarity Index, the Comparative Habitability Index ranges from
0 to 1, with a higher value indicating a higher potential for habitability.
On both scales, Kepler 442b has been assigned a value of approximately 0.84.
Unfortunately, the exoplanet is too dim and small to be directly imaged with our current
telescopes, let alone travel to Kepler 442b, which would take 1,700,000 years on the fastest
space probe ever created.
What we can do, however, is look at its biosphere.
In one study dedicated to examining radiation levels received by potentially habitable exoplanets,
Kepler 442b stood out as particularly interesting.
It receives nearly sufficient sunshine to support a significant biosphere that could
be detectable by the James Webb Space Telescope.
As the JWST studies this world, we might also want it to extend its observation to two other
intriguing exoplanets within the same constellation.
[Kepler 62e] [Kepler 62f]
In the Kepler 62 star system, two planets reside comfortably in the habitable zone.
The remaining trio of planets in the system [Kepler 62b, Kepler 62c, and Kepler 62d] orbit
too closely to the K-type star, causing them to be excessively hot, and unsuitable for
sustaining life.
Scientists find Kepler 62e and Kepler 62f particularly intriguing as they are potentially
water-rich worlds.
These exoplanets have Earth Similarity Index rankings of 0.83 and 0.69 respectively.
Kepler 62e completes an orbit around its star every 122 days, while Kepler 62f has a longer
orbital period of 267 days.
The atmosphere of Kepler 62e is believed to be densely clouded, and the planet is thought
to have a consistently warm and humid climate extending even to its polar regions.
These conditions make it an exceptionally favorable environment for supporting life.
A study from 2014 suggested a possibility of a large moon in orbit of Kepler 62e.
If that's the case, the odds of the exoplanet being a habitable world would increase even
more.
This is because large moons are necessary for the evolution of complex life.
Through tidal forces, they help regulate the planet's rotation and axial tilt, which has
a direct impact on its climate patterns.
Moons also provide a protective shield, deflecting or absorbing potential impacts from asteroids
or comets, thereby safeguarding the planet and its inhabitants.
Although a further located Kepler 62f would mean cooler temperatures on its surface, it
still holds potential to be life-friendly.
But even if this hypothesis holds true, envisioning a technologically advanced civilization seems
challenging, given the absence of land, metals, and the fundamental element of fire.
Processes like metallurgy, vital for technological progress, would seemingly be unattainable.
Nevertheless, nature's complexity opens a possibility of creatures far more inventive
than ourselves, capable of finding alternative ways to surpass our current technological
achievements, perhaps even if they live underwater.
If humanity decided to send a message onboard Parker Solar Probe to any intelligent extraterrestrial
life possibly inhabiting these strange worlds, they would receive it no sooner than 1,850,000
years from now.
But if we sent a radio signal today, it would reach the two exoplanets in a mere 1,200 years
- a blink of an eye on a grand cosmic scale.
While Kepler 62e and Kepler 62f are no ideal twin Earths today, the ever-changing nature
of planetary systems holds the promise that these worlds can undergo transformative changes.
Our own planet was once entirely submerged in oceans, and yet, over time, it transformed
into a diverse world of both land and water.
Researchers contemplate the future development of these exoplanets, speculating that they
too may eventually evolve into environments reminiscent of Earth, with a harmonious interplay
between expansive lands and surrounding oceans.
Meanwhile, even here on Earth we have something as weird as flying fish, so it’s not unreasonable
to assume that were living organisms to exist on these two exoplanets, they could be quite
sophisticated.
One of the biggest challenges in studying distant worlds has been the vast distances
involved.
However, we may not have to wait for super-advanced telescopes to address this challenge.
Data from Kepler and the European Space Agency shows that among all Sun-like stars in the
universe, half could host potentially habitable rocky worlds, and some of these stars could
be lurking in our cosmic neighborhood.
This means there’s a 95% chance of at least one twin Earth hiding somewhere within 20
light-years from us.
How long do you think till we verify a completely habitable world in a close vicinity of our
solar system?
And how will this discovery change the course of human history?
Let us know what you think in the comments.
Make sure to stay tuned here to learn more about our planet and the cosmos.
Thanks for watching.