In 1999, scientists stumbled upon a hidden cosmic gem some 40 light-years away from us:
TRAPPIST-1 – a red dwarf star. Little did they know how lucky they were. Seventeen years later,
our telescopes revealed the star's first planets. And the very next year,
we uncovered four more planets orbiting the M-type star.
Today, TRAPPIST-1 is the most studied planetary system aside from our own.
Its 7 worlds are all rocky, strikingly similar in mass and size to our home planet,
and some possibly containing more water than the Earth’s oceans.
For a very long time, scientists struggled to study distant worlds,
but a lot has changed since the James Webb Space Telescope came into operation.
So how habitable is the TRAPPIST-1 system?
And what would it be like to live on one of its worlds?
Let’s find out this and more!
The James Webb Space Telescope was built to study the early universe,
back when the first galaxies and stars were forming. But what makes it really
special is its ability to analyze atmospheres around distant exoplanets.
The telescope’s Near Infrared Spectrograph and the Mid-Infrared Instrument are able
to measure a different spectrum of light emitted by faraway celestial
bodies. This helps scientists identify the composition and temperatures of planets and
their atmospheres. And on top of that, JWST has a powerful infrared camera that can see
through an exoplanet’s thick cloud cover and help us study its geology.
The problem is, TRAPPIST-1 is an M-type red dwarf, which are the most prevalent in our galaxy,
and the most active stars we know of, emitting powerful flares several times a day. And since
studying an exoplanet’s atmosphere takes observing light as it passess through it, it’s difficult for
scientists to distinguish ordinary light from the stellar radiation caused by the flares.
But the James Webb Space Telescope is much more powerful than any other telescope known
to science. Its precision in detecting brightness fluctuations is comparable to
looking at 10,000 light bulbs, and seeing 4 of them being turned off.
So what has the telescope discovered about the TRAPPIST-1 system so far?
Recent observations showed that the closest planet to the star in the TRAPPIST-1 system
either has a very thin atmosphere, or none at all, and it’s most likely a bare rock.
This innermost planet called TRAPPIST-1b is a scorching hot, rocky world. With a blistering
surface temperature of 450°F [230°C], the planet is too close to its parent star,
much like Mercury in our solar system, which places it outside of the habitable zone.
Slightly farther out, another planet rotates around the red dwarf – TRAPPIST-1c. In the past,
it was believed that the second planet in the TRAPPIST-1 system was similar to Venus,
but the data from James Webb Telescope proved scientists wrong. The planet doesn’t have a
Venus-like thick atmosphere. And while the temperatures on
the dayside of this world are still extremely hot, about 225°F [107°C],
it is now considered the coldest rocky planet ever studied using this new method.
In such harsh conditions, water would have evaporated long ago, even if it was initially
present on these worlds. But according to a new study, the rest of the planetary system might
have stayed cold enough for water to remain there, either in a liquid or frozen form.
The lightest of the planets in this system; TRAPPIST-1d, has around 30% the mass of the Earth,
and a radius of approximately 80% of our planet. Because of such small mass, the
planet probably doesn’t have a dense atmosphere, or an abundance of heavy elements. But it still
bears similarities with Earth, such as the amount of solar radiation it gets from its star. Located
just on the inner edge of the habitable zone, the planet’s temperature without an atmosphere
would be about 48°F [9°C]. To compare, if there were no greenhouse effect on Earth,
the surface temperature would be freezing, about 0°F [-17.5°C].
But what’s exciting about this world is that it could harbor a staggering 250 times more
water than our own planet. Although the planet’s potential habitability remains
uncertain. But there’s one factor that might change this. It’s known as albedo,
which is a measure of the reflectivity of a surface, typically expressed as a percentage.
It quantifies how much incoming solar radiation is reflected back into space by a surface,
rather than being absorbed. In other words, it describes the ability of an object or surface
to reflect sunlight. Albedo values range from 0 to 1, with 0 indicating that all incoming
radiation is absorbed by a 'perfectly black' surface, and 1 indicating that all incoming
radiation is reflected by a 'perfectly white' surface. The Earth’s average albedo is 0.3,
and so if TRAPPIST-1d has the same or similar value, it could provide an environment suitable
for some forms of life. This is because water vapor acts as a greenhouse gas,
but with the Earth-like albedo, the planet would escape the runaway greenhouse state.
Scientists think TRAPPIST-1d is covered by a global ocean. But for life to thrive there,
it needs a tidal heat flux 20 times stronger than what Earth has. Tidal heat flux is like a special
kind of energy generated by the gravitational interactions with nearby celestial objects.
On TRAPPIST-1d, this energy would act like geothermal heat that could sustain chemical
reactions in its gigantic ocean. Some forms of life drive energy from chemosynthesis rather
than photosynthesis even here on Earth. So there’s a possibility that TRAPPIST-1d could
be a unique home for life that doesn’t rely on sunlight. And if the planet has a thin atmosphere,
its twilight zone, or the border between the night and day sides, could be habitable as well.
Among the planets in the TRAPPIST-1 system, the fourth one [TRAPPIST-1e] is the most promising.
It's both dense and possibly quite rocky, sharing similarities with our home planet,
even in composition. Located in the habitable zone of its parent star,
TRAPPIST-1e could hold a thick oxygen-rich atmosphere. And all the hydrogen could have
escaped its atmosphere because of how light it is, which is good news since it’s a greenhouse gas.
If TRAPPIST-1e began with more water than Earth and Mars, and retained it on the surface
over time, its climate could be strikingly similar to what we enjoy on our own planet.
That being said, TRAPPIST-1e is considered one of the most Earth-like planets ever discovered.
Imagine living in a world where a year lasts about 7 Earth days,
and the concept of day and night is something completely different from what we're used to.
Because of the close proximity to their star, all the 7 planets in the system are tidally locked,
with one side always facing their parent star. During a never ending sunset or sunrise,
the sky would be a reddish hue, and you would be able to see the six planets in the sky as
if they were moons, with some appearing larger than the Earth’s moon in the sky.
On its dayside, the planet might even have lands where humans could thrive.
The climate would be much different. Thick storm clouds covering large areas,
massive dust storms distributing heat across the planet and maintaining a temperature
balance necessary for complex ecosystems to flourish, while also generating powerful winds,
tornadoes, and hurricanes. The nightside would be a harsh place, even for expeditions – this
is the realm of arctic cold and towering glaciers that dominate the landscape.
Although a constant twilight might get a bit tiresome,
it offers a crucial advantage, especially for the first settlers. In the distant past,
our ancestors used the ever-shifting constellations as direction guides.
But on TRAPPIST-1e the nearby star is always at a fixed position in the sky,
so it would be like having a permanent North Star to show you the way through the uncharted
territories of this alien terrain, although it would appear several times larger than the Sun.
In our galaxy, there are ten times more of these M-type red dwarf stars than stars like
our Sun. These little red dwarfs hold promise as potential cradles for life,
with trillions of years for life to evolve and flourish in their cosmic neighborhoods.
However, as we've mentioned earlier, even though they’re normally dim,
many red dwarfs can suddenly and dramatically increase their
brightness. This supercharged mode is like a star shooting out solar flares on steroids.
Some scientists think that the flares from the Trappist-1 star might actually
be helpful for life on the nearby planets. These flares give off a lot of energy,
and that energy could have kick-started the creation of important molecules like amino acids,
which are building blocks for life. So, while the high-energy radiation from
flares could be harmful and maybe even sterilize a planet's surface or strip away its atmosphere,
it could also provide the extra energy needed for early forms of life to develop.
Although data shows TRAPPIST-1 is a much safer host star, its flares are about 30 times milder
than those seen in other red dwarfs. But since the seven planets in the TRAPPIST-1
system are tightly packed, the effects would be noticeable. And this means that auroras
on TRAPPIST-1e would be nothing like the ones we know. Human bodies are fragile,
so even weaker but frequent solar flares from the star pose a constant danger. Here,
auroras act as natural alarms, signaling the incoming flare. To survive, inhabitants would
rely on an exponentially thicker ozone layer, and a strong magnetosphere, along with advanced
technology to track and respond to these volatile solar events. For safety, colonizers of the
planet could construct specialized shelters resembling bunkers. These shelters would be
equipped with shielding materials and advanced life support systems, serving as a refuge during
periods of intense space radiation, and they would be built into every habitat.
Moving wouldn’t be much different, as the planet has gravity about 93% that of Earth,
but if you don't find a safe place to hide once solar flares strike the planet,
your arteries might contract, which can impair blood flow, leading to critical health problems.
Exposure to this extreme stellar radiation can also damage the DNA within your cells,
disrupting the normal cell production rate, causing mutations or a growth of abnormal cells.
In this world of constant twilight, growing plants becomes a puzzle. The starlight reaches
the planet’s surface at a low angle, which can cast shadows and limit plant growth. To
overcome this, humans might consider a concept like the hanging gardens of Babylon, letting
vegetation drape from multi-level platforms to catch sunlight from different directions.
Imagine a series of tiered planter boxes, each placed on top of the one below. Plants are
spaced and designed to allow some light to filter down through the tiers. So,
even if a plant on a lower level is partially shaded by the plants above it,
it still gets some sunlight from the sides or through small gaps in between vegetation,
making the most of the available sunlight. The idea is similar to the vertical gardens
created by nature, where every inch of space is optimized for plant growth.
If there’s native flora on the planet, it might not need a human hand to thrive since
it has probably evolved to be completely black to absorb more of the sunlight.
Another idea is that some vegetation might also evolve into bioluminescent organisms,
emitting their own soft glow to compensate for the lack of natural light. This adaptation would
extend their growing hours and enhance their chances of survival in the persistent twilight.
Located a bit farther from its parent star, TRAPPIST-1f only receives about
a third of the starlight compared to what Earth gets from the Sun. This makes this
world much cooler. If there’s no atmosphere around TRAPPIST-1f, its surface temperature
would be approximately -74°F [-59°C], turning any potentially existing water there into ice.
The same would happen on the two outermost planets – TRAPPIST-1g and h. Although the data shows they
are rich in water, their surface would be covered in ice. However, since TRAPPIST-1g is about 30%
more massive than Earth, it could potentially hold onto its atmosphere. If the planet managed
to preserve this heat-distributing layer, and has active volcanism to fulfill greenhouse gasses
needed to sustain that atmosphere, the planet might still be a water world. Or maybe there’s
a subsurface liquid water ocean on this planet that hides exotic forms of life. If it exists,
scientists speculate that the ocean could be 415 miles [670 kilometers] deep. To put this
into perspective, the average depth of the Earth’s global ocean is around 2.3 miles [3.7 kilometers].
The corner of the TRAPPIST 1 system where the seventh planet [TRAPPIST-1h] orbits doesn’t
get bathed in much stellar radiation. If the planet was orbiting inside our solar system,
it would be somewhere between Mars and Jupiter. According to estimations,
the surface of the TRAPPIST-1h is chilling -148°F [-100°C].
TRAPPIST-1 is an aging star that has been cooling for 7.6 billion
years since its birth. The nearby planets were once exposed to extreme conditions
due to the intense heat. In theory, this heat should have caused any water present
on these celestial bodies to turn into vapor and concentrate in their atmospheres. Later,
as extreme stellar winds hit the planets, this water would escape into space.
However, astronomers have been working on more accurate models of planetary atmospheres based
on real data. In the past, it was believed that heat escaped from a
planet's surface through convection, a process similar to hot air rising,
and cold air falling. But celestial objects are more complex than that,
and the gasses in their atmospheres act differently at different altitudes.
Recent research suggests that the TRAPPIST-1 planets might not have heated up enough to
turn their crust and mantle into molten rock. This means that a significant amount of water
might have remained trapped within the rocks, even after the star cooled down.
Currently, the conditions on these planets might be extreme. Although red dwarfs are
known for their remarkable longevity, and so the seven TRAPPIST worlds have billions and trillions
of years to go through countless stages of evolution. Until one day, what is currently
scorching or freezing turns into a more hospitable environment teeming with life as we understand it.
In the upcoming years, the JWST will uncover more about these Earth-like planets. So stay
tuned here to not miss on the biggest discoveries in space science. Let us know what you think about
the potential for life in our cosmic neighborhood, and thanks for watching.