James Webb Telescope Detected Signs of Life on These Exoplanets
Intro The ingredients for life are spread throughout
the Universe.
While Earth is the only known place in the Universe with life, detecting life beyond
Earth is a major goal of modern astronomy and planetary science.
While these vital ingredients have often been observed in the cosmos, scientists have yet
to find them all together at the same spot as they exist on Earth.
That may all change though, thanks to the James Webb Space Telescope.
Latest reports suggest that the observatory has detected signs of life on several exoplanets.
Let's take a closer look.
Exoplanets For centuries, fictional depictions of planets
orbiting other stars have fired our imagination.
From the desert world of Arrakis in Dune to the lush jungles of Yoda's planet Dagobah
in Star Wars, we humans have been fascinated with the idea of exotic, far-off worlds.
We now know that worlds beyond our solar system — known as exoplanets — do exist.
In fact, there are a whole lot of them: Scientists have found over 5,000 exoplanets, and think
that most stars have their own solar systems.
Some exoplanets are surprisingly similar to fictional worlds we've imagined, while others
have turned out to be more exotic than anything we could have dreamed.
Our universe is estimated to have over 100 billion galaxies, each with hundreds of billions
of stars.
If most stars have one or more planets around them, there may be billions of trillions of
planets in the universe.
Every exoplanet discovery teaches us something new about how the universe works.
When we just had our own solar system's eight planets to study, we had a limited view of
what kind of planetary systems are possible in the cosmos.
Now, with over 5,000 exoplanets cataloged, the horizons of planetary science are broader
than ever.
We also sometimes get to see other solar systems forming, which teaches us about our own origins.
It's like watching our very own "How It's Made" show through the world's telescopes.
There are lots of reasons to learn about exoplanets, but perhaps the most compelling is that we
could find another world that hosts living organisms.
If we discover life beyond Earth, it could change the course of human history.
And with continual advancements in exoplanet research, this discovery could happen in your
lifetime.
Even when looking through a powerful ground-or-space-based telescope, stars look like tiny points of
light.
Planets are even tinier and are very difficult to spot next to their bright host stars.
Therefore, scientists rely on indirect methods, like looking at the stars themselves for signs
that planets might be orbiting them.
As these techniques have evolved, we've gone from merely being able to tell if a star has
a planet, to being able to detect characteristics of exoplanets.
Through increasingly sophisticated technologies, we can not only figure out basic exoplanet
traits like mass and diameter but whether a world is solid or gaseous or even has water
vapor in the atmosphere.
A new NASA mission called the Roman Space Telescope is an astrophysics and exoplanets
mission that could launch as early as 2025 and will be able to detect Earth-sized, rocky
worlds.
One of the main goals of exoplanet research is to find planets that resemble Earth.
You'll often hear the term "Earth-like" used to describe worlds that resemble our own.
Generally speaking, this means the planet might have liquid water and an atmosphere
that could support life as we know it.
Life on other worlds may be unrecognizably different from what we know here on Earth,
and even life on our planet is extraordinarily diverse.
But it makes sense to start by looking for worlds that resemble our own.
Looking for Habitable Exoplanets The most basic condition for being able to
sustain liquid water is the planet’s position in relation to its star.
Scientists call the region around a star where liquid water can exist on the surface of a
planet the habitable zone: not so close to the star that water all evaporates, and not
so far from the star that it all freezes.
This area is also known as the “Goldilocks zone”.
We can tell if a planet is in a habitable zone based on the distance of the planet from
its host star and the temperature of that star.
A bigger, hotter star's habitable zone is farther out than that of a smaller, cooler
star.
There could be as many as 40 billion planets in the habitable zone of stars right here
in our Milky Way galaxy.
So far, we've found about 20.
That may not seem like many, but consider this: we may have already found a planet that
hosts life, and we just don't know it yet.
Imagine what our Sun and Earth would look like from a few hundred light-years away.
Using our present-day technologies, you might be able to determine that Earth is a small,
rocky planet that sits in the Sun's habitable zone.
Next, you could look for signs of water in the Earth's atmosphere, to rule out it wasn't
a dry, desert planet like Mars.
Our current technologies are just barely capable of doing this, while upcoming ground and space-based
observatories will be able to do it even better.
By then, you might be able to conclude Earth was habitable.
But to tell if there was life on the surface, you'd need to find gasses in the planet's
atmosphere like ozone that are possible byproducts of life.
Our current and near-future telescopes won't be able to do this, but several proposed space
telescopes might.
Even then, you probably wouldn't be able to say for certain that you'd found life.
Ultimately, it could take something like a telescope that uses our Sun's gravity as a
giant lens to capture a sharp picture of an exoplanet and see signs of life on the surface.
This may sound impossibly futuristic, but the technology is not beyond our reach.
Life might exist in the Solar System where there is liquid water – like the subsurface
aquifers on Mars or in the oceans of Jupiter's moon Europa.
However, searching for life in these places is incredibly difficult, as they are hard
to reach, and detecting life would require sending a probe to return physical samples.
Many astronomers believe there's a good chance that life exists on planets orbiting other
stars, and that may be where life will first be found.
To detect life on a distant planet, astrobiologists will study starlight that has interacted with
a planet's surface or atmosphere.
If the atmosphere or surface was transformed by life, the light may carry a clue, called
a "biosignature".
For the first half of its existence, Earth sported an atmosphere without oxygen, even
though it hosted simple, single-celled life.
Earth's biosignature was very faint during this early era.
That changed abruptly 2.4 billion years ago when a new family of algae evolved.
The algae used a process of photosynthesis that produces free oxygen – oxygen that
isn't chemically bonded to any other element.
From that time on, Earth's oxygen-filled atmosphere has left a strong and easily detectable biosignature
on the light that passes through it.
When light bounces off the surface of a material or passes through a gas, certain wavelengths
of the light are more likely to remain trapped in the gas or material's surface than others.
This selective trapping of wavelengths of light is why objects are different colors.
Leaves are green because chlorophyll is particularly good at absorbing light in the red and blue
wavelengths.
As light hits a leaf, the red and blue wavelengths are absorbed, leaving mostly green light to
bounce back into your eyes.
The pattern of missing light is determined by the specific composition of the material
the light interacts with.
Because of this, astronomers can learn something about the composition of an exoplanet's atmosphere
or surface by, in essence, measuring the specific color of light that comes from a planet.
This method can be used to recognize the presence of certain atmospheric gasses that are associated
with life – such as oxygen or methane – because these gasses leave very specific signatures
in light.
It could also be used to detect peculiar colors on the surface of a planet.
On Earth, for example, the chlorophyll and other pigments plants and algae use for photosynthesis
capture specific wavelengths of light.
These pigments produce characteristic colors that can be detected by using a sensitive
infrared camera.
If you were to see this color reflecting off the surface of a distant planet, it would
potentially signify the presence of chlorophyll.
James Webb Space Telescope It takes an incredibly powerful telescope
to detect these subtle changes to the light coming from a potentially habitable exoplanet.
For now, the only telescope capable of such a feat is the new James Webb Space Telescope.
As it began science operations in July 2022, James Webb took a reading of the spectrum
of the gas giant exoplanet WASP-96b.
The spectrum showed the presence of water and clouds, but a planet as large and hot
as WASP-96b is unlikely to host life.
However, this early data shows that James Webb is capable of detecting faint chemical
signatures in the light coming from exoplanets.
In the coming months, Webb is set to turn its mirrors toward TRAPPIST-1e, a potentially
habitable Earth-sized planet a mere 39 light-years from Earth.
Webb can look for biosignatures by studying planets as they pass in front of their host
stars and capturing starlight that filters through the planet's atmosphere.
But Webb was not designed to search for life, so the telescope is only able to scrutinize
a few of the nearest potentially habitable worlds.
It also can only detect changes to atmospheric levels of carbon dioxide, methane, and water
vapor.
While certain combinations of these gasses may suggest life, Webb is not able to detect
the presence of unbonded oxygen, which is the strongest signal for life.
Leading concepts for future, even more powerful, space telescopes include plans to block the
bright light of a planet's host star to reveal starlight reflected from the planet.
This idea is similar to using your hand to block sunlight to better see something in
the distance.
Future space telescopes could use small, internal masks or large, external, umbrella-like spacecraft
to do this.
Once the starlight is blocked, it becomes much easier to study light bouncing off a
planet.
There are also three enormous, ground-based telescopes currently under construction that
will be able to search for biosignatures: the Giant Magellan Telescope, the Thirty Meter
Telescope, and the European Extremely Large Telescope.
Each is far more powerful than existing telescopes on Earth, and despite the handicap of Earth's
atmosphere distorting starlight, these telescopes might be able to probe the atmospheres of
the closest worlds for oxygen.
Even using the most powerful telescopes of the coming decades, astrobiologists will only
be able to detect strong biosignatures produced by worlds that have been completely transformed
by life.
Unfortunately, most gasses released by terrestrial life can also be produced by non biological
processes – cows and volcanoes both release methane.
Photosynthesis produces oxygen, but sunlight does, too, when it splits water molecules
into oxygen and hydrogen.
There is a good chance astronomers will detect some false positives when looking for distant
life.
To help rule out false positives, astronomers will need to understand a planet of interest
well enough to understand whether its geologic or atmospheric processes could mimic a biosignature.
The next generation of exoplanet studies has the potential to pass the bar of the extraordinary
evidence needed to prove the existence of life.
The first data release from the James Webb Space Telescope gives us a sense of the exciting
progress that's coming soon.
Outro If you liked this video, please take a look
at this one which talks about the rotation of the Earth and why it has suddenly increased!
Do you think there is life on TRAPPIST-1e?
Please share your thoughts in the comments section below.