For nine years, seven months, and 23 days, NASA’s Kepler space Telescope explored the
world beyond in search of a new home for humans.
At first, it looked like an impossible mission.
But by the end of its life cycle in 2018, there was no doubt whatsoever from scientists
and researchers that this legendary telescope had exceeded all expectations.
More than 4,000 exoplanets were identified during and after this planet-hunting mission,
including 50 that share similarities with our Earth.
Kepler’s ability to scan through an enormous crowd of stars and hunt down these special
celestial gems called exoplanets was marveling.
But maybe we shouldn't be surprised anyway because NASA had made sure that the Kepler
Space Telescope was well prepared for the task ahead even before it was launched.
It was equipped with a focal plane array which contained 21 science and 4 Fine Guidance Sensor
CCD modules.
Each module is equipped with field flattener lenses which print the image surface onto
the flat CCD chips and defines the overall wavelength bandpass.
Also, the standard module, which has four output channels, exists as an array of 2200x2048
pixels.
But altogether, the 22 modules combined have 84 channels and 94.6 million active pixels.
Furthermore, Kepler had an impressive image scale of 3.98 arcseconds per pixel as well
as a pixel size of 27 × 27 microns - allowing cosmic scientists to view spatial elements
that were initially too minute for direct visual inspection.
During its lifespan, which lasted almost ten years, the Kepler space telescope probed more
than half a million stars, discovering 2,662 exoplanets from within and beyond our solar
system.
However, continuous analysis of the data provided by the telescope has led scientists to the
discovery of more exoplanets, taking the total number of discovered exoworlds to 4,881 as
of December 2021.
Orbiting distant stars, these exoplanets exist in different forms and are characterized by
different features.
Some are super gigantic worlds similar to the jumbo-sized planets in our solar system,
like Jupiter.
While others travel around their stars closer than how Mercury orbits the Sun, enabling
them to perform a full rotation once every few days.
Meanwhile, there are a few that are midway in between Earth and Neptune in terms of size.
Then you’ve got some very strange and terrifying exo worlds with extreme temperatures hot enough
to dissolve iron.
However, the most significant discovery made by the Kepler space telescope was identifying
a range of exoplanets, including the 50 Earth-like exoplanets we spoke about earlier.
They are said to orbit at a perfect distance around their stars in a region known as the
Circumstellar Habitable Zone or the Goldilocks Zone.
The surface of these areas has the perfect balance of temperature to support the existence
of liquid water.
Not all planets that orbit this zone will support life, but we do know for sure that
the existence of water is a strong signal that life might exist on a planetary body.
Hence it was a thing of joy for scientists when Kepler began sending in evidence after
evidence about planets that could potentially support water.
Like in 2015, when the telescope discovered a supermassive exoworld called K2-18 b.
As one of the several hundreds of exoplanets that are caught in between our planet and
Neptune, the K2-18 b is eight times as big as our Earth and three times bigger than the
red dwarf star it orbits.
Both the exoplanet and the red dwarf star are 110 light-years away in the Leo constellation.
Red dwarf stars are the most abundant type of stars in the Milky Way Galaxy.
They’re very active and literally hidden in shadows and cannot be seen with the naked
eyes.
Following its discovery, scientists probed the K2-18 b with other telescopes like the
Spitzer and Hubble space telescope.
And during the study, experts at the Center for Space Exochemistry Data at the University
College London found evidence of water in the atmosphere of this planet, making it potentially
the only exoplanet known to scientists to have water in its atmosphere and a perfect
temperature on its rocky surface to sustain it.
However, the increased level of activity of the red dwarf could be detrimental to the
existence of life on the planet due to the high-energy radiation that dominates the atmosphere.
Exoplanets are one grey area of space exploration that is seldom talked about most, especially
because of the difficulties involved in identifying them.
Over the years, scientists have devised several methods of tracking them down, ranging from
transit to radial velocity to astrometry, direct imaging, and even microlensing.
However, Kepler is designed to hunt down exoplanets using the transit method.
Under this technique, the telescope observes the level of lighting whenever an exoplanet
travels in front of its host star.
A slight dim of the star’s brightness will signify the presence of an exoplanet.
But once the identification process is completed, other information like the exoplanet’s size
and period as well as the mass of the star can be calculated with the help of Kepler's
Third Law of planetary motion.
From here on, scientists can then derive other important details like the planet's temperature.
The Kepler telescope also discovered other planetary bodies known as extrasolar planets.
Detecting extrasolar is an entirely different complex task that comes with its own difficulties.
Hence, scientists made sure the cameras installed on the Kepler telescope were extra sensitive,
and this paid off as it literally led to the discovery of the first potentially livable
exoplanet known as the Kepler-186f.
Located about 500 light years away, this unique exoplanet is rumored to have seasons and a
climate that mirrors that of Earth.
Further research also shows that the Kepler-186f also has a similar spin and tilt as Earth
which fuels the suggestions that the planet supports life.
Another planet that's been a part of this discussion is the Kepler-1649c.
Ironically, scientists discovered this exoplanet two years after the Kepler telescope had retired.
Sounds weird, right?
Well, the planet somehow escaped the probing eye of Kepler, but scientists were able to
track it down by combining the data provided by the telescope together with the new report
obtained from the exoplanet survey satellite.
During this study, scientists discovered it shared similarities with Earth.
In terms of size, it is about 1.06 times larger than our planet.
Also, it dwells in the habitable zone of a red dwarf star, just like the other exoplanets
we've discussed so far.
The level of starlight it gets from its host star is equivalent to 75 percent of the amount
of light that our Earth receives from our Sun.
This suggests that the temperature levels on the exoplanet might be similar to those
on Earth.
But according to scientists, only 16 of these exoplanets exist, and out of those 16, some
are totally locked with their stars.
So we probably should measure our expectations.
However, new studies show that there could be more of them out there, especially considering
that 20 percent of the entire stars in our galaxy have similarities with the Sun, meaning
there are potentially several billions of habitable Earth-like planets within the Milky
Way galaxy alone.
It's is quite easy to forget, but the discoveries of potentially habitable planets did not entirely
define Kepler’s mission in space.
The legendary telescope also discovered a number of planets that don't support life,
but they are nonetheless special in their own right.
Examples are the huge gas planets filled predominantly with hydrogen and helium.
Quite a few of them are contained in Kepler’s data sheets, including the gas giant planet
called KOK 5ab.
This strange multiple-star system is about half the size of Saturn.
Scientists initially abandoned it after the discovery due the complications around it.
These complications centered around the fact that it rotates around a star in a system
with two other companion stars, rotating on a plane that’s not in alignment with at
least one of the stars.
And all these made it difficult to analyze the planet.
But once scientists are able to crack the code, the KOI 5ab will unravel more mysteries
about planetary formation and related processes to us.
Aside all of the aforementioned types of exoplanets, the Kepler telescope also pioneered the discovery
of super-earth massive planets until it ran out of fuel and was put out of service in
October 2018.
Surprisingly, the timing of the retirement coincided with the 338th anniversary of Johann
Kepler’s death, the German astronomer whom the telescope was named after.
New-age space observatory probes like the $10 billion James Webb Telescope have since
replaced Kepler following its retirement.
However, the memories and data that this planet-hunting telescope left with us will continue to define
how we explore exoplanets and other planetary bodies now and in many decades to come.
What do you make of the exoplanets discovered by the Kepler Space Telescope?
Would it be possible to live on one of them anytime soon?
Let us know your thoughts in the comment section down below.
Be sure to check out this next video over here.