[Music] the kepler telescope was built for one purpose to look at a certain patch in the milky way in search of exoplanets the exoplanet hunter observed over hundreds of thousands of stars and discovered thousands of exoplanets during its lifetime [Music] liftoff of the delta ii rocket launched in 2009 as part of nasa's discovery program kepler's job was to constantly scan a fixed patch of sky within our milky way galaxy to find planetary systems at the time of the launch it had the largest primary mirror ever sent into space and it also had a 96 megapixel
camera to process the light astronomers were interested in finding out just how many stars of planets orbiting around them and how many of these extra solar planets or exoplanets have conditions that are suitable for life to develop in its nine years in space kepler observed 530 536 stars and confirmed the existence of 2 2662 new exoplanets these exoplanets are unlike anything we've ever seen in our solar system before most of them are significantly bigger than earth and orbiting so close to their stars that they complete one revolution every several days and there are some very
strange worlds some have star-facing sides with temperatures that can melt iron and have entire hemispheres covered with oceans of liquid molten rock other exoplanets the size of jupiter orbit not one but two stars if you're standing on the surface of one of these planets you'll be able to see a binary sunset but kepler's legacy is that it successfully found earth-sized worlds orbiting at a safe distance from their host stars inside what's known as a habitable zone or goldilocks zone this is where the temperatures are warm enough for water to condense on their surfaces but not
so cold that it will just freeze up entirely although being in this zone doesn't guarantee the existence of life the presence of water is significant and the foundation of life as we know it one such exoplanet discovered by kepler that has recently generated excitement among researchers is called k218b in september 2019 two scientific teams independently announced that they found signs of liquid water in the planet's atmosphere situated 124 light years away from earth k218b is about eight times the mass of earth and three times as big it orbits a main sequence red dwarf star called
k218 a red dwarf star is the smallest coolest star and by far the most common type of star in the milky way according to kepler's data astronomers estimate that six percent of red dwarf stars have an earth-sized planet in the goldilocks zone at least in our neighborhood to find water on the surface of one such planet is a landmark discovery in the search for potentially habitable alien worlds k218b is also the first planet with water out of all of the exoplanets discovered by kepler in the habitable zone of stars kepler first discovered the planet in
2015 and since then its composition has been studied using other telescopes like the spitzer and hubble space telescope kepler mainly used what's known as the transit method for exoplanet hunting it essentially means that if a planet passes in front of a star the light from the star dims slightly and that's how we can tell that there's a planet there the level of dimming and how long it lasts gives us important information about the size and orbit of the planet however detecting the transit of an extrasolar planet is very challenging for example the diameter of earth
is only 1 109 of that of the sun so for an outside observer of the solar system the passage of earth would dim the output of the sun by only 0.008 kepler's cameras had to be sensitive enough to detect this minute change in the luminosity using the same method way back in 2014 kepler first found a potentially habitable exoplanet kepler-186f ignited the imaginations of space nerds everywhere when nasa announced its discovery now a new study indicates the exoplanet 500 light years away may also have seasons and a climate similar to our own new research out
of georgia tech university has analyzed the planet's spin and axial tilt and found that its tilt is stable like earth's which makes it likely that kepler-186f also has regular seasons and a stable climate similar research on the massive kepler database is going on in research universities all across the world in fact in recent years previous kepler findings that were rejected as potential earth-sized exoplanets due to algorithmic error are getting rediscovered these false positives are now slowly being re-analyzed in conjunction with data from other telescopes one such planet is kepler-1649c in mid-2020 while combing through old
kepler data and matching it against new data from the transiting exoplanet survey satellite or tess astronomers confirmed the existence of another exoplanet with very favorable conditions for life kepler-1649c located 300 light years from earth is very similar to earth in size and estimated temperature this newly revealed world is only 1.06 times larger than our own planet also the amount of starlight it receives from its host star which is also a red dwarf is 75 percent of the amount of light earth receives from our sun meaning the exoplanet's temperature may be similar to our planets as
well kepler-1649c provides yet another example of an earth-sized planet in the habitable zone of a red dwarf star but before we get ahead of ourselves it's important to note that out of the 2662 exoplanets identified by kepler only 16 of them lie inside the goldilocks zone and out of these 16 some of these planets are tidally locked with their parent stars meaning that only one hemisphere of the planet faces the star and this is not ideal for life others are more like a smaller version of neptune than a larger version of earth and planets similar
to neptune are expected to have a significant envelope of hydrogen surrounding any layer of water on the surface with a planetary core of rock and iron if the hydrogen envelope is too thick the temperature and pressure of the water layer beneath would be far too great to support life on top of all of this despite being cooler red dwarf stars tend to be more active than sun-like stars thus the planets may be exposed to higher quantities of damaging ultraviolet radiation than what we're used to here on earth because of this surface temperatures can range between
minus 100 and 116 degrees fahrenheit or minus 73 to 47 degrees celsius that means the surface could on average be colder than antarctica or hotter than earth's most blistering deserts unfortunately we just don't have the technological know-how to study the composition and atmospheres of these alien worlds and comprehensively answer all these questions yet but don't despair based on the statistical analysis of all the kepler observations astronomers now estimate that one in five stars like the sun have planets about the size of earth and a surface temperature conducive to life given that about twenty percent of
stars are sun-like in our galaxy that amounts to several billions of potential habitable earth-like planets just in our milky way alone kepler not only focused its efforts in finding potentially habitable planets in fact the bulk of its discoveries were strange worlds not suitable for life but fascinating nonetheless like the gas giants planets composed mostly of gases such as hydrogen and helium with a relatively small rocky core also known as hot jupiters these planets orbit extremely close to their parent stars and are abundant in kepler's data one such fascinating example of a gas giant is koi
5ab astronomers first flagged koi 5ab as a potential planet way back in 2009 at the time this elusive alien world was only the second planet ever found by kepler it slipped through the cracks a decade ago firstly due to the enormous amount of data that kepler generated and secondly because astronomers noticed that the main koi 5a star had another companion star making analysis very difficult for them indeed the koi 5 system was even more complicated than researchers realized at the time by 2014 scientists had determined that the koi 5 system actually harbors 3 stars and
it still wasn't clear if the planet koi 5ab actually existed or if the 2009 signal was generated by one of the companion stars but thanks to additional data from the test satellite scientists were able to confirm the existence of koi 5ab planetary bodies on stable orbits in a multi-star system is quite a rare find and the discovery of koi 5ab is expected to add a lot to our understanding of planetary formation other exoplanet types identified by kepler include super earths they're more massive than earth yet lighter than ice giants like neptune and uranus and can
be made of gas rock or a combination of both lava planets a super dense larger than earth worlds in close hot orbits around their parent stars some of them known as chithonian planets are likely the remnant cause of evaporated hot jupiters and finally trojan planets planets of various size found in strange locations and sometimes even as companions to larger planets though none have been certainly identified yet kepler was finally retired on the 30th of october 2018 as it ran out of fuel the telescope was deactivated with a good night command sent from mission control the
next month coincidentally kepler's retirement fell on the 338th anniversary of johann kepler's death after whom it's named although not operational anymore these incredible discoveries predict a near future in which astronomers will use new and advanced telescopes on the ground and in space to more deeply understand kepler's numerous finds one such telescope is already slated to go up into space in 2021 the james webb telescope will take a much closer look at some of these kepler objects of interest and hopefully will bring us closer to answering the question are we alone in the universe what do
you think will astronomers find many more strange worlds buried inside kepler's data let us know in the comments section below you
