NASA has been using the Kepler Space Telescope to search for habitable planets since 2009. Recently NASA has found the first habitable Earth-sized planet known as Kepler-186f. The planet is named after the Kepler Space Telescope which had been scanning the universe for exoplanets that may have the right conditions to support life as we know it. Since 2009, the Kepler Space Telescope has managed to find around 1800 exoplanets so far, many of which have been discovered in just the last year or so.
The success of the Kepler Space Telescope can be attributed to the fact that it is the first piece of space technology that is so proficient at detecting tiny changes in light coming from distant stars. The small, periodic dimming of the light of a star is the indicator which scientists use to find exoplanets.
Astronomers are most interested in finding planets that are the same size as Earth and are about the same distance from their star. A planet with similar attributes as Earth may support life. The Kepler Space Telescope has advanced this cause amazingly so far, managing to find many planets that are a similar size to our Earth. Thanks to discoveries made by the Kepler Space Telescope we now know that Earth-sized planets are actually quite common in our galaxy.
Unfortunately, most Earth-sized planets found so far are either too hot or too cold to support life. For example Kepler-20e, the first Earth-sized planet discovered, has an very small orbit that lasts only six days. This makes the planet’s surface temperature an unpleasant 1,400 degrees.
However, the Kepler telescope has also discovered many planets within the “habitable zone” of star systems. The “habitable zone” is the region where planets may be at the proper temperature to possess liquid water. Many of these planets are several times the size of Earth. Unfortunately, these large planets are unlikely to be rocky like Earth, and are probably have liquid or gaseous outer shells.
Kepler-186f is the first exoplanet discovered that is both the right size and distance from its own sun, making it the best candidate for supporting life so far. The size of Kepler-186f is within 10% of Earth’s size. Using Venus and Mars as models for comparison scientists have hypothesized that Kepler-186f most likely has a rocky composition.
“This is a major milestone on the road to finding Earth’s twin,” said Douglas Hudgins, Kepler program scientist at NASA Headquarters in Washington. “Kepler’s results continue to demonstrate the importance of NASA’s science missions, which aim to answer some of the biggest questions about our place in the universe.”
Other planets have been found in habitable zones that are as small as 1.5 times the size of Earth. Prediction models indicate that the chances of a planet possessing a rocky composition increase significantly the closer you get to the size of Earth. This makes Kepler-186f the most exciting exoplanet discovery to date.
Kepler-186f is the right size and is the correct distance from its’ star. This is good news, however these characteristics alone don’t guarantee that a planet is habitable. Other crucial information is needed before we begin launching space-probes to other star systems in search of life.
The atmospheric compostition of exoplanets such as Kepler-186f is one of the most important things that we need to about an exoplanet that may support life. The atmosphere plays a crucial role in many ways such as regulating the planet’s temperature and protecting the surface from solar radiation. The significance of atmosphere on a planet’s habitability can be seen on a planet in our own solar system. Venus is a similar size to Earth and orbits within the habitable zone, but has a greenhouse-filled atmosphere that makes it far too hot to support life.
Learning about the atmospheres of distant planets is challenging. NASA has plans to launch the James Webb Space Telescope into space in 2018. The Webb Telescope has mirrors that are an amazing seven times larger than the famous Hubble Telescope.
The James Webb Space Telescope observes changes in light when a planet passes in front of a star. Certain wavelengths of light are absorbed by the chemicals in the planet’s atmosphere while others are allowed to pass through. This creates a cosmic fingerprint that can reveal just what the atmosphere is made of. It takes an extremely powerful telescope, capable of detecting infrared, like the Webb Telescope to collect this type of data.
Sadly, the Kepler-186 system is 500 light-years from Earth. This means that the light from its star is too dim to gather the detailed light signatures needed to decipher further details about the exoplanet.
Another piece of space equipment will be launched soon that may help. The Transiting Exoplanet Survey Satellite (TESS) will be launched in 2017 to conduct an all-sky survey to find exoplanets in our solar neighborhood. TESS will be scanning stars that are thirty to one hundred times brighter than those surveyed by the Kepler Telescope. This means we’ll be able to learn more about an exoplanet’s composition soon after its’ first discovery. The TESS has wide-field cameras that cover an area of the sky 400 times larger than Kepler.
The Kepler Space Telescope has shown that Earth-sized planets are relatively common, it’s expected that Kepler-186f is just the beginning, and we’ll soon find hundreds more similarly sized planets orbiting in the habitable zones of stars.