On April 18th, 2018, The Transiting Exoplanet Survey Satellite (TESS) was launched into space with a mission of giving scientists a better understanding of exoplanets: planets orbiting together in a solar system. However, the TESS mission wouldn’t have started if it weren’t for its predecessor: Kepler.
On March 7th, 2009, the Kepler Telescope, named after astronomer Johannes Kepler, took to the skies and began a four-year mission to explore planetary systems. It discovered everything from planets that could potentially host life, to solar systems with double stars. This, along with many other discoveries, gave scientists a deeper understanding of the processes of forming a solar system. But if these planets are so far away, how can NASA possibly study them?
NASA employs a genius method. Instead of focusing on the planets themselves, astronomers focus on the brightness of stars.
By taking snapshots of a star system over a given period of time, astronomers can compare the brightness of stars. If a planet passes in front of the star, the brightness of the star dims slightly.
Bigger planets tend to dim the star’s brightness more than smaller ones. The duration of when the planet covers the star helps scientist determine how large a planet is in combination with other information. The frequency, how often a star passes in front of a star, is another hint scientist use. For instance, planets that are close to a star have tend to be rocky planets. Equipped with this plethora of information, scientists can conclude features about a planet.
Additionally, the closer the planet is to the sun, the faster it will orbit. Using the orbital duration of the planet, astronomers can determine how far the planet is to their star. Scientists then use this to determine if the planet is habitable for life. Depending on the planet’s proximity to the sun, the planet might be too hot, too cold, or just right for life. Astronomers call the habitable zone the “Goldilocks zone”. They hope that these planets have the right conditions for fostering life. (1)
Are we alone?
But what does the Kepler mission mean for us? Scientists can use this information to understand how our solar system formed. Our own solar system is so stunningly diverse, yet we know very little about it. As of today, Kepler has discovered around 2,400 planets with 2,000 awaiting confirmation. This all comes from looking at 15,000 stars in the night sky. As we look forward to what TESS has to discover, Kepler is a huge milestone in humanity’s quest for extraterrestrial life.
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