How Many Planets Could Support Life in the Milky Way?

Astronomers have recently estimated that there are 50 billion planets and 300 billion stars in our galaxy, the Milky Way.  With the Kepler Mission, scientists have been able to identify exoplanets in the Milky Way and so far have identified 1,235 planets.  Based on this information, Kepler Science Chief William Borucki has said that they have extrapolated from that data that there are 50 billion planets.  Scientist believe that of these 50 billion planets, 500 million could be located in the “habitable zone” of their stars, meaning that they could support life. 

How much is 500 million?  If you took 500 million 3^rd graders and placed them touching finger-tip to finger-tip, those kids would make 50 and half circles around the Earth¹.  500 million is an awful lot of planets that could potentially support life! 

1)    Assumes each 3^rd grader has an average arm span of 52 inches.  Five hundred million kids touching finger-tip to finger-tip would reach 26,000,000,000 inches.  The Earth has a diameter of 7,926.41 miles or 504,357,468 inches.  26,000,000,000 inches divided by 504,357,468 inches is 51.55 times.

NASA’s Kepler Mission Discovers Its First Rocky Planet: Kepler-10b

In January, NASA announced that Kepler has found its first rocky planet which they named “Kepler-10b”.  This is really exciting news because this is the first time we have discovered a rocky planet orbiting a sun other than ours.  Other planets that have been discovered have been gas planets, like Jupiter.  Kepler-10b cannot support life because it is too close to its sun (called Kepler 10).  In fact, Kepler-10b is 20 times closer to its sun that Mercury is to our sun.  Thus, Kepler-10b is not in the “habitable zone” meaning that It is too hot for water and therefore it is unlikely that life can be found on this planet.  Kepler-10b has a very fast year - it orbits its sun in .84 days!  Click this link to see a video on NASA about the discovery: Kepler-10b Discovery.

Is there life on other planets?

Maybe.  NASA is working to find out.

In March 2009, NASA launched the Kepler Mission on Discovery Mission #10 with the goal of finding other Earth-like planets in the universe.   Kepler is an unmanned space observatory that monitors over 145,000 stars (remember, our sun is a star) and provides data to determine if there are life-supporting planets orbiting those stars.  Planets outside of our solar system are called “exoplanets”. 

Kepler finds exoplanets by watching stars.  As you know, stars give off light.  Kepler watches the stars to see if there is a disturbance, or flicker in the light.  If that flicker happens repeatedly at regular times, Kepler has discovered a planet.   This link is an interactive tool for kids to learn how Kepler is spotting planets:  Kepler Exoplanet Transit Hunt.  Check out the Kepler: A Search for Habitable Planets for more some great information from NASA.

There is a great app for the IPhone and IPad called “Exoplanet” which is a daily updated database of all discovered exoplanets.