Interview: Alan Boss and Kepler's Two Earth-Like Planets

Earth Planet
This artist's conception provided by the Harvard-Smithsonian Center for Astrophysics depicts an Earth-like planet orbiting an evolved star that has formed a stunning "planetary nebula." Earlier in its life, this planet may have been like one of the eight newly discovered worlds orbiting in the habitable zones of their stars. (Harvard-Smithsonian Center for Astrophysics, David A. Aguilar)
Friday, January 09, 2015 


NASA’s Kepler Space Telescope has been churning out a lot of exoplanet discoveries outside of our solar system since it’s second mission, named K2, launched in 2013. But researchers are especially excited about two new exoplanets, Kepler 438-b and Kepler 442-b, whose size, location, and star type mean they could be rocky planets, like Earth.

Its latest discovery of these two Earth-like planets, announced at the American Astronomical Society meeting on Tuesday, 9 January 2015, is a major achievement for astronomers. At the meeting, researches revealed 554 new candidates found by the telescope, bringing its total to 4,175, eight of which live in the so-called “Goldilocks zone” where the host star is the appropriate distance to keep the exoplanet’s water in liquid form. The two exoplanets astronomers are most excited about could potentially harbor evolved life as we know it here on Earth.

DTM staff scientist Alan Boss was part of the science team for Kepler’s primary mission in 2001. In an email interview, Boss answered questions about the goal of the first Kepler mission, and the achievements the telescope has accomplished since then.  

When did you start working on the Kepler mission?

I joined the Kepler science team in 2001, just before it was selected for flight by NASA. I served on the team throughout the prime mission phase, which ended in 2012-13. I co-chaired the Second Kepler Science Conference at NASA Ames in November 2013.

What was your position during Kepler’s first mission?

I was a member of the Science Working Group.

What was the goal of the initial mission? How has it changed overtime?

The primary goal is to assess the frequency of Earth-like planets, and also to inform the census of exoplanets in general. These goals have not changed with time, and have been met with spectacular success. Kepler is by far the most accomplished planet finding telescope in the world.

Did you expect to find this many planets? 

We certainly hoped to find a few Earth-like planets, optimistically maybe around 1% of stars, but the numbers have turned out to be about ten times higher than our most optimistic guesses. Earth-like planets are common, not rare.

What, in your own words, are these two "twin earths" like? Climate? Habitability? Composition? Etc. 

All we know for sure right now about these exoplanets is that they are just slightly larger in size than Earth, and that they orbit at distances from their stars where they receive just about the same amount of heating from their central stars as the Earth receives from the Sun. They will certainly be studied much more in the future in order learn whether or not they habitable worlds, and maybe even inhabited.

Anything else you'd like to add? 

This is an excellent example of how long it can take to make a huge advance in astronomy. Bill Borucki of NASA Ames was thinking about what would become Kepler when I was a postdoc at NASA Ames in 1979-81. 35 years later, Bill's conception and execution of the Kepler planet transit survey has finally paid off with a huge jackpot of new exoplanets, pouring out of the Kepler data pipeline, like a Las Vegas slot machine that hit five cherries!

This artist's conception provided by the Harvard-Smithsonian Center for Astrophysics depicts an Earth-like planet orbiting an evolved star that has formed a stunning "planetary nebula." Earlier in its life, this planet may have been like one of the eight newly discovered worlds orbiting in the habitable zones of their stars. (Harvard-Smithsonian Center for Astrophysics, David A. Aguilar)


Written by Robin A. Dienel
9 January 2015



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