Kepler on Trial

An artist's depiction of the Kepler Space Telescope. Credit: NASA/Kepler Mission.

Three hundred seventy-nine years ago, the famed astronomer Galileo Galilei went on trial.  Today, it’s Kepler’s turn.  And I don’t mean Johannes Kepler; I mean the eponymous NASA spacecraft.  While Galileo was on trial for saying that the Earth went around the sun, which was heresy in Rome in 1633, the Kepler Mission is on trial for nothing more than the common inquisition of our time.  The government must decide whether the Kepler Mission deserves a share of the scant funding available for space missions in this bruised economy.

The Kepler Mission, which detects transiting exoplanets, is coming to the end of its nominal three-year mission.  Today, several Co-Investigators (Kepler Mission leaders) will propose to Congress to extend the mission at the NASA Astrophysics Senior Review.  If Kepler does not obtain additional financial support, it will “close its eyes forever,” in the words of Co-Investigator Natalie Batalha in the First Kepler Science Conference last December.

Why should we extend the Kepler Mission?

The new catalog release introduces 1091 new candidates, bringing the total number of planet candidates to 2,321.  These new planets are, on average, smaller and colder than the planets yet discovered, indicating that Kepler is on the verge of detecting true Earth-size planets in the habitable zone.  To quote the new catalog of Batalha et al.,

“The progression toward smaller planets at longer orbital periods with each new catalog release suggests that Earth-size planets in the Habitable Zone are forthcoming if, indeed, such planets are abundant.”

If Kepler does not obtain additional financial support, it will “close its eyes forever.” – Natalie Batalha.

Natalie Batalha, Co-Investigator of the Kepler Mission, holding an artist's model globe of the first confirmed rocky exoplanet, Kepler 10b. Credit: NASA/Kepler Mission.

But what if small planets are not abundant?  Bear in mind that the number of planets increases for smaller planets at larger orbital distances, implying small planets should be very abundant!  Kepler just needs more time to find them.

Extending the mission will grant Kepler the opportunity to achieve the mission objective: finding the frequency of true Earth analogs (Earth-size planets at orbital periods of one year).

Wasn’t Kepler supposed to have found the Earth analogs by now?

Yes, it was.  However, when the mission was initially designed, no one knew what the typical change in brightness for a star on very short timescales (or “jitter”) was.  The jitter is important because it introduces noise to the stellar light curve, which makes it more difficult to detect a planetary transit of a particular depth.  When the Kepler team designed the mission, they only knew the jitter of the sun, which is 20 parts per million, and so they used this as an estimate of typical stellar jitter.  However, Kepler has since shown that most stars have a jitter of 30 parts per million.  This additional noise in the light curve increases the number of transits required to detect a transit of a given depth.  To see more transits of a particular planet, we need more time.  That’s why Kepler needs an extended mission to achieve its mission goal.

But Kepler has still done a lot of cool stuff, right?

Absolutely!  Here are some treasures Astrobites has written about:

Are there any reasons against extending the Kepler Mission?

This is an important question to ask, and the review panel might ask this of the Kepler team.  Like many high-quality things, Kepler is expensive.  The personnel and large computing power required to run and improve the pipeline (without which data processing would be practically impossible), the high bandwidth required to download large volumes of data from this distant spacecraft, and other operational costs make Kepler more expensive – requiring a hundred million dollars over the next five years – than many other major telescope missions, including the Spitzer and Hubble Space Telescopes.

Yet, Kepler is revolutionizing science.  Three hundred seventy-nine years since Galileo went on trial for believing the Earth went around the sun, we still commend his courage in challenging widely held beliefs in order to promote real understanding of the Solar System and our place in the universe.  Kepler has staggered the world with its riches of planets: diverse star systems with multiple planets, miniature solar systems, super-Earths, rocky worlds, habitable worlds, and, hopefully soon, an Earth analog.  Tell me this does not revolutionize our understanding of Earth, the Solar System, and our place in the universe.  Tell me these are not riches.  Tell me that the Kepler Mission does not deserve to keep its eyes open.

About Lauren Weiss

A Planet Hunter and midnight playwright, Lauren is a graduate student at UC Berkeley. She works with Geoff Marcy to characterize exoplanets. After graduating from Harvard, Lauren received her MPhil degree from Cambridge, where she hosted an astronomy podcast called the Astropod ( in 2011. Her greatest desire for the coming era of astronomy is that we will find Yoda on another planet.

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  1. The one point I would question is the half-billion dollar figure. Last I heard, the cost to continue basic Kepler operations was in the 15M/yr range, rising to 25M/yr if you maintain the current Kepler team. Real money, but still far from 500M. Are there any sources where we can check these numbers?

    • Thank you, Dr. Pepper, you are absolutely right. My mistake! The cost of maintaining Kepler for the next five years is about 100 million dollars, not half a billion.

  2. If the extended mission is not funded, maybe the Kepler exoplanet crowd can follow the lead of the “Pale Blue Dot” project and raise research funds through a non-profit adopt-a-star program.

  3. This is somewhat of an emotional comment. The US is I think has an inferiority complex right now. The economic downturn has made it worse.Why do we have to be great?
    What does it mean. The country was founded on hard work and escape from a class society and oppression. Now we have become just what we escaped from. Money and power in the hands of a few are now dominating. I have worked for 40 years and do not not have much money. I write music, love gardening
    and exploring nature and scenery.
    These are the reasons I have any meaning and some kind of deeper happiness in my life, not the job and money. Astronomy and Cosmology have fed into this mix. Nasa which used to be only for defense has sent robitic missions to other planets and has succeeded in doing almost the impossible. Hubble images offer an alternative to mindless tv and entertainment. Now we have Kepler, a total success, like Hubbel to discover for sure in the first time in Human history that there are planets in inconceivable numbers in the Universe. It could ontinue for many yers just like the rovers. Mabey we will not be able to build the robotic spacecraft
    because of the budget cuts until the economy improves. But Kepler should be extended for a few million dollars, which is nothing in the budget, even at the cost of other missions. The data will take years to analyze, anyone can access it. Also the US is good at building
    space telescopes and robotic rovers. The technology will be used elsewhere. We need a movement to extend the Kepler mission. I know this is kind if an irrational outburst, but I think people in the future will appreciate Kepler’s findings.
    Bill Gordon



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