Kepler Mission Gets Four More Years

NASA officials have announced that the Kepler mission will be extended through September 30, 2016.

This decision was a no-brainer. Now Kepler can continue doing what it was designed to do: find planets encircling other stars like the Sun.

Kepler in space
An artist's impression of the Kepler spacecraft, which is basically a wide-field photometer fed by a 37-inch (0.95-m) telescope.
NASA / Ames Research Center
In case you've missed it, the spacecraft has already discovered more than 2,000 exoplanet candidates since its launch in March 2009. It's been staring at more than 145,000 stars near the Cygnus-Lyra border, watching for little dips in each star's light caused by a planet passing in front of it. This transit technique is especially good at finding companions close to their host stars, and Kepler's main objective is to find as many small ones — sized like Earth — as possible.

Finding Earths requires extremely careful measurements. A planet like ours, passing in front of a star like ours, yields a brightness dip of just 85 parts per million (0.0085%). If the planet is orbiting far enough from a Sun-like star to be in the star's "habitable zone," its orbital period will be roughly one year and, consequently, its transits would only happen this often. So the mission was designed to last 3½ years, until the end of September 2012, in order to record three transits of Earthlike exoplanets in Earthlike orbits.

But Kepler's dilemma, as I detailed last July, is that star brightnesses are twice as "noisy" on average as astronomers expected. The up-and-down churning of gas in 12th-magnitude dwarf stars (considered best bets for detecting Earth clones) causes their brightness to vary by about 20 ppm, on average, over time scales of a few hours. This noisier background means that Kepler needs to record seven or eight successive transits, not just three, to coax out believable signatures for small planets.

Kepler control center at LASP
The Kepler spacecraft is controlled from the operations center at the Laboratory for Atmospheric and Space Physics at the University of Colorado. It's staffed by students and LASP professionals.
So NASA's decision to let Kepler keep watching all those stars for four more years was logical — but not a sure thing. The spacecraft is in great shape, but an extended mission would require about $60 million, a lot of money given the space agency's lean budget. A few weeks ago Kepler managers made their pitch before a high-level review committee, which fortunately agreed that the mission is a gold mine of scientific discovery and should get the needed funding.

Remember, Kepler is doing more than discovering boatloads of exoplanets. Its continuous, extremely precise brightness measurements are revealing all kinds of things about the 145,000 target stars themselves. For instance, astronomers are now able to deduce accurate masses for many of those stars — a key characteristic that's difficult to obtain by other means. And Kepler's contributions to asteroseismology (how stars vibrate and jiggle by tiny amounts, revealing their interior structure) has been off the charts.

I've said this before, but it bears repeating: when its mission is finally over, whether due to a cutoff of extended-mission funding or some fatal malfunction, Kepler will be recognized as one of the most successful spacecraft that NASA ever launched.

By the way, the same review panel also gave a green light to mission extensions for the infrared Spitzer Space Telescope (to 2014) and the U.S.-funded portion of the European Space Agency's Planck microwave-background observatory (for one more year).

17 thoughts on “Kepler Mission Gets Four More Years

  1. Melrod

    The ‘Artist’s Impression’ illustration of Kepler states it is a 38 inch (0.95 cm) telescope. Hasn’t NASA figured out the metric system yet? And it’s actually closer to 0.97 METERS! Talk about no-brainers.

  2. Anthony BarreiroAnthony Barreiro

    This is indeed very good news. Friends and family who have little interest in astronomy often ask me about exoplanet discoveries they’ve learned of through the news. Thoughts of planets orbiting other stars and the possibility of life beyond our own solar system excite people’s imaginations and lead to many teachable moments — the distances to other stars in our galaxy; the relative sizes of stars, planets, and planetary orbits; the photometry of detecting transits; and the conditions that sustain life on our planet Earth and possibly on other worlds — to name just a few that have come up in the casual conversations of one amateur in the past few months. Keeping Kepler in operation is good not just for the science of exoplanets, but also for the public reputation of science generally, astronomy in particular, and robotic space telescopes specifically. If people are still interested after talking about Kepler, I might mention the James Webb Space Telescope and NASA’s funding dilemmas. Best wishes to the Kepler team for the discovery of many more planets, and a few promising Goldilocks planets.

  3. Kris

    I’m guessing that to find a planet in the ‘noise’, investigators would look for credible periodicity in the noise that would indicate the possible presence of a planet. To narrow it down, bounds on the periodicity could be constructed to constrain investigations of possible planets to a star’s habitable zone.

  4. Mark

    I am glad the folks at NASA decided to keep Kepler going. The fact that it was even considered for cancellation was perplexing to me. This mission is providing the first real steps toward answering one of the most fundamental questions humans have been asking throughout history: is there life beyond earth? I look forward to hearing about more discoveries from this incredible robot.

  5. Rod

    Yes it will be exciting to see what the future holds for Kepler exoplanet findings. If folks go to the Kepler home page, 61 exoplanets are *confirmed*. I prefer this type of science to hype. With some 2300 or more candidates, it appears that confirming as real exoplanets is not an easy task.

  6. Bruce

    Dittos to Robert, Anthony and Mark. I’d like to add that because it takes at least three transit observations for any presumptive planet detection to be seen by Kepler, the initial mission always seemed to short to me. The “goldilocks” combo of earthlike planet in earthlike orbit around sun-like star will produce a hard to detect (weak) signal even under ideal conditions. This signal will also have a period of about 1 year, longer for hotter stars and shorter for cooler ones. And, by design, even when everything is working perfectly, there are required periodic (monthly and quarterly) gaps in the data when the machine has to be repositioned for data transmission and heat shield reorientation. Therefore it’s a given that some transits will be missed, at least in part. Even a perfect earth/sun analog could be missed if the planet’s transits were in phase with Kepler’s download schedule. My point is that more Kepler time is definitely called for, even without the discovery that most sun-like stars are noisier than the sun. Up with the Kepler planet count!

  7. Bruce

    And to Rod, friend, as usual, you attempt to bring us back down to earth with your reflective, anti-hype, the proof will be elusive line of thinking. Ok, fine, so only 61 Kepler exoplanets are “confirmed.” But even the conservative Kepler professionals say that they’re confident that “90–95%” of the announced candidates will ultimately be confirmed. That would mean that at least 2070 of the 2300 unconfirmed candidates are real! Therefore I refuse to be deflated, I remain elated. Once more I say Up with P(Kepler)!

  8. Rod

    Bruce thanks for the comments but my fact stands. Followup observations are underway to confirm all of the 2300+ candidates however this will take time to be sure as the European site demonstrates, Astronomers did not expect to find such noisy stars as Kepler reveals. This indicates flaring is greater for many stars assumed to be similar to the Sun as well as in H-R diagram age. Stronger flaring and activity will have an impact on defining a "habitable exoplanet" similar to earth. We can be grateful that our Sun is not so noisy and flaring Bruce.

  9. Bruce

    Yes, Rod, the greater than expected flaring is a very significant finding, maybe second only to the overall planet haul itself in importance. So, evidently our sun, an “ordinary” middle of the main sequence, middle of it’s hydrogen burning phase, middle of the metallicity range star is atypically quiet. A violation of the old Copernican principle, perhaps? What do you think this could mean?

  10. Rod

    Bruce, you raise an interesting question about our quiet Sun compared to Kepler findings and the Copernican principle. For the time I will leave the Copernican principle alone for possible future discussion. I checked the April 2011 MAST data I uploaded into my home DB and compared to April 2012 MAST data for Kepler findings I uploaded. Here is a quick descriptive stat report. The average diameter for 1235 candidates in April 2011 was 4.211 earth radii with average a = 0.1498 AU. In April 2012 we have 2321 candidates reported with average earth radii = 3.787 and average a = 0.134 AU. It is clear that the Kepler data favors exoplanets packed in close to their host stars. If these stars are more variable than our Sun with more flaring, many of the Kepler exoplanets are the place to go to get severe sunburn and skin cancer as well as deep fried. Enjoy.

  11. Bruce

    Rod, your averages reveal an intrinsic detectability bias in the data. Kepler is picking off the low hanging fruit, so to speak. The big boys and the star huggers stick out like sore thumbs. Also, the further out a planet orbits the less likely it would transit at all. But, suppose we actually knew the real, complete planetary census data for this set of stars. The average orbital size would have to be much, much larger than your tiny 0.134 AU for these few detected so far. As for the average planetary radii, I’m less certain due to all the hot Jupiters being discovered, but I’d expect it to be less than your figure of 3.787, but maybe not a lot less. For comparison I crunched the numbers for our MVEMJSUN and we get an average orbital semi major axis of 8.45 AU and an average R(earth) of 3.926.

  12. Rod

    Bruce you are looking at our solar system and comparing which is a good idea. The MAST website at list 2321 candidates as of the end of Feb/12. My numbers are based upon that data. 2177 show semi-major axis <=0.38 AU which is Mercury or closer in orbit to their host stars. That is nearly 94% are in very close orbits to their host stars, assuming all 2321 candidates are real exoplanets. This explains my averages posted earlier.

  13. Bruce

    Rod, it’s surprising and significant to be discovering so many close in planets. If tight solar systems prove to be the norm then the hunt for habitability will be more challenging than what’s been hoped for or expected. The greater than expected flaring would also narrow (and for some even eliminate) the HZ’s of many stars. Earth and it’s “rock steady” sun are looking more designed all the time.

  14. CelticHunter7

    NASA Kepler webpage lists the primary objective lens aboard Kepler as 0.95 Meters. 0.95 Meters = 37.401575 US-Inches. There would be no rounding ‘up’ since 37.401575 is below the 00.500000 mark. Thus, it would mathematically be rounded ‘down’ to 37 US-Inches.

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