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‘Citizen Science’ and Kepler

“With your help, we are looking for planets around other stars.” So begins a first-time user’s introduction to Planet Hunters, an online citizen science project that delivers exactly what many of us have been hoping for since the first Kepler results came in — a chance to use our own computers to help analyze data taken by the mission. Kepler has been in operation for the better part of two years now, accumulating what Yale astronomer Kevin Schawinski calls ‘another mountain of data to sort through.’ What better way to sort than with distributed computing?

Schawinski is a co-founder of Planet Hunters, and was deeply involved in the creation of the successful Galaxy Zoo project several years back. In the latter, the involvement of average citizens in astronomy took off, to the tune of hundreds of thousands of Web users sorting through a million images of galaxies and classifying them. Kepler presents its own challenges, monitoring almost 150,000 stars in the constellations of Cygnus and Lyra. The trick with Kepler is to look for the characteristic dimming of a star that could signify a planetary transit.

From the Planet Hunters site:

NASA’s Kepler spacecraft is one of the most powerful tools in the hunt for extrasolar planets. The Kepler team’s computers are sifting through the data, but we at Planet Hunters are betting that there will be planets which can only be found via the remarkable human ability for pattern recognition.

This is a gamble, a bet if you will, on the ability of humans to beat machines just occasionally. It may be that no new planets are found or that computers have the job down to a fine art. And yet, it’s just possible that you might be the first to know that a star somewhere out there in the Milky Way has a companion, just as our Sun does. Fancy giving it a try?

Not every star that dims is experiencing a transit, but some are, and our profoundest hope for Kepler is that it will tease out the signature of a planet not so different from our Earth, a small world in an orbit that would keep water liquid at the surface. Planet Hunters draws on the fact that Kepler data are being released into the public domain. It’s not directly tied to the Kepler mission, but should serve as a useful adjunct to what the Kepler team is doing as it sorts through Schawinski’s ‘mountain.’ The more human intelligence on the job, the better.

Not that computers aren’t critical to the work at hand. But another co-founder of Planet Hunters, Yale’s Meg Schwamb, notes what a good set of eyes and human intelligence bring to the data our computers deliver to the desktop:

“…computers are only good at finding what they’ve been taught to look for, whereas the human brain has the uncanny ability to recognize patterns and immediately pick out what is strange or unique, far beyond what we can teach machines to do.”

That’s the great virtue, proven over time, of the Galaxy Zoo project. In the case of Planet Hunters, the method is to answer a series of questions about the light emitted by a particular star over time, its light curve. Such graphs help astronomers identify the dimming caused by a planetary transit. Planet hunter extraordinaire Debra Fischer notes that even with data from an instrument as precise as the Kepler telescope, picking out the transit signal is exceedingly hard. “Planet Hunters is an experiment,” adds Fischer. “We’re looking for the needle in the haystack.”

Here’s a Planet Hunters video that walks you through the basics of using the site:

Planet Hunters Tutorial from The Zooniverse on Vimeo.

Have a look at some of the Planet Hunters introductory material to see how absorbing this work can be. Light curves are stuffed with scatter and often reveal nothing but statistical noise. Some, however, show variability with time. Variability in a light curve is readily caused by starspots, but there are planets hiding within some of these curves, and human classification supplements computer analysis to flag patterns whose variability appears particularly promising. Obviously, large planets with short orbital periods are the easiest targets, while small planets with long periods — the ultimate quarry in the eyes of many planet hunters — require long observation.

It should be obvious by now that citizen science can make serious contributions. If Planet Hunters finds a possible transiting planet, the procedure is to match that potential world up against the Kepler team’s own list of transiting planets. It may be that the light curve is already under investigation, and users will be notified of that fact.

If not, and if several of the Planet Hunters team are flagging the same data, the science team investigates and, if a discovery appears in the offing, the team will obtain spectroscopic data using the Keck instrument in Hawaii. A transit candidate that gets through all these tests will be submitted for publication, with the Planet Hunters participants involved listed as co-authors. Interested? I hope the Planet Hunters site is ready to go, because I expect the initial response will be robust.


Comments on this entry are closed.

  • Carl Keller December 16, 2010, 11:29

    Thanks for the link, Paul. I already have an account, and started using the application. The site froze on me, and picked up later.

    Citizen science is a great thing. Scientific American’s old column, ‘The Amateur Scientist’, featured making your own oil drop experiment, seismometers, logic circuits from relays, and of course, telescopes. The modern computer formalizes and facilitates greater participation with useful results.

  • Erik Anderson December 16, 2010, 13:05

    Once the Kepler data are ~fully~ released to the public, I’ll be interested. Wikileaks, anyone? ;-)

  • Jeff Honeyman December 16, 2010, 14:28

    Note that if you’re using Internet Explorer, for now you’re out of luck if you want to participate in this effort (though the site does say Planet Hunters hopes to add IE support in early 2011). “Planet Hunters requires a modern web browser,” says the home page, and shows (with their logos) Firefox, Safari, Chrome, and Opera.
    Not that I care too deeply, but since IE still covers a substantial user base, that’s a bit of a counterproductive, snarky, tech marketing attitude that just pumps up some smug opinion-holders and deflates some others. . Isn’t “the more, the merrier” — or at the very least, “the more eyeballs and CPU cycles, the better” — part of the optimal use model for this sort of endeavor?

  • Mike December 16, 2010, 14:50

    This looks like a great project. And part of the Galaxy Zoo group too.
    I’m sure Planet Hunter will generate a big interest, who doesn’t want to help discover an exoplanet?
    It also reminds me of Planetquest@home, a BOINC distributed computing project that is still in the development stage. Planetquest@home will make use of the Kepler data base to re-examine the light curves of eclipsing binary stars discovered by Kepler to search for signs of planetary transits in those EB light curves.
    Planet Hunter requires a much more hands-on approach from its participants and it might be a lot more fun for that reason.

  • Reyn December 16, 2010, 15:46

    I wonder if they have any plans to release all the raw data, maybe in text file form. That would really allow people to play with it. I’m also somewhat surprised that this needs to be done by hand. Does anyone know if they use or are working on any algo’s to identify potential targets?

  • Lewis December 16, 2010, 21:02

    I wondered the same thing as Reyn; there are stochastic learning algorithms (i.e., Markov models and neural nets, etc) to observe other distinct phenomena like aberrant mitotic divisions in precancer cells; it seems that a phenomenon like this would be quantifiable by machine. Still I’m excited to participate and will look at the tool ASAP.

  • Michael Simmons December 16, 2010, 22:45

    Reyn, this is the software your looking for…


    I’d rather use this to hunt though Kepler data.
    Perhaps a web based version is needed.

  • Leigh December 17, 2010, 7:24

    Reyn, Their site says the following:

    “This is a gamble, a bet if you will, on the ability of humans to beat machines just occasionally. It may be that no new planets are found or that computers have the job down to a fine art. And yet, it’s just possible that you might be the first to know that a star somewhere out there in the Milky Way has a companion, just as our Sun does. Fancy giving it a try?”

  • Luigi December 17, 2010, 13:12

    If I may drift a bit OT towards the hypothetical field of ‘Interstellar Archeology’: do you think Kepler would be able to spot the transit of a planet (or moon) sized artificial structure? And with enough data for us to be able to tell its shape (or other properties) is definitely non-natural?
    Obviously I’m thinking of something like a Kardashev I+ (‘1.3’??) civilization, way ahead of us but not quite dyson sphere / ringworld capable, assuming such structures are actually possible.

  • Reyn December 17, 2010, 21:22

    Thanks for the responses, the systemic console looks really intriguing. I’m definitely going to have to play with that a bit.

  • dragozzine December 18, 2010, 3:06

    Reyn- All the Kepler data will be released eventually. In Feb 2011, the first 120 days of data will be released. It’s released in an astronomer “fits” format, but this is not that different from txt if you’re a bit computer-savvy. (I’m sure someone, somewhere will put all these into txt files.)

    As was pointed out, the Kepler Team already has algorithms to find planets, but tricky planets around variable stars, for example, are tough and I can’t imagine “neural nets” being good enough to solve the problem. Most of these machine-learning techniques require a large database of “solved” problems (done by humans) to start with, so Planet Hunters would be needed anyway.

    Michael- the systemic console currently only analyzes radial velocity data; Planet Hunters is using photometric data (to look for transits) from Kepler. You can look up the various ways to find exoplanets to see the difference.

    Luigi- anything that dims the star by ~0.1% or more periodically is detectable. That large artificial structures could be seen by Kepler and other transit searches was suggested in 2005 by Luc Arnold. The paper is here:

    It is for a technical audience. He suggests that a civilization wanting to send a clear communication to put multiple transiting objects in the same orbit with a prime-number spacing…

    On a related note, this reminded me of the suggestion by someone in the past about METI, i.e. the goal of sending messages to extraterrestrial civilizations. Whatever it’s controversy, the author (whom I can’t remember) suggested sending our signals out to systems in the ecliptic plane because those civilizations observing Earth would see it as a transiting planet and would be more likely to know that it existed, just as Kepler is revealing unprecedented number of small planets.

    In any case, I’m on the Kepler Team and I’m still having fun on Planet Hunting, so I recommend joining and helping out.

  • andy December 18, 2010, 6:14

    I’d rather use this to hunt though Kepler data.
    Perhaps a web based version is needed.

    Systemic console is primarily for the handling of radial velocity data, though there is some functionality for incorporating transit times in the fit. The Kepler data is photometric, so does not work with Systemic.

  • Luigi December 19, 2010, 7:09

    dragozzine – Many thanks, I could follow most of the paper.

    Concerning the usefulness of taking into account our (and the milky way’s) ecliptic plane with respect to SETI/METI, I’ve found mentions in these two (interesting) papers:
    Nussinov: http://arxiv.org/abs/0903.1628
    Zaitsev: http://arxiv.org/abs/physics/0610031

    Planethunters.org seems an excellent idea. The user interface and tutorial are also very well designed.

  • NS December 19, 2010, 15:05

    A small about of Kepler data has been released as text files here:


    I wrote a VERY simple curve plotter for it (just for fun; probably there are much better ones available) and even with that the periodic blips of the transiting planets were easily visible.

  • NS December 19, 2010, 17:41

    “small about”

    “small amount” of course — must have been typing half-asleep…

  • ljk December 23, 2010, 23:23

    Kepler Spacecraft Enters Safe Mode

    By Keith Cowing on December 23, 2010 10:48 AM

    “On Dec. 22, 2010, Kepler experienced a safe mode event. A safe mode is a self-protective measure that the spacecraft takes when something unexpected occurs. During safe mode, the spacecraft points the solar panels directly at the sun and begins to slowly rotate about a sun-aligned axis. This safe mode orientation provides the vehicle with the maximum power, and limits the buildup of momentum from the solar wind.”