Kepler Data Visualized

By Sean Carroll | February 9, 2011 9:29 am

Last week the Kepler satellite released results indicating that the mission had discovered over 1200 planetary candidates (most of which are expected to be actual planets) orbiting stars in our neighborhood of the galaxy. In technical terms, that’s a “buttload.” A back-of-the-envelope calculation implies that there might be a million or so “Earth-like” planets in our Milky Way galaxy. A tiny fraction of the hundred billion stars we have, but still a healthy number.

But you know what’s really cool? The data visualization. (Hat tip to Flowingdata; thanks to Lee Billings for pointer to the original post.)

In this image, the size of the dot is proportional to the size of the planet, while the distance from the center is proportional to the distance at which its orbiting its star. The color and height measure the same thing, the temperature of the planet. (Greenhouse effect not included.)

Here’s a video that offers transitions between different presentations of the data. Unfortunately, it’s kind of hard to read the labels on the various axes unless you go to the HD version.

A couple of science results pop out — you could have figured them out without the visualization, but it makes it much easier. First, most of these planets are closer to their stars than Earth is to the Sun. Second, most of the planets are equal to or a bit larger than the Earth. Both features make sense in terms of Kepler’s search technique — the mission looks for tiny dips in the brightness of stars as planets pass in front, which favors larger planets with shorter orbits. It’s unclear whether the overall planet distribution also shares these features.

  • psmith

    It is this kind of research that leaves me overwhelmed by awe and amazement. And I am sure it is only going to get better and better as we refine our techniques in ways we can’t even imagine now.

    For me it is a given we will discover large numbers of exoplanets rather like our own. But will we answer the ultimate question, do any bear life and even more importantly do any carry intelligent life?

    This is where Fermi’s Paradox comes in. Where are they? I would love to know what your opinion is about Fermi’s Paradox.

  • Lab Lemming

    As far as I can tell, these results suggest that our solar system is unusual in that our planets have a size gap between Earth and Neptune. Explanation here:

  • Meng Bomin

    It seems to me that there should be a way of statistically analyzing the distribution of planets based upon the data collected. Kepler has a dinstinct bias toward closer, larger objects because a closer object’s transit is visible to a greater number of outside observers as the angle of viewing is wider. In the case of the earth, the band of stars from which a Kepler-like method could find us is about 1° wide (.5° above and below the ecliptic), whereas a closer planet would have a wider field of possible discoverers. A larger planet increases that angle at the margins and gives a stronger signal, making it generally more easy to spot against the noise.

    So, given that, it seems that one should be able to compare predicted distributions of planetary discovery with the actual data. Now, obviously there will be a good deal of uncertainty, as Kepler’s view is limited, but the distribution of planets found should give some sort of bounds for what to expect as our picture of the topic becomes more complete.

  • tobyvoss

    Axes labels perfectly readable in the linked video if viewed in HD and fullscreen. Embedded video doesn’t work for me.
    Further gripes:
    * Why are only Mercury, Mars, Earth and Jupiter included? Has Venus clandestinely been demoted from planet to … myth?
    * While the planet-candidate temperature gives a good indication of habitability, it would be nice to somehow represent properties of the respective primary star.

  • Ted Bunn

    My back-of-the-envelope implies a lot more than a million Earth-like planets. Kepler looked at about one out of every million stars in the Galaxy and found some Earth-like planets, so that’s of order a million right there. But on geometrical grounds alone the probability of finding any given planet can’t be more than a few percent: the probability of an eclipsing geometry is R_star / R_orbit. Throw in the fact that they won’t have found anything with long periods, plus no doubt other reasons their efficiency isn’t optimal, and a better estimate is at least 10^8, if not 10^9.

    Am I wrong?

  • Pingback: Ted Bunn’s Blog » Blog Archive » Kepler stuff()

  • LG
  • nick anderson

    Sean uses an estimate of 100 billion stars in the Milky Way galaxy. I thought the “old” estimate was 200 billion and the new estimate based on a recent major collaboration is 400 billion which clearly will affect the statistical estimates of exo-planets.

    For those interested in the best single source for the various arguments regarding the possibility of other “intelligent” life in the universe (including a discussion of the Fermi paradox), I recommend the recent book by Paul Davies, The Eerie Silence.

  • psmith

    #7, nick – thanks for that pointer. Paul Davies is an impressively intelligent and lucid writer.

  • Lee Billings

    Hey Sean,

    Thanks very much for talking about this work I did with Jer Thorp, who deserves the bulk of the credit. I’m wondering, though, if you could perhaps update your main link so that it points to my initial post on BoingBoing (, where all this originated, instead of second-hand sources.


    Lee Billings

  • Sean

    Lee, thanks — I updated the post.

  • réalta fuar

    @Ted Bunn You’re exactly right, I think. My back of the envelope calcs give numbers exactly the same as yours. When was the last time Sean Carroll was wrong by two or three orders of magnitude? I would have thought a value of one million would have raised immediate flags concerning the Fermi Paradox. I don’t happen to think the larger numbers are even particularly promising in regards to the existence of ETIs.

  • Terry Doyle

    Anyone wanting a free explanation of the “Fermi Paradox” can look at

    The idea that a) there ought to be intelligent life out there b/c it’s here on earth and there are so many stars in the galaxy and b) WTF are they? seems to be less of a paradox than a puzzle for which there has been an inordinate amount of speculation.

  • Kamrom

    I dont think theres much problem at all with what was said here. This merely talked about “earth-like” bodies. It didnt really say anything about life itself. “Earth-like” to me seems something within a reasonable temperature gradient, with enough variety to create large scale chemical compounds, while having a predictable and stable day/night structure.

    Basically, I think they are saying that there could be a million planets that could *potentially* support life *as we know life to exist as.* But what compels me is what the NEXT satellite thingy will bring.

    Think about that for a second. Within ten years or so (my hope at least) we’ll probably be able to determine things like atmosphere and colors of distant worlds. At that time, it would be appropriate to review the material. But for now, saying there are likely millions of earth potentials is not a bad statement.

    Edit: If they spoke about this in the videos, then my apologies. I cant hear them right now.

  • Torbjörn Larsson, OM

    our solar system is unusual

    Well, as of date _all_ found systems are unusual. Kepler found one with _only_ planets between Earth and Neptune (IIRC).

    This is why astronomers are now preparing to buckle on research on planet system formation. There seem to be many ways to form a system, and many outcomes.

    Until we have more statistics and/or models it seems premature to make claims on the precise statistics to pick individual systems. (Which btw I note wasn’t presented – how rare would the SS be when picked out of the given distribution? Not so rare, I think.)

    a better estimate is at least 10^8, if not 10^9.

    That is what I get too, but it depends on how you define “Earth like”. I was happy with 0.5 -2 Earth radius in habitability zones.

    Paul Davies is an impressively

    outspoken deist. I can’t read anything from him without observing the religiously motivated need to find humans rare compared to bacteria, whether it is Rare Earth or (paradoxically) Shadow Biospheres.

    A more healthy read may be the one recommended in my astrobiology course, “If the Universe Is Teeming with Aliens… Where Is Everybody? Fifty Solutions to Fermi’s Paradox and the Problem of Extraterrestrial Life”, Stephen Webb.

  • tom30


    Is the current Kepler data, which suggest that ~1/3 of stars in the galaxy have at least one planet, a lower limit ? After all, the mission still has more data to collect and would not yet have been able to claim a secure detection of a solar system having the same planetary configuration as our own.


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About Sean Carroll

Sean Carroll is a Senior Research Associate in the Department of Physics at the California Institute of Technology. His research interests include theoretical aspects of cosmology, field theory, and gravitation. His most recent book is The Particle at the End of the Universe, about the Large Hadron Collider and the search for the Higgs boson. Here are some of his favorite blog posts, home page, and email: carroll [at] .


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