• How do you manage to fit an entire solar system onto a screen?
    Solar systems are huge, so in order to get it all to fit while keeping the orbital ellipse as accurate as possible, planet sizes and orbital distances are scaled using logarithms. This spreads out the planets close to the star and packs the distant planets together.
  • Why are a few planets in The Encyclopedia missing from Exoplanet Explorer?
    In some cases there is just not enough data to make an estimate about a star or planet, even though it’s listed on the Encyclopaedia. This could be for a number of reasons such as a newly discovered planet that’s been announced, but not officially published yet, so there’s no scientific data available.
  • Will you update the app with new planets when they are discovered?
    Of course, but not the instant they appear on the Encyclopaedia because the data on the Encyclopaedia is maintained by hand, and there’s always a few glitches that have to be manually worked around. I’ve written an an elaborate script that does most of the work, it takes the data, converts it to a format that Exoplanet Explorer can read, then visits other sites filling in as much missing information as possible. At the end of it all, it prints out an error list that I go through manually to correct what I can. Because of this process Exoplanet Explorer isn’t live, but it won’t be too far behind. If I tried to build this functionality into the app, so that it’d download straight from the encyclopaedia, then there’s a risk that a mistake in that data (even a simple typo) could break the app until I was able to release a patch. It’s much better to be stable and a little behind than run the risk of a crash.
    Once the app’s development is further along, I plan to have it download the massaged data from this website, so it’ll be easier to keep it up to date. Until then, I’ll be doing an update every time there’s new data, even if the app hasn’t changed much.
  • Why are there sometimes no stars nearby when I zoom out from a system?
    In a number of cases, although we know the direction a star is in releation to the Earth, we don’t know how far away it is, so it’s not possible to put it on the 3D map. Also, many stars are quite far away, so for performance reasons, many stars that are over 400LY away will appear to be on their own when zoomed out. You can see the estimate of what’s visible in the Stats page, under the entries for stars closer than 400LY and stars that are too far away.
  • How do you determine the radius of a planet from the mass?
    In many cases, the method of detection results in a mass, but not a radius for a planet, so the radius has to be estimated to be able to make a 3D model of the system. To do this, the planets have been divided into two groups, gas giants and rocky planets based on their mass category. Using the tables from this paper , the app calculates the radius of rocky worlds assuming that they are 30% ice/ 70% rock. It’s crude, but it’s just to get an idea of the relative sizes.Gas giants are estimated using the same paper, under the assumption that all gas giants are 1AU from their parent star and contain 10% heavy elements. Again, it’s rough, but it gives an estimate of radius that’s close enough to get an idea of how big the planet is.
  • Why are mass and size measurements in terms of Sol and  Jupiter?
    That’s the way the data is presented by the Exoplanet Encyclopaedia.
  • Why aren’t distance measurements in Parsecs?
    Although the source data supplied distances in Parsecs, I opted to display it in Light Years which are more familiar. One Parsec = 3.26 light years, so the conversion is easy enough.
  • Why do a few star systems have weird orbits?
    The methods and scale I’ve chosen to represent the systems in 3D results in a few extreme cases where planets have very tight orbits that look wrong. This can’t really be avoided without scaling these offending systems differently to rest of the app.
  • Why doesn’t Exoplanet Explorer do…?
    Got an idea? Feel free to contact me.
  • I’ve found a bug!
    Please, please, please let me know here, not on Android Market! This goes doubly for those of you who post those annoying “problem x, uninstall” messages on Google’s comment system. There’s over 600 devices that run Android and nobody on the planet has one of each to test their apps on. If you help me fix it, you’ll get a better app in return.
  • I’m seeing problems with ads in the free version!
    I’ve had a number of people report this in Solar Explorer as though they think the app is supposed to have ads covering everything up. It’s not and I can’t reproduce it, so I don’t know why it’s doing it. Actually, I don’t even know what the problem looks like. Unfortunately, the people reporting this pull the “problem x, uninstall” manoeuvre and disappear leaving me no way to find out more because of Google’s poor market comment system.If you see problems with ads covering up text, then please report it on this blog. The app isn’t supposed to do that!
  • Why do I keep getting payment issues or download issues?
    Google’s systems are full of bugs. The paid and free versions of Exoplanet Explorer are also available on SlideMe, a much friendlier marketplace. Unfortunately, I’ve no control over payments or downloads, so it’s all Google’s fault if something goes wrong.