Good choice, Tiana.
Astronomy turned out to be one of the most interesting classes I've ever been in. Towards the end of the course my professor recommended a free iPhone / iPad app to us, called Exoplanet. This app kicks butt.
In its basic functionality, the app displays a list of all extrasolar planets discovered to date (planets that exist outside of our own solar system). At the time of writing, there are 551 of these -- a small number considering the estimated number is somewhere upwards of 50 billion, just in our own galaxy. The discovery of extrasolar planets is a very new science, since this technology is constantly improving, so the app gets updated every day with new discoveries.
You can sort and filter the list of exoplanets however you please, but some orderings may prove to be more interesting than others.
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| Sort and filter the list of exoplanets |
For example, if you sort by mass in ascending order you can view the smallest planets, which at this point in technology will be the ones closest to Earth's size.
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| Exoplanets sorted by mass, ascending order |
If you tap any one of the planets in the database, it'll show you the details of that planet, complete with attractive animations.
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| Details for exoplanet 'Gliese 581 e' |
The animation here is showing you how the planet was discovered using the radial velocity technique, which basically means it was discovered by observing a Doppler shift in the planet's host star as the planet and its star orbit a common centre of mass.
More details are seen when you scroll down. The mass of the planet is measured in Earth or Jupiter masses, for relativity. Its semi-major axis is the distance from its host star, measured in Astronomical Units, where 1 AU is the distance from Earth to to our Sun. Eccentricity is how elliptical the planet's orbit is -- 0 means it orbits in a perfect circle, whereas 1.0 would be a straight line. With the exception of Mercury, the eccentricities of the planets in our own solar system are all between 0 and 0.1 (very slightly elliptical).
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| Details for exoplanet 'Gliese 581 e' |
Most of the exoplanets in the database are large and Jupiter-like. However, this is likely because of the limits of technology -- think about it: the larger planets are going to be easier to discover. What's really exciting is that newer technologies are discovering more and more Earth-like planets -- yes, increasing the probability that one might harbour extraterrestrial life. (Sorry, I couldn't resist.) In fact, just this month a planet was discovered that has a relatively high probability of being habitable.
Another really cool feature of the app is the "Milky Way" menu option. It makes you feel very insignificant. Really. When you download the app (because you really should), click on it and then use your fingers to zoom in until you get to Earth. I'll wait.
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| Milky Way feature - zoom and rotate to find Earth |
The remaining options on the home menu are great, as well -- news to keep you updated on exoplanetary science, correlation diagrams so you can plot different planets' features against each other, and comprehensive yet straightforward background information for the curious.
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| Main menu |
Overall, super impressive app. Developed and maintained by a real astronomer, and updated daily with new discoveries. Every feature is highly customizable, even the 'Milky Way' component.
And, for the super-nerd, push notifications to tell you in real time when a new planet is discovered.
