
Our solar system, to scale.
Eight planets, count 'em--four terrestrial ("Earth-like"), close to the sun; four jovian ("Jupiter-like"), much further away from the sun. If you think there should be
nine planets, then I'm not sure which solar system you live in...

What about extrasolar planets, orbiting other stars? More and more of them are being discovered all the time--what generalizations can be made about these planets, compared to our solar system, and as a whole? (Video link: "
Kepler Orrery (large & small systems).")

(This is the ninth Astronomy 210L laboratory at Cuesta College, San Luis Obispo, CA. This course is a one-semester, optional adjunct laboratory to the Astronomy 210 introductory astronomy lecture, taken primarily by students to satisfy their general education science transfer requirement.)

Let's consider two common methods of discovering extrasolar planets, taking into consideration that these methods do not actually "see" these extrasolar planets directly.
The first method involves observing an extrasolar planet either pass behind or in front of its star as it orbits the star, such that their combined brightness will fluctuate over time. (Video link: "
Distant Planet Flaunts its Light.")
The second method involves observing an extrasolar planet pull on its star as it orbits the star, such that the star will be observed to "wobble" over time, much like the ball pulls back on the hammer thrower as they revolve. (Video link: "
2010 Asian Games - Men's Hammer Throw Final.")

For this lab you will be accessing an enormous amount of data on these extrasolar planets, in order to find patterns and correlations.

One way to organize data is with a
histogram, or "bar chart," where each type of category is tallied up, and their numbers are shown as different heights.

Another way to organize data is with a
scatter plot, or "correlation diagram," where one characteristic is plotted versus another characteristic along horizontal and vertical axes.

So taking all the extrasolar planets from the data set, here shown superimposed on the "same" solar system... (Video link: "
Kepler Exoplanet Candidates.")

...and plotting two properties versus each other on scatter graph, may show the resulting data points seeming to form a pattern, and thus indicating a correlation...

...or may instead seem randomly spread out, and in this case indicating no correlation between the two properties.
So these two types of graphs, bar charts and scatter plots, are very powerful and elegant ways to organize data and to find interesting results that may suggest underlying causes and effects among extrasolar planet properties.

Your personal experience with these tools may vary.