This one is an interesting one. This is a relatively simple comic that relies only on scale to get its point across. The point being that there are tons and tons of planets in our galaxy and we need to learn about every one of them as soon as possible.
As a point of reference, an exoplanet is a planet that is outside of our solar system and thus orbits a different sun. We only have a few ways of finding exoplanets. The main method being to observe stars and notice when they seem to get dimmer. This means that some body of matter has passed "in front" of that star (more correctly, between that star and us, blocking some of the light from reaching us).
This comic was made in response to scientists finally having the right equipment and finding a roughly Earth-sized planet. Previously, we had only found planets approximately Jupiter size or larger.
Exoplanets have been discussed before in comic 786: Exoplanets.
[An enormous diagram of dots, mostly of varying shades of brown and greenish yellow, with a number of smaller blue dots and larger red dots.]
All 786 known planets (as of June 2012) to scale.
Some planet sizes estimated based on mass)
This [indicating a small section of 8 planets out of the several hundreds] is our solar system. The rest of these orbit other stars and were only discovered recently. Most of them are huge because those are the kind we learned to detect first, but now we're finding that small ones are actually more common. We know nothing about what's on any of them. With better telescopes, that could change. This is an exciting time.add a comment!