Mankind has a rich history of looking up at the stars and telling stories about them.  One of the best “story lines” is the existence of other worlds, and speculation about the possible inhabitants of those worlds.

It’s hard to believe that the existence of exoplanets has only been confirmed since 1992, with the detection of several terrestrial-mass planets orbiting a pulsar (PSR B1257+12).  The first planet found orbiting a main-sequence star was 51 Pegasi b (in 1995).  You remember 51 Pegasi b, don’t you?  Bellerophon?

Image from NASA - super-Earth size comparison with "default" Earth

Some of you are out there right now bouncing off the walls.  No, I haven’t forgotten Campbell, Walker, and Yang and their 1988 discovery.  It was there in 1988, it just wasn’t confirmed until 2002.

Given that our current detection methods are so primitive, and that we’ve really only been looking for a short time, we might find that planets are very common throughout the Cosmos.  We’ve already found that planets come in more variety than imagined, and we have fun speculating on what type of life might be found on them.

NASA - artist's impression of Chthonian planet

The way we now discuss finding exoplanets now, you’d think all we had to do was pick a star, any star, and start counting.  That’s not at all how it works.  Planets are extremely difficult little critters to locate.  They’re very poor light sources, for one thing, emitting only one millionth the light of their parent stars.  They also tend to get “washed away” in the glare of the parent star.

So, exoplanets are extremely difficult to locate.  Even more difficult would be locating the “signature” of biological life.  In astronomy (as in all things) it’s helpful to know what you’re looking for before you start looking.  As we’re not sure what kinds of life might be “out there”, we’re uncertain yet as to what we should be looking for.

NASA/GSFC/Marc Kuchner - size comparison of different exoplanet types

In the short amount of time we’ve been looking since 51 Pegasi b, an amazing array of planet types has been discovered.  Bellerophon itself is a “Hot Jupiter”, just one type in a crowd; and that’s a pretty interesting crowd.  Check it out:  Super-Earth, Hot Neptune, Hot Jupiter (said that), helium planet, coreless planet, Chthonian planet, carbon planet, iron planet, ocean planet, terrestrial planet, Goldilocks planet, gas giant, eccentric Jupiter, and pulsar planet.

Amazing.  The diversity alone is staggering.  Who know what life forms have evolved to fill these niches.