What is an Exoplanet?

The first time I was exposed to exobiology I was twelve years old.  I received a Star Trek Collectible Card Game deck for Christmas and read each card intently.  One of the skills of some of the officers was exobiology.  Of course at the time I looked up the meaning but there was not much written about it.  Science teachers at school dismissed it as science fiction.  The Merriam-Webster dictionary defines exobiology as "a branch of biology concerned with the search for life outside the Earth and with the effects of extraterrestrial environments on living organisms."  I suppose if my science teachers were well read they would know the first NASA funded exobiology project was in 1959 and that it was certainly a legitimate field of study in the 1990s.  Today, many exobiologists (also known as astrobiologists) work all over the world in this growing field of study.

The timing of this blog entry coincides with some great news.  NASA announced today that a solar system was discovered containing seven Earth sized planets.  Three of these planets are in what is known as the habitable zone or 'Goldilocks Zone'.  Recall the fairy tale "Goldilocks and the Three Bears" where the titular character would find the object 'just right' for her use.  The habitable zone is a region around a star where, based on a set of criteria, a planet could support liquid water.  Liquid water is biochemically important to life.  Some have proposed the habitable zone be extended to include other solvents for theoretical organisms of different biochemistry.

The star at the center of this solar system is an ultra-cool dwarf star.  It is so cool that all seven of the planets in the system orbit closer to their host star than Mercury does to our own.  An artistic rendering of the star system is shown below courtesy of NASA/JPL-Caltech.

TRAPPIST-1 Star System (NASA/JPL-Caltech)

I reached out for a comment from Astronomer Dr. Sarah Rugheimer at the University of St. Andrews

"This discovery is very important for two reasons. One, these planets' atmospheres, should they exist, can be detected with JWST, providing a unique system with three habitable planets. Second, due to the ultracool host star they orbit, many questions remain about the stability of such planet atmospheres and the UV environment of the host star. These planets offer us a laboratory of a diversity of Earth-sized planets in one system to learn more about planetary evolution."

A link to her webpage is provided below:

http://www.st-andrews.ac.uk/~srm26/

Note: JWST - James Webb Space Telescope - to be launched 2019.

To answer the question posed as the title of this blog entry, an exoplanet is simple a planet orbiting a star that is not our sun.  Can you see them from your backyard? No.  However, backyard astronomers can plot light curves of variable stars.  A variable star is simple a star that's magnitude changes irregularly or at regular intervals.  In some cases when a planet transits across the face of a star its magnitude will decrease measurably.  Backyard astronomers can plot the magnitude of the star  over a specific time interval and note possibly regularities.  This information can be used for professional astronomers in their search for exoplanets.  There are several people in the Calgary Centre of the Royal Astronomical Society of Canada who do this very thing.

I hope you keep tuned for more news in the field of astrobiology and its influence on the way we see the universe!