Astronomers Stephen Kane and Dawn Gelino at NASA’s Exoplanet Science Institute at Caltech are giving scientists and the public a chance to explore potentially habitable extrasolar planets in a way once described only in the imaginations of science writers.
For example, in the Star Trek universe characters often talked of worlds categorized as “Class M” planets; Earth-like places inhabited by various aliens. Today, exoplanets have become reality and big business for budding astronomers. New detection techniques, better sensitivity, atmospheric measurements and new theoretical modeling have unveiled a host of planet more diverse that imagined in science fiction.
Like Star Trek’s “Class M” planets, astronomers today can accurately characterize the orbits of exoplanets and infer properties of their atmospheres and surface conditions — though an alphabetical classification system has yet to be realized. (Star Trek’s M designation was likely inspired by the more than century-old stellar color-luminosity classification: OBAFGKML.)
Most importantly, we have been looking at normal exoplanets long enough now, at least 17 years, that many of the known planets pass through or remain in the Habitable Zone (HZ) of their parent stars. This is the orbital “sweet spot” where temperatures are just right for potentially life-bearing water oceans to remain stable.
We now know that some of these HZ planets are small enough to be rocky and Earth-sized. What’s more, even the Jovian sized planets in these regions could have large habitable moons (of which Saturn’s giant moon Titan is the archetype for potentially millions of similar moons throughout the galaxy.) And, many of the candidates, largely identified by NASA’s prolific Kelper mission, are within the HZ of their host stars.
Scientists are now facing a housekeeping task of keeping an “address book” of all the exoplanets out there among the stars. A new addition is the online Habitable Zone Gallery (HZG). This database tracks the orbits of exoplanets in relation to the HZ of their host stars.
The website provides an interactive display showing HZs in bright green. The site has tools, graphics, and movies that can be easily used in educational presentations. Users can go hunting for to those planets that spend substantial amounts of time within the HZ.
Fifteen of the most promising systems cataloged to date have planets that spend all of their time in the HZ. It’s intriguing to look at those exoplanets that are in elliptical orbits that dip in to and out of the HZ on a roller coaster ride around their parent stars. The software shows surface temperature skyrocketing and them plummeting along the course of an orbit. Could these worlds of long cold winters and brief torrid summers hold life?
Many of these systems are close enough to be scrutinized by future large space telescopes. This database is a great finding chart for targeting potential abodes of life. This will help identify target planets for follow-up observations and even SETI searches.
Image credit: Habitable Zone Gallery