Teachers conduct the high school lesson Thermally
Habitable Zones at a 2005 Journey through the Universe
educator workshop in Hilo, Hawaii. As part of the grade 9-12
Unit of the Are There Other Neighborhood Like Our Own? Module,
this lesson uses bulbs of different wattage to serve as remarkably
good analogs to different luminosity stars. Temperature sensitive
liquid crystal strips, positioned radially relative to the bulb,
identify the Thermally Habitable Zone around the ‘star’, which is
the annular region around the star where liquid water can exist.
This physical analog very effectively demonstrates that the higher
the luminosity of the star, the farther away, and wider is its Thermally
Habitable Zone. The wider the Zone the higher is the probability
that a planet formed in that zone—a planet potentially capable of
supporting life.
The lesson also includes discussion of the lifetime of stars, with
the shortest lifetimes for the higher luminosity stars. Thus
stars appropriate for astronomers to explore for Earth-like planets
are those with reasonably wide Thermally Habitable Zones, but also
lifetimes long enough for life to evolve—stars like our Sun. |