The Goldilocks Zone

Today, we welcome EPIC 201367065 d to our Goldilocks list.  Perhaps you recall the tale of Goldilocks and The Three Bears.  If so, you recall how Goldilocks entered the home of the three bears and found three bowls of porridge sitting on the kitchen table.  Tasting from each bowl, Goldilocks found the porridge of the first bowl she tasted too hot, the second too cold, but the third bowl of porridge was just right.

Goldilocks ate the third bowl of porridge.

If you understand the simple temperature-based tale of Goldilocks and the porridge, you know all that you need to know about life.  Earth, our home planet, is exactly like the third bowl of porridge.  Our temperature is just right.  If our little blue planet were nudged just a bit nearer to our Sun, we would all burn up and float away as puffs of gas and smoke.  If pushed a bit farther away from the sun, our oceans and streams would all freeze solid and at some point all life as we know it would cease.  Hence, we reside in the Goldilocks zone, sometimes called the life zone or habitable zone.

Theoretically, billions of habitable exoplanets (those outside our own solar system) could exist in Goldilocks zones around Sun-like stars spread all across the Milky Way.  At present, about thirty such planets have been firmly identified.  The nearest of the Goldilocks planets is tau Cet e.  Tau Cet e is 12 light-years distant from us.

Goldilocks zone planets are being added to the list regularly.  Kepler-186f, at 561 light-years, was added last spring.  The discovery of EPIC 201367065 d, spinning away out there at 147 light-years, was announced just this January.  I find myself somewhat comforted by the knowledge that these possible homes exist out there.  We may need them.  So long as we don’t discover the exoplanets teeming with aging Elvis impersonators or vacuum salesmen, we have hope.

As a final note, porridge, for anyone interested, is an equivalent our oatmeal.  And I should note that, technically, Goldilocks was guilty of breaking and entering the three bears’ residence.

   --Mitchell Hegman    Illustration by NASA Ames/SETI Institute/JPL-CalTech