Earth and Goldilocks

In my childhood I read the story of goldilocks and three bears. Where a small girl enters a cottage   owned by three bears and finds three bowls of porridge. One is too hot and the other is too cold but the third one is just right. She finds three beds where one is too big and the other too small but the third bed is just right.

I was surprised to read an article by an astrobiologist where they described Earth as a Goliddlock planet in the Goldilock zone. In astrobiology, the goldilocks principle applies to a range of distance that a planets orbit can be from the star and maintain the temperature that are just right for liquid water.

The Goldilock zone or habitable zone is the range of distance with the right temperature for water to remain liquid and the planets that fall within this zone are called Goldilock planets. There are 1780 confirmed planets beyond our solar system and as many as 16 are located within their star’s habitable zone. Goldilock zone is determined by astronomers to be between 0.95 AU to 1.67 AU where AU is the astronomical unit which is the average distance between the earth and sun and Earth falls nearly within the range at 1 AU..

Even if the planet is habitable it does not mean that it is inhabited. It depends on a lot of other factors like atmospheric pressure, composition, gravity, etc, to make it a habitable planet. Moon is in habitable zone but too small and gravity low so that there is no atmosphere and hence not inhabited.

A recently detected planet 493 light years away from earth Kepler-186f is close to earth’s size and is located in its solar system’s habitable zone.  This is the first planet which is just right to be inhabited. But this has a basic assumption that liquid water and atmosphere is need for a planet to be inhabited but what if there are species which can tolerate and grow in different atmospheric conditions and different range of temperature and gravity.  Only time will tell.