Stars and Habitable Zones

The more scientists study Earth and other objects that surround us in space, the more variables we realize must be carefully controlled for life to exist. Many times before, in our posts, our videos, our books, and our printed quarterly, we have discussed the growing list of parameters that must be carefully chosen. NASA posted a graphic of different kinds of stars in the cosmos and whether they could support life. This picture of stars and habitable zones adds to our understanding of the unique qualities of our Sun.

Water is essential for life. Science defines life as having properties such as moving, breathing, eating, reproducing, and responding to outside stimuli. We don’t discuss “rock people” or “gas people” because they don’t fit that definition. For that reason, scientists are interested in stars and habitable zones–the just-right “Goldilocks zone” surrounding a star where water can exist as a liquid.

In their daily posting on apod.nasa.gov for January 31, 2020, NASA gives the distribution of Goldilocks zones for G spectral stars like our Sun, which are yellow, K dwarf stars, which are orange, and M stars, which are red. The other spectral groupings, such as blue stars, are not considered because of their high radiation levels and activity, which would make life impossible.

The most common type of star in our galaxy, making up 73% of all stars in the Milky Way, are M stars. These red stars have very active magnetic fields and massive radiation. Their Goldilocks zone would be minimal and very close to the star. Orange K stars make up 13% of the stars in the Milky Way. They have a modest Goldilocks zone but are fairly active with some radiation levels. Yellow G type stars like our Sun, make up only 6% of the stars in the Milky Way. These stars have very large Goldilocks zones, and they are very quiet compared to K stars.

As we consider stars and habitable zones, we must realize that the type of star is just the beginning of the variables necessary for a star system to support life. Other critical factors include the size of the star, the location of the planet relative to the star, and the shielding a planet has for protection from the radiation of the star. Also, the stability of the star’s location in the Milky Way is another factor that goes into a life-supporting planetary system.

Our existence is not a product of chance. The more we learn about the Earth, the Sun, and the stars and habitable zones within the Milky Way, the more we understand that the statement, “In the beginning, God created the heaven and the earth” is a massive understatement of what God did to make a place for us to exist.

— John N. Clayton © 2020