Why You Should Worship the Sun (an Orange One, That Is)

We know from experience that our solar system's sun (Sol by name) does a fab job of supporting life on Earth. We worshipped him for eons and then got away from him with this science stuff and all, but let's let bygones be bygones. Sun worship is the most logical form of theism, if you stop and think about it. The sun gives heat, warmth, light, and life to earth. It keeps the solar system's planets in line and is the ultimate life-giver. So, for ages, it made complete sense to worship this mighty beautiful yellow force in the sky. Now times have changed (sorry, Sol). 

But take heart because it may be time to start worshipping a new type of star--this time with the blessing of science. The latest research shows that our star may not be the best candidate for long-term life sustenance. Edward Guinan of Villanova University in Pennsylvania and his colleagues compared the likelihood of different types of stars harboring planets capable of supporting carbon-based life like our own. The group presented its results at the International Astronomical Union Conference in Rio de Janeiro in August of 2009. The results were nothing short of stunning. Researchers used archival data from the now-defunct International Ultraviolet Survey Satellite to study ultraviolet (UV) and X-ray emissions from various star types and the damage they cause to DNA structures. The calculations were done and then compiled. All stars have a habitable zone, a "goldilocks zone," an area around the host star where temperatures are suitable for orbiting planets to keep liquid water on them. 

Earth's sun is a medium-high to average-high star of average brightness and mass. Stars larger than the Sun produce intense UV radiation that can cause five times more DNA damage than stars similar to the Sun. Ultraviolet light also has a higher energy output than visible light, so it can penetrate a planet's atmosphere much more easily. 

A typical orange K-type dwarf star about
80% the mass of our sun

What happens to stars that are smaller and fainter than the sun? There are two main classes of such stars: They are red dwarf stars (M-dwarfs) and orange dwarf stars (K-dwarfs). These stars are more life-friendly than our dear Sol because they emit less ultraviolet radiation. But small red stars tend to rotate faster than the Sun, so their magnetic fields are stronger. The higher surface magnetic fields of M-dwarfs transport energy into the outer layers of the star, causing violent stellar eruptions called coronal mass ejections. These flares cause a surge of ultraviolet and X-ray radiation that can destroy a planet's atmosphere over time. 

Additionally, M-dwarfs have that annoying tendency of being so faint that the planets that orbit them must be quite close to the star to receive enough heat to support life. This small distance often makes the planet tidally locked, with one side of the planet always facing the star at all times. Imagine our planetary system like a rotisserie chicken, churning over a flame to evenly "cook" us to keep temps normal. M-dwarfs and their planetary systems are not like this and would have wildly uneven temps, with one side very hot and the other very cold, and likely no magnetic fields since said planet cannot rotate to generate a magnetic field to protect any life on the planet from solar radiation.

So it looks like orange K-dwarfs may be the best habitable zone-friendly stars for planets, with lower UV levels than Sun-like stars. Additionally, K-dwarfs tend to live between 30 and 70 billion years verses our Sol's mere 9-10 billion years, which would give longer time periods for the evolution of life to occur. In our galaxy, K-type stars make up about 15 percent of the stellar population, making them much more common than stars like our Sol. Not that we don't appreciate our precious Sol for all he's done! After all, he's brought us this far!