I learned about this a couple weeks ago, but as folks can see from the long tenure John Milton enjoyed at the top of this site, I haven’t devoted as much time to writing as usual as of late. More on that in another post.

But for now, one of the most significant discoveries, at least in my lifetime, was made in late September, when astronomers found the only planet besides Earth that is the right size and in the correct position to support life.

Credit: Lynette Cook; This illustration offers a glimpse of the Gliese 581 system from the perspective of planet G.

Orbiting around a red dwarf star in what is known as the Goldilocks Zone some 20 light years away, the planet known as Gliese 581g exists in an area of its galaxy that is neither too close or too far away from the star to foster ideal temperatures for life. According to Carnegie Institute astronomer Paul Butler,

This is really the first ‘Goldilocks’ planet, the first planet that is roughly the right size and just at the right distance to have liquid water on the surface. …

Everything we know about life is that it absolutely requires liquid water. The planet has to be the right distance from the star so it’s not too hot, not too cold …  and then it has to have surface gravity so that it can hold on to a substantial atmosphere and allow the water to pool.

As we know, Gliese 581g does have water on it, and some scientists think it most probably has liquid water, given the temperate weather conditions. It’s believed that the average temperature range varies between -84 to -49 F with no atmospheric effects added in, while the numbers jump to -35 to 10 F with greenhouse gas effects figured in. That sounds pretty chilly, but half, or more, of the planet’s surface is on the dark side sitting away from its sun, while the bright side could, as I’ve read, approach as high as 160 F.

Either way, it’s  a huge leap forward for science and for those interested in the question of whether life exists on other planets. Remember, of course, that when we say “life,” we don’t mean highly developed mammals like humans or apes, but most likely, we are referring to microbes and other simpler forms. With this discovery and others like it that have turned up water sources elsewhere in the cosmos, perhaps the only question that remains is: Not whether some form of life exists elsewhere, but how long will it be until we, in fact, discover it too?