Planet Profile: Gliese 581g

Official Name: Gliese 581g
Unofficial Names: Zarmina's World, Zarmina
Discovered: September 29, 2010
Discoverer: Steven S Vogt et al.
Mass: 3.1 - 4.3x that of Earth
Orbital Period: 37 days

Welcome to Gl 581g, or as Steven S Vogt and others have begun calling it, Zarmina's World or just Zarmina in honour of his wife. This is perhaps the most amazing planet yet discovered by Man because it is the first known planet other than Earth and Mars to rest solidly within the habitable zone of its parent star. It orbits the star Gliese 581, a red dwarf some 20.5 ly (or roughly 6 parsecs) from our sun.

As yet there remain enough credible scholars who doubt its existence to prevent it from being officially accepted as a discovered world. Astronomers Francesco Pepe and Mikko Tuomi performed their own analyses of the data gathered by Vogt and his team and concluded that the planet does not exist. However, Guillen Anglada-Escude and Rebekah Dawson, after performing their own analyses, say that the existing data support's Vogt. Only time will tell which is correct.

If Zarmina does exist, however, it will have amazing implications. Let me put it to you this way. Gl 581 is 6.3 parsecs (abbreviated "pc") from our sun. Stars that have decent habitable zones (and therefore candidates for having habitable planets) are typically yellow stars like our sun, red dwarfs like Gl 581, or somewhere in between. The number of stars like that within a 6.3pc radius from our sun are ~116 (roughly 85% of the total number of stars within that distance). Of those 116 stars, we have found 1 with a habitable world. That's about 0.86% of those stars. I know that doesn't sound like much, but bear with me.

There are between 100 billion and 400 billion stars in the Milky Way galaxy alone. Assuming our stellar neighbourhood is typical, 85% of those stars will have decent habitable zones. That's between 85 billion and 340 billion stars. And if we assume that 0.86% of those stars have habitable worlds, that leaves us with 731 million to 2.9 billion worlds that would resemble Earth, Mars, and Zarmina. That is a truly staggering figure. And that's for our galaxy alone, not even counting the rest of the universe!

Before 2010, we had no real idea how many habitable worlds could be out there. There were guesses, but they were shots in the dark. Zarmina provides us with the first actual example of a habitable world beyond our own solar system, and gives us a solid figure to work with for the first time in history, making our projections educated guesses rather than shots in the dark. We have our first real glimpse into what the universe beyond our solar system is like. And that is why this planet is so special.