In the current "Big Bang" theory, which is the dominant theory of how the universe began, and may very well be wrong, the universe isn't old enough for any of its M type stars to evolve off the main sequence as they stay on it for tens of billions -perhaps a 100 billion years. In comparison, our Sun which is a G type star will stay on the main sequence for right around 10 billion years, according to current theories and has used about 5 billion of those up. I will post a link for the stellar classification which goes from type O the largest downward in size to B, A, F, G, K and M. There are ten sub-types in each class running from 0 to 9.
Even though the 1.9 Earth-mass planet is not in the habitable zone, a planet of 7 Earth masses in the same system is. This planet was discovered by the well-known Michel Mayor and his team at the Geneva Observatory. Mayor, along with Didier Queloz discovered the first ever planet detected outside of our solar system on 6 October 1995. This was the 51 Pegasi b planet. So far it is the only planet detected in the 51 Pegasi system, and is larger than the 1.9 Earth mass planet in the Gliese system by a factor of 80. Michel Mayor says it's "amazing to see how far we have come since we discovered the first exoplanet around a normal star in 1995...This is tremendous progress in just 14 years."
Due to its size, it is quite likely that the 7 Earth-mass planet in the Gliese system is not a rocky world like Earth is. In fact, it is conceivable that the planet could be entirely covered by a huge and deep ocean. It is the first likely 'water world' candidate discovered. However, as water is such an abundant element in the universe, astronomers believe there may be countless numbers of these worlds to be discovered. This planet orbits Gliese 581 in about 67 days. It is very fascinating to speculate about what other types of life may be in other solar systems. The water worlds are a good place to start theorizing about other forms of life, as scientists believe life on our planet started in its oceans.
The planets in the Gliese system, as in many other systems (although it is not the only way planets can be detected now) were found by the "wobble" method. When a planet or even a star orbits around another star, astronomers can look at images of the star's light spectrum taken at different times. By comparing the results, astronomers can see a detectable "wobble" in the star's light, and from this they can even tell what the mass of the planet is and how long it takes to orbit the parent star.
Originally, most astronomers only thought life could evolve around stars of stellar types F, G and K. They thought the red dwarf M stars were simply to dim-and many thought that it was unlikely M stars would even have planets due to their small mass. This has certainly been proven wrong.
It is estimated -and of course this is a very, very round number estimate, that there are approximately 70 sextillion stars in the visible universe. That's 7 X 10^22 power of stars. M stars would be about 75% of this number of stars! For reasons yet to be understood, the universe favors creation of low-mass stars over the larger ones. If even just a tiny percent of M type stars can be found to support life, the possibilites for what might be out there in the universe are truly astonishing. The "Steady State" theory of creation is one that posits a universe infinite in space and eternal in time. This theory is coming back into vogue with some scientists. If this theory is correct-and there are many reasons to believe that creation and the universe might be infinite -then who knows what we may discover if we don't blow ourselves up first-or erase ourselves off the face of the planet by any number of other means.
The image is an artist's conception of what a planet in the Gliese 581 system could look like. Here are some links: http://www.universetoday.com/2009/04/21/nearly-earth-sized-planet-watery-world-spotted-near-another-star/
http://en.wikipedia.org/wiki/Stellar_classification . I will return to gryphons and mythical creatures the next time I am online. It may not be today as my back is still killing me and I haven't slept in awhile. Thanks again for your great comments and all the best to anyone stopping by!