The second Earth: Gliese 581 D

The planet is clearly getting small for us. With global warming and all the stuff on high lately, and the population snowballing every instant, the world has become a small place. It’d have been much fun to live in medieval ages, when travels and journeys across the globe took sensible and rational amount time and not a day or two. In earlier times, some people took delight in exploring new worlds and were they were known as explorers and adventurers. Now there is nothing left to explore. In other words, for people like them, the world has ended. So we just have to make our world bigger.

We can leave the earth and move on. But where do we go?

Terrestrial planets

It is my sincere belief that one day we will go on to live on other planets as well. Planets which support life, just as shown in Star trek. However, there are many limitations. Theoretically, life can exist anywhere, since life worms develop according to the atmosphere they are in, and learn to sustain in any habitat. However, it doesn’t mean human can do that. We canonically belong to earth and hence we can survive only in earth like environment. The closest any planet comes to have an earth like environment is Mars, where there isnt a drop of water. All the other planets are either gas giants, with no place to set your foot on, or they have ridiculous surface temperatures. In fact no planet in our solar system is habitable (except perhaps Mars, where it is possible to live in a Hub settlement).

For a planet to be habitable, it must satisfy certain criteria, i.e. it must lie with a habitable zone. Habitable zone is the relative location of a planet from and suitable energy source like a star, which would be ideal for habitation, and would be capable of supporting life( i.e. capable of providing water, rocky surface, atmosphere of suitable density, gravity, planetary rotation, and most importantly a star to provide the planet with energy). It is not to be confused to be planetary habitability, a term which refers to the intrinsic factors necessary to support a civilization.

If a planet lies within the habitable zone, it doesn’t mean that it would be like our earth. Rather, there would be a sound probability of that planet being able to support human settlement. It’s still a hypothetical assessment so far, but we have actually discovered two candidates for our next earths. Gliese 581 C and Gliese 581 D Both of these planets lie in the Libra constellation in the system of Gliese 581 star, which is a red dwarf.

Gliese 581 system lies 20 light years away from us. The planets Gliese 581 C and D both were initially thought to be under habitable zone. However, recently scientists have argued that 581 C would be just outside the habitable zone due to its proximity to the red dwarf. Gliese 581 D however, clearly is a habitable planet.

581 d is super-earth planet (planets with mass more than that of the earth, but less than 10 times that value) with mass nearly 8 times that of Earth. In late April 2009 new observations by the original discovery team concluded that the planet is within the habitable zone where liquid water, and therefore, life, could exist.

Earlier, scientist thought that the planet was too cold to support life. However, the same would be the case with earth, if it were not for the green house effect which contributes significantly to maintaining the proper temperature for us. Similarly, taking in account the speculated green house effect of 581 D’s atmosphere, it would support life.

Wikipedia - According to Stephan Udry, "581 d could be covered by a 'large and deep ocean'; it is the first serious Ocean planet candidate." Gliese 581 d is probably too massive to be made only of rocky material, but we can speculate that it is an icy planet that has migrated closer to the star.

Artist's impression of Gliese 581 D, the new earth

So maybe someday people would be blogging from 581 d, soon after we settle there (assuming that the planet isn’t already occupied by 'other worldly' people). Let us suppose that we start right now for that planet right now. (Helios is actually the fastest man-made space object at 70.2 km/s or 252,792 km/h.) This means at 20 light years it would take about 85,350 years to get there. Doesn’t sound realistic.Nevertheless I believe space travel will improve exponentially with time.

It’s still early to predict. But if you were to ask me if we humans would go to live in Libra constellation someday, I’d be willing to take my chances and place a bet. Remember, no matter how stupid it sounds, we eventually will have to ditch the Earth someday, when our sun will grow up to be a red giant, and burn us out if we stay. In fact, the increase in solar temperatures (10% after every billion years aprox.) is such that in about a billion years, the surface of the Earth will become too hot for liquid water to exist, ending all terrestrial life. Of course till then, perhaps even Gliese 581 D may not exist, but we still would have to leave this world if we want to live.

Here are some few comments from the public to the news article few years back when they first announced the discovery of the second earth.

“Yeah, but gravity is gonna be a bitch once you get there.... Don't take any women because they'll complain about the 50% increase in weight.”

“…gonna suck when we find out it blew up 19 years ago”