Scouring Space for Life: More Earths out there than we thought?

The conditions on Earth are perfectly tailored for sustaining life; ozone that keeps the planet from being too hot or too cold, oxygen and water are all key components in the advancement of the human race. It was once believed that it was in the realm of science fiction to believe that another planet could be discovered with similar habitable conditions to Earth and if by some chance this planet did exist, humans would never be able to find it. This is an understandable theory, seeing that there are billions of stars in the universe and the current limits of technology only allow humans to monitor a relatively small fraction of the sky. In recent years however, astronomers have been focused on attempting to identify planets that could possibly sustain life. Though this seems to be one of the largest and costly games of finding the needle in the haystack, astronomers have actually made a great deal of progress in the field and have gained more understanding into possible planetary conditions that could support life, along with the discovery of a few planets that are considered candidates for sustaining life.

One of the main problems in attempting to find planets that are capable of sustaining life is the theoretical understanding of what conditions are necessary for forms of life to survive on a planet; it has been discovered that conditions do not actually have to be identical to that of Earth. In our solar system, the Earth is the perfect distance away from the sun, but few other planets have the advantage of being the right distance away from the star that they orbit. Planets that are too close to their star are almost completely ruled out of consideration for being able to sustain life, because scorching temperatures destroy their atmosphere and subsequently all chances for life. In the case of planets that are farther away from their star, the case becomes a little harder to interpret. While it is more difficult for life to exist on a cold planet, it is not impossible. Raymond Pierrehumber of the University of Chicago believes that the traditional greenhouse gases, such as CO2 are not necessarily the only gases that can create a life sustaining atmosphere. It is his belief that hydrogen, a gas that does not negatively respond to cold temperatures (such as the case for carbon dioxide and water vapor), could create a greenhouse effect that creates an atmosphere. In the case of planets with a hydrogen atmosphere, the planet would be able to keep water in liquid form, which is a key part of a planet’s ability to sustain life. At this point however, planets with a hydrogen atmosphere are simply a theory, but this theory is very important in redefining astronomer’s previous assumptions about the necessary conditions to sustain life on a planet.

While a planet with a hydrogen atmosphere is merely a theory, the planet Gliese 581d is reality. This planet, which orbits a red dwarf star, is believed to have qualities that would allow for life on the planet. It is believed that the planet is the right distance away from its star to have an atmosphere; the only issue is that one side of the planet is never exposed to its star. While scientist originally felt that this eliminated the possibility for Gliese 581d to sustain life, recent developments suggest otherwise. Some astronomers theorize that, because 581d orbits a red dwarf star that creates a more effective penetrating form of sunlight, it may be possible for the star to heat both sides of the planet. Scientists are still investigating planet 581d, as they continue their hunt for a planet sharing in the Earth-like ability to sustain life.

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