The smallest extrasolar
On April 5, 2007, a team of astronomers in a European observatory in Chile discovered another planet found outside our solar system. This accomplishment was made through the use of a High Accuracy Radial Velocity for Planetary Searcher (HARPS) installed in a 3. 6 meter telescope (NASA). The smallest extrasolar planet known to date, it was dubbed Gliese 581c after Gliese 581 – the name of the star it orbits. Belonging to the constellation Libra, the planet is 20. 5 light years away or 190 trillion kilometers from Earth. Still, its parent star belongs to the 100 nearest stars to our sun.
Studying the planet up close using current space technology and within a man’s lifetime is still a remote possibility. This is because at the speed of light, it would take two decades of interstellar travel to reach it, about one decade to explore it and another two decades for the return trip. Gliese 581c’s diameter is 1. 5 times bigger than our Earth and is 5 times more massive (The Economist). It completes a full 10. 9 million kilometer orbit in a span of 13 days compared to our planet which accomplishes this in 365 days (Layton). This means that a year on Gliese 581c is equal to just about a week on Earth.
It travels round in between two other planets – Gliese 581d which is farther away and Gliese 581b which is nearer to their parent star (BBC News). Initial information reveals that Gliese 581c does not rotate (The Seattle Times). Unlike here on Earth where days consist of alternating night and day, one side of this planet is always day and the other always night. Gravity is also 1. 6 times stronger there so that if a person weighing 150lbs on Earth would stand on Gliese 581c’s surface, his weight would increase to 240lbs (The Seattle Times).
The new discovery is very significant because it features the first extrasolar planet with the potential to support extraterrestrial life. The initial criterion used in seriously considering this probability rested on theoretical calculations revealing that the planet’s location is within an ideal zone around its parent star. Compared to Earth, the planets around Gliese 581 orbit much closer around it but because the star is cooler, this distance is still favorable to water formation. Known as the Goldilocks zone or habitable zone, temperatures allow for water not to be frozen or in vapor form but in its liquid state.
Water is important in the formation and sustenance of life. The estimated range of temperatures on Gliese 581c is 0 – 40oC or equivalent to 32 – 104oF (The Economist). The average temperature on the side of the planet facing the star would be 20oC. The melting point of water is known to be from 0oC and above. Aside from being in the habitable zone, Gliese 581c can also be able to maintain life based on the presence and characteristics of its atmosphere. The occurrence of life related gases such as methane and oxygen would be a step further in this direction.
The parent star Gliese 581 is classified as a red dwarf which at 3,000oC, is 50 times less than the brightness and energy of our sun (Than & Sample). It is also a third smaller and way older. Yet, it is stable and has a relatively longer lifespan. The latter is based on the fact that red dwarfs have enough hydrogen to burn as energy, enabling them to last far into the geological future (Haas). Since it took billions of years on Earth for human beings to evolve, the parent star’s longer lifespan is favorable if evolutionary processes were to take place on the planet.
Further information has to be obtained to find out the other features of the planet because for now, its small size prevents it from being seen using even the most advanced telescopes such as the Hubble. It is a recognized need that more sensitive instruments have to be developed for direct study to be possible. The HARPS used in the discovery of Gliese 581c is a spectrograph. It merely splits the light emitted by stars where particular patterns reveal the pull of existing planets around it, an indirect way of astronomical investigation (Begley).
Subsequent theoretical calculations then yielded the presumed characteristics of the planet. Computer imaging software, based on planet-formation models, predicts that the planet’s surface may either be rocky or completely covered by oceans (Than). The latter is less likely according to astrobiologists so that Gliese 581c is regarded more as terrestrial or a planet composed of silicate rocks similar to the Earth and moon. If this would be established, the environment in Gliese 581c is anticipated to exhibit exceptional diversity.
Some regions would be dry with no air whereas in others, water and gases would abound a lot more compared to our planet (Science Daily). As the more than 250 previously discovered extrasolar planets were either too near or too far from their parent star or much like Jupiter whose dense, hot gases are hostile to life, the primary aim for scientists is to determine the certainty of biological life on Gliese 581c. Current space related projects such as the Terrestrial Planet Finder of the U. S. and the Darwin Mission of Europe were initiated to serve this purpose (The Economist).
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