The Habitable Zone
There are approximately seven billion people living on the Earth right now. Who can picture 1 million people, let alone 7 billion people? Yet the total incomprehension of it does not make the fact any less true. Nobody has ever seen an alien or an organism that has not originated from Earth, yet it does not make the prospect any less valid. Most citizens of Earth cannot imagine living anywhere else but on this blue planet, but that should not make the possibility of it any less real. Space, like the future, is always ahead of us, and no one can predict what it has in store for us or what ideas will be found. Outside of the Earth, life in the universe is not such an inane thought as was once believed. Firstly, there are a number of variables that affect the habitable zone of stars. There is also an insurmountable number of possibly habitable planets that could support life. Finally, evidence of life in outer space have been found, though the evidence is slim.
IN 1953, Hubertus Strughold and Harlow Shapley were the first to mention habitable zone, though the term they used was “Liquid Water Belt” (Handover). Put simply, the definition of a habitable zone is the distance from a host star a planet has to be to maintain liquid water (Palmer). To calculate the length of a star’s HZ, variables such as a planet’s luminosity, temperature, solar irradiance, and distance from the sun are needed. ("Habitable Zone”). Since Earth has such large amounts of H2O, it is not unreasonable to think everywhere else is the same, but in reality it is not. Unbeknown to some, water is actually quite the hot commodity in the universe. A planet has to within a HZ to support water and subjectively to support complex life. If a planet is too close to its host star, then there would be too much emitted heat absorbed and water would be nonexistent because said water would just vaporize. The opposite would happen if a planet is too far away: there would not be enough heat absorbed and any water on the planet would freeze (“Habitable Planets”). Because of this, the Habitable Zone is also called the “Goldilocks Zone”; the distance needs to be “just right”, not too hot, not too cold (“Goldilocks Zone”).
The luminosity of the star plays a role on the length of the HZ as well. The more light a stars radiates, the larger that star’s HZ will be (Palmer). More light brings along more heat. As well as luminosity, another variable is time. As times ticks by, a star’s luminosity increases, and as it increases the margins of the zone will expand. This indicates that, with time, planets within a HZ could change (Lissauer). Then there is the Greenhouse Effect, a planet with a plentiful hydrogen atmosphere might be able to extend its HZ. The Greenhouse gas would be able to absorb heat and extend the HZ up to fifteen astronomical units (AU). One AU is defined as the distance between the earth and the sun (Baalke). Though the range extended would depend on the type of...