The Search For Life
As we explore the universe and venture into the great beyond, we humans recognize an apparent desire that is always lingering in our subconscious. This desire to understand our place in the universe. Are we alone? How common is life in the universe? This article will take you on a journey to explore our solar backyard and what lies outside of our picket fence. Our journey begins at home, with a simple equation, the Drake equation. The equation accounts for the necessary amount of time, the number of planets that contain a livable environment, planets with life, intelligent life, and the rate that planets, stars, and galaxies form.
The Drake Equation
The Drake equation deduces the probability of intelligent life in our universe. However, without the data or technology, this equation won’t be accurate. It has only been 29 years, January 1992, since the first exoplanet was discovered. Since then, we have confirmed 4,375 exoplanets and have another 5,900 candidates!
Exoplanet Discovery Methods
The process for becoming an exoplanet starts with the first recording of that exoplanet and must be observed three times. Exoplanets can be recorded through various methods and use any combination of the methods for confirmation. The direct imaging method is very rare and occurs when an astrophysicist captures an actual image of the exoplanet candidate. The transit method, the most common method used to find exoplanets and done by observing dips in the luminosity of an exoplanet’s parent star(s). For example, our star the Sun is our parent star. If Earth were to be observed from the outside looking in when we pass by we would see a dip in light from the Sun. What we see as a solar eclipse on Earth, is how astrophysicists observe exoplanets. Next, using the radial velocity method, or trying to see a Doppler shift of red or blue coming from the position of a star that is caused by the gravity of orbiting planets. The astrometry method is where the vibrations are very precise and show the star shifting because of the orbiting planets. The gravitational microlensing method is where an astrophysicist uses the passing of a star in front of another star to peer into the depths of that star’s solar system, like looking through a keyhole.
Of the 4,375 exoplanets confirmed, we can begin to classify and cluster the observed exoplanets. The different types were gas giants, like Jupiter and Saturn, that also contained the new planet type, hot Jupiters. These hot gas giants are Jupiter-sized stars or larger that are orbiting very close to their parent star causing them to be extremely hot. Neptunian-sized stars are stars of similar size to Uranus and Neptune, it is also speculated that they have a rocky core. Super-Earths, terrestrial planets that are larger than Earth but smaller than Neptune. Our earth is considered a terrestrial planet, or anything Earth-sized or smaller that contains carbon, rock, water, or silicate.
The Ingredients for Life
The best way for humans to understand what is necessary to create life, we must first look at where there is life. On Earth, life is abundant and can be seen everywhere, but without chemistry and molecules, none of us would exist. With a few elements, carbon, oxygen, hydrogen, and nitrogen we have organic chemistry, or what is contained in almost all life forms. Specifically for humans, we also require phosphorus and calcium, without those elements we wouldn’t have a skeletal system and couldn’t move. In organic chemistry, those four elements help to create the compound necessary for life, amino acids. All life is comprised of approximately 20 amino acids. A famous experiment called the Miller-Urey experiment, created by Stanley Miller and Harold Urey in the 1950s that showcased how amino acids could’ve been created in the early days of the Earth.
The experiment illustrates the way this could happen in nature. Water found from the oceans containing different gas molecules that are probably from volcanos gets struck by lightning. The event causes a reaction and amino acids begin to form. Then after millions to billions of years, life adapts and evolves until it becomes “intelligent.”
What is intelligent life? What is considered intelligent versus unintelligent? Are dolphins or chimpanzees intelligent? What makes a species intelligent is defined as the ability to communicate outside of our planet using waves. As humans, we have only recently been considered an intelligent species when Voyager 1 began communicating the message of Earth in 1977. Based on this definition dolphins and chimpanzees are still considered primitive species but maybe one day we’ll come in contact with another intelligent species.