1.0 – INTRODUCTION
Our Galaxy, named the Milky Way, – and even though it contains billions and billions of stars – is swarming with exoplanets1. Exoplanets, known as planets situated outside of our solar system that orbit other stars, have become an active part in the research field of astronomy2. A multitudinous amount (over more than 3,500) of exoplanets have been discovered since 1992, orbiting stars other than our sun1, which has led scientists and astronomers to believe that the universe is flooded with other worlds. In January of 1992, astrophysicists Aleksander Wolszczan and Dale Frail came across the first discovery of an exoplanet2. They founded three exoplanets orbiting the pulsar PSR1257+12 in an unforeseen environment2. In 1995, another discovery was made by astronomers Michel Mayor and DidierQueloz, who founded the first exoplanet around a main sequence (“normal”) star, calling it 51 Pegasi b (Fig 1.0)2. The planet, a gas giant, is believed to be about half the size of Jupiter4. By using a technique called microlensing, 2,000 extragalactic planets for every one star beyond the galaxy was founded by scientists at the University of Oklahoma (Fig 2.0)5. Since the first discovery of an exoplanet, which was founded two decades ago, the number of known exoplanets has doubled every 27 months6. As of this writing, approximately 3,588 exoplanets have been confirmed7.
1.1 – STATEMENT OF AIM
This purpose of this report is to go in-depth and discuss the current state of knowledge on exoplanets, as well as review two main themes: how exoplanets are studied and detected (what scientists look for in their search for exoplanets) and the importance of their study, including current and future proposed missions.
2.0 THE SEARCH FOR EXOPLANETS
To get a better understanding of our universe, and to find out even more about the origins of life, research in the area of exoplanets is critical8. One thing that scientists and astronomers must address in the current search for exoplanets is to discover Earth-like planets that are in a star’s habitable zone8. The habitable zone (Fig 3.0) is a region where life can potentially exist, due to the planet’s surface temperature which allows for the formation of water in the liquid form to flow8. Agencies and other institutions including NASA are in search of a special kind of planet: One that is of similar size to the Earth, orbiting a sun-like star in the region of the habitable zone10. The Kepler Telescope (Fig 4.0) is known for identifying several small and rocky planets in this region1. Earth, for example, is in the habitable zone of the sun which explains why our planet has liquid water such as oceans and lakes6. Water, being the main support system for all life on Earth, is important, because as we know it, life on Earth began with water6. Techniques in observation have now advanced to a level where scientists are able to find “Super Earths” (planets that are less than 10 Earth Masses) that might be habitable11. Absorption features and the transmission spectrum of a planet can help to characterize a planet’s atmosphere and its habitability11. What creates a planet’s spectral fingerprint is its spectrum, which contains traces of atmospheric species11. In order to detect these species, biomarkers are used, and if a strong abundance is detected, it suggests a biological origin11. The investigation for the signs of life is wholly based on the supposition of extraterrestrial life and the fact that it may share essential characteristics with life on Earth11. Because life on Earth requires liquid water (as a solvent as well as a carbon-based chemistry), life based on a different chemistry would generate signatures in the atmosphere which would be considered foreign11. Therefore, it is assumed that there is potential for extraterrestrial life similar to life on Earth11. There are many things that are problematic about having a Super-Earth in a red dwarf’s habitable zone. Red dwarfs have generally not been considered feasible successors for hosting habitable planets12. Red dwarfs, characterized as small and dim, are relatively close to the habitable zone that surrounds them12. For one, it would be a difficult environment to live in because of radiation12. Another problem is the phenomenon of tidal locking, defined as when a planet keeps its side faced towards the sun, taking in almost all the heat12. Therefore, it would be too cold on one side because it would be dark with freezing temperatures, and too hot on the other because that side would be the one receiving all the sunlight, as well as being the side with hot temperatures. So, the habitable zone would have to lie somewhere in the middle, making it suitable for life13. Another problem with red dwarfs are solar flares, that shoot off a star several times per day, showing huge increases in UV radiation, which in turn could potentially sterilize the surface of a neighbouring planet12. With the advancement of technology, the search for Earth-like planets will continue, and the potential for finding exoplanets that have the ability to support life will increasingly become more likely to find.
3.0 THE IMPORTANCE OF STUDYING EXOPLANETS
The hunt for other worlds like our Earth has brought upon intense excitement and interest surrounding the discovery of exoplanets7. The current and near-future approved missions (Fig 5.0) are helping to extend the frontiers of knowledge in the study of exoplanets, mainly to search for habitable worlds14. Some important exoplanet missions include: The Transiting Exoplanet Survey Satellite15 (also known as TESS), and the future known mission: The James Webb Space Telescope (JWST), scheduled to launch in 201915. The TESS Mission (Fig 6.0) is a satellite used to discover exoplanets by using the transit method, and during a two-year period, it will monitor the brightness of over 200,000 stars15. Designed to identify planets, it will recognize a wide range of planets, for example, from Earth sized planets to gas giants15. It will also search for temporary drops in brightness of stars and will cover quite a wide span of orbital periods15. The James Webb Space Telescope (Fig 7.0) will be optimized for infrared wavelengths and will be able to analyze the history of the universe, having the ability to find galaxies that formed in the early universe as well as the formation of other solar systems15. Space missions are now able to give us statistics, such as the number, size and orbital distances of planets, from terrestrial planets to gas giants11. By doing so, it will help to characterize other planets11. Future space missions are also said to characterize the atmosphere of a planet and the observation techniques that are being used will have advanced to the point where we could find planets of less than 10MEarth (Super Earths) which, around small stars, may be habitable11.
There are also great benefits that come with space research, such as the socioeconomic aspect. Space research has become a way to unify humanity by increasing connectedness, communication, and self-awareness through images such as “The Day the Earth Smiled”, shown in Figure 8.016.
4.0 – CONCLUSION
The study of exoplanets is truly interesting because exoplanets have the capacity to solve mysteries about our own Solar System. The approaches for finding life have certainly been centered on Earth life, its features, and characteristics because Earth is the only example of life as we know1. Space missions like the James Webb Space Telescope will aide in capturing images of distant planets with our ever expanding knowledge5. Not every planet is the same age and working out what a planet looks like when it’s still young will help to understand what Earth might have looked like, both physically and chemically. As we discover and learn more about exoplanets and what they can teach us about our own world and worlds beyond what we can understand, the potential for advancement as a human race will only increase in knowledge and advancement.