Discovering Deep Space

Have you ever wondered how astronomers know so much about the mysteries of the universe? How do they discover so much about places outside of our solar system? Astronomers use highly advanced satellites that are on the ground and in space. These satellites all have different purposes that help astronomers discover and learn new things about space. 

For example, the Kepler Space Telescope’s purpose is to discover Earth-sized exoplanets. The James Webb Space Telescope(JWST) is designed to study the first galaxies made after the Big Bang as well as the formation of solar systems and planets that could potentially be habitable. The Atacama Large Millimeter Array Radio Telescope(ALMA) which is a ground-based telescope located in the Atacama Desert in Chile, detects radio waves in the universe that are used to image the formation of stars, planetary systems, and galaxies. This helps us understand the origins of our solar system and Earth. There are hundreds and hundreds of more telescopes that each have a unique purpose.

One question still remains: What do these telescopes search for to learn about the universe? These telescopes observe brightness, position, and gravitational effects around stars to determine if there are exoplanets orbiting the star. There are multiple different techniques a telescope can use to find exoplanets. One technique is called the transit method. This is the most commonly used method, and it has discovered the most number of exoplanets out of all the techniques. The transit method looks at a star's brightness over a period of time. If the brightness of a star dips periodically, that shows that an exoplanet is present around the star. This is because when the exoplanet passes in between the satellite’s view and the star, the star’s brightness dims as it is partially blocked by the exoplanet. The next most commonly used method is the radial velocity method also known as the wobble method. The radial velocity method observes small shifts in a star’s movement over time due to the gravitational effect a planet has on its star. These small shifts are known as wobbles, and this is caused due to the star and planet orbiting around a shared center of mass. These wobbles change the frequency of light emitted by the star periodically. A star’s light becomes more blue as it comes closer to the viewer, and becomes more red as it moves away. This light change is called the Doppler effect. Observing the Doppler effect provides astronomers with lots of information about the star and the exoplanet that orbits it. The final major technique is called gravitational microlensing. Although there are other smaller techniques that helped to find very few exoplanets, I will only be explaining the main techniques. The gravitational microlensing method requires an alignment of two stars from the viewer’s perspective. The foreground star will bend the light of the background star causing a temporary increase in the brightness of the background star. This warping of light is due to Einstein's general theory of relativity. If an exoplanet orbits the foreground star, it will also bend the light creating another temporary increase in brightness. This increase of brightness lasts a much shorter period since the exoplanet is smaller than the foreground star. Analyzing the small peak in brightness caused by the exoplanet allows astronomers to determine some of its characteristics.

After a telescope detects an exoplanet using one of the methods, it uses spectroscopy to learn more about the exoplanet. In particular, astronomers will study how electromagnetic radiation passes through an exoplanet’s atmosphere. They can observe light absorption and emission to determine the chemical composition of the atmosphere. This greatly helps astronomers learn about all the unique kinds of exoplanets in the universe, and if they might be habitable.

Additionally, astronomers use gravitational waves to learn about things they cannot see such as neutron stars or black holes that are very far away. There are gravitational waves ranging from radio waves to gamma rays everywhere in space. These waves are ripples in spacetime that are created by massive cosmic events such as two black holes merging. Astronomers use these ripples to learn more about the black hole such as how big it is and how far away it is. Studying all these gravitational waves is a part of radio astronomy. Since I am only covering the surface of radio astronomy, feel free to learn more about it if you’re interested.

Source:EXOPLANET DETECTION METHODS: AN OVERVIEW OF TECHNIQUES AND LIMITATIONS