In a previous article, we discussed the different ways that scientists could utilize to detect and discover new exoplanets. In this article, we are going to discuss which are the Top 5 Exoplanet Detection Mechanisms!

The Top 5 methods to detect exoplanets are:

5) Astrometry

This method has scientists determine if measurements in a stars position in the sky has moved over time. This method is theoretically possible to utilize, but is very hard to implement because it requires looking at very minute wobbles in the orbits of planets. These wobbles indicate an irregularity in the orbits of stars, which can indicate he pull of an object such as an exoplanet.

Astrometry is the oldest method used to search for extrasolar planets. As early as 1943 astronomer Kaj Strand, although his claim remains unproven and is seen as highly skeptical by scientists today. When done successfully, astrometry is much more accurate as it does not depend on the distant planet being in near-perfect alignment with the line of sight from the Earth, and also can help determine the size of the planet with greater detail. This means that astrometry can be used for a greater number of stars, if done properly. [1]

However, this sensitivity is also a downside as the degree of precision that is required can seldom be be achieved by the most advanced telescopes today.

Number of Exoplanets Found: 1

4) Direct Imaging

This method works best for young planets that emit infrared light and are far from the glare of the star. Direct imaging works well for exoplanets with large orbits that don’t cross the stars orbit. However, this method doesnt allow for the detection of several exoplanets at once and doesnt help scientists find exoplanets around bright stars. There are plans for future missions and projects that would make direct imaging easier for astronomers. Planets were first found using this method in 2008 and have had more finds since then as photography improves to meet the demands of finding exoplanets.

Number of Exoplanets Found: 50

3) Gravitational Microlensing

This method was predicted in 1936 by Einstein using his General Theory of Relativity. When one star in the sky appears to pass nearly in front of another, the light rays of the background source star become bent due to the gravitational attraction of the foreground star. It was not until 1989 that the first objects were discovered using this method, but the first exoplanets were found using this technique was made in 2003. Microlensing, furthermore, is most sensitive to planets that orbit in moderate to large distances from their star.

This technique is great for exoplanets very far away from Earth and exoplanets that either orbit far from their stars or are free floating. This is because microlensing is capable of finding the most distant and the smallest planets of any currently available method for detecting extrasolar planets.However, this method is not great for finding the same exoplanet 2 times, nor is it good at finding many exoplanets at once. Microlensing, furthermore, is most sensitive to planets that orbit in moderate to large distances from their star. However, downsides to using this method is that microlensing events do not repeat. Moreover, microlensing only lets astronomers know the rough estimation of the distance of the detected planet form Earth. 

Number of Exoplanets Found: 96

2) Radial Velocity

The radial velocity of an object with respect to a given point is the rate of change of the distance between the object and the point. That is, the radial velocity is the component of the object’s velocity that points in the direction of the radius connecting the point and the object. Therefore, when applied to exoplanets, this shift in movement between planets corresponds to gravitational tug of its smaller exoplanet.

When viewed from a distance, these slight movements affect the star’s normal light spectrum, or color signature. The spectrum of a star that is moving towards the observer appears slightly shifted toward bluer (shorter) wavelengths. If the star is moving away, then its spectrum will be shifted toward redder (longer) wavelengths.

This is great for finding big exoplanets with close orbits to their orbiting star and great for measuring exoplanet mass as well as great for us by ground-based telescopes. the radial-velocity method that it cannot accurately determine the mass of a distant planet, but only provide an estimate of its minimum mass. This is a serious problem for planet hunters, because mass is the leading criterion for distinguishing between planets and small stars.

Number of Exoplanets Found: 802

1) Transit

This is by far found the most exoplanets out of every method available. A transit occurs when a planet passes between a star and its observer, so will occur when the exoplanet passes in front of the star. When this occurs, the light curve will show a dip in brightness.

Thee resulting data can provide scientists with crucial information that can help determine a variety of different exoplanet characteristics. The first exoplanets found using transit method was in 1999, with many more found later and many different options to move forward with this method. http://www.exoplanetes.umontreal.ca/transit-method/?lang=en

This method is great for finding exoplanets in close orbits, measuring exoplanet diameters, and is a great method for use by space telescopes. Disadvantages of this method include not being able to measurer the mass of the exoplanet being observed, being unable to determine whether the blocking plant is actually a small start, and is not ideal for finding exoplanets that dont cross their star.

Number of Exoplanets Found: 3176

Sources And Further Reading

https://exoplanets.nasa.gov/alien-worlds/ways-to-find-a-planet

[1] = https://www.planetary.org/articles/wobbly-stars-the-astrometry-method