EXOPLANETS (OR EXTRASOLAR PLANETS)

An extrasolar planet (or exoplanet) is a planet that doesn’t belong to our solar system and doesn’t revolve around the Sun. 

The first exoplanet was discovered in 1992, revolving around a pulsar.

In 1995 the first exoplanets orbiting a regular star (Sun-like named 51 Pegasi) were located by Michel Mayor and Didier Queloz. Due to their discovery, they won the 2019 Nobel Prize in Physics. 

In May 2022, it was announced that 5000 exoplanets had been discovered. This number is gradually increasing

Our solar system. On the right is the Sun. We see all eight planets. Earth’s satellite (the moon) is also visible. The eight planets of our solar system are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. Some of the planet’s satellites are marked. Up until now (2022), 53 of Jupiter’s satellites have been named. In the picture, we see only four satellites, which are the most important.
Καλλιτεχνική απεικόνιση ενός κίτρινου αστέρα με τους 6 περίπου πλανήτες του. Μέχρι το 2022, τέτοια άμεση παρατήρηση δεν ήταν εφικτή

DETECTION METHODS

The method to detect an extrasolar planet is indirect. We measure the impact it causes on the star around which it orbits. The most common methods are:

a/ The orbit of one or more exoplanets around a star can diminish the star’s brightness. This reduction occurs only when the exoplanet passes through Space between the host star and the Earth.

b/ When an exoplanet orbits a star, the center of gravity becomes offset causing the star to wobble “back and forth.” For example, the Earth is making the Sun move approximately 500 kilometers. 

c/ There are more methods to detect exoplanets, although their effectiveness is questionable and depends on the system under observation. 

The effort to detect exoplanets intensifies because we want to know if extraterrestrial life exists. We want to know its form and the conditions under which it develops.

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