The planets in the solar system are known to revolve in orbit around the Sun. There are planets, however, that move in an orbit around other stars and not the Sun. These are called extrasolar planets or Exoplanets.
They are not easily seen with the help of telescopes as the bright light of the star they orbit around hides them. Astronomers use different techniques and methods to spot and study these planets.
The first-ever evidence of an Exoplanet was found in 1917 though a confirmed detection occurred first in 1992. At present, there are over 4900 Exoplanets in more than 3600 planetary systems. All the stars have one or more planets orbiting around them.
Exoplanets can be discovered in several different ways. One of the most common ways is to spot wobbly stars. A star with planets orbiting around it has an off-centre orbit that makes it look like it is wobbling from a distance.
This method has made it possible to discover so many planets outside the solar system. However, this method helps find only large planets because smaller ones create tiny wobbles which are difficult to detect. Moreover, such methods suffer from observation bias whereby most planets are detected close to the stars.
In 2009, NASA had launched Kepler, a spacecraft designed to detect Exoplanets. It searched for planets of varied sizes orbiting around stars of different temperatures. Some of the planets detected by Kepler included those located in the habitable zone of the star where life can exist. It used the Transit Method.
In this method, the way a star's brightness changes during the planet's transit are noticed to figure out the size of the planet. The time between transits helps find out how distant the planet is from the star. The Transiting Exoplanet Survey Satellite (TESS) mission is expected to find more Exoplanets located near bright stars.
Discovery of Exoplanets
One of the most recent special Exoplanets discovered by scientists is the TOI-2180b. It is of the size of Jupiter and is 379 light-years far from the Earth. It is a gas giant like Uranus, Jupiter, Saturn, and Neptune. It is unique because it takes 261 days to complete a revolution which is not normal for Exoplanets. The TESS of NASA helped Tom Jacobs to discover this Exoplanet.
Most Exoplanets detected so far are in the Milky Way galaxy. The discovery of Exoplanets has led to an increased interest in the search for extra-terrestrial life which involves looking for habitable planets around stars.
FAQs on Exoplanets
Q.1. Which is the biggest Exoplanet found to date?
The HR 2562 b is the largest of the Exoplanets confirmed to date, which is about 30 times more massive than Jupiter.
Q.2. What is the least massive Exoplanet?
Draugr is the least massive of the Exoplanets discovered so far with a mass twice that of the Moon.
Q.3. Which is the hottest Exoplanet?
The hottest Exoplanet discovered so far is the Kepler-70b.
Q.4. Is there any Exoplanet like the Earth?
Kepler-452b is an Exoplanet located at a distance from its star analogous to the Earth and the Sun. Though about 60% bigger than our planet, it is a rocky planet in a habitable zone of a star similar to the Sun.