exoplanets like earth

Exoplanets definition that helps to know everything about exoplanets

Exploring exoplanets outside our solar system grips a long-term hope for human existence. For a long time, Astrologists have tried to find planets outside the solar system. They have continuously tried to find these kinds of planets. Even though it was a myth in past at present they have managed to find exoplanets. In discovering exoplanets at present several exoplanets like earth have been found. Exoplanets are also known as extrasolar planets.

These extrasolar planets are located considerably far from our earth but according to scientists they have an environment that is favorable for life’s existence. Even though these exoplanets lie very far from the earth the indirect detection methods developed by scientists, astrologists and mathematicians have eased the search and discovery of these planets.

Exoplanets Definition

In 2006 International Astronomical union mentioned 3 facts to consider as a planet. To become an exoplanet these facts remain to be same.

  1. It should orbit around a star (Just like earth and other stars orbit around the sun)
  2. It should have a spherical shape and there should be considerable gravity to hold this spherical shape.
  3. This gravitational force should be strong enough to expel other matter outside space from this planet.

As mentioned above extrasolar planets are planets located outside our solar system. The exoplanets can be identified as rocky extrasolar planets such as Venus and even gaseous planets such as Saturn and Uranus. These extrasolar planets are formed by a similar mix of matter formed in our solar system. But according to NASA scientists, this mixture can vary. The more interesting this gets the more time it takes to reach out to these planets. The distance between these extrasolar planets and our solar system is hundreds and thousands of light years. 

Exoplanet types

Scientists have categorized these extrasolarplanets into 4 main types. Because these extrasolar planets are located very far from the earth they are strongly bonded with the orbits of other stars. Because of this to take a year on those planets only takes a few days in the time zone of our earth. Some of these extrasolar planets are bound to orbit around two stars. It is discovered that there are several noticeable differences between these planets from our solar system’s planets. Some of these planets barely see their star’s light and some stay completely dark without light (Sunless planets).

1. Gas Giants

Jupiter is the largest planet in our solar system. This is a gaseous planet. Gaseous planets consist of helium and hydrogen as the main gases. Even Saturn comes under this gas giant’s category. There are several extrasolar planets identified in this category.

2. Neptunian Planets

Unlike Jupiter and Saturn, these do not have gases like hydrogen and helium. These have a surface. These types of extrasolar planets have an atmosphere and orbit cores Neptune and Uranus in our examples for these kinds of Neptunian planets. HAT-P-26 and GJ436 J are some other planets that lie outside our solar system that come under this category. 

3. Super-Earths

These kinds of extrasolar planets have a larger mass than our earth. Formed with various types of rocks and gases they are not as heavier as Neptune and Uranus. As the name implies super earth is larger several times our earth. But several times smaller than planets like Neptune. So you could get a general idea about the size of these planets. Some examples of these kinds of extrasolar planets are GJ15Ab, and 55 Canaries E.

4. Terrestrial Planets

Mercury, Venus, and Mars come under this category. Terrestrial planets can be also called rocky planets. Even though these are half of the size of the earth they have a radius twice as the radius of the earth. According to scientists, these terrestrial planets have signs of atmosphere, oceans, and habitats. The surface and cores of these planets are formed of rocks, iron, and solids or liquids. However, it is not still concluded the fact that these planets have an atmosphere to these planets. TRAPPIST-1e and TRAPPIST-1 d are some examples of terrestrial planets.

Discovering exoplanets

The first extrasolar planet orbiting a Sun-like star was found in 1995 by Swiss astronomers. And for physics, they won a Nobel prize in 2019. The name of the first ever found exoplanet was 51 Pegasi b. The size and mass help to a great extent in categorizing these extrasolar planets. To identify the extrasolar planets which lie outside our solar system, 5 methods are used. But from those five methods, 2 methods are mainly used. Namely, these two methods are the Transit method and the radial velocity method. The extrasolar planet discoveries which have been done up to now are done from the “Kepler space telescope” in project “Kepler mission” which was launched in 2009. Explanations for the main two methods used in identifying extrasolar planets are given below.

Kepler space telescope
Kepler space telescope

• Transit method

Most of the exoplanets which have been identified and known by us are identified using this method. Simply this can be elaborated as below. When an extrasolar planet travels in between an examiner and a star, a transit happens. In this scenario, the planet reduces the light. It’s like a shadow. This proves the fact that there’s an extrasolar planet. This transit method can be used to understand the time takes for a complete revolution and the properties of its atmosphere.

• Radial velocity Method

If a planet orbits around a star, those orbit planets cause the stars to wobble. This wobble causes a change in the velocity of that star. Because of this, the examiners can identify the colour difference of the star. The gravitational tug of the stars affected their orbit of planets. This affects the colour change when it is examined through a telescope. When the star travels toward the examiner the colour of the star turns blue and when travels away from the examiner it turns into red. Examining the change of colour, measuring velocity, and whether it moves because of the extrasolar planet helps us to determine the facts that whether an extrasolar planet exists or not in that location.

Exoplanets like Earth

Earth twin or the Earth analog is an exoplanet that has similar characteristics to Earth. This comes under the category, of Super-Earth. Organizations and individuals have been searching for extrasolar planets like Earth for a long time, trying to make colonies in space. Even though exoplanets have been spread all over the universe they are extremely rare. Up to now, there have been 5200+ exoplanets found from them extrasolar planets which could have life just like earth are very few. According to the data from the Kepler space mission, there are almost 40 million planets that are suitable for life but approximately about 10 light years away from earth. And according to astrological parameters, 24 exoplanets are confirmed suitable for living.

• Kepler-22B

In this Earth analog, the real state has not been still proven but it has been found that its 2.4 times larger and is a gaseous planet such as Uranus. But theoretically, it’s a planet that has an ocean.

• Kepler-69 C

On this planet, the exact size and combination have not been still yet found or revealed. This planet is located 2700 light years away and it takes around 242 days to complete a revolution around its star.

• Kepler-442 B

• Kepler-452 B

• Trappist–1E

• Gliese 667

Sources – NASA.gov / ESA / Wikipedia / space.com