Although there are a large variety of planets which can exist according to our laws of physics, there is a special class of exoplanets which grasp our attention more than anything else.
Earth like exoplanets are planets which are similar in size and temperature to that of Earth’s and can potentially be birthplaces for living organisms much like the ones found on Earth.
The study published in ‘Nature’ found that two of the planets have orbital periods of about 1.5 days and 2.4 days respectively, and the third planet has a less well determined period in the range of 4.5 to 73 days.
Astronomers focused the Belgian TRAPPIST telescope on the star now known as TRAPPIST-1, a Jupiter-sized star in the constellation Aquarius that is one-eighth the size of our Sun and significantly cooler.
This chart shows stars visible on a clear dark night in the Constellation Aquarius. The position of dwarf star TRAPPIST-1 is marked. ESO
The planets were found by calculating the dim in the brightness of the star as the planets passed in front of it, blocking some of its light.
By measuring how much light is blocked, astronomers can calculate the size of the planets. A red dwarf is a type of star which is much cooler than our Sun, and the Milky Way galaxy is full of them.
Once the astronomers know the size of the planet they can predict its distance from the star and thereby predict its surface temperature.
Red dwarfs emit most of their energy in the form of infrared radiation suggesting that if life exists on these planets then it might have evolved by drawing energy from infrared rays.
Another artist’s rendering of the exoplanet.
About 20 years ago, astronomers around the world weren’t even sure that planets existed outside our solar system, but in the last few years we have found more exoplanets than in all of human history. It is predicted that on an average every star in our Milky Way has about 1.6 Earth-like exoplanets which orbit their star. With about 300 billion stars in our galaxy, that’s almost 500 billion Earth-like planets in Milky Way alone. And the observable universe has about 100 billion galaxies!