Science & Technology

Sister Solar System and Earth's cousins

After discovering Earth-like planets in 2014 and 2015, the NASA took a step towards finding life outside our own solar system by discovering a new one with seven Earth-sized exoplanets

By Shreeshan Venkatesh
Published: Thursday 23 February 2017
The seven planets could have some liquid water and maybe life on the surface. Credit: NASA
The seven planets could have some liquid water and maybe life on the surface. Credit: NASA The seven planets could have some liquid water and maybe life on the surface. Credit: NASA

Solar system with seven Earth-sized exoplanets

The National Aeronautics and Space Administration (NASA) announced on February 23 the discovery of a solar system with seven Earth-sized exoplanets about 39 light years away from our sun. The discovery is being seen as very significant as the planets found orbiting dwarf star TRAPPIST-1 could potentially harbour life.

NASA has called the newly discovered solar system a ‘sister solar system’ to our own. The dwarf star TRAPPIST-1 is a low-mass, dim, ultracool star (with an effective temperature under 2,430 degrees Celsius) in the Aquarius constellation. All seven planets, apparently, have earth-like masses and could potentially host liquid water- considered a critical factor for the existence of life. While the presence of water largely depends on other properties of the planets, six of the inner planets are thought to be made up of rock and having surface temperatures ranging from 0-100 degrees Celsius, deemed conducive for life.

The TRAPPIST-1 solar system is a compact system in which the innermost planet takes about 1.5 days to orbit the sun while the sixth planet takes 13. Earth takes 365 days to complete the same journey around our sun. The seventh planet is the least observed and has been seen to orbit the star just once thus far. Three of the planets fall in the conventional “habitable zone” of the solar system, but due to the compact nature of the system and the low temperature of the star, scientists believe that even the farthest planet could host liquid water and extra-terrestrial life if it has an atmosphere that traps heat effectively.

The compact nature of the solar system could also have other effects.

Three of the planets fall in the conventional “habitable zone” of the solar system. Credit: NASA/JPL-Caltech


The dwarf star is comparable to Jupiter in our own solar system and the entire system is reminiscent of Jupiter and its moons in our own solar system. It is thought that planets might be affected by the star and each other due to proximity. One of the effects that is being investigated now is that of tidal locking where the celestial body’s orbital period matches its rotational period. This is commonly seen on the moons of Jupiter as well as our own moon where the moon takes 28 days both to move around the earth as well as to rotate on its own axis.

This would imply that one face of the planets would be constantly facing the star while the other side would constitute the “dark side” of the planets. So, while one side is constantly hot, the other could be devoid of direct heat from the star and this could do some strange things to the temperature profiles and gradients of the planet.  

Although the initial indications are promising, scientists maintain that the discovery of the potentially for life in solar system does not automatically mean the presence of water or life and that there is a lot that remains to be ascertained about the system like the atmospheric composition of the planets.

Earth-sized exoplanets are speculated to be several in number in the galaxy. The past few years have seen a number of newly discovered exo-planets that resemble our home planet although discovery itself is simply the first step in the search for habitable and inhabitated planets. The focus now is going to be on studying the conditions prevalent in the TRAPPIST-1 system.

Back in 2014, Kepler 186f became the first validated Earth-size planet in the habitable zone of another star. The next year, the NASA discovered a six billion-year-old planet, named Kepler 452B. The planet so closely resembled its cousin Earth that it was basically “Earth 2.0”.

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