Spitzer Space Telescope reveals a seven Earth-size planetary system in Habitable-Zone

Seven Earth-sized planets have been observed by NASA's Spitzer Space Telescope around a tiny, nearby, ultra-cool dwarf star called TRAPPIST-1. Three of these planets are firmly in the habitable zone. This illustration show a possible surface for one of them. Credits: Credits: NASA/JPL-Caltech

This week NASA has announced the discovery of the first known star system containing seven Earth-size planets orbiting a single star, which was achieved by NASA's Spitzer Space Telescope. Out of those seven worlds, three of them are located in the so called ‘goldilock’ zone which is the circumstellar habitable zone (CHZ), or simply the habitable zone, an area that given the star brightness and distance to the planet it will be able to contain liquid water. 

This discovery sets a new record for the most number of habitable-zone planets found around a single star outside our own Solar System, these worlds are capable of containing liquid water given the right atmospheric conditions, which is a key element for hosting life as we know it, but not all seven planets are likely to harbour water, however three of these planets have a higher chance for this to be a reality.

This illustration shows the seven TRAPPIST-1 planets as they might look as viewed from Earth using a fictional, incredibly powerful telescope. The sizes and relative positions are correctly to scale. Credits: NASA/JPL-Caltech JPL-Caltech

The star system lies at 40 light-years from Earth, in the Aquarius constellation, which is a relatively close by distance is astronomical terms, still, been realistic it is out of our reach, however finding life elsewhere is a hot topic in astronomy these days, Thomas Zurbuchen, associate administrator of the agency’s Science Mission Directorate in Washington said: “This discovery could be a significant piece in the puzzle of finding habitable environments, places that are conducive to life. Answering the question ‘are we alone’ is a top science priority and finding so many planets like these for the first time in the habitable zone is a remarkable step forward toward that goal.” 

The TRAPPIST-1 system as seen by Spitzer. Credit: Nature

The exoplanet system has been named TRAPPIST-1, which derives from The Transiting Planets and Planetesimals Small Telescope (TRAPPIST) in Chile. The discovery of this system dates back to May 2016, when initially only three planets were observed, aided by other and bigger ground-based telescopes, including the European Southern Observatory's Very Large Telescope (Very Large Telescope, VLT), and later on Spitzer confirmed the existence of two of these planets and discovered five additional ones. 

Artist's concept of what the TRAPPIST-1 planetary system may look like. Credits: NASA/JPL-Caltech JPL-Caltech

Using the data from the Spitzer telescope, the team precisely measured the sizes of the seven planets and developed first estimates of the masses of six of them, allowing their density to be estimated. The interesting thing here is that based on their densities, all of the TRAPPIST-1 planets are likely to be rocky. Further observations will determine whether these worlds are rich in water and more importantly if this may be in liquid form.

When compared with our own star, the Sun, TRAPPIST-1 star is an ultra-cool dwarf star, of the spectral type M8 V, a red dwarf, so the conditions are right for the existence of liquid water on planets orbiting very close to it, closer than is possible on planets in our solar system. All seven of the TRAPPIST-1 planets are in orbits closer to their host star than Mercury is to our sun. To put it into perspective, a person on the surface of one these planets could potentially see geological features or clouds of neighbouring worlds, since they would appear even larger than moon in our sky, which is amazing. 

However, given that they are so close to the TRAPPIST-1 star, they may also be tidally locked to it, which means that the same side of the planet is always facing the star, and that makes one side perpetual day and the other night-time always. This may cause weather patterns totally unlike those on Earth, such as strong winds blowing from the day side to the night side, and extreme temperature changes. How could may life adapt to it if there is any over there remains an open question. NASA's upcoming James Webb Space Telescope, launching in 2018, with much greater sensitivity, will no doubt help sort these questions and many more.

Credit: NASA, Wikipedia, Nature, JPL-Caltech