NASA has discovered 7 earth-sized exoplanets that have the possibility to support life, all in the same system! These planets orbit TRAPPIST-1, an ultra-cool dwarf star. This is the first time we find this many terrestrial planets around a singular star where we can also measure their masses and radii. Thomas Zureichen, Associate Administrator and Science Mission Director at NASA said in a briefing announcing the discovery,”Finding a second earth is not just a matter of if, but when.” This system is located about 40 light years, or about 378,429,218,903,232 kilometers, away from our blue planet in the constellation Aquarius. That may sound tremendously far, but in galactic terms, it is relatively close. Zureichen also said in the same briefing,”Three of these planets are in the habitable zone, where liquid water can pool on the surface. In fact, with the right atmospheric conditions, there could be water on any of these planets.”
TRAPPIST-1 itself was discovered in 1999 during the Two Micron All-Sky Survey. TRAPPIST-1 is a very dim and ultra-cool red dwarf that is almost impossible to see. It is 8% the mass of our Sun, or for another comparison, if the Sun were a basketball, TRAPPIST-1 would be a golf ball.
When the system was later studied in 2015 by a team of astronomers, led by Michael Gollin of the University of Liege in Belgium, they initially found three planets (TRAPPIST 1b, TRAPPIST 1c, and TRAPPIST 1d). On February 22, 2017, astronomers studied the system closer and discovered 4 additional exoplanets. This discovery was made using the TRAPPIST telescope at the La Silla Observatory in Chile. The work also employed The Very Large Telescope at Paranal and NASA’s very own Spitzer Space Telescope, among others. It turns out that TRAPPIST 1d was actually 3 different planets! They also found an additional 2 planets, TRAPPIST 1g and TRAPPIST 1h, bring the total to 7 exoplanets.
Even though these planets may have a lot of similarities to earth, they also have their differences. All seven of these exoplanets are likely to be tidally locked, meaning only one side is facing the star at all times. This has caused some to speculate about the possibility of life on any of these planets. Tidal locking can cause extreme temperature changes in different parts of the planets. Some tidally locked planets might be uninhabitable because the side facing the star would become extremely hot, while the other side would grow extremely cold. Some theories say that if the planets have some sort of way of distributing this temperature, these planets could still foster life.
Another difference that the TRAPPIST planets have with earth is the duration of their orbits. Six of these seven planets make a full orbit in 1.5 days to 12.4 days, depending on the planet’s distance from TRAPPIST-1. The farthest planet takes about 20 days to make a complete orbit. There is no transition of night to day and day to night on these planets because of the tidal locking previously mentioned. Depending on where you are on the planet, it could be day or night the whole time.
These planets are also likely to have very different sky views too. Because these planets are so close together, if you were on any of these planets, you would most probably see the other planets without the aid of a telescope! All seven of these planets orbit their star closer than the distance Mercury, the closest planet to our Sun, orbits our Sun! When the innermost planet and the outermost planet in the TRAPPIST system are farthest apart, they are almost 30 times closer together than Earth and Venus. The reason for this close proximity is because TRAPPIST-1 is 2,000 times dimmer than our Sun and about the size of Jupiter, making its gravitational pull much weaker than that of our Sun.
On a final note, it is important for us as human beings to seek outside of this planet for our own understanding and the understanding of this universe, something we don’t have a firm grasp on and we never will unless we go out there and explore. As the great Carl Sagan once said:
”Since, in the long run, every planetary society will be endangered by impacts from space, every surviving civilization is obliged to become spacefaring–not because of exploratory or romantic zeal, but for the most practical reason imaginable: staying alive.”
Bodkin, H. (2017). Nasa discovers new solar system TRAPPIST-1 – where life may have evolved on three planets. The Telegraph. Retrieved 25 February 2017, from http://www.telegraph.co.uk/science/2017/02/22/nasa-announcement-live/
Witze, A. (2017). Seven-planet system discovered in Earth’s backyard Seven Earth-sized exoplanets discovered circling nearby star. Retrieved 25 February 2017, from http://www.nature.com/news/these-seven-alien-worlds-could-help-explain-how-planets-form-1.21512
Yeager, A. (2017). New solar system found to have 7 Earth-size planets. Science News for Students. Retrieved 25 February 2017, from https://www.sciencenewsforstudents.org/article/new-solar-system-found-have-7-earth-size-planets