What Is TRAPPIST-1 And Can The 7 Earth-like Planets Orbiting It Support Life?

The search for extraterrestrial life has always been a powerful motivator for space exploration. Breakthroughs have happened in terms of better technology and new information, although we have yet to find concrete evidence of life beyond Earth. Planets in star systems other than our own Solar system have been studied by scientists in the hope of finding an environment that could sustain life. The type of environment required, on the other hand is a matter of debate. Since we know that Earth supports carbon-based life forms that need some essential things, such as water and heat from the Sun, we have a better chance of finding recognizable life in a place that is somewhat similar to Earth. Therefore, most of the search for alien life consists of searching for planets or moons that bear a similarity to our home planet.

What is the Trappist-1 System?

TRAPPIST-1 is an ultra-cool dwarf star in the constellation of Aquarius about 39.5 light years away from our Solar System. Hardly bigger than the largest planet in our Solar System, Jupiter, this star was discovered in 1999 during the Two Micron All-Sky Survey, or 2MASS, conducted between 1997 and 2001. It was carried out in two different locations: at the U.S. Fred Lawrence Whipple Observatory on Mount Hopkins, Arizona, and at the Cerro Tololo Inter-American Observatory in Chile.

An artist's depiction of the TRAPPIST-1 star and it's Seven Planets

An artist’s depiction of the TRAPPIST-1 star and it’s seven planets. Source- wikipedia

Later in 2015, astronomers discovered 3 Earth-sized planets orbiting the star and named it the TRAPPIST-1 system, after the ‘Transiting Planets and Planetesimals Small Telescope’ that was used for its observation. After more careful study, the total number of planets orbiting the star was brought up to 7 in February of 2017.  While 3 of these lie inside the habitable zone, any of these 7 planets could be capable of supporting life.

Why is this System so special?

The star is about 10% of the Sun’s diameter and less than 10% of its mass. Due to the small size, the orbits of the seven planets lie much closer to TRAPPIST than the eight planets of our own Solar System.  All of them revolve in an orbit that is less than 1/5th the size of Mercury’s orbit, which might make them very hot. However, the star burns at about 2500 K compared to the Sun’s 5800 K, so three of the seven planets lie inside ‘The Goldilocks Zone’. What this basically means is that the planets orbit at just the right distance from the star to allow the sustainability of life, which only happens at the right temperature and in the presence of liquid water.

TRAPPIST-1 compared to our Solar System

TRAPPIST-1 compared to our solar system. Source- wikipedia

Additionally, the three planets closest to the star are tidally locked, just like how the Moon is tidally locked to the Earth. This means that one face of the planet always faces the TRAPPIST-1 star, while the other is stranded in perpetual darkness. It is still unknown if the star’s mild temperature is enough to make these three planets unsustainable or not. Even if that is the case, it is believed that the presence of a viable atmosphere on these planets could allow the heat to be dissipated evenly across their surfaces.

The reason that these planets are exciting is that they are all ‘rocky’, just like Earth, and their sizes are comparable to our own planet! Finding seven suitable candidates for life in a single system is spectacular in itself, but the fact that these planets are only about 40 light-years away from us makes their discovery monumental in terms of space exploration.

What would it be like to live on the TRAPPIST-1 planets?

At some point in the future, we might be able to visit these planets, and when we do, we know one thing for sure – the view would be spectacular! Since the star is very cold and dim relative to the Sun, it is believed that the days on any of the planets would be much darker than they are on the Earth. This is because the low temperature of the star lets the heat travel more in the form of infrared light, rather than the visible light we have on Earth. We would have to get used to this state of perpetual twilight.

The most exciting thing about walking on one of these planets would be the view that we’re offered when we look up into the sky. We would be able to view several of our planetary neighbors and they wouldn’t just be specks of light like Mars in Earth’s night sky, but rather huge balls like the Moon. We would even be able to see the textures of these planets, just as we can see the craters on the Moon.

Also, years on that planet would be much shorter, and the seasons would change even faster on these planets. Since the planets revolve so near to their star, the most distant planet completes the orbit in just 19 days, while it takes the closest planet only 36 hours!

An artist's depiction of the TRAPPIST-1 star

An artist’s depiction of the TRAPPIST-1 star. Source- wikipedia

How do we learn more about this system?

Scientists use a technique called transit photometry to learn about distant planets. This basically means that they observe the light from stars like TRAPPIST-1 and figure out details of the planets close to it by the change in the properties of light when they pass in front of the star. Everything we know is determined through shadows, so we have a limited amount of information about important stuff like the composition of the atmosphere, type of terrain etc.

How Transit Photometry Works

How Transit Photometry Works

This can be resolved by using better telescopes and better imaging techniques that are available in the Hubble telescope, which is currently the most powerful telescope in space. However, NASA is scheduled to launch the James Webb Telescope in 2018, which is 100 times more powerful than Hubble. Also, since it will be positioned farther away from the Earth, the resolution of images is exponentially higher due to the absence of any kind of disturbance. It is expected to shed significantly more light on the TRAPPIST system.

The Hubble vs The James Webb Telescope

The James Webb Telescope vs The Hubble . Source- www.womanium.org

The ideal scenario would be the detection of bio-signatures like methane and ozone in the atmosphere, which are indicative of the existence of past or present life.

What implication would the existence of life on TRAPPIST-1 have?

TRAPPIST-1, which is an ‘M-dwarf’ type of star, burns very slowly and at a relatively low temperature, which allows it to have a lifespan of about a trillion years, which is much longer than our Sun’s 4.6 billion year life span to date. If life does exist on TRAPPIST-1, it could have had an ample amount of time to evolve into a more complex form than is found on Earth.

The existence of life in this system also increases the probability of finding life elsewhere in the universe, since ‘M-dwarf’ stars are the most common types of all stars! Just imagine the possibility that the incalculable number of these stars could have had an incalculable number of planets supporting life for incalculably long stretches of time. Finding life in the TRAPPIST-1 system would help us understand the requirements for habitability better and pave the way for future discoveries. Suffice to say, we are in for some exciting years ahead!


  1. What’s the significance of TRAPPIST-1 : Second Thought – YouTube
  2. TRAPPIST-1 – Wikipedia
  3. System with 7 Earth-size Exoplanets – Space.com
  4. Hubble Space Telescope searches for signs of life in TRAPPIST-1 atmospheres – News.com (Australia)
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About the Author:

Harsh Gupta graduated from IIT Mumbai, India with a Bachelors degree in Chemical Engineering. His pedantic and ‘know-it-all’ nature made it impossible for him not to spread knowledge about (hopefully) interesting topics. He likes movies, music and does not shy away from talking and writing about that too.

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