I found myself elated on February 24, when I found four separate articles on Reddit concerning the discovery of new exoplanets surrounding a (relatively) nearby star. As an active spectator in the search for a new home, my flower twitched uncontrollably at the prospect of coming closer to the realization of humanity’s “Plan B.” However, there is still much development that must happen on the technological end before we can even think about researching Earth-like planets orbiting Sun-like stars. For now, we must settle for smaller stars like TRAPPIST-1.
TRAPPIST-1 is known as an ultra-cool dwarf star located roughly 40 light years away from us, within the constellation of Aquarius. It is named for TRAPPIST, or the TRAnsiting Planets and Planetesimals Small Telescope. The TRAPPIST team and the other telescopes around the world later discovered the seven exoplanets surrounding it. To clear some things up, an exoplanet is any planet that is not in our solar system. An ultra-cool dwarf star is, as the name suggests, very small and relatively cold. TRAPPIST-1 is only slightly larger than Jupiter, but very dense, as it is only 12 times less massive than the Sun. While this seems discouraging, ultra-cool dwarf stars are currently the focus for finding and researching exoplanets for a variety of reasons.
Ultra-cool stars are the most common in the universe, and because of their slow rate of nuclear fusion, they are estimated to remain roughly the same size for up to 100 billion years. This is drastically different from our Sun, which is estimated to become a red giant in only five billion years. The size of ultra-cool stars is also used to discover planets using what is called the “transit method.” Exoplanets are generally too small to directly detect through any telescope, but scientists can capture them by recording their shadows as they pass in front of, or transit, the star. Ultra-cool stars are better for this method because the shadows produced by these transits are much more pronounced, making the process of confirming an exoplanet up to 50 times faster. Also, since the stars are so small, planetary orbits can occur once a week instead of once a year. The TRAPPIST-1 team is unfortunately limited to this sort of method due to technological constraints, but the use of ultra-cool stars lets us begin our research decades before we can even approach solar-sized stars.
So where’s the cool stuff? What do we know about the terrain of these seven exoplanets (known as TRAPPIST-1b through h)? As of writing this article, not much. Just the discovery of this star and its exoplanets is very recent news, and research regarding the specific nature of each planet is ongoing. Using mass calculations and orbital eccentricity, the TRAPPIST-1 team can get an idea of each exoplanet’s terrain, and if it is mostly rocky or if it contains significant amounts of water. They will also use the Hubble telescope and NASA’s James Webb telescope, which is scheduled to launch in 2018, to determine the chemical composition of the atmospheres of each exoplanet in order to see if they can support life.
This discovery is a very exciting new step in the search for life in the universe. For more information, the TRAPPIST-1 team has made a beautiful and comprehensive website at www.trappist.one which explains most of my article better than I can. Get hyped!
From TRAPPIST-1’s website, this image gives perspective on the size difference between the dwarf star and our own Sun.