Hello! Today I wanted to talk about Trappist-1, and you’ll see why I find it so fascinating soon.
The Trappist-1 solar system is one of the most fascinating solar systems in the Milky Way that I have come across. It can create music through planetary orbits that are naturally harmonized, has rocky earth-like planets, and is a pocket-sized system (the entire thing fits within Mercury’s orbit!) I’ve been wanting to write about this system for a while now, so here’s everything I’ve learned about it so far (in a nutshell).
I used a program called Stellarium to visualize the location of the Trappist-1 system relative to the sky of the Northern hemisphere in the evening. It is located near the constellation Aquarius (in the region encircled by a white circle, to the left of the water bucket of Aquarius)
Trappist-1 is a red dwarf star with seven Earth-sized exoplanets orbiting around it. Located 39 light years from Earth, this solar system is arguably one of the most interesting within the Milky Way for a few reasons. The orbit of all 7 exoplanets around the Trappist-1 star can fit comfortably within mercury’s orbit around our own sun. The seven planets are named starting with Trappist-1b as the closest planet to the star, through to Trappist-1h as the furthest planet from the star (b-h for the 7 planets). It is estimated that most of the inner six exoplanets (Trappist-1b through to Trappist-1g) have a rocky composition like Earth. However, Trappist-1f is estimated to have less of a rocky composition and more of a volatile-rich composition. It is thought that its tidal locking to Trappist-1 creates a perpetually frozen “night-time” side (containing ice-water) and a perpetually hot “day-time'' side with possible liquid water. Most of the exoplanets are thought to be tidally locked to their star, which allows for a unique opportunity to quantify how tidal locking affects Earth-like planets in our galaxy.
Side note: tidal locking of a rotating body is when each side of the planet/body faces a distinct side and does not change. For exaxmple, the Moon is tidally locked to the Earth, and we only see one side that perpetually faces our direction and is illuminated by the sun.
Since most of the exoplanets in the Trappist-1 system have a rocky composition and orbit close to their star, the system is a great analogue for our own inner solar system. It allows us to observe Earth-like planets in an orbit around a star that is much smaller and cooler than our own sun. The red dwarf Trappist-1 is 10x smaller than our own sun, and its red colour makes it a much cooler star than our sun.
There are four exoplanets of major interest that lie in the goldilocks zone of Trappist-1 and are very likely to contain liquid water on their surface; Trappist-1d, Trappist-1e, Trappist-1f, and Trappist-1g. Trappist-1d orbits on the inner edge of the goldilocks zone for its star and it likely contains some liquid water, but not much. The most Earth-like exoplanet in this system is Trappist-1e. It orbits comfortably in the goldilocks zone of Trappist-1 and is the most likely of the seven exoplanets to contain liquid water on its surface in a large amount. Although, all seven Trappist-1 exoplanets are potential keepers of liquid water on their surfaces, including the furthest planet, Trappist-1h. Trappist-1h could harbour liquid water on its surface if it has an internal process that traps heat within it; it would need a process like this to explore the possibility of it having liquid water since it is so far away from its star and is naturally very cold. It would need to have some sort of internal energy process that keeps heat trapped inside, therefore enabling liquid water to form.
Light curves for all seven exoplanets orbiting around Trappist-1. These light curves were observed using the Spitzer Space Telescope in 2016. Taken from Gillon et al., 2017.
Not only are these Earth-like exoplanets great research targets for composition purposes, but they also contain orbital resonance. Most of the exoplanets can create tunes when their orbital frequencies are dialed up to a human hearing range. The same type of orbital resonance exists for some of Jupiter’s biggest moons, suggesting that the Trappist-1 system formed in a similar way to the Galilean moon system. In addition, the Trappist-1 star and Jupiter share size proportions making this a great comparison.
The website System Sounds takes this orbital resonance to the next level by converting the frequencies of the Trappist-1 planet orbits and converting them into approximate musical notes. You can fiddle around with the orbital speeds of the planets to create different tunes on the website based on this pattern of orbital resonance. Try it for yourself! https://www.system-sounds.com/trappist-sounds/play/
This summer, I helped to run a virtual space camp and the kids had a blast learning about Trappist-1 through system sounds. The auditory and visual component showcasing the orbits of the Trappist-1 planets and their corresponding sounds was extremely beneficial to assist in the learning process.
The website also has the same feature but for Jupiter’s moons, as discussed earlier (they also share orbital resonance with one another). Callisto, Ganymede, Io and Europa are featured (the biggest moons) and create orbital resonance with one another that can be measured in notes and tunes in the human hearing range.
References
Gillon, M., Triaud, A., Demory, BO. et al. Seven temperate terrestrial planets around the nearby ultracool dwarf star TRAPPIST-1. Nature 542, 456–460 (2017). https://doi.org/10.1038/nature21360