Mysterious Worlds Beyond Our Own

Tzvetelina Dimitrova

On Earth, we often find ourselves looking out into the night sky wondering at the mysteries that lie beyond the solar system we call home. What are the planets like beyond our planetary neighborhood? Could their landscapes resemble our own? Or could they hold mysteries beyond our Figure 1 Trappist-1 exoplanetary system NASA/JPL- modern comprehension? On exploring the Caltech image. newly discovered planets are considered to topic of mysterious exoplanets, TRAPPIST- lie within the habitable zone of the star. 1 is certainly the right place to start. TRAPPIST-1 is a planetary system located Timeline at a distance of 39 light years (in miles) Although the central TRAPPIST-1 star from the Sun, within the constellation was discovered in 1999 during the Two Aquarius [1]. The planetary system consists Micron All Sky Survey(2MASS) [2], the of at least seven planets (Figure 1), which detection of a planetary system is a orbit about an ultra-cool red dwarf star that relatively recent development. In May of is 12 times less massive than the Sun, and 2016, Michael Gillon and his team at the slightly larger than Jupiter [1]. This system University of Liege in Belgium published is of importance in the exoplanet field, findings of three Earth-sized planets because of its central dwarf star. Planets that orbiting the star. They used the method of orbit about ultra-cool red dwarfs tend to transit photometry, with the Transiting have similar planetary characteristics to Planets and Planetesimals Small Telescope earth in several different aspects. The (TRAPPIST) at the La Silla Observatory discovery of seven temperate terrestrial in Chile[3]. On June 6th, the first transit of planets is a significant discovery because the planet TRAPPIST-1d was detected! this is the greatest number of planets Not long after, on October 11th, the first detected in any system. Three of these transit of planet 1h was observed as well. Now let us journey far beyond our bounds Almost a year later, on August 31st 2017, on earth, and dive into the most notable exciting news broke! A scientific paper properties of the TRAPPIST-1 planetary reported Ultraviolet observations, which led system! The innermost planet, to the suggestion that the outer planets TRAPPIST-1b, is a rocky planet sharing might host water. some characteristics of our solar systems very own planet Venus as its atmosphere Following these discoveries, is incredibly hot and thick. TRAPPIST 1- multiple series of scientific papers have b’s size is comparable to that of Earth, been published on the planets. These new although its atmosphere has a much papers outlined the more recently greater reach, and its density is relatively discovered characteristics of the system. At low. TRAPPIST-1c is the third largest this point, a record-breaking total of seven planet of the system, and it is also the most planets had been observed. All these seven massive. Similar to planet 1b in planets were discovered using the transit atmosphere and composition, the most method, during which the recorded intriguing fact about this planet is the brightness of a host star is observed for proximity of its orbit around the host star, periodic dips suggesting an orbiting body which causes a year on this planet to last a (Figure 2). Following these discoveries, the mere 58 hours! TRAPPIST-1d is the next course of action called for smallest planet and falls into the inner investigations into the atmospheric edge of the habitable zone of the red dwarf conditions of the planets, as well as their star, although recent studies conducted by habitability and likelihood of liquid water. the University of Washington suggest it to be uninhabitable and Venus like [4]. TRAPPIST-1e is a relatively Earth like exoplanet, with a comparable size, mass, temperature, and, stellar flux to that of Earth. Out of all of the planets in the system, TRAPPIST-1e has the most potential to be a habitable ocean planet, and for this fact has been deemed the most

Figure 2 - Spitzer Space Telescope transit data of TRAPPIST-1. Credit: ESO/M. Gillon et al.TRAPPIST-1 worthy of further study (Figure 3). Further out into the habitable zone, TRAPPIST-1f is a partially rocky planet theorized to host liquid water oceans on its surface under the right atmospheric conditions. TRAPPIST-1g is thought to be just barely within, or just barely outside of the habitable zone, and is also thought to be a likely candidate to host some form of water. The last and outermost planet of the system is TRAPPIST-1h. Although not significantly smaller than earth, it has a relatively low density which suggests the presence of water, and or ice. At its orbital distance from its host star, this planet is within the frost line, the point at Figure 3 "Planet hop from TRAPPIST-1e - Voted best 'hab zone' vacation within 12 parsecs of Earth" NASA Exoplanets Exploration which common planetary compounds are Program's Exoplanet Travel Bureau poster thought to freeze [5]. Regardless of whether or not the planets of the TRAPPIST-1 Sources Cited system prove to be habitable to human life, [1]Gillon, Amaury Triaud Michael. “1.” TRAPPIST, Retrieved they are surely the first of their kind to be 6 02 2020, from www.trappist.one/. discovered, and promise to be a hub for [2] Gizis, John E.; Monet, David G.; Reid, I. Neill; Kirkpatrick, J. Davy; Liebert, James; Williams, Rik J. (2000). "New fascinating future research! Neighbors from 2MASS: Activity and Kinematics at the Bottom of the Main Sequence". The Astronomical Journal. 120 (2): 1085–1095. arXiv:astro-ph/0004361. Bibcode:2000AJ....120.1085G. doi:10.1086/301456.

[3] Gillon, M., Jehin, E., Lederer, S. et al. Temperate Earth- sized planets transiting a nearby ultracool dwarf star. Nature 533, 221–224 (2016). https://doi.org/10.1038/nature17448

[4] Kelley, P. (2018, November 20). Study brings new climate models of small star TRAPPIST 1’s seven intriguing worlds. Retrieved from https://www.washington.edu/news/2018/11/20/study- brings-new-climate-models-of-small-star-trappist-1s-seven- brings-new-climate-models-of-small-star-trappist-1s-seven- intriguing-worlds/ intriguing-worlds/

[5] Kelley, P. (2018, November 20). Study brings new climate models of small star TRAPPIST 1’s seven intriguing worlds. Retrieved from https://www.washington.edu/news/2018/11/20/study-