TJO Newsletter Summer 2017

SOMETHING MIGHT BE BREWING By Guadalupe Tovar

Many may ask what makes a new planet system so changes the atmospheres of the orbiting planets on a regular special if we have hundreds more. This is when the basis, making them less suitable for life. TRAPPIST-1 comes in to steal the show with not one, or All the planets in the TRAPPIST-1 system transit two, but seven new brews for everyone in the room! The field their star, meaning that they pass in front of it and we are able of is one of the newer fields of astronomy but also to see the repeated shadows that are cast during transit on the one of the most rapidly growing. Since 1995, when the first light curves. In February 2017, astronomers announced that the was detected scientists have discovered over 3,000 planetary system of this star is composed of at least seven news exoplanets. Of those exoplanets 581 are multi-planet terrestrial planets (Northon, 2017). systems1. Located within the of , the TRAPPIST-1 planetary system is located about 40 light away from our Solar system. TRAPPIST-1, the star at the center of the system, was discovered in 1999 during the Two Micron All-Sky Survey2. In 2015, the system was studied by a team at the University of Liège. They made their initial exoplanet detections using the TRAnsiting Planets and PlanetesImals Small Telescope, TRAPPIST. The name of the system, TRAPPIST, represents the telescope's nationality and Figure 1. Artist rendition of the Trappist-1 system (Credit: stems to Belgium's famous Trappist beer, named after the NASA) Roman Catholic religious order, which the astronomers used to Astronomers have found five planets, cleverly named b, c, e, f toast their discovery. Since the star hosted the first exoplanets and g, are similar in size to Earth. The other two named d and discovered by this telescope, the discoverers referred to it as h are intermediate in size between Mars and Earth (Gillon, "TRAPPIST-1". Cheers to finding your first exoplanets 2016). Three of the planets (e, f and g) orbit within the habitable TRAPPIST! zone, which means the planetary surfaces can support liquid TRAPPIST-1 is an ultra-cool dwarf star that is water! approximately 12 times less massive than the Sun and only Our only data point of an inhabited world today is slightly larger than Jupiter. The star is very faint which means Earth. The fact the TRAPPIST-1 system provides us with 3 it is not visible to the naked eye from the Earth. It has a cool new habitable worlds who orbit the same star makes future temperature of 2,280 °C or 4,130 °F (Gillon, 2016), and its age observations of this system a brew worthy of waiting in a long has been estimated to be in the range of 3 to 8 billion years line for. The transit signals allowed astronomers to measure the (Rodrigo Luger, 2017). The star is fairly active. This means orbital periods of the planets which in turn helped calculate the that once every three days the star emits flares out towards the sizes of the planets. By knowing the exact time at which the planetary system. The observed flaring activity possibly planets transit, scientists were able to measure their masses,

1 https://exoplanetarchive.ipac.caltech.edu/ 2 http://www.ipac.caltech.edu/2mass/

15 TJO Newsletter Summer 2017 which gave information on their densities and bulk properties, SOURCES CITED concluding the planets are made up of a rocky composition3. Gillon, M. (2016). Temperate Earth-sized planets transiting a nearby ultracool dwarf star. Nature, 533, 221–224.

Northon, K. (2017, February 23). https://www.nasa.gov/press- release/nasa-telescope-reveals-largest-batch-of- earth-size-habitable-zone-planets-around.

Rodrigo Luger, M. S.-O. (2017). A seven-planet resonant chain in TRAPPIST-1. Nature, Volume 1, id. 0129 . Figure 2. Artist rendition of all 7 planets and their host star

(Credit: NASA) The planets have sizes and masses similar to the Earth and Venus. By knowing the distance of the planets to their star, and the temperature of the star, it was deduced that they receive a similar amount of light to many of the planets in the Solar system, from Mercury to beyond Mars. During transit, some of the starlight goes through the atmosphere of the planets, getting transformed by the chemical composition of the atmosphere. This means that we can remotely study the climates of terrestrial worlds beyond our Solar system! The TRAPPIST-1 system is a key target for future studies and observations. The 7 worlds are providing humanity with its first opportunity to discover evidence of biology beyond the Solar system.

Figure 3. Artist rendition of a sunset a person would see if they were on one of the habitable zone planets in the Trappist-1 system (Credit: NASA)

3 http://www.trappist.one/

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