Free Astronomy Magazine September-October 2016

SPACE CHRONICLES scope, will help determine the full composition of these atmospheres and hunt for potential biosigna- tures, such as carbon dioxide and ozone, in addition to water vapor and methane. Webb also will ana- lyze a planet's temperature and surface pressure — key factors in assessing its habitability. These planets are the first Earth- sized worlds found in the Search for habitable Planets EClipsing ULtra-cOOl Stars (SPECULOOS) sur- vey, which will search more than 1,000 nearby red dwarf stars for Earth-sized worlds. So far, the sur- vey has analyzed only 15 of those stars. “These Earth-sized planets are the first worlds that astrono- mers can study in detail with cur- rent and planned telescopes to determine whether they are suit- able for life,” said de Wit. “Hubble has the ability to play the central atmospheric pre-screening role to tell astronomers which of these Earth-sized planets are prime can- didates for more detailed study with the Webb telescope.” This double- transit, which oc- curs only every two years, pro- vided a combin- ed signal that offered simulta- neous indicators of the atmo- spheric charac- teristics of the planets. The researchers hope to use Hub- ble to conduct follow-up obser- vations to search for thinner at- mospheres, composed of elements heavier than hydrogen, like those of Earth and Venus. “With more da- ta, we could perhaps detect meth- ane or see water features in the atmospheres, which would give us estimates of the depth of the atmo- spheres,” said Hannah Wakeford, the paper's second author, at NA- SA's Goddard Space Flight Center in Greenbelt, Maryland. Observations from future telescopes, including NASA's James Webb Space Tele- n T he TRAPPIST-1 system, consisting of several known Earth-sized planets or- biting a red dwarf star, would fit deep inside the orbit of the sun's inner- most planet, Mercury. [NASA, ESA, and A. Feild (STScI)] are a promising first step in learn- ing more about these nearby worlds, whether they could be rocky like Earth, and whether they could sus- tain life,” said Geoff Yoder, acting associate administrator for NASA's Science Mission Directorate in Wash- ington, D.C. “This is an exciting time for NASA and exoplanet research.” The planets orbit a red dwarf star at least 500 million years old, in the constellation of Aquarius. They were discovered in late 2015 through a series of observations by the TRAn- siting Planets and PlanetesImals Small Telescope (TRAPPIST), a Bel- gian robotic telescope located at the European Southern Observato- ry’s (ESO’s) La Silla Observatory in Chile. TRAPPIST-1b completes a cir- cuit around its red dwarf star in 1.5 days and TRAPPIST-1c in 2.4 days. The planets are between 20 and 100 times closer to their star than Earth is to the sun. Because their star is so much fainter than our sun, researchers think that at least one of the planets, or pos- sibly both, may be within the star's habitable zone, where moderate temperatures could allow for liquid water to pool. On May 4, astrono- mers took advantage of a rare si- multaneous transit, when both planets crossed the face of their star within minutes of each other, to measure starlight as it filtered through any existing atmosphere.