Forty light-years from Earth, the ultra-cool dwarf star TRAPPIST-1 holds potential. What for? Habitable exoplanets.
Scientists from Massachusetts Institute of Technology (MIT) and Belgium’s University of Liège have set their sights on the star system, and discovered three exoplanets that are similar in size and temperature to Venus and Earth.
Their research was published in Nature today. And the researchers have noted the three planets are prime targets for further atmospheric studies, including a biosignatures search.
TRAPPIST-1 is more cool and red than the solar system’s sun, and is barely larger than Jupiter. Lying in the Aquarius constellation, the star is quite dim, escaping the naked eye and even large amateur telescopes, according to the European Southern Observatory.
For the study, the researchers utilized the TRAPPIST (TRAnsiting Planets and Planeteslmals Small Telescope), which is operated out of Chile by the University of Liège. According to MIT, the 60-cm telescope focuses on 60 nearby dwarf stars, monitoring the stars at infrared wavelengths.
It was a gamble. Since other exoplanet searches are designed to target hotter stars, the researchers had to design their own survey. The endeavor was heralded by lead authors Michael Gillon and Emmanuel Jehin, who built TRAPPIST.
Dips in the infrared light from TRAPPIST-1 tipped the researchers off to the exoplanets’ existence.
“Basically, the smaller the star the better for exoplanet characterization,” study coauthor Julien de Wit, a postdoc at MIT’s Dept. of Earth, Atmospheric, and Planetary Sciences, told R&D Magazine. “The reason is that the signal we are looking for is proportional to the planet-to-star area ratio (the transit depth is directly related to that ratio).”
Following their observations, the team deduced that the two planets closest to the star completed their orbits in 1.5 and 2.4 days, respectively. The third planet’s orbit is thought to be anywhere between four and 73 days. Additionally, the team believes the planets are tidally locked, but contain areas with temperatures below 400 Kelvin, making them potentially suitable for water and life.
With the Hubble and Spitzer telescopes, scientists can glean some initial insights about these exoplanets, including whether the atmosphere is large and clear, and contains certain molecules like water and methane.
“The fact that the star is cool is beneficial because it’s brighter in the infrared where molecules are more active (i.e. interact/absorb the most light)—so (it’ll) lead to a better signal quality in this spectral region of interest for atmospheric characterization,” said de Wit.
Observation of the planet’s atmospheric qualities will only be bolstered when the James Webb Space Telescope (JWST) launches in 2018. “Assuming the planets have an atmosphere, JWST will lead more detailed information about their composition, temperature, and pressure,” according to de Wit. “All together, this will help us assess their habitability.”
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