For a craft that was launched in 1990, the Hubble Space Telescope continues to provide us with awe-inspiring firsts. This time, researchers pointed its venerable lens in the direction of Earth-size planets beyond our solar system to give us the first glimpse into their atmospheres, according to a new study.
In May, researchers shared the discovery of three Earth-like worlds orbiting an ultracool dwarf star named TRAPPIST-1, 40 light-years away. Ultracool dwarf stars are at the end of the range of what classifies as a star, at half the temperature and a 10th the mass of the sun, so it was a first to find planets orbiting this star. The three exoplanets also appeared to be in the "habitable zone" of the star, meaning liquid water could pool on their surfaces.Based on the planets' proximity to TRAPPIST-1 and their respective temperatures and size, researchers believed the planets might be similar to our own, with a rocky structure with habitable regions, rather than being gas giants like Jupiter. Many of the first exoplanets discovered fell into the uninhabitable gas giant category. But without more insight about the atmosphere of these planets, the researchers could only make an educated guess.
About two weeks before their findings were released on May 2, the researchers took another look at the star system using NASA's Spitzer Space Telescope, which gave them a better understanding of the orbit of the planets. They predicted a rare event called a double transit, in which the two planets closest to the star would pass in front of it almost simultaneously.
"When a planet passes in front of its star, a tiny fraction of the stellar light goes through the planet atmosphere before reaching us, meaning that it carries with it information about the atmosphere it just went through," said Julien de Wit, lead study author and a postdoctoral associate at MIT.
De Wit realized that Hubble would be in a position to observe this event if it was pointed in the direction of the star system and suggested that his team reach out to NASA with a proposal to capture it. The double transit would occur two weeks later, so they had only a few days to reach out.
In his proposal, de Wit outlined the rarity of the double transit, which wouldn't occur again for two years, as well as the unique opportunity to "see" the atmosphere of these exoplanets for the first time. The proposal was reviewed and accepted immediately.
Source : edition.cnn.com/
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