Astronomers use an old trick to open new window on extrasolar planets
Two teams of astronomers used a technique for finding extrasolar planets to directly measure one such planet. The approach could allow the study of more exoplanets' atmospheres than ever before.
In this artist's conception Tau Boötis b looks at its sun.
NASA
A method astronomers have used for nearly 20 years to indirectly find planets orbiting other stars has for the first time been used to take the direct measure of an extrasolar planet itself.
The approach not only yields precise estimates of a planet's mass, a critical piece of information that can help determine a planet's bulk composition. It also can reveal its orbital inclination. And perhaps most important, it could allow astronomers to study atmospheres of more extrasolar planets than ever before.
The reason: The technique doesn't require a star to backlight a planet's atmosphere as the planet passes in front of its star. Until now, this kind of backlighting, during what's known as a transit, has provided the only window astronomers have had on the make-up of an extrasolar planet's atmosphere. And the number of transiting planets so far is only about one-third the number of planets discovered by two international teams of astronomers who used this approach and whose findings are published this month.
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The orb the teams observed, known as tau Bootis b, was discovered in 1996 by a group led by astronomer Geoffrey Marcy at the University of California at Berkeley. It orbits a star nearly 51 light-years from Earth in the Northern-Hemisphere constellation Bootes.
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