Direct imaging of extrasolar planets and the discovery of a young Jupiter


Tuesday, September 08 2015 - 12:00 pm, PDT
Bruce Machintosh
Stanford University

Be among the first to learn about an exciting new exoplanet discovery—a Jupiter-like planet called “51 Eri b” that orbits a star a 100 light years away in the constellation of Eridanus.

Using a powerful new imaging device, astronomers have spied a Jupiter-like exoplanet 100 light-years distant in the constellation of Eridanus.  Unlike most planets found around other stars, 51 Eri b has been seen directly.  The instrument employed to make the discovery has also made a spectroscopic analysis of the light reflected from the planet, and has detected gases similar to those in Jupiter’s atmosphere.

Because GPI not only images exoplanets but also spreads their light for chemical analysis, astronomers can search for such common gases as water and methane in their atmospheres.  Researchers had expected to see methane in directly-imaged exoplanets based on the temperature and chemistry of these worlds, but had failed to detect these molecules in large quantities using earlier instruments.  However, the observations of 51 Eri b made with GPI have clearly revealed a methane-dominated atmosphere similar to that of Jupiter.

An extraordinarily complex instrument the size of a small car, GPI is attached to one of the world’s biggest telescopes – the 8-meter Gemini South instrument in Chile.  It began its survey of stars last year.

The host star, 51 Eri, is very young, a mere 20 million years old, and is slightly hotter than the Sun. The exoplanet 51 Eri b, whose mass is estimated to be roughly twice that of Jupiter, appears to orbit its host star at a distance 13 times greater than the Earth-Sun distance.  If placed in our own solar system, 51 Eri b’s orbit would lie between those of Saturn and Neptune.

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