Astronomers have spied a new alien world that they believe strikingly resembles a young Jupiter. Using a new instrument, the Gemini Planet Imager, they spotted 51 Eridani b, still warm and luminous from its formation. But what can this distant exoplanet, orbiting a star approximately 100 light years away, teach us about the solar system Jupiter calls home?
"51 Eridani b is so young, it actually 'remembers' its formation in some sense," said Bruce Macintosh, of the Kavli Institute for Particle Astrophysics and Cosmology (KIPAC) at Stanford University, in an interview with The Kavli Foundation.. "The conditions of whatever process made it haven't been erased by time. Its temperature, size and mass depend on whether it forms in the way we think Jupiter formed in a slow, step-by-step process, or maybe through some much faster, sudden collapse process that's very different. We can't really say which of those is true right now, but as we study it more we will be able to."
Macintosh led the team that discovered 51 Eridani b, using the Gemini Planet Imager, mounted on the 8-meter Gemini South Telescope in Chile. With a mass only about twice that of our Solar System's king planet, 51 Eridani b stands as perhaps the coldest and smallest exoplanet ever to be directly imaged; previous record-holders have possessed in the vicinity of five times Jupiter's mass. What's more, 51 Eridani b bears the strongest exoplanetary signatures so far of the gas methane, which is prominent in Jupiter's atmosphere.
"Most of the planets that have been imaged before look a little bit like stars, whereas 51 Eridani b looks like a planet," said Macintosh.
The results were published yesterday in the journal Science.
In the Kavli interview, Macintosh explained how astronomers designed the Gemini Planet Imager specifically to detect young exoplanets still warm and luminous from their formation. The Imager includes a special mask, called a coronagraph, which suppresses the overwhelmingly bright glare of parent stars, allowing for easier detection of their comparatively dim exoplanets. Extremely clean, dust-free mirrors and an "adaptive optics" system to cut down on image-blurring effects from Earth's atmosphere also ensure that the Imager is powerfully well-suited to its task compared to other instruments.
"You put all those factors together and the Gemini Planet Imager is five to 10 times more sensitive than its predecessors," said Macintosh. "That sensitivity allowed us to pick out 51 Eridani b."
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The new paper on 51 Eridani b is authored by an international collaboration including Eric Nielsen, also a member of KIPAC.
To see the full discussion with Macintosh, visit: http://www.kavlifoundation.org/science-spotlights/most-jupiter-exoplanet-ever-seen-qa-bruce-macintosh
Journal
Science