UT/Keck: Distant Giant Planets Form Differently Than 'Failed Stars'

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UT/Keck: Distant Giant Planets Form Differently Than 'Failed Stars'

Post by bystander » Wed Feb 12, 2020 4:52 pm

Distant Giant Planets Form Differently Than 'Failed Stars
McDonald Observatory | University of Texas, Austin | W. M. Keck Observatory | 2020 Feb 10
A team of astronomers led by Brendan Bowler ... has probed the formation process of giant exoplanets and brown dwarfs, a class of objects that are more massive than giant planets, but not massive enough to ignite nuclear fusion in their cores to shine like true stars. Using direct imaging with giant ground-based telescopes, they studied the orbits of these faint companions orbiting stars in 27 systems. These data, combined with modeling of the orbits, allowed them to determine that the brown dwarfs in these systems formed like stars, but the gas giants formed like planets. ...

In the last two decades, technological leaps have allowed telescopes to separate the light from a parent star and a much-dimmer orbiting object. In 1995, this new capability produced the first direct images of a brown dwarf orbiting a star. The first direct image of planets orbiting another star followed in 2008. ...

Brown dwarfs, as defined by astronomers, have masses between 13 and 75 Jupiter masses. They have characteristics in common with both planets and with stars, and Bowler and his team wanted to settle the question: Are gas giant planets on the outer fringes of planetary systems the tip of the planetary iceberg, or the low-mass end of brown dwarfs? Past research has shown that brown dwarfs orbiting stars likely formed like low-mass stars, but it's been less clear what is the lowest mass companion this formation mechanism can produce. ...

Population-Level Eccentricity Distributions of Imaged Exoplanets and Brown Dwarf Companions:
Dynamical Evidence for Distinct Formation Channels
~ Brendan P. Bowler, Sarah C. Blunt, Eric L. Nielsen
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