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My first first-author paper is now on @arxiv! ( https://arxiv.org/abs/2101.09371 )
We found that WASP-107b, an exoplanet the size of Jupiter but just 1/10th its mass, is orbiting its star backwards in a nearly polar orbit, possibly due to an interesting gravitational dance… (1/9)
We found that WASP-107b, an exoplanet the size of Jupiter but just 1/10th its mass, is orbiting its star backwards in a nearly polar orbit, possibly due to an interesting gravitational dance… (1/9)
WASP-107b is an interesting world: it has a super-puffy atmosphere being blasted away by intense radiation from its star, & our team in collab. with Caroline Piaulet recently discovered a distant planetary companion at ~2 AU in the system ( https://arxiv.org/abs/2011.13444 ) (img: @NGKids)
This was exciting because it might explain why WASP-107b is in such a peculiar orbit. The gravitational influence of this outer planet could cause WASP-107b’s orbit to precess, like is shown in this movie (created with Nbody simulation code REBOUND and animated with @matplotlib)
For an inclined outer planet, this would mean an observer might at times see the planet’s orbit aligned with the rotation axis of the star, but at other times they might see the orbit wildly misaligned, perhaps even retrograde and/or near-polar like we see for WASP-107b
Side fun fact: in the animation in looks like the orbit is ‘hoola-hooping’ around its star - this is an effect of general relativity called ‘precession of the perihelion.’ This was a famously observed “problem” with Mercury’s orbit from 1859 until 1915 when Einstein came along
How do we know the alignment? We measured the red/blueshift of light from the star as WASP-107b passed in front of it. We saw it first block redshifted light (the side rotating away from us), then block blueshifted light, meaning it was orbiting retrograde to the star's rotation
From the relative amplitude of the red/blueshift we determined the orbit must be closer to polar than to orbiting around the star’s equator. In fact we’re likely seeing the star itself from a near-polar line-of-sight, so the fact the planet transits at all implies a polar orbit
The precession idea suggests this orbit exists by chance, although it could be an outcome of planet formation. Petrovich et al. recently showed that a gravitational dance between the two planets in the early circumstellar disk might force a polar orbit ( https://arxiv.org/abs/2008.08587 )
There are only 3 other systems like this known, where the inner planet is on a misaligned orbit and an outer planetary companion has been detected: HAT-P-11, pi Men, and Kepler-56. We need to find more of these systems to determine what process is most likely in the population!
Here's the Rossiter-McLaughlin effect, animated!
https://twitter.com/RyanRubenzahl/status/1354177561056538624?s=20
https://twitter.com/RyanRubenzahl/status/1354177561056538624?s=20
