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Systemic - Characterizing Extrasolar Planetary Systems

This just in…

25 Mar 2010, 22:47 UTC
This just in…
(200 words excerpt, click title or image to see full post)

With HAT-P-13c rapidly coming ’round the mountain, there was a very timely update on astro-ph last night. Josh Winn and his collaborators have obtained an additional slew of radial velocities which (1) demonstrate using the Rossiter-McLaughlin effect that the inner planet b’s orbit is likely well aligned with the stellar equator, (2) modify the orbital parameters, including the period of the outer massive planet, and (3) hint at a third body further out in the system.
How do these updates affect the unfolding story?
The Rossiter-McLaughlin measurement gives a measurement of the angle “lambda” = -0.9±8.5 degrees, which is the angular difference between the sky-projected orbital angular momentum vector and sky-projected stellar spin vector. A non-intuitive mouthful. If we’re viewing the star edge-on, then lambda = -0.9 degrees amounts to a determination that the planet’s orbital plane is well-aligned with the star’s equator. (See this post for a discussion of what can happen if the star’s rotation axis is tipped toward the Earth). The good news in this measurement is that it makes it a-priori more likely that planets b and c are coplanar, that happy state of affairs which will permit direct measurements of planet b’s interior structure and ...

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