Comments on: Why does HD 209458 b wear an XXL?

By: systemic - hot and bothered

systemic - hot and bothered — Sun, 21 Jan 2007 21:53:13 +0000

[...] A lot of astronomers are currently interested in the size question for the extrasolar planets, and we’ve written a number of oklo.org posts that cover the subject. [See 1. here, 2. here, 3. here, 4. here, 5. here, 6. here, 7. here, 8. here, and 9. here.] [...]

By: systemic - TrES-2

systemic - TrES-2 — Fri, 08 Sep 2006 07:11:28 +0000

[...] I’ve written several oklo posts about the size problem for the short-period extrasolar planets [see here, here, here, here and here]. In a nutshell, within the aggregate of transiting exoplanets that orbit stars bright enough for high-precision follow-up, there’s a full range of size discrepancies. HD 149026 b is much smaller than would be predicted for a standard-issue Jovian planet of its mass and temperature. TrES-1 has a radius that agrees very well with the theoretical predictions. HD 189733 is somewhat on the large side, and HD 209458 b, famously, is much larger than predicted. [In tomorrow’s post, I’ll give an update on the hydrodynamical simulations that we’ve been doing with the goal of eventually sorting out whether HD 209458 b is caught in Cassini state two.] [...]

By: systemic - Shallow Water

systemic - Shallow Water — Fri, 16 Jun 2006 23:01:20 +0000

[...] In a previous post, I talked about how the theoretical models that provide reasonable matches for the other 9 transiting planets predict that HD 209458 b’s radius should be slightly larger than Jupiter’s radius. The observations, on the other hand, make it clear that the planet is actually has a diameter about 1.35 times larger than Jupiter. HD 209458 b is by far the best-studied exoplanet, so it’s of more than passing interest to understand why it’s so large. [...]

By: systemic - Radius anomalies?

systemic - Radius anomalies? — Sat, 03 Jun 2006 20:40:57 +0000

[...] Readers of oklo.org are well aware that our theoretical understanding of the radii of hot Jupiters isn’t all it could be. For example, the transiting planets TrES-1 and HD 209458 b have very similar masses and surface temperatures, and yet HD 209458 b has a radius that is roughly 25% larger than TrES-1’s. In a previous post (see also this post), we outlined some of the hypotheses that might explain this discrepancy in radii. [...]

By: systemic - XO-1

systemic - XO-1 — Thu, 18 May 2006 21:11:55 +0000

[...] The preliminary indications are that this planet, which has a measured radius of 1.3 plus or minus 0.1 Jovian radii, is somewhat larger than expected. Our theoretical models predict that XO-1 should have a radius of 1.05 Rjup if there’s a 20-Earth mass core, and 1.11 Rjup if the planet is core-free. If the large radius is confirmed, then we’ll be faced with the same radius problem that we’re facing with HD 209458 b (as explained in this oklo post from Dec. 2005). An interesting clue may be provided by the fact that the XO-1 parent star, like HD 209458 is not particularly metal rich. [...]

By: systemic - Photometric Imaging

systemic - Photometric Imaging — Tue, 04 Apr 2006 23:55:24 +0000

[...] I should emphasize that transit observations using HST are of blockbuster-level scientific value. The exquisite HST photometry allows a very accurate measurement of the planetary radius, which in turn puts strong constraints on our theoretical models of the planetary interior (see this post for more information). The transit also strongly constrains the elements of the planetary orbit, and the color-dependence of the light curves permits the measurement of atmospheric constituents such as sodium and carbon monoxide. [...]