If the weather on Uranus, examined here yesterday, isn’t exotic enough for your taste, consider the situation on Jupiter-class worlds around other stars. A ‘hot Jupiter’ orbiting extremely close to its star spawns weather like nothing we’ve ever experienced, as modeled by computer simulations coming out of the University of Arizona. And while we can’t actually image these objects yet, we can certainly deduce a great deal about them from observations made during the times they transit their star.
On that score, well-studied HD 189733b is an early example of pushing the envelope. Located 63 light years from Earth, this transiting planet orbits once every 2.2 days, scooting along a mere three million miles from its primary. Spitzer Space Telescope data culling variations in starlight during the frequent planetary transits have allowed us to peg daytime temperatures on worlds like these, usually in a range somewhere between 2000 and 3000 degrees Fahrenheit (1300 and 1900 degrees Kelvin). What stands out in studies of HD 189733b, though, is the nightside, where temperatures reach almost 1300 degrees Fahrenheit (1000 degrees Kelvin) despite the obvious lack of light.
Considering how close this planet is to its star, that nightside reading is deeply interesting. It implies a robust heat transfer mechanism in the form of strong winds, a finding that may be generalized across the entire family of hot Jupiters. Much work has already gone into this. Have a look, for example, at this story on David Charbonneau’s work on HD 189733b’s atmosphere, followed by Geneva studies by Frédéric Pont that seem to identify haze there. Adam Showman (University of Arizona), who led the work we’re looking at today, is now producing the computer models that firm up the hot Jupiter picture. Says Showman:
“These planets are 20 times closer to their star than Earth is to the Sun, and so they are truly blasted by starlight… Because these planets are so close to their stars, we think they’re tidally locked, with one side permanently in starlight and the other side permanently in darkness. So, if there were no winds, the dayside would be extremely hot and the nightside would be extremely cold.”
Showman’s group performed 3-D simulations that factored in the absorption of all that blazing starlight and the ways in which a planet loses heat to space. The models explain the observed data for HD 189733b and suggest the kind of winds we’re talking about — jet streams with speeds reaching over 11,000 kilometers per hour. Winds like that, moving from west to east, push the hottest regions on the planet away from the ‘high noon’ region, Showman adds, and move them further east by about thirty degrees of longitude.
And I used to think that Venus was a good description of hell… Maybe it still is, but ‘hot Jupiters’ with supersonic winds and dayside temperatures that would melt lead now seem an even better way to view it. In any case, note the considerable distance we’re moving from early exoplanet work, which produced the first mass and orbital information about these distant worlds. Now we’re actually looking at planetary weather patterns for objects we cannot yet see directly. The science of exoplanet mapping is indeed in its infancy, but great things are coming.
Hi Paul;
This is a fascinating article.
When we are eventually able to image the atmospheric turbulance and cloud patterns of such hot Jupiters, the amazing pictures will no doubt grace the covers of many paper based periodicals and magazines. With the development of optical VLBI telescopes and the rapid progress being made in optical imaging, perhaps this could happen this very century if not within the first half of the 21st century. Interstellar probes to these hellish worlds will no doubt provide increadible and detailed images of atmospheric clouds and turbulance patterns to the delight of all those who view the images. Audio clips from such worlds that detail the sound of wind storms will be fascinating as well. Then, if all goes according to the desires of organizations like Tau Zero and Centauri Dreams, manned missions to these extra solar worlds or regions safely distant but proximate to them will provide the whole global community with delight, fascination, and pride at what we humans can do when we put our minds to it.
Thanks;
Jim
My question is, “How do these planets keep their atmosphere?”
It seems to me that no matter how much these planetary types have, their atmospheres would be blasted away by solar storms and flares within a few millennia.
Not sure how well it is possible to justify extending this over all hot Jupiters: in contrast to HD 189733b, the planet Upsilon Andromedae b seems to have a very poor efficiency at transporting heat to the nightside, as noted in a previous Centauri Dreams post.
Stellar activity of planetary host star HD 189733
Authors: I. Boisse, C. Moutou, A. Vidal-Madjar, F. Bouchy, F. Pont, G. Hébrard, X. Bonfils, B. Croll, X. Delfosse, M. Desort, T. Forveille, A.-M. Lagrange, B. Loeillet, C. Lovis, J. M. Matthews, M. Mayor, F. Pepe, C. Perrier, D. Queloz, J. F. Rowe, N. C. Santos, D. Ségransan, S. Udry
(Submitted on 24 Nov 2008)
Abstract: Extra-solar planet search programs require high-precision velocity measurements. They need to study how to disentangle radial-velocity variations due to Doppler motion from the noise induced by stellar activity.
We monitored the active K2V star HD 189733 and its transiting planetary companion that has a 2.2-day orbital period. We used the high-resolution spectograph SOPHIE mounted on the 1.93-m telescope at the Observatoire de Haute-Provence to obtain 55 spectra of HD 189733 over nearly two months. We refined the HD 189733b orbit parameters and put limits on the eccentricity and on a long-term velocity gradient.
After subtracting the orbital motion of the planet, we compared the variability of spectroscopic activity indices to the evolution of the radial-velocity residuals and the shape of spectral lines. The radial velocity, the spectral-line profile and the activity indices measured in HeI (5875.62 \AA), Halpha (6562.81 \AA) and the CaII H&K lines (3968.47 \AA and 3933.66 \AA, respectively) show a periodicity around the stellar rotation period and the correlations between them are consistent with a spotted stellar surface in rotation. We used such correlations to correct for the radial-velocity jitter due to stellar activity.
This results in achieving high precision on the orbit parameters, with a semi-amplitude K = 200.56 \pm 0.88 m.s-1 and a derived planet mass of M_{P}=1.13 \pm 0.03 M$_{Jup}$.
Comments: 9 pages, 2 tables, 9 figures, accepted for publication in A&A on 20/11/2008
Subjects: Astrophysics (astro-ph)
Cite as: arXiv:0811.3923v1 [astro-ph]
Submission history
From: Isabelle Boisse [view email]
[v1] Mon, 24 Nov 2008 16:49:32 GMT (171kb)
http://arxiv.org/abs/0811.3923
On the Semimajor Axis Distribution of Extrasolar Gas Giant Planets: Why Hot Jupiters Are Rare Around High-Mass Stars
Authors: Thayne Currie (Harvard-Smithsonian Center for Astrophysics)
(Submitted on 19 Feb 2009 (v1), last revised 23 Feb 2009 (this version, v2))
Abstract: Based on a suite of Monte Carlo simulations, I show that a stellar-mass dependent lifetime of the gas disks from which planets form can explain the lack of hot Jupiters/close-in giant planets around high-mass stars and other key features of the observed semimajor axis distribution of radial velocity-detected giant planets.
Using reasonable parameters for the Type II migration rate, regions of planet formation, and timescales for gas giant core formation, I construct synthetic distributions of jovian planets. A planet formation/migration model assuming a stellar mass-dependent gas disk lifetime reproduces key features in the observed distribution by preferentially stranding planets around high-mass stars at large semimajor axes.
Comments: 13 pages, 3 figures, 1 table; Accepted for publication in The Astrophysical Journal Letters
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR)
Cite as: arXiv:0902.3459v2 [astro-ph.EP]
Submission history
From: Thayne Currie [view email]
[v1] Thu, 19 Feb 2009 21:01:04 GMT (145kb)
[v2] Mon, 23 Feb 2009 03:17:25 GMT (145kb)
http://arxiv.org/abs/0902.3459
The secondary eclipse of CoRoT-1b
Authors: R. Alonso, A. Alapini, S. Aigrain, M. Auvergne, A. Baglin, M. Barbieri, P. Barge, A.S. Bonomo, P. Borde, F. Bouchy, S. Chaintreuil, R. De la Reza, H.J. Deeg, M. Deleuil, R. Dvorak, A. Erikson, M. Fridlund, F. Fialho, P. Gondoin, T. Guillot, A. Hatzes, L. Jorda, H. Lammer, A. Leger, A. Llebaria, P. Magain, T. Mazeh, C. Moutou, M. Ollivier, M. Patzold, F. Pont, D. Queloz, H. Rauer, D. Rouan, J. Schneider, G. Wuchterl
(Submitted on 9 Jul 2009)
Abstract: The transiting planet CoRoT-1b is thought to belong to the pM-class of planets, in which the thermal emission dominates in the optical wavelengths. We present a detection of its secondary eclipse in the CoRoT white channel data, whose response function goes from ~400 to ~1000 nm.
We used two different filtering approaches, and several methods to evaluate the significance of a detection of the secondary eclipse. We detect a secondary eclipse centered within 20 min at the expected times for a circular orbit, with a depth of 0.016+/-0.006%. The center of the eclipse is translated in a 1-sigma upper limit to the planet’s eccentricity of ecosomega<0.014. Under the assumption of a zero Bond Albedo and blackbody emission from the planet, it corresponds to a T_{CoRoT}=2330 +120-140 K. We provide the equilibrium temperatures of the planet as a function of the amount of reflected light.
If the planet is in thermal equilibrium with the incident flux from the star, our results imply an inefficient transport mechanism of the flux from the day to the night sides.
Comments: 6 pages, to appear in A&A, submitted 18 march 2009, accepted 7 July 2009
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:0907.1653v1 [astro-ph.EP]
Submission history
From: Roi Alonso [view email]
[v1] Thu, 9 Jul 2009 20:00:14 GMT (330kb)
http://arxiv.org/abs/0907.1653