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HD 80606b Transit Bagged

An email from Greg Laughlin confirms that the planet HD 80606b has indeed been caught in a transit, a roughly 15 percent probability now turned into hard data. Laughlin (UCSC) and team recently wrote up their Spitzer infrared observations of this mutable gas giant, a world with an orbit so eccentric that it almost mimics a comet, swinging out to 0.85 AU from its star, then rushing in to a breathtaking 0.03 AU for a brief, searing encounter. The possibility of a transit has been on his mind ever since.

“If you could float above the clouds of this planet, you’d see its sun growing larger and larger at faster and faster rates, increasing in brightness by almost a factor of 1,000,” Laughlin said at the end of January in this JPL news release. His team captured what happens on this world as its atmosphere heats rapidly and produces 5 kilometer per second winds that create vast storm systems, gradually easing as the planet moves away from its star. I’ve already run the resultant image (which also became the cover of the late January issue of Nature that the paper ran in), but let’s see it again. After all, we’re looking at the most realistic image yet made of an exoplanet.


Image: The planet HD80606b glows orange from its own heat in this computer-generated image. A massive storm has formed in response to the pulse of heat delivered during the planet’s close swing past its star. The blue crescent is reflected light from the star. Credit: D. Kasen, J. Langton, and G. Laughlin (UCSC).

Of course, HD 80606b isn’t your normal exoplanet, not even by the exotic standards of the many ‘hot Jupiters’ we’ve found. Most of these — gas giants orbiting tightly around their parent stars — are assumed to be in tidal lock, with one side always facing the star. HD 80606b, on the other hand, is spinning, which gave the scientists the chance to collect data showing how its atmosphere responds to the changing temperatures.

From a recent systemic story:

Our interpretation of the light curve is that we’re seeing the planet heat up rapidly, from a temperature of roughly 800K to a temperature of about 1500K over a time period lasting roughly five or six hours. This indicates that the starlight is being absorbed at quite a high level in the atmosphere, where the air is thin and the heat capacity is low.

Who would have thought the storm systems of Jupiter were trivial? But compared to HD 80606b’s activity in the less than a day it takes to move through periastron, Jupiter dishes up little more than a tropical breeze. Observers worldwide went to work on the mid-February transit opportunity, covered by regular updates on Laughlin’s systemic site, even as they battled weather issues in eastern Europe and Scandinavia. The transit discovery paper notes that only five of the known transiting planets have a period of more than five days, with HD 80606b becoming the sixth and having much the longest period, a full 111.4 days.

All this has me wondering how anyone with an interest in astronomy could fail to be drawn to the exoplanet hunt in this remarkable period of discovery. Congratulations to Greg, whose tireless work on this sizzling world called the attention of astronomers to the transit possibility, and provided a continuing forum for discussion. It was fine work all around, and let’s hope Greg’s team wins approval on its recent request for more Spitzer time later this year and in 2010 to again study HD 80606b.

The discovery paper is Moutou et al., “Photometric and spectroscopic detection of the primary transit of the 111-day-period planet HD 80606 b,” submitted to Astronomy & Astrophysics (abstract). The Nature paper is Laughlin et al., “Rapid heating of the atmosphere of an extrasolar planet,” Nature 457 (29 January 2009), pp. 562-564 (abstract).

Addendum: David Kipping (whose work on exomoons we have examined previously in these pages) reports that he also detected the HD 80606b transit at the University Observatory of London. More on that catch in his team’s paper, “Detection of the transit by the planetary companion to HD 80606,” available here. Writes Kipping, “We are all very pleased here to have detected such a challenging target from the city limits of London. Due to the very long transit duration we are able to pin down the system parameters to a very high precision despite only using ground based telescopes. It really is a truly bizarre world, as Greg pointed out in his quotes in your article!” Nice catch!

Comments on this entry are closed.

  • george scaglione February 26, 2009, 15:33

    hello all.is it just me or do i seem to see more and more stories on planets that have either been found or shall be searched for (to include “class m ” types.don’t get me wrong for a second i know that there are alot of planets out there to include probably,most probably,other earth like “class m” worlds as well! but excuse me,the real question – how many intelligent worlds that include civilizations that have space flight?! i read about that too recently and i would tend to agree with the opinion expressed in that article.those are probably very few.would like to know how everybody else sees it? but yes this can turn out to be a great avenue for discussion.perfect sort of thing for a group like ours.i am proud to get in the first comment here as well, as far as i can see… but thanks everybody,your friend george

  • andy February 26, 2009, 17:08

    Well, this is substantially awesome, especially the hints of a large spin-orbit misalignment, which implicates the Kozai mechanism at work in generating the high eccentricity.

  • Dave Moore February 26, 2009, 18:29

    What is the Kozai mechanism?

  • Colin Weaver February 27, 2009, 8:45

    As a humble software engineer, I have no scientific insight to add here.

    I just wish to say that this post, amongst others on this site, has once again stimulated my sense of awe and wonder into overdrive.

    What a wonderful time to be alive. I am grateful to have the opportunity to learn of such wonders.

  • andy February 27, 2009, 16:57

    Dave Moore: the Kozai mechanism is a coupling between orbital inclination and eccentricity that occurs for highly inclined orbits. There’s some discussion about it at the Gravity Simulator website.

  • Administrator February 27, 2009, 20:59

    Colin Weaver writes:

    What a wonderful time to be alive. I am grateful to have the opportunity to learn of such wonders.

    I can only echo this comment — what a pleasure it is to be able to write about such wonders every day, and with Kepler’s launch imminent, just consider how much we’ll have to talk about re exoplanetary discovery in coming months…

  • Davey March 3, 2009, 11:23

    If it weren’t a gas giant, HD 80606b would almost sound like Priplanus! ;-)

  • ljk July 2, 2009, 15:10

    Ground-Based Photometric Searches for Transiting Planets

    Authors: Tsevi Mazeh (Tel Aviv University)

    (Submitted on 30 Jun 2009)

    Abstract: This paper reviews the basic technical characteristics of the ground-based photometric searches for transiting planets, and discusses a possible observational selection effect. I suggest that additional photometric observations of the already observed fields might discover new transiting planets with periods around 4-6 days.

    The set of known transiting planets support the intriguing correlation between the planetary mass and the orbital period suggested already in 2005.

    Comments: Proceedings of IAU Symposium 253 “Transiting Planets”, p. 11-19

    Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

    Journal reference: 2009IAUS..253…11M

    DOI: 10.1017/S1743921308026185

    Cite as: arXiv:0907.0007v1 [astro-ph.EP]

    Submission history

    From: Avi Shporer [view email]

    [v1] Tue, 30 Jun 2009 20:26:44 GMT (32kb)


  • ljk July 9, 2009, 13:16

    Inflating and Deflating Hot Jupiters: Coupled Tidal and Thermal Evolution of Known Transiting Planets

    Authors: N. Miller (UCSC), J. J. Fortney (UCSC), B. Jackson (NASA Goddard)

    (Submitted on 7 Jul 2009)

    Abstract: We examine the radius evolution of close-in giant planets with a planet evolution model that couples the orbital-tidal and thermal evolution. For 45 transiting systems, we compute a large grid of cooling/contraction paths forward in time, starting from a large phase space of initial semi-major axes and eccentricities.

    Given observational constraints at the current time for a given planet (semi-major axis, eccentricity, and system age) we find possible evolutionary paths that match these constraints, and compare the calculated radii to observations.

    We find that tidal evolution has two effects. First, planets start their evolution at larger semi-major axis, allowing them to contract more efficiently at earlier times. Second, tidal heating can significantly inflate the radius when the orbit is being circularized, but this effect on the radius is short-lived thereafter. Often circularization of the orbit is proceeded by a long period while the semi-major axis slowly decreases.

    Some systems with previously unexplained large radii that we can reproduce with our coupled model are HAT-P-7, HAT-P-9, WASP-10, and XO-4. This increases the number of planets for which we can match the radius from 24 (of 45) to as many as 35 for our standard case, but for some of these systems we are required to be viewing them at a special time around the era of current radius inflation. This is a concern for the viability of tidal inflation as a general mechanism to explain most inflated radii. Also, large initial eccentricities would have to be common.

    We also investigate the evolution of models that have a floor on the eccentricity, as may be due to a perturber. In this scenario we match the extremely large radius of WASP-12b. (Abridged)

    Comments: 18 pages, 14 figures, 2 tables, Accepted for publication in ApJ

    Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

    Cite as: arXiv:0907.1268v1 [astro-ph.EP]

    Submission history

    From: Neil Miller [view email]

    [v1] Tue, 7 Jul 2009 18:43:19 GMT (500kb)


  • ljk September 1, 2009, 21:26

    The Transit Ingress and the Tilted Orbit of the Extraordinarily Eccentric Exoplanet HD 80606b

    Authors: Joshua N. Winn, Andrew W. Howard, John Asher Johnson, Geoffrey W. Marcy, J. Zachary Gazak, Donn Starkey, Eric B. Ford, Knicole D. Colon, Francisco Reyes, Lisa Nortmann, Stefan Dreizler, Stephen Odewahn, William F. Welsh, Shimonee Kadakia, Robert J. Vanderbei, Elisabeth R. Adams, Matthew Lockhart, Ian J. Crossfield, Jeff A. Valenti, Ronald Dantowitz, Joshua A. Carter

    (Submitted on 29 Jul 2009 (v1), last revised 1 Sep 2009 (this version, v3))

    Abstract: We present the results of a transcontinental campaign to observe the 2009 June 5 transit of the exoplanet HD 80606b. We report the first detection of the transit ingress, revealing the transit duration to be 11.64 +/- 0.25 hr and allowing more robust determinations of the system parameters.

    Keck spectra obtained at midtransit exhibit an anomalous blueshift, giving definitive evidence that the stellar spin axis and planetary orbital axis are misaligned. The Keck data show that the projected spin-orbit angle is between 32-87 deg with 68.3% confidence and between 14-142 deg with 99.73% confidence.

    Thus the orbit of this planet is not only highly eccentric (e=0.93), but is also tilted away from the equatorial plane of its parent star. A large tilt had been predicted, based on the idea that the planet’s eccentric orbit was caused by the Kozai mechanism.

    Independently of the theory, it is noteworthy that all 3 exoplanetary systems with known spin-orbit misalignments have massive planets on eccentric orbits, suggesting that those systems migrate differently than lower-mass planets on circular orbits.

    Comments: ApJ, in press [13 pg]

    Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR)

    Cite as: arXiv:0907.5205v3 [astro-ph.EP]

    Submission history

    From: Joshua N. Winn [view email]

    [v1] Wed, 29 Jul 2009 20:00:30 GMT (276kb)

    [v2] Tue, 18 Aug 2009 13:18:47 GMT (277kb)

    [v3] Tue, 1 Sep 2009 12:39:50 GMT (277kb)