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Habitable Planets Conference Update

The exoplanet hunt has entered a significant new phase, one focused on transiting planets and the useful things we can learn about their physical properties and atmospheres through such events. Driven by CoRoT and Kepler, we’re now in position to use those transits to spot smaller worlds than ever, down to terrestrial size, and naturally the focus is on Earth analogs located in the habitable zones of their stars.

So think of it this way: We’ve gone from a broad-brush approach based largely on radial velocity methods to a more selective hunt, one that will take us to the realm of planets that can have liquid water on their surfaces and aren’t so different from our own. Not that the continuing work on characterizing planetary systems is of any less importance, but we’ve found plenty of gas giants, and now we’re trying to learn something about how common these smaller worlds may be.

Putting an exclamation point on this focus is a conference called Pathways Towards Habitable Planets, to be held in Barcelona from the 14th to the 18th of this month. The European Blue Dots Team (BDT) is an initiative made up of researchers who focus on finding habitable worlds, with international assistance. The purpose of its Barcelona conclave is to bring together space agencies from around the world to discuss how to learn more about planets of the kind Kepler and CoRoT may find.


A glance through the program shows how wide-ranging this discussion is likely to be. Some examples: Differing cultural views on the ‘are we alone’ question (Jean Schneider, CNRS-Paris Observatory). Tidal constraints on habitability (that one, as you might expect from discussions here) is from Rory Barnes (University of Arizona). A coronagraph concept for direct imaging and spectroscopy of exoplanetary systems (John Trauger, JPL). And an old Centauri Dreams friend: David Kipping (University College, London) discussing habitable exomoons.

Image: One way to study habitable exoplanets is through a space telescope coupled with a starshade concept like New Worlds Observer. This is a simulated image of the inner solar system taken at 10 parsecs with a 4-meter telescope. The Earth is clearly visible as a pale, blue dot. Venus is harder to make out due to the zodiacal light. The inclination of this image is 60 degrees. Credit: Phil Oakley.

The proceedings are to be published in the spring, but we should have copies of some of these papers for review in the near future. It’s good to see that Webster Cash (University of Colorado, Boulder) will be presenting the latest on his New Worlds Observer, a space-based starshade design that would be able to perform spectroscopy on exoplanetary light to look for biological markers. Long championed here, this powerful concept has had its ups and downs re funding but clearly remains viable.


Comments on this entry are closed.

  • tacitus September 7, 2009, 15:44

    Of related interest, here’s a very interesting diary post from one of the Kepler team of scientists on their first look at some of the tens of thousands of light curves coming back from the spacecraft. You can really tell that they must be like kids in a candy store to have so many weird and wonderful light curves to view and explain:


    I particularly love the speculation:

    Some of these have such high frequency oscillations that they look like human voice recordings. I joked with him that we should play a few through the sound card to see if we could hear “hello, Earthlings!”. A civilization that can modulate the brightness of their star to transmit such messages would be awesome, indeed.

    I know it’s far fetched, but if intelligent life is extremely rare on a galactic scale, then it would be beyond the realm of imagination to consider the possibility that stars like Cepheid variables (stars visible across intergalactic distances and useable as standard candles) could be used as a communications medium in some way.

    And if you want to see some of the first light curves for yourself, there’s a Powerpoint presentation available from the Kepler web site:


  • andy September 7, 2009, 16:13

    Oh wow I hadn’t realised there was a known transiting Neptune-class planet in the Kepler field… given that there are (currently) only two such planets known, that’s a stroke of luck.

    As for the lightcurves in that presentation, the “binary with circumbinary planet?” one is very odd… the “planet transit” feature recurs twice per binary orbit. Figuring out a stable configuration that would do that is going to be an interesting challenge.

  • Ronald September 8, 2009, 8:48


    not directly, but maybe indirectly related: do you know, are you going to cover, the recent findings with regard to the extreme suitability of the Antarctic Plateau, particularly ‘Ridge A’ for optical telescopes?

  • Administrator September 8, 2009, 9:56

    Ronald, do you have a pointer on this? Haven’t been following anything re optical telescopes in Antarctica of late. I’ll be glad to look into it.

  • Ronald September 8, 2009, 14:32

    Paul: hereby, two links to articles;

    Astronomers find coldest, driest, calmest place on Earth

    Camera at South Pole to determine if its night sky is ideal for new telescope

  • ljk September 9, 2009, 12:55

    A Survey of Multiple Planet Systems

    Authors: Jason T. Wright

    (Submitted on 4 Sep 2009)

    Abstract: As of August 2008, over 30 multiple exoplanet systems are known, and 28% of stars with planets show significant evidence of a second companion. I briefly review these 30 systems individually, broadly grouping them into five categories: 1) systems with 3 or more giant (Msini > 0.2 M_Jup) planets, 2) systems with two giant planets in mean motion resonance (MMR), 3) systems with two giant planets not in MMR but whose dynamical evolution is affected by planet-planet interactions, 4) highly hierarchical systems, having two giant planets with very large period ratios (> 30:1), and 5) systems of “Super-Earths”, containing only planets with (Msini < 20 M_Earth).

    It now appears that eccentricities are not markedly higher among planets in known multiple planet systems, and that planets with Msini < 1 M_Jup have lower eccentricities than more massive planets. The distribution of semimajor axes for planets in multiplanet systems does not show the 3-day pile-up or the 1 AU "jump" of the apparently-single planet distribution.

    Comments: 17pp, 3 figures. To be published in proceedings to the Torun, Poland conference on "Extrasolar planets in multi-body systems: theory and observations", held August 2008. Multiplanet systems discovered since then are not discussed

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

    Cite as: arXiv:0909.0957v1 [astro-ph.EP]

    Submission history

    From: Jason Wright [view email]

    [v1] Fri, 4 Sep 2009 20:58:40 GMT (22kb)


  • ljk September 10, 2009, 12:47

    On the Period-Mass Functions of Extrasolar Planets

    Authors: Li-Chin Yeh (1), Yen-Chang Chang (1), Wen-Liang Hung (1), Ing-Guey Jiang (2) ((1)National Hsinchu University of Education, Hsin-Chu, Taiwan, (2)National Tsing-Hua University, Hsin-Chu, Taiwan)

    (Submitted on 9 Sep 2009)

    Abstract: Using the period and mass data of two hundred and seventy-nine extrasolar planets, we have constructed a coupled period-mass function through the non-parametric approach. This analytic expression of the coupled period-mass function has been obtained for the first time in this field. Moreover, due to a moderate period-mass correlation, the shapes of mass/period functions vary as a function of period/mass.

    These results of mass and period functions give way to two important implications: (1) the deficit of massive close-in planets is confirmed, and (2) the more massive planets have larger ranges of possible semi-major axes. These interesting statistical results will provide important clues into the theories of planetary formation.

    Comments: 3 pages, 1 figure, in Proceedings of the 10th Asian-Pacific Regional IAU Meeting, page 80-82, 2009

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

    Cite as: arXiv:0909.1604v1 [astro-ph.EP]

    Submission history

    From: Ing-Guey Jiang [view email]

    [v1] Wed, 9 Sep 2009 01:53:27 GMT (57kb)


  • ljk September 10, 2009, 12:55

    Transit Lightcurves of Extrasolar Planets Orbiting Rapidly-Rotating Stars

    Authors: Jason W. Barnes

    (Submitted on 9 Sep 2009)

    Abstract: Main-sequence stars earlier than spectral type ~F6 or so are expected to rotate rapidly due to their radiative exteriors. This rapid rotation leads to an oblate stellar figure. It also induces the photosphere to be hotter (by up to several thousand Kelvin) at the pole than at the equator as a result of a process called gravity darkening that was first predicted by von Zeipel (1924).

    Transits of extrasolar planets across such a non-uniform, oblate disk yield unusual and distinctive lightcurves that can be used to determine the relative alignment of the stellar rotation pole and the planet orbit normal. This spin-orbit alignment can be used to constrain models of planet formation and evolution.

    Orderly planet formation and migration within a disk that is coplanar with the stellar equator will result in spin-orbit alignment. More violent planet-planet scattering events should yield spin-orbit misaligned planets. Rossiter-McLaughlin measurements of transits of lower-mass stars show that some planets are spin-orbit aligned, and some are not.

    Since Rossiter-McLaughlin measurements are difficult around rapid rotators, lightcurve photometry may be the best way to determine the spin-orbit alignment of planets around massive stars.

    The Kepler mission will monitor ~10^4 of these stars within its sample. The lightcurves of any detected planets will allow us to probe the planet formation process around high-mass stars for the first time.

    Comments: 14 pages, 9 figures, accepted to ApJ

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

    Cite as: arXiv:0909.1752v1 [astro-ph.EP]

    Submission history

    From: Jason Barnes [view email]

    [v1] Wed, 9 Sep 2009 17:28:47 GMT (1630kb)


  • daniel September 11, 2009, 13:25

    there is this interesting paper too of the possibility of detection of circumbinary planets by radial velocity…

    The Radial Velocity TATOOINE Search for Circumbinary Planets: Planet Detection Limits for a Sample of Double-lined Binary Stars – Initial Results from Keck I/Hires, Shane/CAT/Hamspec and TNG/Sarg Observations
    Authors: Maciej Konacki, Matthew W. Muterspaugh, Shrinivas R. Kulkarni, Krzysztof G. Hełminiak
    (Submitted on 26 Aug 2009)

    Abstract: We present preliminary results of the first and on-going radial velocity survey for circumbinary planets. With a novel radial velocity technique employing an iodine absorption cell we achieve an unprecedented RV precision of up to 2 m/s for double-lined binary stars. The high resolution spectra collected with the Keck I/Hires, TNG/Sarg and Shane/CAT/Hamspec telescopes/spectrographs over the years 2003-2008 allow us to derive RVs and compute planet detection limits for ten double-lined binary stars. For this initial sample of targets, we can rule out planets on dynamically stable orbits with masses as small as ~0.3 to 3 MJup for the orbital periods of up to ~5.3 years. Even though the presented sample of stars is too small to make any strong conclusions, it is clear that the search for circumbinary planets is now technique-wise possible and eventually will provide new constraints for the planet formation theories.

    Comments: to appear in ApJ

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

    Stellar Astrophysics (astro-ph.SR)

    Cite as: arXiv:0908.3775v1 [astro-ph.EP]

    Submission history

    From: Maciej Konacki [view email]
    [v1] Wed, 26 Aug 2009 09:11:47 GMT (258kb)