≡ Menu

Exoplanet Transits: Maxing Out Our Resources

I’m a great believer in getting the most out of older systems. The computer I do most of my work on is now eight years old. I have access to newer equipment, but I built this box with an eye toward longevity and I’m still happy with it. With the pace of technological change, it’s definitely gotten creaky despite additional memory, a new video card and various other upgrades. That means that Windows gets slower and slower on it, but then, I rarely use Windows, being an open source guy to the bone. Linux has always been my choice.

Now the nice thing about Linux is that, no matter which version I run (and I’ve run quite a few by now), I can get snappy performance out of this old box. The astronomical analogy isn’t too far to seek — these days we’re talking about building larger and larger Earth-based telescopes, and in fact have just inaugurated the Gran Telescopio Canarias on a 7,874-foot mountaintop in the Canary Islands, an instrument that has the largest segmented mirror — 10.4 meters — built so far for an optical-infrared telescope. All of which is great news, but consider how exoplanetary science also manages to pull good data out of much smaller, less heralded equipment.

Thus the June transit of HD 80606b, a gas giant of roughly Jupiter size some 200 light years away. About a dozen observatories went to work on the planet on the night of June 4, with a keen interest in tracking it because the previous transit, last February, had only been partially observed. The gas giant orbits once every 111 days and the transit is roughly twelve hours long, so astronomers adopted the tag-team approach to work on the event. Handing HD 80606b from Massachusetts to Florida (see below) to Indiana to Hawaii, various observatories captured some six hours of observations despite iffy weather along the route.


Image: Rosemary Hill Observatory in rural Levy County, Florida, in a shot from 1996 that shows Comet Hyakutake to the right of the dome, with the Pleiades and Venus on the left. Credit: Francisco Reyes/Rosemary Hill Observatory.

Thus an instrument like the 30-inch reflector at Rosemary Hill Observatory in Florida was able to play a key role in a string of observations that also included the 10-meter Keck I telescope in Hawaii. Useful observations, too, because HD 80806b’s orbit is an elongated ellipse whose cause is thought to be the pull of a companion star. According to this University of Florida news release, the recent observations have shown that the planet’s orbit is not aligned with the star’s rotation, evidence that this theory is correct. In any case, what a pleasure to be reminded that careful work can keep older equipment very much in the hunt.

Planet-hunter Greg Laughlin (UC-Santa Cruz) also commented on the collaboration, from which this:

This is just the sort of project that underscores the great value of ad-hoc collaborations. The Florida ingress observations, for example, were made using the University of Florida’s recently refurbished Rosemary Hill Observatory, 30 miles from Gainesville. The DeKalb observations, made by Indiana amateur Donn Starkey, produced reduced data that were among the best in the entire aggregate. Mount Laguna Observatory, run by San Diego State University, has generated many cutting-edge exoplanet observations, including critical photometry in the Fall 2007 HD 17156b campaign. The University of Hawaii 2.2m telescope turned out photometry with astonishing rms=0.00031 precision. And as the cherry on top, the simultaneous commandeering of not one but two major telescopes on Mauna Kea? It seems that perhaps someone has made a Faustian bargain.

The latest transit of HD 80606b was last Thursday morning. We’ll see what turned up.


Comments on this entry are closed.

  • andy September 29, 2009, 16:29

    HD 80606b is a good example of just how much damage you can do to a planetary system: an extremely eccentric planet in an orbit with a high inclination to its star’s equator (at least according to current measurements, hopefully there’s been another measurement of the Rossiter-McLaughlin effect this time around).

    Another good target for such a transit collaboration would be the potential ~31 hour transit of HAT-P-13c in April 2010, the second companion (either a massive planet or low-mass brown dwarf) in a system already known to contain one transiting planet. As has been noted by Greg Laughlin at systemic, HAT-P-13 is a system that offers a detailed window into the internal structure of gas giant planets.

  • Carl September 29, 2009, 17:40

    Linux is my primary choice, for sure. I kept Windows for various reasons, shrunk the volume, and partitioned the disk with the installation DVD. There is no Windows installer, the LInux LOader being able to boot either OS.

  • djlactin September 30, 2009, 2:54

    Is there any chance of applying long-baseline interferometry to extract yet more detail from the data?

  • ljk October 4, 2009, 22:56

    Giant Planet Atmospheres and Spectra

    Authors: Adam Burrows (Princeton University), Glenn Orton (NASA/JPL)

    (Submitted on 1 Oct 2009)

    Abstract: Direct measurements of the spectra of extrasolar giant planets are the keys to determining their physical and chemical nature. The goal of theory is to provide the tools and context with which such data are understood. It is only by putting spectral observations through the sieve of theory that the promise of exoplanet research can be realized.

    With the new {\em Spitzer} and HST data of transiting “hot Jupiters,” we have now dramatically entered the era of remote sensing. We are probing their atmospheric compositions and temperature profiles, are constraining their atmospheric dynamics, and are investigating their phase light curves.
    Soon, many non-transiting exoplanets with wide separations (analogs of Jupiter) will be imaged and their light curves and spectra measured.

    In this paper, we present the basic physics, chemistry, and spectroscopy necessary to model the current direct detections and to develop the more sophisticated theories for both close-in and wide-separation extrasolar giant planets that will be needed in the years to come as exoplanet research accelerates into its future.

    Comments: in EXOPLANETS, edited by S. Seager, to be published in the Spring of 2010 in the Space Science Series of the University of Arizona Press (Tucson, AZ) (refereed)

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

    Cite as: arXiv:0910.0248v1 [astro-ph.EP]

    Submission history

    From: Adam Burrows [view email]

    [v1] Thu, 1 Oct 2009 20:00:19 GMT (666kb)


  • ljk October 16, 2009, 12:34

    Transit detections of extrasolar planets around main-sequence stars – I. A sky map for Hot Jupiters

    Authors: René Heller (1), Dimitris Mislis (1), John Antoniadis (2) ((1) University of Hamburg (Hamburger Sternwarte), (2) Aristotle University of Thessaloniki)

    (Submitted on 15 Oct 2009)

    Abstract: The findings of more than 350 extrasolar planets, most of them nontransiting Hot Jupiters, have revealed correlations between the metallicity of the main-sequence (MS) host stars and planetary incidence. This connection can be used to calculate the planet formation probability around other stars, not yet known to have planetary companions.

    We locate the promising spots for current transit surveys on the celestial plane and strive for absolute values of the expected number of transits in general. We used data of the Tycho catalog for about 1 million objects to locate all the stars with 0m < m_V < 11.5m on the celestial plane. We took several empirical relations between the parameters listed in the Tycho catalog, such as distance to Earth, m_V, and (B-V), and those parameters needed to account for the probability of a star to host an observable, transiting exoplanet.

    The empirical relations between stellar metallicity and planet occurrence combined with geometrical considerations were used to yield transit probabilities for the MS stars in the Tycho catalog. Magnitude variations in the FOV were simulated to test whether this fluctuations would be detected by BEST, XO, SuperWASP and HATNet. We present a sky map of the expected number of Hot Jupiter transit events on the basis of the Tycho catalog.

    The comparison between the considered transit surveys yields significantly differing maps of the expected transit detections. The sky-integrated magnitude distribution predicts 20 Hot Jupiter transits with orbital periods between 1.5 d and 50 d and m_V < 8m, of which two are currently known.

    In total, we expect 3412 Hot Jupiter transits to occur in front of MS stars within the given magnitude range. The most promising observing site on Earth is at latitude = -1.

    Comments: accepted by AandA October 3 2009, 9 pages, 3 figures including 5 transit sky maps, 1 table

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

    Cite as: arXiv:0910.2887v1 [astro-ph.EP]

    Submission history

    From: René Heller [view email]

    [v1] Thu, 15 Oct 2009 14:17:52 GMT (3690kb)