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Archive for July, 2009

Latest ’606 news

July 30th, 2009 2 comments

An unsung advantage of long-period transiting planets is that the occultations occur on a civilized timescale. An interval of 111.4357 days is long enough not to feel pressured, rushed, or in constant danger of getting scooped. This is in stark contrast, to, say, managing your affairs with a fixed 2.2185733 day turn-around time.

Earlier this summer, there were two papers, one by Pont et al. and one by Gillon which presented complete, leisurely analyses that combine all of the available photometric and RV data for the HD 80606 system taken through the Valentine’s Day 2009 transit. These papers adopted a fully Bayesian approach to analyzing the heterogeneous data sets, and were able to improve the system’s vital stats: The planet has a radius very similar to Jupiter. The full duration of the transit is close to 12 hours (and uncertain to a bit more than an hour). With high confidence, the planet’s orbit is badly misaligned with the stellar equator — just as expected from the Kozai migration hypothesis.

Last night, Josh Winn sent me a new preprint that reports results from an extensive campaign that he spearheaded to observe the June 4th/5th 2009 transit. June, to put it mildly, is not exactly an ideal time to observe HD 80606 from Earth. The nights in the Northern Hemisphere are short, and the star sets early. At any given spot, you can get at best a few hours of uninterrupted data. Nevertheless, it was of great interest to bag the transit. The ingress was weathered out during the February event, and so the analyses of Pont et al. and Gillon had to lean rather heavily on the Good Reverend Bayes.

Josh’s strategy was to recruit an East-to-West swath of observers in Massachusetts, New Jersey, Florida, Indiana, Texas, Arizona, California, and Hawaii. The idea was that 168 electoral votes would be enough to tilt the contest in favor of the good guys.

The multi-state strategy paid off. By stringing together the individual photometric blocks, the first half of the transit was nicely resolved. At the finish line, on the summit of Mauna Kea, the Keck telescope stepped up to the podium to obtain a series of mid-transit spectroscopic measurements that further confirmed the severe spin-orbit misalignment.

.ppt-ready higher resolution version

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.

Categories: worlds Tags: , ,

Saros 136

July 29th, 2009 Comments off

My UCSC Astronomy Dept. colleague Enrico Ramirez-Ruiz sent me a cool graph the other day. It amounts to a photometric transit observation of an R~1700 Km satellite of a habitable terrestrial planet.

Enrico writes:

The attached figure shows the main power voltage to LAT (Large Area Telescope instrument on the Fermi Satellite). There is a regular pattern of increasing voltage when the battery is being charged, a plateau when charging is complete but we are still in sunlight, and discharge when Fermi moves out of sun. You can see a sudden dip in voltage at 3:30 UT when the sun is blocked.

Last week’s total solar eclipse prompted me to think back to the last millennium, to July 11, 1991, when the previous eclipse of Saros series 136 occurred. My fellow graduate students and I drove down to the center line near the tip of the Baja Peninsula. I wrote down my recollections, which we later adapted for one of the chapter vignettes in The Five Ages.

The partial eclipse phases lasted for more than an hour. Even as an ever-larger fraction of the Sun was obscured, the change was so gradual that eyes adjusted continuously. The slackening of the daylight went unnoticed until about fifteen minutes before totality, as more than 90 percent of the Sun’s face was obscured. Due to the reduced sunshine over a swatch of the Earth as large as the diameter of the Moon, the morning was unusually cool for a Mexican July. By 10:00 A.M., the temperature was only in the seventies. The thermometer dropped slightly as the eclipse progressed, and when the daylight finally began to visibly dim, the air seemed almost chilly. The surface of the ocean looked dull and flat, but without the slate gray color of a cloudy day. Cumulus clouds billowed over the distant spine of mountains like an accelerated film.

All at once, the dunes were awash in subtle shadowy ripples, like caustics at the bottom of a midday swimming pool. The ripples drifted slowly across the sand, their contrast flickering. The bands persisted for less than a minute, and then seemed to evaporate. The wind seemed to grow stronger.

With only a minute left, the sky grew darker every second. The air was alive with flapping fruit bats that had been fooled into emerging by the unnatural dusk. A dangerous stray glance at the sun gave a moment’s impression of a starlike point. With five seconds left, the black shadow of totality swept toward us across the water at nearly two thousand miles an hour.

The starlike impression of the Sun was superseded by the disk of the Moon easing into place. A final, fleeting, brilliant burst of light flashed out as the Sun shone through a valley on the limb of the Moon. Totality descended, the stars leapt out, and the nebulous electric blue corona arced away from the black disk.

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A look inside an extrasolar planet

July 28th, 2009 1 comment

Image Source.

Cranking out a paper invariably takes longer than one expects. Last week, I was confident that Konstantin and Peter and I would have our HAT-P-13 paper out in “a day or so”, and then it ended up taking the whole week. As of ten minutes ago, however, it’s been shipped off to the Astrophysical Journal Letters. It’s also been submitted to astro-ph, hopefully in time to make tomorrow’s mailing.

In the meantime, here’s a link to (1) the .pdf of our text, and (2) the two figures (one, two) both in .gif format. The two figures are 800 pixels across, all the better for dropping in to presentations.

Put briefly, HAT-P-13 is an absolutely remarkable set-up. The presence of the outer perturbing body in its well-defined orbit allowed us to show that the system has undergone long-term evolution to a “tidal fixed point”. In this state of affairs, secular variations in the orbital elements of the two planets have been damped out by tidal dissipation, the apsidal lines of the orbits have been brought into alignment, and most importantly, the two orbits precess at the same rate. The paper shows how the eccentricity of the inner planet is a sensitive function of the planet’s interior structure, and in particular, the degree of central concentration (parameterized by the “Tidal Love Number”, k_2).

Here’s a schematic that shows what’s going on:

Right now, the eccentricity of the inner planet is determined to rather modest precision e=0.021 +/- 0.009. The system is transiting, however, and so when Warm Spitzer measures the secondary eclipse time, the error on the eccentricity measurement will drop dramatically. The situation will also benefit from an improved measurement of the planet’s radius. When improved measurements come in, it’ll be possible to literally read off the planet’s core mass and, in addition, the value of the much-discussed tidal quality factor Q.

Categories: worlds Tags: , , , ,

Lucky 13

July 23rd, 2009 4 comments

In reviewing grant proposals and observing proposals that seek to study extrasolar planets, one notices that two cliches turn up with alarm-clock regularity. Number one is Rosetta Stone, as in this or that planetary system is a Rosetta Stone that will enable astronomers to obtain a better understanding of the formation and evolution of planetary systems. Number two is ideal laboratory, as in this or that system is an ideal laboratory for studying the processes that guide the formation and evolution of planetary systems.

A terse unsolicited e-mail from Gaspar Bakos always means that a big discovery is in the offing, and today was no exception:

Hello Greg,

You may like this.
http://xxx.lanl.gov/abs/0907.3525

Best wishes
Gaspar

Indeed! HAT-P-13b and c constitute a really exciting discovery. For a number of reasons, this system is a Rosetta Stone among extrasolar planets, and in large part, this is because the system is an ideal laboratory for studying processes such as tidal dissipation and orbital evolution.

HAT-P-13 harbors the first transiting planet that has a well-characterized companion planet. In this case, the outer companion has a P=428 day orbit, an Msin(i) of 15 Jupiter masses, and an eccentricity, e=0.7. In the following diagram, the orbits and the star are shown to scale; the small filled circles that delineate the outer orbit show the position of the outer planet at 4.28 day intervals.

Illustrator-editable PDF of the above

Of obvious interest is the question of whether planet c can be observed in transit. The a-priori probability is seemingly enhanced by the transit of the inner planet. (Give that one to the good Reverend Bayes). The next opporunity rolls around in April 2010, with the opportunity to observe secondary transit following a bit more than two months later.

It’ll be quite something if planet “c” does transit. A sense of the wide open spaces in the system can be obtained by plotting the star and the two planets to scale with their respective separations at the moment of inferior conjunction. Given the width restriction of the blog post format, one needs to present this plot vertically:

There’s a lot more to say about the HAT-P-13 system — so much in fact, that Peter Bodenheimer, Konstantin Batygin and I are furiously writing an ApJ letter. Should have it out the door in a day or so, with a roundup to follow here on oklo.org immediately thereafter…

Categories: detection Tags: , , ,

Panthéon

July 18th, 2009 Comments off

The opportunity to see Paris was a real high point of my recent trip to Europe. I have to admit, arriving from small-town California, speaking no French, I felt every bit Mr. Country Mouse. As the midwestern saying goes, it’s hard to keep the boy down on the farm once he’s seen Paree.

Travelogue slideshows get real old real fast, but nevertheless, I’ll indulge in a couple of posts that touch on my Paris visit. On my first day there, I visited the Paris Observatory (more on that later in the week). The next two days were taken up with walking all over the city.

The Panthéon probably left the biggest impression. It was a chilly, rather gloomy day. The soaring interior was a somber chamber of echoes. I’ve always been interested in the events surrounding the French Revolution — the ideal of a Republic seems to find no better expression than in a secular cathedral. Foucault’s pendulum is the centerpiece. Its slow precession silently, subtly underscores the ascendancy of a rational world view. Chills down the spine.

A stone spiral staircase leads down to the crypt.

Where I found the grave of Joseph Louis, comte Lagrange, its stone inscription just visible among the shadows.

Categories: worlds Tags:

reintroduction

July 16th, 2009 Comments off

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i-Phone snapshot of Difference Engine #2.

The systemic console started life over five years ago as a web-based applet for analyzing radial velocity data. The original version was a collaboration between Aaron Wolf (then a UCSC Undergraduate, now a Caltech Grad Student) and myself, and the Java was coded in its entirety by Aaron. Our goal was to clarify the analysis of radial velocity data — the “fitting” of extrasolar planets — by providing an interactive graphical interface. The look and feel were inspired by sound-mixing boards, in particular, the ICON Digital Console built by Digidesign:

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Over the intervening years, the console has expanded greatly in scope. Stefano Meschiari has taken over as lead software developer, and has directed the long-running evolution with considerable skill. The console has been adopted by planet-hunting groups world-wide, as well as by classroom instructors and by a large community of users from the public.

Tuesday’s post pointed to our new peer-reviewed article (Meschiari et al. 2009) that describes the algorithms under the console’s hood, and now that the code base has matured, we’re developing documentation that can serve the widely varying needs of our users. We also intend to return the systemic backend collaboration to the forefront of relevance. A great deal of very interesting work has been done by the backend users, and it can be leveraged.

As the first step, we’re updating and expanding the tutorials, which have been largely gathering dust since November 2005. Following the page break, the remainder of this post updates tutorial #1. If you’ve ever had interest in using the console, now’s the time to start…

Read more…

Categories: worlds Tags:

Upgrade

July 14th, 2009 2 comments

oklo.org is heading into its fifth year, and we’ve just hit something of a milestone: this is the 300th post. A great deal has been learned about extrasolar planets in the past half-decade, and I’ve found that participative reporting has been a great way to keep up with, and even, sometimes, to influence the course of events.

We’ve also just hit another big milestone with the release of the Systemic Console Paper. Our manuscript has just been accepted for publication in the peer-reviewed journal Publications of the Astronomical Society of the Pacific, and the article is now available on astro-ph.

In coming posts, we’ll be highlighting the many new features of the console, and we’ll be updating the now badly-out-of-date tutorials. If you are interested, then by all means download the latest “cutting edge” version, which is available on Stefano’s website.

And finally, if you use the console, and find it useful, please consider citing Meschiari et al. 2009 in your publications.

Categories: detection Tags:

Zollverein

July 5th, 2009 Comments off

Tourist ideals of Germany often draw in the magic-marker post card Neuschwanstein Castle, cruises on the Rhine and Oktoberfest. Less often mentioned is Essen’s Zeche Zollverein, an abandoned coal mine and coking plant that in 2001 was placed on the Unesco World Heritage List. Like almost nowhere else on Earth, the Zeche Zollverein manages to connect the planet’s distant past to its present and to its long-term future.

On the day that I visited the complex, it was oppressively warm and humid. The sky glared bluish white, with cumulus clouds slowly boiling up. At present, it’s rare to have such tropical-seeming conditions at 51 degrees north latitude, but in a billion years, as the Sun runs further through its hydrogen, the damp heat will be much more the rule.

The Zollverein site, which halted industrial activity on June 30, 1993, was almost entirely deserted as we wandered through. Thick green undergrowth is everywhere. Saplings are sprouting from crevices in the maze of tanks and rusting pipes. It was easy to imagine that the Anthropocene has already ended, that the carbon dioxide concentrations have already peaked.

When the complex was at its peak in the early 1970s, it was producing 8,600 tons of coke per day, along with ammonia, benzene and raw tar. The coal came from a mine on the site that tapped an underground seam deposited 300 million years ago during the Carboniferous period. The coal-forming forests of that time sequestered so much carbon that the oxygen concentration in the atmosphere spiked to more than 30%. Carnivorous dragonflies with 2.5-foot wingspans took to the skies.

Image Source.

Now, with the hive of activity gone, rusting iron defines the landscape, and recalls a past that’s an order of magnitude more distant than the Carboniferous. Three billion years ago, the rise of photosynthesis (which eventually made the coal forests possible) caused Earth’s first rise of free oxygen. Iron dissolved in the oceans precipitated as iron oxide — rust — to form the banded iron formations, which, after lying undisturbed for billions of years were mined to make the steel.

Steel that now slowly rusts in the silent, saturated air.

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