The exoplanet prediction market

Posted on February 20, 2007 by greg

At first glance, the market capitalization of the Chicago Board Options Exchange, and the list of astronomers active in the field of extrasolar planets would appear to have nothing to do with one another. These two disparate entities are connected, however, by the fact that they’ve both undergone explosive growth over the past decade, and both are continuing to grow. They signify highly significant societal trends.

I think it’s safe to predict that in 25 years, the market for financial derivatives, and the level of economic activity associated with exoplanets will both be far larger than they are now. It’s interesting to ask, will there be an unanticipated co-mingling between the two? And if so, how will it occur?

One very realistic possibility is the development of an exoplanet prediction market, in which securities are issued based on particular fundamental questions involving the distribution of planets in the galaxy. Imagine, for example, that you’re an astronomer planning to devote a large chunk of your career to an all-or-nothing attempt to characterize the terrestrial planet system orbiting Alpha Centauri B. In the presence of a liquid, well-regulated exoplanet prediction market, you could literally (and figuratively) hedge your investment of effort by taking out a short position on a security that pays out on demonstration of an Earth-mass planet orbiting any of the three stars in Alpha Centauri.

Prediction markets have been adopted in a very wide range of contexts, ranging from opening weekend grosses for big-budget movies, to forecasts of printer sales, to the results of presidential elections. A highly readable overview of these markets by Justin Wolfers (who was featured last week in the New York Times) and Eric Zitzewitz of the University of Pennsylvania is available here as a .pdf file. The ideosphere site contains a wide variety of markets (trading in synthetic currency) and includes securities directly relevant big-picture questions in physics, astronomy and space exploration. Here’s the price chart for the Xlif claim,

which pays out a lump-sum of 100 currency units if the following claim is found to be true:

It’s very interesting to compare the bullish current Xlif price quote of 72 with the far more bearish sentiment on Xlif2, which is currently trading at an all-time low of 17,

and which pays out if “extraterrestrial intelligent life is found prior to 2050”, and more specifically,

Recently, open-source software has been released that makes it straightforward to set up a prediction market. We’ll soon have the world’s first exoplanet stock market up and running right here at oklo.org. In the meantime, feel free to submit specific claims (in the comments section for this post) that might lend themselves to securitization…

Lonely Planet Guide to the Hyades

Posted on February 9, 2007 by greg

It’s been a hectic week, and now that it’s February, my New Year’s resolution to write 2-3 posts per week managed to lose its shaky option on my priorities.

Eugenio stopped by my office this afternoon to outline his latest code developments for the console. He’s mostly finished implementing a Bulirsch-Stoer integrator. Once this algorithm is tested and operational, it will produce very significant speed-ups for the fitting and the stability analysis of tough multiple-planet systems such as 55 Cancri and GJ 876. Then it’ll be on to a rollout of the bootstrap method for computing uncertainties for the orbital elements in the planetary fits.

“So did you see the new planet?” he asked.

“Huh?” I hadn’t heard anything about it.

Turns out that Bunei Sato and his collaborators have detected a periodic radial velocity variation for the star Epsilon Tauri. Their preprint is on the Astrophysical Journal’s website, but it doesn’t seem to have hit the preprint server yet. This star is a prominent member of the nearby Hyades cluster, and is easily visible to the naked eye as part of the well-known “V”-shaped asterism near Aldeberan in the sky.

Eps Tau is bright enough to have garnered 40 different names in the Simbad catalog, and it’s now listed in the console menu and on the systemic backend as HD 28305. This is one of the most straightforward radial velocity datasets that you’ll come across, and thus makes a good system for first-time users to fit. A few debonair moves with the downloadable console conjure up a model planet with a period of 594 days, an orbital eccentricity e=0.15, and a minimum mass 7.6 times that of Jupiter:

Epsilon Tauri is one of the four stars in the Hyades that are currently nearing the end of their lives and are evolving through the red giant phase. It’s 14 times larger than the Sun, and it’s luminosity is 97 times the solar value. It weighs in at 2.7 solar masses, making it the most massive star known to harbor a planet.

So what’s the story? The Hyades are a metal-rich cluster. One would naively expect that the supersolar composition of the precursor star-forming giant molecular cloud would have lead to a large fraction of the cluster members harboring readily detectable planets. It’s also true that stars somewhat more massive than the Sun should harbor a higher-than-average fraction of giant planets. Eps Tauri scores on both counts.

It’s important to keep in mind, however, that a cluster environment will have a strong effect on giant planet formation. Currently, the Hyades are 600 million years old, and the cluster has lost a large fraction of its O.G.s to the general galactic field through the process of dynamical escape. If we extrapolate back to the cluster’s early days, we find that the Hyades would have resembled the Pleiades 500 million years ago, and would have looked like the Orion Nebular Cluster during the first few million years of its existence.

The UV radiation environment in the original Hyades cluster was fierce. The protostellar disks of the individual Hyads were likely photoevaporated before the growing planetary cores were able to reach the runaway gas accretion phase that gives rise to Jupiter-mass planets (see our paper on this topic). When we get the full inventory of planets in the Hyades, I think we’ll find plenty of Neptunes and terrestrial planets, but almost nothing in the Jovian range. Indeed, work by Bill Cochran and the Texas RV group has demonstrated that the Hyades are generally deficient in massive planets.

My guess is that Epsilon Tauri b is an example of a planet that formed through the gravitational instability mechanism. Gravitational instability should generally produce more massive planets (e.g. HIP 75458 b, and HD 168443 b and c) and its efficacy will be little-affected by UV radiation from neighboring stars. It likely occurs once per every several hundred stars that are formed, and so it’s perfectly reasonable that there’s one star in the Hyades that has a planet formed via the GI mechanism.

a bunch of cool new stuff

Posted on February 2, 2007 by greg

Stefano and Eugenio have both been working hard on the systemic console and backend, and as a result of their efforts, we’re now able to roll out a number of new features.

The backend now features a systemic wiki in which users can collaborate on a wide variety of writing projects related to systemic in particular and extrasolar planets in general. Features include discussion pages for individual systems, the framework for a comprehensive console and backend manual, and an exoplanetary news wire. Our first news service is being provided by Mike Valdez, who combs astro-ph every day and extracts any new preprints that are germane to the those interested in exoplanets. Stefano wrote the code from scratch, so there are endless possibilites for customization. Give it a try.

On the console front, Eugenio has aggregated a uniform listing of the literature sources of all of the radial velocity data sets provided by the console. This information is in a file vels_list.txt, which is now included in the systemic.zip package. If you are using the console for scientific research that you intend to publish, it’s now a snap to get the correct citations for any of the individual systems included on the console.

Many users have expressed interest in what our own solar system would look like to a dedicated radial velocity observer on another star. Eugenio has put together an expansion pack that contains 17 manufactured data sets based on the Solar System. A second expansion pack contains an analogous set of manufactured data sets for various plausible configurations of planets orbiting Alpha Centauri A and B. Both are available on the downloads page for the downloadable systemic console.

Check it out!

mp3s of the spheres

Posted on January 18, 2007 by greg

New users are still streaming into oklo.org. If you’re a first-time visitor, welcome aboard. You’ll find information that you need to get started in this post from several days ago.

The EZ-2-install downloadable systemic console is the primary software tool that we provide for analyzing data from extrasolar planetary systems. The tutorials 1,2, and 3 are the best way to learn how to use the console. Over the past few months, we’ve been adding a range of new capabilities that go beyond the features described in the tutorials and which improve the overall utility of the software. We’ll be explaining how these new features work in upcoming posts, and for our black-belt users, we’re also putting the finishing touches on a comprehensive technical manual.

When we designed the console, our main goals were to produce a scientifically valuable tool, while at the same time make something that’s fun and easy to use. Early on, we settled on the analogy with a sound mixing board, in which different input signals (planets) are combined to make a composite signal.

We’ve pushed the audio analogy further by adding a “sonify” button to the console. When sonification is activated, you can turn the stellar radial velocity curve into an actual audible waveform. If you create a system with several or more planets, these waveforms can develop some very bizarre sounds. From a practical standpoint, one can often tell whether a planetary system is stable by listening to the corresponding audio signal. Alternately, the console can be used as a nonlinear digital synthesizer to create a very wide variety of tones.

Here are links (one, and two) to past posts that discuss the sonification button in more detail. If you come up with some useful sounds, then by all means upload the corresponding planetary configurations to the systemic back-end.

Armchair Planet Hunting

Posted on January 15, 2007 by greg

The Associated Press just published an article on how the Internet has facilitated an increasing number of collaborations between amateur and professional astronomers. The systemic project is one focus of the AP piece, and we’re seeing a jump in traffic as a result. If you are a first-time visitor to the site, welcome aboard!

There are several ways that you can use and participate in systemic. Our project home page is a weblog (updated fairly frequently) that gives an insider’s perspective on the latest developments and discoveries in the fast-moving fields of extrasolar planets and solar-system exploration. We write for a target audience of non-astronomers who are interested in astronomy. To get a flavor for the blog, keep reading the posts below, or have a look at a few of our past articles, such as our take on last Summer’s big “is Pluto a planet debate”, our exploration of what planets and galaxies really look like, or our series [1, 2, 3, 4] on the feasibility of detecting habitable terrestrial planets in the Alpha Centauri System.

You should see a set of links just to your right:

These links give you information that you can use to start participating in the actual discovery and characterization of extrasolar planets. (Despite the fact that we’re rocket scientists, we’ve been unable to consistently sweet-talk Microsoft IE into correctly displaying our site. On some versions of IE, you may have to scroll all the way down to the bottom of this page to see the links). The Downloadable Systemic Console is our Java-based software package that allows you to work with extrasolar planet data. The Systemic Backend is a collaborative environment that has the look and functionality of a social networking site. Registration and participation are free. The nearest well-characterized extrasolar planets (GJ 876 b, c and d) are 14.65 light years away, and so the news of useful modern innovations such as pop-ups and spyware hasn’t had time to propagate to those far-distant worlds. Hence the systemic backend is completely free of annoying ads!

One final note: there are two separate channels for registration on systemic. The first, accessed through the “login” tab on the site header above, is part of the WordPress package that runs the blog. Registration on the blog allows you to comment on our frontend posts. The second, accessed through the “backend” tab on the site header or the link to the right, gives you access to the collaborative php-based environment that constitutes the systemic backend. You can register for either or both, and you don’t need to give your real name or any real-world identifying information other than an e-mail address.

Tune in regularly for more news and updates.

year 2.0

Posted on November 15, 2006 by greg

As of tomorrow, oklo.org will have been on the air for one year. We’re pleased with the response that we’ve gotten thus far, and we’re looking forward to rapid progress during year two. A big thank-you is definitely in order to everyone who’s either worked on the site or made regular visits or participated in the ongoing collaborative research!

In recent weeks, the user base on the systemic back-end has grown substantially, and we’ve been pushing the limits of what our ISP is geared to provide. Bluehost provides a very cost-effective package for hosting weblogs and running small-scale sites, but it’s become abundantly clear that one can’t expect to run a web 2.0 startup for $6.95 per month. At that level of expenditure, we’ve been limited to the use of 20% of one processor with a maximum job length of 60 seconds. Stefano has stretched our ration with clever use of cron command, but nevertheless,

has become a refrain tiresomely familiar to backend users, and our attempts over the past week to shift the backend to alternate stop-gap servers have been thwarted by various software incompatabilities.

I’m thus very happy to report that an order has been placed for a dedicated server that will obliterate the current problems. It will be located in downtown Santa Cruz on a high-speed T3 line. We should have everything up and running on it within 2 weeks. It’s spec’d to run the full systemic simulation, the new connection is ready to handle a hoped-for shout-out from boing-boing or slashdot, and the joint package should deliver a much more satisfying end-user experience.

In the meantime, however, keep sending in those fits. Neither sleet, nor snow, nor server overloads shall… We’re very eager to build up a solid distribution of fits for Systemic Junior.

Viewed from afar (Challenge 004)

Posted on November 13, 2006 by greg

The fourth systemic challenge turned out to be somewhat less challenging than the first three. Quite a few entrants figured out that the data-set corresponds to our own solar system. Among a large number of excellent models, Mark Kilner turned in the fit with the lowest chi-square: 1.0401. In addition to Jupiter, Saturn, Earth, and Venus, he topped off his system with a spurious Mercury-mass planet in a 5.62 day orbit, which allowed him to take the prize. Nice one, Mark!

Eugenio created the challenge 004 synthetic data set after a conversation in which we decided that it’ll soon be feasible to push the precision of the radial velocity method down to an instrumental error of 0.1 m/s. Even more optimistically, we assumed that the Sun, viewed from afar, exhibits negligible radial velocity noise (more on that soon).

Our Solar System, expressed in the Jacobi orbital elements used by the console, is given by:

The true three-dimensional model that Eugenio actually integrated to produce the synthetic data set also includes the correct values for the planetary inclinations and nodes. Because of the sin(i) degeneracy for Keplerian orbits, the current version of the downloadable systemic console does not include the inclinations and nodes as fitting parameters.

The synthetic data set was created with the KeckTAC program, which mimics realistic observing strategies. In an all-out effort on a particular star, one would combine repeated individual observations to get a composite observation that averages over the effect of short-period oscillations (p-modes) of the star itself. This is the strategy that is being currently used by the Swiss team in their campaigns on stars such as HD 69830 and HD 160691. In the challenge004 dataset, there are 1171 radial velocity measurements spread out over 24 years.

Eugenio describes the procedure he used to fit the data:

Image Source.

With the contests wrapped up, we’re now in the business of getting the fits completed for the Systemic Jr. data set. Eugenio recently incorporated an F-test module into the console, which can be used to determine whether the addition of a planet is warranted. We’ll have a post up shortly that explains in detail how this works. In the meantime, see the discussion on the backend, or download a new console and give its new modules a whirl.

Apsidal

Posted on November 7, 2006 by greg

In 1999, Upsilon Andromedae burst onto the international scene with the first known multiple-planet system orbiting a sunlike star. Eight years later, we know of twenty-odd additional multiple-planet systems, but Ups And remains a marquee draw. No other system evokes quite its exotic panache. No other extrasolar planets have garnered names that have stuck.

High in the cold and toxic atmosphere of Fourpiter, Upsilon Andromedae shines with a brilliance more dazzling than the Sun. Twopiter is occasionally visible as a small disk which, near conjunction, subtends about one-tenth the size of the full Moon in Earth’s sky. Dinky, which lies about four times closer to the star than Mercury’s distance to our Sun is lost in the glare.

To date, Upsilon Andromedae has accumulated a total of 432 published radial velocities from four different telescopes. The full aggregate of data is available on the downloadable systemic console as upsand_4datasets_B06L. The velocities span nearly two decades, during which the inner planet, “Dinky”, has executed well over 1000 orbits.

In earlier versions of the console, use of the zoom slider on an extensive data set would reveal a badly undersampled radial velocity curve at high magnification. Eugenio’s latest console release has addressed this problem, however, and the radial velocity model curve now plots smoothly even with the zoom slider pulled all the way to the right.

It’s interesting to look at the best radial velocity fit to all four data sets. The planets are very well separated in frequency space, and so it’s a straightforward exercise to converge on the standard 3-planet fit. Upsilon Andromedae itself is a little too hot (6200K) to be an ideal radial velocity target star, and so the chi-square for the best fit to the system is above three, with a likely stellar jitter of a bit more than 14 meters per second. If Ups And were a slightly cooler, slightly older star, we’d potentially be able to get a much more precise snapshot of the planet-planet interactions. (In that Department, however, there’s always 55 Cancri.)

The best fit shows that the apsidal lines of the two outer planets are currently separated by 30 degrees, and are executing very wide librations about alignment. This configuration continues to support the formation theory advanced two years ago by Eric Ford and his collaborators. They hypothesize that Ups And originally had four giant planets instead of the three that we detect now. The outer two (Fourpiter and, uh, “Outtathere”) suffered a close encounter followed by an ejection of Outtathere. Fourpiter, being the heavier body, was left with an eccentric orbit. Now, 2.5 billion years later, the memory of this disaster is retained as the system returns every ~8,000 years to the eccentricity configuration that existed just after the disaster.

Systemic Jr.

Posted on November 5, 2006 by greg

The activity this week has all been under the hood, and as a result, the systemic front-end has languished without news. Apologies for that! A slew of updates are on the spike.

Stefano is now officially on the roster at Oklo HQ, and we’re very happy to have him here. The atmosphere is caffeine-fueled startup. He’s already implemented numerous updates and improvements to the systemic backend which, when coupled with Eugenio’s progress on the console, put our web 2.0 story into high gear.

There were a number of times last week when the oklo.org site was temporarily unavailable. Our ISP restricts us to no more than 20% of a full processor load, and exceeding this causes the site to shut down for 5 minutes. We’re now in the process of temporarily mirroring the backend on a machine at Lick Observatory, and quite soon we’ll have a dedicated server up and running.

The systemic Junior datasets have now been added to the downloadable systemic console. Eugenio writes (see the backend discussion forum for the full description):

As soon as the Lick Observatory server is online, the backend will be able to accept fits to the Systemic Jr. data sets. In the meantime, please save your fits on your local machine. Some of the Systemic Jr. systems may seem familiar. It’s best however, if all of the datasets are approached without a pre-conceived notion of what might be generating them. Once the Systemic Jr. data sets have been fitted, we’ll be able to do a very interesting analysis which will give us some much-wanted information about the nature of the galactic planetary census.

Threaded console available!

Posted on October 30, 2006 by greg

This weekend, Eugenio posted an updated version of the downloadable systemic console. The Java code in this version is fully multithreaded, which means that we’re finally able to provide the much-needed and much-requested “stop” button.

For previous console releases, clicking multi-parameter minimization — “polish” — with integration enabled would often cause the console to effectively freeze as the computer worked it’s way through an exceedingly long bout of computation. With the new version, progress is indicated both by a graphical redrawing of the fit, and by a running tally of the number of Levenberg-Marquardt iterations that have been completed. If things appear to be progressing too slowly, it’s now possible to abort to the latest model state by pressing the stop button.

A “back” button will be activated shortly, which will allow you to step backward through your work to revisit earlier model configurations in the session. These features should significantly improve the overall usability of the console.

Another area where progress has been rapid is in the stability checker. Eugenio has put a lot of detailed information on this new functionality on the general discussion section of the backend. In short, the stability checker can now be used as a full fledged integrator which can write time series data to user-specified files. In a post that will go up shortly, we’ll look at how the stability checker can be used to answer some interesting dynamical questions.

Systemic Jr. is also just about ready to go. Assuming that there’s no unforseen snags, we’re looking to launch it on Nov. 1 (next week). In the meantime, download a fresh console, and give the new features a spin.

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delineating connections

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