Agglomeration

[A continuation of posts 1, 2, 3, and 4 on the formation of Jovian planets.]

dust bunny on a flatbed scanner

The idea that the planets in our solar system arose from a flattened, rotating cloud of gas and dust dates back to Kant and Laplace in the 1700s. Their so-called nebular hypothesis drew part of its original support from the spurious suggestion (by William Herschel and others) that the spiral “nebulae” such as M31 in Andromedae might be solar systems caught in the early phases of formation.

By the late 1800s, however, it had become clear that spiral galaxies are most certainly not protoplanetary disks. This realization removed a primary pillar of observational support for the nebular hypothesis, and forced theories of planet formation to rest largely on assumptions and theoretical arguments. For the majority of the twentieth century, astronomers trying to figure out how the planets came to be were forced to work backward from the more or less static clues that are provided by the condition of the solar system today. Not a happy situation. Science works best with direct observations. To really understand how planets form, we really need to see the formation process in action.

As it turned out, protostellar disks around newborn stars were observed before the discovery of the first extrasolar planets. In the early 1980’s, the IRAS infrared satellite discovered that Beta Pictoris, a young, apparently ordinary, sun-like star 53 light years from Earth, was glowing unexpectedly brightly in infrared light. When Beta Pictoris was examined with careful follow-up observations, it was found to be orbited by a large flattened disk of dusty particles. After this first discovery, many more protoplanetary disks were discovered. Beautiful examples occur, for example, in the Orion Nebula, where they are imaged by the Hubble Space Telescope in stark rigid detail against a glowing backdrop of nebulosity. From careful study of these disks, we know that they generally contain anywhere from 1 to 100 times the mass of Jupiter, and are composed primarily of hydrogen and helium gas, along with swarms of dust and icy particles.

If we assume that giant planets do not condense directly out of these disks as the result of gravitational instability, then we need a coherent picture for forming the planets that we know actually do exist. The current best-guess scenario for forming Jovian-mass planets is called the core accretion theory.

In the core accretion picture, planets start small, through the buildup of dust.

If you have a hardwood floor, you can develop a hands-on sense of how dust agglomeration works by refraining from vacuuming under the bed. If you do this, you will notice that the dust does not accumulate in a uniformly thick layer with time. Rather, the presence of slight air currents swirls the dust around, and causes it to build up into dust bunnies. Look at a dust bunny under a magnifying glass, or put it on a flat-bed scanner and import it into photoshop (that is what I did to generate the image at the top of this post). It’s mostly air. The dust – hair, dandruff, unidentifiable strands of ticky-tacky, has a structure that takes up a large volume in comparison to its mass. This property makes it effective at scooping up more material. Once dust agglomerations begin to grow, their subsequent growth becomes easier. A similar agglomerative process may be at work in building up the dust agglomerations that are present in protostellar disks.

Even so, the initial growth of dusty, icy objects in a proto-planetary disk seems fraught with difficulty. The problem is that as the dust-ice agglomerates become larger and larger, they experience a headwind from the gas in the disk. This headwind causes them to spiral inward, eventually vaporizing as they get close to the central star. Some mechanism must exist to concentrate the dusty debris and allow it to build in size more quickly than it can be destroyed through spiraling inward. There seem to be two reasonable candidates for sequestering dust. The protoplanetary nebula might contain vortices, that is, storm systems in the disk itself, in which regions of the disk participate in a hurricane-like flow pattern. Numerical simulations show that disk vortices, if they live long enough, can trap and concentrate solid particles in their centers. Another possibility is gravitational instability (of a more restricted type than dramatic variety described in post #3). If the gas in the disk is flowing very smoothly, then the solid particles in the flow will have a tendency to settle to a thin layer at the disk mid-plane. If this mid-plane layer grows dense enough and massive enough, then a gravitational runaway can occur. The solid particles, the dust, the ice, the gravel can rapidly form larger and larger objects. Once these objects attain a certain size, several tens of kilometers, say, they are safe from the drag force exerted by the nebular gas. A best-guess scenario has tens of trillions of kilometer-size planetesimals emerging in the disk a hundred thousand years or so after the disk forms.

three initial phases of giant planet formation
Trillions of planetesimals sounds like a lot. Nevertheless, the disk at that stage would not have seemed particularly crowded. The density of gas would have been thousands of times less than the density of air, and the distance between kilometer-sized bodies would be measured in thousands of miles. If you could transport yourself to a random point in the middle reaches of the disk, there would seem to be only relentlessly empty blackness. No view of the stars, no view of the young forming sun. It would seem as if nothing had changed from the earlier molecular cloud phase.

A thermometer, however would indicate that a difference does exist. Whereas the molecular cloud was incredibly cold, 5 or 10 degrees above absolute zero, the temperatures in the protostellar disk are much warmer, ranging from hundreds, even thousands of degrees very near the star, down to several tens of degrees above absolute zero in the farthest reaches of the disk.

Roboscope

DSS2 Red Image of GL581

Last week, we posted Kent Richardson’s light-curve for the nearby red dwarf star GL 581 (Sloan DSS image pictured above). Kent’s photometry was taken during a predicted transit window, and along with data from David Blank and collaborators in Australia, it contributed to rule out the possibility of planetary transits by the red dwarf’s steamy Neptune-mass companion.

Like Marlon Brando in On the Waterfront, GL 581 b “could’ve been a contender”, and connoisseurs of the might-have-been should be sure to read the oklo posts [1,2] that talk about what this planet would have taught us if only it was transiting…

No need to despair, however. There’s a whole slew of candidates on the transitsearch.org candidates list which remain entirely unexplored.

Kent obtained his data with a robotic telescope located at the San Diego Astronomy Association’s dark site at Tierra Del Sol, California, approximately 60 miles east of downtown San Diego:

sdaa roboscope

Kent reports,

There are three major components of the installation: The dome and telescope, the data cabinet, and the satellite antenna. The details of each are as follows:

Dome
Robo Dome by Technical Inovations, Inc.
Meade 8″ LX-200 Classic f/10
Meade f3.3 Focal reducer
SBIG ST-7 CCD camera w/ CFW-8 filter wheel
Lumicon 80mm finder scope w/ Meade DSI Pro camera
Meade 8x50mm finder scope with Logitec web cam

Data cabinet
Compaq Presidio desktop computer
The Sky for telescope control
CCDSoft for ST-7 control
Meade Autostar Suite for DSI control
Logitec Image Studio for web cam control
Digital Dome Works for dome control
Tachyon Networks Inc. satellite network computer

Satellite Antenna
Tachyon Networks Inc. satellite dish

The photo shows the site. The data cabinet has been wrapped to protect it from the winter rains we have been experiencing. You can also see a second pier and electrical outlet which will enable us to install another dome and telescope when funding is available.

We’re definitely looking forward to seeing more data from this rig when the California weather finally improves.

In other news, Transitsearch.org and the American Association of Variable Star Observers have just announced a joint campaign to search for transits of the recently discovered planet orbiting HD 33283. There’s one last, fleeting window of opportunity this season before the star goes behind the Sun: April 26, 10:31 – April 27, 20:22 (UT). Details of the campaign can be found here.

Seize the moment!

Metal

aluminum foil on a flatbed scanner


51 Peg
is an ordinary star in nearly every respect. It is, however, more metal-rich than the Sun by nearly a factor of two, which gives it a metallicity in excess of all but a few percent of the stars in the local galactic neighborhood.

When Astronomers talk about metallicity, they mean the fraction of a star’s mass that is contained in elements that are heavier than hydrogen and helium. To an astronomer, carbon, nitrogen, krypton, and radon are all “metals”. In the Sun, metals comprise a bit less than 2% of the total mass.

Nearly every parent star in the first wave of extrasolar planets (including 55 Cnc, Tau Boo, and Ups And) came in with considerably higher-than-average metallicity, and the strong connection between high stellar metallicity and the detectable presence of an extrasolar planet was on fairly secure footing by 1997. This connection has been quantified very clearly, and is perhaps the most important and dramatic result that come out of the first decade of investigation of extrasolar planets. The figure from Debra Fischer and Jeff Valenti’s recent paper is fast on its way to iconic status:

the planet metallicity correlation

The planet-metallicity connection is telling us something important about the planet formation process, namely, that the core-accretion mechanism for forming giant planets is correct. (More on this coming up soon.) It also tells us how to efficiently find more planets. If you want to find planets, look at metal-rich stars.

Purists should definitely argue that by skimming the readily detectable planets from metal-rich stars, one is skewing the statistical properties of overall census of planets, while introducing additional systematic trends into a planetary catalog that is already shot through with biases both subtle and overt. “A targeted quick-look Doppler survey of metal-rich stars is the moral equivalent of eating candy for breakfast!”

I fully agree.

There are, however, scientifically compelling and unassailably selfless arguments for why it’s important to locate as many extrasolar planets as quickly as possible. I think the most important reason is that quick-look radial velocity surveys (such as N2K) are the best way to locate planets that transit bright parent stars. Once identified, objects like HD 149026b yield up a simply incredible amount of information.

But I’ll be straight with everyone. I’ve always wanted to be in on the discovery of new planets.

In 2000, I worked with Debra Fischer on a small-scale survey of metal-rich stars that wound up being the precursor project to N2K. It’s hard to imagine that the year 2000 once seemed like the distant future. At that time, it appeared that in addition to the planet-metallicity correlation, that there was also a planet-stellar mass correlation. The census of short-period planets known in 2000 was noticeably concentrated around stars somewhat more massive than the Sun, that is, early G and late F type stars.

I therefore drew up a list of 20 stars that we could observe using the then-undersubscribed CAT (Coude Auxilliary Telescope) on Mt. Hamilton. The criteria for inclusion were that a candidate star be (1) at least moderately metal-rich, (2) bright, (3) more massive than the Sun, and (4) not known to be on any other radial velocity survey lists. We needed stars brighter than about magnitude 6 because the CAT telescope has a mirror diameter of only one meter.

Rapidly, it became clear that Henry Draper catalog numbers are not a very effective way to mentally keep track of the stars. There was confusion, for example, one night when I asked Debra if I could add “HD Twenty –Six Seven Five” to the evening’s observing list. She thought that I meant “HD 2675 “(which had already set), when I actually had “HD 20675” in mind. We eventually realized that since we needed to keep both the stars and their metallicities straight, the best course of action would be to name the stars after heavy metal bands. At the high-metallicity end, we drew on speed-metal and death-metal outfits (e.g. Slayer, Sepultura), wheras at the lower-metallicity end, we resorted to hair-metal and even glam-metal bands (i.e. Warrant, Skid Row). Here’s our final list of stars in the survey:

table of heavy metal bands

(The original twenty star survey was reduced to eighteen after AC-DC turned out to be a spectroscopic binary, and W.A.S.P. turned out to be chromospherically active.)

rates

In astronomically inclined households, the first wave of extrasolar planets to be discovered, 51 Peg, 70 Vir, Ups And, Tau Boo, are all still household names.

cactus pad

With the later additions to the census, however, such as HD 33283 b et al., even the discoverers can have a hard time keeping the names in mind. In part, this is because it’s tough to keep a bunch of random Henry Draper Catalog numbers at the tip of the tongue. It’s also because planets #184, #185, and #186 don’t quite pack the same panache as planets #2, #3, and #4. Maybe it’s time to start naming these planets?

It’s easy to get the impression that the rate of discovery of extrasolar planets is increasing rapidly with time. Interestingly, however, this hasn’t been the case recently. The planet discovery rate peaked in 2002, with 34 planets detected, and the rate over the last four years has been flat, at about 25 planets per year. (The present year has brought us six new worlds during the span between New Years Day and Earth Day):

rate of planet detection

The detection rate has flattened for several reasons. After a decade’s worth of planet discoveries, the Doppler radial velocity method remains the most productive technique. The radial velocity method is most efficient when one has a bright parent star. Most of the suitable stars with V magnitudes brighter than 8 are already on the Doppler Surveys. The readily detectable short-period planets orbiting these stars have mostly been found. The much longer orbital periods of the outer planets mean that one must be increasingly patient as one waits for new discoveries from venerable stars. Indeed, the detection rate of planets over the past several years would be even lower, were it not for targeted Doppler surveys such as N2K, which are specifically designed to find new planets quickly by surveying metal-rich stars.

The transit and microlensing methods have a lot of promise for upping the planet detection rate, but to date, very few planets have been discovered with these techniques. In an upcoming post, we’ll look in more detail at the reasons why this has been the case.

It’s interesting to compare the planet detection rate with the history of minor planet detections. Ceres, the first minor planet to be discovered, was found in 1801, followed by Pallas in 1802, Juno in 1804, and Vesta in 1807. A thirty-eight year gap followed, until the discovery of Astraea in 1845. The 100th asteroid, Hecate, was found in Ann Arbor Michigan in 1868, and asteroid #188 (equal to the number of extrasolar planets currently known) Minippe was found ten years later in 1878. The rate has increased rapidly since then. As of last November, there were 120,437 numbered asteroids:

discovery rate for asteroids

I think it will take about 15 more years to find 120,437 planets.

2010

correlations?

As I’ve mentioned earlier, Jean Schneider’s authoritative Extrasolar Planets Encyclopedia has introduced a slick .php-based approach that’s keeping the systemic team on their toes. At Schneider’s site, one can interactively produce correlation diagrams for the known extrasolar planets. As more planets are discovered, these diagrams (for example the a-e plot and the Msin(i)-a plot) are beginning to show a fascinating richness of detail.

The inclusion of date of discovery as one of the plottable parameters attracted my attention.

For example, a plot of the Log of the planetary period versus discovery date shows hints of interesting structure:

planetary period vs. discovery date

Over the past few years, the majority of newly detected planets can be divided into a population with P<10 days (the hot Jupiters), and a population with P>200 days (the eccentric giants). There is a statistically significant gap in the period distribution in the intermediate-period regime. This gap tells us something significant about the planet formation process. My interpretation is that the migration process is not readily halted until a planet reaches the region of the disk where the dyanamics of the protostellar disk gas are subject to the laws of ideal MHD. More on that later.

From a more practical standpoint, the paucity of intermediate period planets has made it tough going for the transitsearch.org collaboration. When planetary periods are less than about 10 days, the discovery team is usually able to complete a photometric search for transits before the planet is publicly announced. When a planetary period exceeds 200 days, it’s generally hopeless to mount an exhaustive transit search, even with a distributed network.

You’ll get another very interesting diagram if you plot the Log of the planetary mass as a function of discovery date. As usual, I’ve redone the axes and annotations with Adobe Illustrator to get that familiar oklo.org look-n-feel:

planetary mass vs. discovery date

In this log-linear space, the lower envelope of detected planet mass is a linear function of time. This allows for an easy extrapolation to estimate the discovery date of the first Earth-mass planet orbiting a nearby main-sequence star…

Three new planets

Yesterday, John Johnson and the California-Carnegie Planet Search Team posted an astro-ph preprint announcing the discovery of three new extrasolar planets. All three radial velocity data sets have been added to the Systemic Console, and the transit predictions have been placed on the transitsearch.org candidates list.

HD 86081 b has an orbital period of 2.1375 days, which makes it a long-sought “missing link” between the weird, ultra-short period planets discovered by the OGLE survey and familiar hot Jupiters such as HD 209458 b and 51 Peg. HD 86081 b has been checked photometrically for transits, but unfortunately, they don’t occur. Because HD 86081 b orbits so close to its parent star, the a-priori transit probability was a healthy 17%.

HD 224693 b and HD 33283 b have longer periods of 26.73d and 18.179d, respectively. The parent stars are excellent targets for the transitsearch.org project, as neither one has been monitored photometrically during the centers of the transit windows. The a-priori transit probability for HD 33283 b is an impressive 6.2%, whereas HD 224693 tosses in a 3.2% chance. That’s a 9.4% chance that a small-telescope observer will be a world-famous astronomical hero sometime during the next year…

Dust off those CCD cameras!

GL 581. Flat, unfortunately.

wheat

Regular visitors to oklo.org are familiar with GL 581 b, a Neptune-mass planet in a 5.366 day orbit around a nearby M-dwarf star. I’ve developed a fascination with this planet, because if it can be observed in transit across the disk of its parent star, then we will learn an incredible amount about the planet’s interior structure. In a nutshell, if the planet has a small transit depth then we’ll know it’s made of rock and metal, and if it has a larger transit depth, then we’ll know it’s made mostly of water.

The a-priori geometric probability that transits by GL 581 b occur is 3.6%. Because the planetary orbit is fairly well known, the time windows during which transits can occur are fairly narrow. The expected transit depth for the planet (if it’s made of water) is a respectable 1.6%, which means that observers with small telescopes will be able to detect the transits if they are occurring.

For more details on the GL 581 campaign, please read (1) this oklo post, “clouds”, and then (2) this oklo post, “two for the show”. For information on how amateur astronomers and small-telescope observers can participate in the search for transiting extrasolar planets, see our website for transitsearch.org. Over the coming months, we’ll be integrating transitsearch.org much more tightly into the oklo site. The systemic project and the transitsearch project both have a common goal of facilitating meaningful public participation in cutting-edge extrasolar planet research.

Every 5.366 days, I’ve been peppering the transitsearch.org observers mailing list with exhortations to observe GL 581 during the transit windows. The weather has not been very cooperative, and many opportunities worldwide were thwarted by clouds, but we now have two data sets that indicate that transits by GL 581 b are unlikely to be occurring:

gl581 photometry

The top data set (from April 2nd) was obtained by David Blank and Graeme White (of James Cook University) using a robotic Celestron C14 stationed at the Perth Observatory. The observations were made through an uncalibrated R filter. The operation of the telescope is made possible by the Perth Observatory staff Jamie Biggs and Arie Verveer, with Carl Pennypacker participating remotely from UC Berkeley. The bottom data set, from April 12th, was obtained by Kent Richardson, using the transitsearch.org robotic telescope, which was set up by Tim Castellano, and which is located in San Diego.

Sadly, neither data set shows any hint of a transit. In addition, David Blank has another data set in hand from March 28th, which also shows no sign of transit. I’ll update the post shortly to include that set as well. Several more observations will be required to really scratch GL 581 b off the list, but at this point it doesn’t look good for transits.

So yeah, I’m a little bummed out. But look at the bright side. A worldwide network of small-telescope observers has obtained an important astronomical result, demonstrating the feasibility of the transitsearch.org approach. If we keep observing the candidates, eventually we’ll hit pay dirt.

Q

This post continues the oklo.org posts: (1) the black cloud, and (2) disks.

spiral waves in m51

There are two competing, completely distinct theories that describe how a giant planet like Jupiter can be generated from a protostellar disk of gas and dust. The first theory, formation via gravitational instability, lends itself to large-scale hydrodynamical simulations and extraordinary animations that can be downloaded over the Internet. It’s an easy theory to grasp. The second theory, formation via core accretion, presents a more complicated chain of events, but nevertheless contains the story that seems (in my opinionated opinion) to be most nearly correct. Let’s look at what these two theories say, and let’s examine the evidence in favor of and against each.

In the gravitational instability picture, the outer lagging remnants of the molecular cloud core fall in and land on the protostellar disk, causing it to grow in mass. As the disk mass increases, it begins to be influenced by its own gravity. That is, it starts to feel a tendency to fragment in response to its own weight. Simultaneously, the pressure of the gas in each nascent fragment pushes back and partially offsets the fragment’s inclination toward collapse. Pressure thus acts as a small-scale stabilizing influence against collapse. In addition, the differential rotation of the disk (material closer to the star orbits faster) tries to sheer a growing fragment apart. Differential rotation thus acts as a large-scale stabilizing influence against gravitational collapse.

The question boils down to the following: Does gravity win, allowing a Jupiter-mass planet to rapidly form as a condensation in the disk, or do shear and pressure win, keeping the disk free of giant-planet fragments?

The situation lies within the general framework of a linearized hydrodynamical stability analyses, and can be analyzed mathematically. The analysis leads to a so-called stability criterion, the famous Toomre Q:

toomre q

Where c_s is the sound speed in the disk, kappa is the epicyclic frequency, G is Newton’s gravitational constant, and sigma is the disk surface density. If Q<1 at any radius in the disk, then the disk is unstable with respect to m=0 (ringlike) disturbances. If Q is slightly greater than 1, computer simulations show that the disk is prone to strong non-axisymmetric instabilities, and hence experiences exponential growth of disturbances and eventual fragmentation.

As with any seemingly abstruse physical phenomenon, The disk instability analysis can be illuminated with an analogy. In this case, the appropriate analogy involves a rock band, a house party, kegs of free beer, and uninvited punks and thugs.

Neophyte rock bands need to attract audiences for their shows. Hence, they need to provide inducements. Free beer does the trick. Free beer, or more precisely, flyers posted all over a college campus advertising a party serving free beer, act in analogy to the self-gravity of a disk. As I have discovered (through direct experience, back in my reckless, rock-band fronting youth), such a course of action can lead to instability. If you flyer a campus with news of free kegs, then dozens to hundreds of punks and thugs, whom no-one has ever seen before, and whom no-one wants to see again, will descend upon the hapless band’s house-party show. Amplifiers are destroyed. Holes are kicked in sheetrock. The cops show up, and the band does not play. This outcome can be profitably compared to a disk that undergoes a gravitational collapse into Jovian-mass fragments.

our bass player

[Above: Our bass player (at a show of ours that was shut down by the cops after several songs). He later graduated with a Ph.D. in Physics, after defending his dissertation on 2D quantum black holes.]

In practice, however, the police do not always show up at house-party shows. Sometimes, the band gets to play. This happier outcome is abetted by two stabilizing effects. Just as in the case of the disk gravitational instability, one of these stabilizing effects operates on large scales, and the other operates on small scales. On the large scale, one can create an analog of “differential rotation” with a lack of specificity on the flyers regarding the precise time of the show. Punks drift in. They see that they don’t particularly like how the band sounds. They see the long lines to the kegs. They drift away. The band plays its entire set to a modest audience, and the cops don’t show up. Support on small scales, the analog of “pressure” is provided by a quite different effect: body odor. The thugs that show up invariably smell poorly, and the unpleasantness associated with a sweaty throng of them will drive some away. If the pressure is high enough, that is, if the thugs smell badly enough, then the show proceeds, and instability is again averted.

For readers familiar with the linearized analysis that leads to the Toomre Q criterion, here’s an illustration of how the analogy can be applied to the standard WKB dispersion relation:

dispersion relation analogy

In a future post in this series, we’ll explain why the weight of observational and theoretical evidence seems to be shifting against the gravitational instability hypothesis. The computer simulations, which become ever more impressive with each inexorable tick of Moore’s law, show that in order for fragments to form and then last as planets, the rate of cooling in the disk must be extremely efficient. Rapid cooling robs a nascent fragment of its ability to produce pressure, and hence permits gravitational collapse. Perhaps more importantly, the computer simulations also show that a disk will suffer from a whole panoply of instabilities before its mass grows large enough to trigger the full-blown collapse of Jupiter-like planets.

These instabilities take the form of spiral waves of the same type that occur in spiral disk galaxies such as M51, shown in the HST photo at the top of the post. In a protostellar disk, the spiral wave action pushes pulse after pulse of gas out of the regions of the disk that are in the most danger of fragmenting directly into planets. Some of this gas is forced to large distances from the central star, while the majority flows inward and eventually winds up on the star. In all likelihood, most protoplanetary disks manage to avoid direct fragmentation.

Simulation showing the development of spiral waves in a self-gravitating disk

Lone Star

Frequent visitors to oklo.org will have noticed that the new posts have dried up over the past several days. I was out of town to attend the 2nd annual Mitchell Institute Symposium at Texas A&M. This is a conference that brings together speakers from a broad range of sub-disciplines in Astronomy and Physics. Ten gallon hats off to Texas! I had a great time. Warm weather, informative talks, and the Aggies all called me “Sir”. My plan for next week is to get the UCSC Banana Slugs to start up with that tradition.

As part of the conference, I was asked to give a public talk on Extrasolar Planets. It was an all-day scramble on the laptop to get all my slides together into a coherent whole, but the talk ended up being a lot of fun. The audience was highly informed and engaged. The TAMU Physics Department definitely got the word out. I was completely stunned this morning to find that I was on the the front page of the Bryan-College Station Eagle, and I was even recognized at the College Station Airport cafe while I was waiting for my flight out. Unbelievable.

Here’s a link to a quick-time movie, as well as a .pdf file with the slides that I showed during the talk. I’ve also put the sound files (you had to be there to know what I’m talking about) here, here, and here in .wav format. A future oklo post will go into much more detail about what’s being heard in these files, and how they are generated.

If you’re new to the site, here’s a bit of information. Oklo.org is the home base for the systemic collaboration, which is a public participation research project aimed at obtaining a better characterization and understanding of extrasolar planets. Everyone is invited to participate, and details and updates are given regularly in our systemic faq posts.

We have been developing both the oklo.org site, as well as the systemic console using a Mac OS-X platform. We have been testing both the site and the console using Internet Explorer, and we have gotten generally good results, but it is clear that some users are experiencing problems. We are working hard to clear these issues up. We’re astronomers by trade, and, and sadly, at the moment, it’s strictly amateur hour when it comes to website development. As an example, you should see a menu of links directly to your right. I recently saw the oklo.org site on a Windows-IE combination in which the links had been mysteriously pushed all the way down to the bottom of the page. I had to scroll all the way down to even see them.

Also, if you are a Macintosh user, run the console in Safari. There is a still a Java issue with the Firefox on OS X. Firefox should, however, work fine on both Linux and Windows machines if your Java libraries are up to date…

Give us a place to stand

In early June of 2001, I was sitting at my desk at the NASA Ames Research Center trying to debug a computer simulation. Outside my window, the traffic was gridlocked on Highway 101. The distant folds of the Diablo Range shimmered in the California Sun. The phone rang, jarring me out of my abstracted state of mind.

yucca

“Dr. Laughlin? Its Robin McKie of the London Observer.”

His voice seemed friendly and reasonable, and I’ll admit that I was pleased to have warranted a call from an overseas reporter. To the best of my recollection, our conversation started something like this:

“Well the reason I’m calling is because I recently saw an abstract of your work concerning this so-called idea of `Astronomical Engineering’, and I was wondering if you could take a few minutes to fill me in on what its all about?’’

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