Notes & Queries 10/23/09

On Perfect Mornings

Stan Getz’ version of ‘Early Autumn’ is to me the definitive take on this standard, though so many fine musicians have attempted it that I’m sure to draw an argument from jazz buffs. But every year when the leaves have just begun to turn, the Getz interpretation runs through my mind on my morning walk, as it did today. A fine breeze was in the air and it carried the scent of approaching rain. The leaves wrapped the scene in muted gold and vermilion, not as bright as in some years, but lovely just the same.

So perfect was the moment that it called up a quote from J.B Priestley that I only imperfectly remembered. When I got back to my desk, I looked up the exact wording:

I have always been delighted at the prospect of a new day, a fresh try, one more start, with perhaps a bit of magic waiting somewhere behind the morning.

Early CoRoT Results Available

Early results from CoRoT are now appearing in a special issue of Astronomy & Astrophysics (Vol. 506 No. 1), running this week with over fifty papers made available online. Launched in late 2006, CoRoT has detected seven planets that have been confirmed by ground-based follow-up observations, a challenging process that has produced such interesting places as CoRoT-7b, whose discovery is recounted and mass discussed in these papers (Didier Queloz and team calculate the mass at about five times that of Earth).

Based on density calculations, CoRoT-7b should be a rocky planet, the first confirmed to date, and it was subsequently joined by a second planet in the same system, a super-Earth of about eight Earth masses. The range of papers here extends beyond exoplanet hunting to astroseismology, a primary goal of mission planners. Detecting and quantifying oscillations in red giants and other stellar types shows how complicated these processes can be. It’s heartening to note that CoRoT is slated to operate until 2013.

The Mind in the Machine

Wouldn’t a human brain translated somehow into a computer environment simply go mad, being a consciousness evolved for an environment so radically different in terms of its inputs that adaptation outside a physical body would be impossible? Athena Andreadis considers the matter in Ghost in the Shell: Why Our Brains Will Never Live in the Matrix, published last week at h+ Magazine. Her essay is an elegant reminder that biological systems and engineered technologies are not necessarily compatible:

A human is not born as a tabula rasa, but with a brain that’s already wired and functioning as a mind. Furthermore, the brain forms as the embryo develops. It cannot be inserted after the fact, like an engine in a car chassis or software programs in an empty computer box.

An uploaded brain could, the thinking goes, cope with the immense times and distances involved in interstellar travel, thus opening up the stars to our electronically adapted selves. But while we may be able to tweak the brain to stay sharp beyond the conventional human lifespan, Athena will have none of the notion that uploading a consciousness will be the way to immortality.

Large portions of the brain process and interpret signals from the body and the environment. Without a body, these functions will flail around and can result in the brain… well, losing its mind. Without corrective “pingbacks” from the environment that are filtered by the body, the brain can easily misjudge to the point of hallucination, as seen in phenomena like phantom limb pain or fibromyalgia. Additionally, processing at light speed will probably result in madness, as everything will appear to happen simultaneously or will change order arbitrarily.

Just as seriously, the University of Massachusetts biologist speculates that without the physical context, we are endangering our sense of empathy, without which we are “at best idiot savants, at worst psychotic killers.” Andreadis considers the mind an emergent property, an artifact of its brain. Transferring it demands the brain that houses it, without which continuity of consciousness is lost. No immortality there — the original mind still faces death no matter what the uploaded one does.

But what about replacing a brain in a living person, renewing our minds even as we rebuild our 100 billion neuronal processors? Even using embryonic stem cells, the take here is that cell replacement will be slow and small-scale in order to make continuous consciousness possible and to preserve existing neuronal and synaptic networks. Thus renewing a single human brain could be such a lengthy process that it never catches up with the aging of the body. Such efforts, though, may well pay off in specific areas, such as the treatment of neurodegenerative diseases.

Long lifespans could lead to long-term crewed space expeditions, but this essay notes we’ll need tools to repair mutations caused by cosmic radiation if we plan to spend long periods in environments outside the Solar System. Andreadis doesn’t rule out keeping a brain functional for periods longer than our current lifespan, but her doubts about mind transfers are pungent reading for those pondering a Matrix-like future inside the machine.

Re-Experiencing Spacetime

Have a look at the Pleiades the next time viewing conditions are good. When the light you’re seeing left these stars, Copernicus had just published De revolutionibus orbium caelestium (1543), giving the Sun rather than the Earth primacy of place in the universe. Now look at the Orion Nebula, whose light left as the Roman Empire was crumbling. Each astronomical vista takes us on a chronological journey, as SEED Magazine shows us in a slide show based on Michael Benson’s new book Far Out: A Space-Time Chronicle (Abrams, 2009).

The images are lovely, and by the time you’ve worked through to the Hercules Cluster, you’re dealing with light that left when the most complex life Earth had to offer was the trilobite. That would be 485,000,000 years ago, and the connection of Earthly chronology with celestial spectacle refreshes our perception of time and space as entwined. That’s something we take intellectually for granted but sometimes need to experience in new ways. Like the dazzling departure from the Solar System in the film version of Contact, these images give the jaded a much needed ‘sense of wonder’ boost.

Rosetta Swingby in November

Keep an eye on the Rosetta Blog as the ESA comet-investigating spacecraft swings by the Earth to gain a gravity assist that will begin the final leg of its ten-year journey to comet 67/P Churyumov-Gerasimenko. This is the last of Rosetta’s four gravity assists and the third Earth swingby, during which Rosetta will study the Earth-Moon system from its unusual perspective. Closest approach is 0745 UTC on November 13, with a trajectory correction burn just completed. More on the Rosetta mission site.


Updating the Dinosaur Killer

Sankar Chatterjee (Texas Tech) and a team of researchers have been looking at something known as the Shiva basin, that area west of India that is heavily laden with oil and gas resources. Chatterjee believes the Shiva basin is in fact a huge, multi-ringed impact crater, one caused by a bolide perhaps as much as 40 kilometers in diameter, big enough, as the scientist says, to create its own tectonics. The supposed dinosaur killer impactor in the Yucatan, by contrast, is thought to have been between eight and ten kilometers wide. Is Shiva basin the crater left by the actual extinction event?

Mostly submerged, Shiva’s outer rim forms a 500-kilometer ring with a central peak extending some three miles from the ocean floor. One result of such a strike, if the team’s theories hold up, is that the volcanic eruptions at the nearby Deccan Traps may well have been enhanced, not to mention the ensuing formation of the Seychelles Islands, which would have broken off the Indian tectonic plate. We’ll learn more about this theory when the team goes to India to look at rocks from the center of the presumed crater. Says Chatterjee:

“Rocks from the bottom of the crater will tell us the telltale sign of the impact event from shattered and melted target rocks. And we want to see if there are breccias, shocked quartz, and an iridium anomaly.”


Image: This diagram shows a three-dimensional reconstruction of the submerged Shiva crater (~500 km diameter) at the Mumbai Offshore Basin, western shelf of India from different cross-sectional and geophysical data. The overlying 4.3-mile-thick Cenozoic strata and water column were removed to show the morphology of the crater. Credit: Sankar Chatterjee, Texas Tech University.

On a similar note, I see that a new title focusing on the Tunguska event is coming to our shelves, and let’s hope it attracts the interest of people still unaware of the power of such impacts. The Tunguska Mystery (Springer, 2009) works through the various investigations into the nature of the impactor, and from the press release I’ve seen notes the urgency of solving the asteroid vs. comet question, given our need to protect against future strikes. The author, Vladimir Rubtsov, has been a prolific writer of popular science articles published in Russia and internationally.

I hasten to add that I haven’t seen this one yet, but I’ll update this note when I’ve had the chance to page through the book. From the Amazon site I learn that Dr. Rubtsov “…joined the laboratory of Dr. A. V. Zolotov in Kalinin (now Tver), where for three years [he] studied the problem of the Tunguska explosion.” That was back in the 1970s, and was followed by a doctoral thesis with an interesting title: “Philosophical and Methodological Aspects of the Problem of Extraterrestrial Civilizations.” We’ll see how the scientist pulls together current thinking on Tunguska, the nature of whose impactor strikes me as less of a mystery than a fairly well constrained scientific question still in the process of being solved.


HD 209458b: Comparing Exoplanet Atmospheres

We’re making progress at detecting the signatures of organic chemicals on other planets. Mark Swain (JPL) and team have already made a name for themselves in this arena by their detection of carbon dioxide in the atmosphere of the ‘hot Jupiter’ HD 189733b, which followed earlier Hubble and Spitzer observations that revealed water vapor and methane there. Now they’ve used the same observatories to study another hot gas giant, HD 209458b, which orbits a star 150 light years away in Pegasus.

The result: A detection of basic materials necessary for life. Swain spells out what the team found and its significance:

“[HD 209458b is] the second planet outside our solar system in which water, methane and carbon dioxide have been found, which are potentially important for biological processes in habitable planets. Detecting organic compounds in two exoplanets now raises the possibility that it will become commonplace to find planets with molecules that may be tied to life.”


No one is suggesting these planets are habitable (at least not by any kind of life we currently understand), but the work demonstrates our progress at refining the tools of spectroscopy, splitting light into its components to tease out the signatures of different chemicals. At this stage, we’re showing the method is workable on those exoplanet atmospheres now within range of our study. We’re now entering the phase of characterizing and comparing such atmospheres, a process that helps us build the expertise that will eventually lead, let’s hope, to finding organic chemicals on Earth-like planets.

Image: The basic chemistry for life has been detected in a second hot gas planet, HD 209458b, depicted in this artist’s concept. Two of NASA’s Great Observatories – the Hubble Space Telescope and Spitzer Space Telescope, yielded spectral observations that revealed molecules of carbon dioxide, methane and water vapor in the planet’s atmosphere. HD 209458b, bigger than Jupiter, occupies a tight, 3.5-day orbit around a sun-like star about 150 light years away in the constellation Pegasus. Credit: NASA/JPL-Caltech.

The comparison of just two planets in this manner is already intriguing. While the relative amounts of water and carbon dioxide are similar, methane is a different matter. HD 209458b shows a greater abundance of methane than HD 189733b. Swain again:

“This demonstrates that we can detect the molecules that matter for life processes. The high methane abundance is telling us something. It could mean there was something special about the formation of this planet.”

What that something might be remains an open question, but as we begin to compare hot Jupiters using existing tools like Hubble and Spitzer, we’ll build a context in which to place these findings. That will teach us more about how hot Jupiters form, but it will also sharpen our analytical tools for studying the kind of interesting worlds we hope Kepler and CoRoT will find, planets that might be capable of sustaining life as we know it. When that day comes, we’ll want to be sharp enough to distinguish life signs from the host of other processes that could produce a similar chemical composition.


Beyond Darwin: The Future of Exoplanet Imaging

After we’ve found an Earth-like planet with a potential for life, what further things can we do to investigate it? A team led by Jean Schneider (Paris Observatory) asks this question in a new paper, speculating that there are things a technological society does that leave a sure trace. Given the right instruments (no small requirement), we might look, for example, for Carbon Fluoro Compounds (CFCs). Well known for their damaging effects on our ozone layer, CFCs absorb infrared light at characteristic wavelengths, making their signature a revealing one.

Spotting an Extraterrestrial ‘Techno-Signature’

Schneider calls markers like this ‘techno-signatures’ (as opposed to the more familiar ‘bio-signatures’). They’re spectral features that can’t be explained by complex organic chemistry. Find CFCs in the atmosphere of a distant world and you’ve got a snapshot of technological chemical synthesis at work. We might speculate as to whether the average civilization produces CFCs in abundance, or for that matter, whether such cultures would simply move through a period of CFC production before scouring them from their ecosystem.

That could leave us with a relatively tiny window of observing time, just as with radio waves, where we listen for an extraterrestrial signal knowing that our own culture is gradually going silent as it turns to cable and satellite. Schneider’s team also ponders the possibility of detecting artificially produced light on a planet, noting that earth’s total energy production is about 40 TW. This is roughly one millionth of the sunlight energy reflected by the whole planet, making artificial light at this power level an unlikely catch.

In fact, seeing alien city light would demand an aperture with a diameter of 1.5 kilometers. It’s a sobering perspective, and only one of many in this absorbing paper, which also touches on Luc Arnold’s speculations about detecting artificial constructions that might transit in front of a distant civilization’s star (we’ve discussed Arnold’s work before on Centauri Dreams). Clearly, we’re pushing into a technology area well beyond the proposed Terrestrial Planet Finder and Darwin missions, but as long as we’re doing so, why not push even farther?

Direct Imaging and Its Limits

Thus Schneider posits our finding a promising planet around a nearby star, like Centauri B. His assumption is that finding biomarkers on this world would trigger two types of projects, the first being an attempt to directly visualize living organisms. What would it take to pull in a direct image of an organism with a size of ten meters? Let me quote from the paper on the staggering numbers:

A spatial resolution of 1 meter would be required. Even on the putative closest exoplanet alpha Cen A/B b, the required baseline would be at 600 nm B = 600,000 km (almost the Sun radius). In reflected light the required collecting area to get 1 photon per year in reflected light is equivalent to a single aperture of B = 100 km. In addition, [if] this organism is moving with a speed of 1 cm s-1 it must be detected in less than 1000 sec. To get a detection in 20 minutes with a SNR of 5, the collecting area must then correspond to an aperture B = 3 million km.

And there you are: Snapping a photo of our ten-meter cousins on Alpha Centauri Bb is going to take a light-collecting area so vast that the project is rendered phantasmagorical. More realistic in these circumstances, I think, to turn to FOCAL, the telescope sent to the Sun’s gravitational focus in a mission design conceived by Claudio Maccone (and an idea originally developed by Jean Heidmann). For all the tough technology that one would require, it’s simplicity itself compared to an aperture of 3 million kilometers.

Beyond the Conceptual Horizon

Schneider’s take on the second project — getting a human or even robotic mission to a nearby star — is also sobering. For one thing, such a mission would need shielding from cosmic rays and interstellar dust. A water shell one meter thick could provide protection, but we still have the problem of accelerating up to 0.3 c or whatever cruising velocity we hope to use. Dust is worse still. Let me turn to the paper again for the grim numbers:

As for the threat by interstellar dust, a 100 interstellar grain at 0.3 the speed of light has the same kinetic energy than a 100 tons body at 100 km/hour. No presently available technology can protect against such a threat without a spacecraft having itself a mass of hundreds of tons, in turn extremely difficult to accelerate up to 0.3 c.

Schneider’s team, in discussing these matters, talks in terms of a ‘conceptual or knowledge horizon,’ one which limits us to making biomarker detections and then leaves us frustratingly unable to probe deeper until, in their view, many centuries of technological obstacles have been overcome. But as we wait for that horizon to shrink, what can we realistically hope to do? In addition to advanced spectroscopy, large, space-based interferometers could conceivably allow many of the following direct imaging possibilities:

  • Direct imaging of habitable moons of giant planets
  • Highly improved transit spectroscopy for transiting planets
  • Detecting planetary moons by astrometry (measuring the displacement of the planet’s position due to the gravitational pull of the moon)
  • Constraining planetary radius for transiting planets
  • Direct measurement of planetary radii

All of this leads up to what could be the ultimate step, at least in terms of forseeable technology. That would be the direct imaging of surface features like oceans and continents on a world light years away. And as the paper notes, this approach may also allow us to detect forests and savannahs there, investigating the equivalent of the ‘red edge’ of terrestrial vegetation at 725 nm.

We can hope the time frame for moving beyond these limits is shorter, and that we are not as far from seeing other worlds up close as Epicurus was some 2300 years ago when he first predicted that such places must exist. But in noting the Greek philosopher, the paper also reminds us that even as today’s technology would have been inconceivable to Epicurus, what may emerge in an indefinite future could help us overcome these obstacles in ways we cannot yet imagine.

Reference (and a Thought on Preprints)

The paper is Schneider et al., “The far future of exoplanet direct characterization,” accepted at Astrobiology and available as a preprint. And a note on the arXiv site: Now and then I hear people say that a preprint site like arXiv is all we need to consult. After all, the thinking goes, all new scientific papers appear there.

But nothing could be further from the truth. For one thing, many papers appear in print only, depending on the journal involved and its policies. But more significantly, a preprint may or may not be identical to the published version. I’ve seen many papers that have undergone substantial revision after the preprint first appeared. We look at preprints at Centauri Dreams to get word of what’s coming in the research, but what eventually appears in the journals should always be considered the gold standard.

Addendum: A note from Jean Schneider points out that the Darwin mission is no longer a part of ESA’s program. Indeed, the current Web site on the idea will soon be taken down. Our near-term future in space-based exoplanet detection beyond Kepler and CoRoT is looking more and more problematic.


HARPS Bags 32 New Exoplanets

More than 75 exoplanets in thirty different planetary systems is an impressive score, and that’s what HARPS has compiled since its installation in 2003. The High Accuracy Radial Velocity Planet Searcher is the spectrograph for the European Southern Observatory’s 3.6-meter telescope at La Silla (Chile). Built by a consortium led by Michel Mayor (Geneva Observatory), HARPS does its work by measuring the minute changes in a star’s radial velocity that flag the presence of an unseen companion.

Most of the roughly four hundred exoplanets discovered to date have been found through radial velocity methods. The figure of 400 includes the latest results from HARPS, which is back in the news with the announcement of 32 new exoplanets, found as part of a five year program using observing time given to the HARPS consortium in return for building the instrument. One of the new worlds is Gliese 667 Cb [see andy’s note below], a six Earth-mass planet in a triple star system. The planets announced today range from five times the mass of Earth to up to five times the mass of Jupiter.

Discussing the low-mass worlds HARPS has located, Stephane Udry (Geneva University) draws an interesting conclusion, as quoted in this BBC story:

“From [our] results, we know now that at least 40% of solar-type stars have low-mass planets. This is really important because it means that low-mass planets are everywhere, basically. What’s very interesting is that models are predicting them, and we are finding them; and furthermore the models are predicting even more lower-mass planets like the Earth.”


At a stroke, HARPS has boosted the known population of low-mass planets by thirty percent. No wonder Udry is encouraged. HARPS’ long suit is its sensitivity, enabling it to detect the signature of these smaller worlds. 28 planets with a mass of less than twenty times that of Earth have been found, and HARPS is responsible for 24 of them. Most of the new low-mass candidates reside in multi-planet systems, with up to five planets per system.

The new planets were announced today at the ESO/CAUP conference Toward Other Earths: Perspectives and Limitations in the ELT Era, now taking place in Portugal. Out of the work, eight papers are in the submission process at Astronomy & Astrophysics. We’ll know more as these papers become available, but we do know the HARPS consortium’s target list focused on solar-like stars, low mass dwarfs and stars with lower metal content than the Sun. The results include several giant planets in M-dwarf systems and, interestingly enough, three candidate exoplanets that showed up around metal-deficient stars.

Addendum: This ESO news release has more, including a brief video interview with Michel Mayor.