Centauri Dreams on the Air

Theoretical physicist Michio Kaku interviewed me for his public radio show Explorations last Thursday. The show is to run November 1, but I’m told that some of the public stations that carry it are currently doing their fund-raising, so the schedule may be thrown off. Dr. Kaku’s Web page carries a list of stations, and the show will be available for download on the Web.

Michio KakuMichio Kaku is is the co-founder of String Field Theory, and is the author of international best-selling books such as Hyperspace, Visions, and Beyond Einstein. He also holds the Henry Semat Professorship in Theoretical Physics at the City University of New York.

Much of the conversation was devoted to interstellar propulsion concepts, with a few even more speculative issues thrown in. In particular, Kardashev’s three levels of civilization. A brief refresher:

Nikolai Kardashev was a Russian astronomer who sought to classify extraterrestrial civilizations based on energy output. A Type I civilization would be capable of harnessing the entire energy output of its planet. Type II would be able to draw on all the energy available from its star, while Type III would exploit the energy resources of its galaxy. In Kardashev’s view, the output of each stage is 10 billion times larger than the previous one. These are staggering numbers, but Kaku thinks they can be ‘bridged by any modestly expanding civilization.’

Listen to him in his book Visions (New York: Anchor Books, 1997):

Assume, for the moment, that our own world economy grows at a rather anemic rate of 1 percent per year, which is very conservative. Since economic growth is fueled by increased consumption of energy, we would find a corresponding growth in energy as well. Within a hundred to a few hundred years, our world will approach a planetary Type I civilization.

At such a growth rate, the transition from a planetary Type I civilization to a stellar Type II civilization will take longer, perhaps 2,500 years. A more realistic growth rate of 2 percent per year would reduce that figure to 1,200 years. And a 3 percent annual growth rate would reduce that even further to 800 years.

Eventually, the energy needs of a Type II civilization will outgrow even the energy output of its star. It will be forced to go to nearby star systems in search of resources and energy, eventually transforming it into a galactic civilization. (Visions, p. 323).

As to the transition to Type III, Dr. Kaku believes it will be a lengthy one, because it will require mastery of interstellar travel. But he thinks that within a hundred thousand to a few million years, a Type II civilization could make the transition to a Type III.

My view is that if a Type III civilization existed in our own galaxy, its presence would be blindingly obvious. Kaku disagrees; he says that would be like expecting ants along the side of a superhighway to understand that they were in the presence of an alien technology when, in fact, the most they would be looking for would be other, perhaps bigger, ants. Kaku’s speculations on how a Type II culture might grow into a Type III using self-replicating probes make for fascinating reading, and I want to return to them in the near future.

Enigmatic Titan Has Everyone Stumped

The news from Titan could not be more curious. Radar imagery shows dark areas that may be smooth plains choked with ice, or perhaps pools of liquid methane. The early photographs showed few topographical features, due largely to the diffuse glare that reduces shadows under Titan’s thick atmosphere. But processed radar images showed rough terrain interspersed with darker areas that seem to be flat. Variations in elevation appear to be no more than 150 feet in the area most closely studied, according to this article in the New York Times (free registration required).

And what are these strange surface streaks in the equatorial region? Early speculation is that they are ridges of ice or deposits of some kind of windblown material.

Surface streaks on Titan

Image: This medium-resolution view shows some of the surface streaks of Titan’s equatorial terrain. The streaks are oriented roughly east to west; however, some streaks curve to the north and others curve to the south, perhaps due to the topography of this region. North is a few degrees to the right of vertical. The scale is .85 kilometers (.53 miles) per pixel. This image was taken on Oct. 26, 2004, by Cassini’s imaging science subsystem using near-infrared filters. Credit: NASA/JPL/Space Science Institute

From the Times article:

“Dr. Ralph Lorenz of the University of Arizona reported that measurements of Titan’s surface heat ‘were consistent with a surface covered in organic material’ and that the dark regions were richer in organics than the brighter areas…Even though Titan’s mass is estimated to be half water and half rock, any lake would not be liquid water. It would be frozen solid on a surface with temperatures as low as minus 290 degrees Fahrenheit.”

Here’s a San Francisco Chronicle story about Si-Si the Cat, a region of possible lakes (named after a scientist’s daughter noticed it looked like a Halloween cat in the image).

And despite the fact that Titan would surely have received many hits from large objects in its life, no craters were visible in the latest round of images, suggesting that craters have filled in with water ice and what would probably be a rain of hydrocarbons from the sky. Titan’s atmosphere is primarily nitrogen, but methane is also plentiful.

The Cassini team points to the problems with our current view of Titan: the black-and-white radar image covered only 1 percent of the moon’s surface, a strip of land 75 miles wide and 1,250 miles long. An excellent ESA page showing how these images are cleaned up through various digital processing methods can be found here.

Cassini will make 44 more close passes of Titan in the next four years, and Huygens is scheduled to land in January. Assuming Huygens makes it down safely, what will it encounter on the surface? It may well come down in a hydrocarbon brew of methane, propane or butane, but the craft is designed to float, and we may get half an hour or so of data if all goes well. Clearly, we’re only at the beginning of this story.

Early Planet Formation Around Beta Pictoris

Astronomers from Japan’s Ibaraki University, the Japan Aerospace Exploration Agency, the University of Tokyo, and the National Astronomical Observatory of Japan have analyzed the dust disk surrounding the star Beta Pictoris, with intriguing results. Using an instrument called the Cooled Mid-Infrared Camera and Spectrometer (COMICS) and the Subaru telescope, the team found that ring-like distributions of planetesimals (something like the asteroid belt in our own Solar System) occur at three locations, measured as 6, 16 and 30 AU from the star. An unseen planet some 12 AU from the star may be what is keeping these belts intact.

Dust ring around Beta Pictoris

The disk around Beta Pictoris, a young star whose disk is more or less edge-on to our solar system, has been studied for some twenty years. Working in the infrared, Yoshiko K. Okamoto of Ibaraki University in Japan and his colleagues have provided new details of its structure.

Image: Depiction of a possible planet (upper left) flanked by bands of dust within the debris disk surrounding the star Beta Pictoris (upper right). © K. Kanba, ISAS/JAXA.

What apparently keeps these rings of dust replenished are repeated collisions between planetesimals in the debris belts. We’re looking at the structure of a planetary system in the making; our own early solar system may well have grown through similar collisions. The Beta Pictoris results have already been published in Nature: Okamoto, Y. K. et al. “An early extrasolar planetary system revealed by planetesimal belts in Beta Pictoris,” Nature, Vol. 431, pp.660-663 (2004).

The Subaru instrument is an 8.2 meter optical-infrared telescope at the summit of Hawaii’s Mauna Kea. . Here is an article on the Beta Pictoris find in Science News.

NASA TV Coverage on Titan Findings

A Cassini close encounter news briefing will be available on NASA TV at 12 PM EST today. Live interviews on the Titan flyby will appear in segments from 3 to 7 PM EST this afternoon. A science briefing occurs tomorrow at 12 PM EST (all programs subject to change without notice, adds NASA).

For more, check both the Cassini-Huygens home page and the Cassini Imaging Team page. Also, a nice interview with Jonathan Lunine, of the Lunar and Planetary Laboratory at the University of Arizona, is here. Back to the usual interstellar rounds soon, but for now, Titan is too fascinating to ignore.

Closeup of TitanThis image is one of the closest ever taken of Saturn’s hazy moon Titan. It was captured by Cassini’s imaging science subsystem on Oct. 26, 2004, as the spacecraft flew by Titan. At its closest, Cassini was 1,200 kilometers (745 miles) above the moon, 300 times closer than during its first flyby on July 3, 2004. Credit: NASA/JPL/Space Science Institute.

A few salient facts: Cassini came within 1200 kilometers (750 miles) of Titan’s surface. At the time of the encounter, the spacecraft was 1.3 billion kilometers (826 million miles) from Earth, making for a transit time of 1 hour 14 minutes for data to arrive.

Says Mark Leese, a member of the Huygens team at the Open University (UK), who are involved in the Science Surface Package (SSP) and the Huygens Atmospheric Instrument (HASI):

“The combination of images, spectrometer measurements and RADAR data from this close flyby should help to prepare us for the [Huygens] mission ahead. In addition, Cassini’s measurements of the atmosphere should confirm that the Titan atmosphere model used to design the probe entry system is correct.”

Sources: Various NASA Web pages; Cassini Imaging Central Laboratory for Operations site; news release from the Particle Physics and Astronomy Research Council (UK).

A View of Xanadu

We’ll soon have many more images, but for now, this view of Titan taken on the 24th may give a foretaste of what’s to come. Here’s the image, along with NASA’s description, of the extraordinary feature that recalls Coleridge:

In Xanadu did Kubla Khan
A stately pleasure-dome decree:
Where Alph, the sacred river, ran
Through caverns measureless to man
Down to a sunless sea.

View of Xanadu

NASA’s commentary:

“This image taken on Oct. 24, 2004, reveals Titan’s bright “continent-sized” terrain known as Xanadu. It was acquired with the narrow angle camera on Cassini’s imaging science subsystem through a spectral filter centered at 938 nanometers, a wavelength region at which Titan’s surface can be most easily detected. The surface is seen at a higher contrast than in previously released imaging science subsystem images due to a lower phase angle (Sun-Titan-Cassini angle), which minimizes scattering by the haze.

“The image shows details about 10 times smaller than those seen from Earth. Surface materials with different brightness properties (or albedos) rather than topographic shading are highlighted. The image has been calibrated and slightly enhanced for contrast. It will be further processed to reduce atmospheric blurring and to optimize mapping of surface features. The origin and geography of Xanadu remain mysteries at this range. Bright features near the south pole (bottom) are clouds. On Oct. 26, Cassini will acquire images of features in the central-left portion of this image from a position about 100 times closer.” Credit: NASA/JPL/Space Science Institute.

Titan isn’t sun-less, and we’re not exactly positive about those seas, but today’s close pass by Cassini should provide plenty to talk about. More on the Cassini home page.