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Brown Dwarfs May Have Planets

by Paul Gilster | Oct 22, 2005 | Exoplanetary Science | 2 Comments

If brown dwarfs, those 'failed stars' that never make it to the stage of full nuclear burning, can have planets around them, then the speculations of Karl Schroeder's novel Permanence (New York: Tor Books, 2002) may be closer to reality than Centauri Dreams once thought. Schroeder imagines human colonies, artificially sustained through extraordinary technologies, on planets surrounding a variety of brown dwarf stars, an entire civilization of humans living in the spaces between the 'lit' stars we see in the night sky. Now the Spitzer Space Telescope has found the signs of early planet formation around six young brown dwarfs located some 520 light years away in the Chameleon constellation. Ranging in size from between 40 to 70 times the mass of Jupiter, the brown dwarfs are between 1 and 3 million years old. And five of them have disks made up of dust particles that are clearly sticking together, in what looks suspiciously like the early stages of planet formation. The astronomers...

SETI and Drake: Part II

by Paul Gilster | Oct 21, 2005 | Astrobiology and SETI | 5 Comments

Yesterday we looked at Milan ?irkovi?'s paper “The Temporal Aspect of the Drake Equation and SETI" (Astrobiology Vol. 4 No. 2, pp. 225-231), and pondered whether there might not be a 'communications window' -- an interval for any society between when it reaches the technological capacity for interstellar communication and the point when it becomes a 'supercivilization' unlikely to use conventional SETI methods to contact us or anyone else. If so, that 'window' would have a profound effect on how many civilizations we might be able to contact via SETI, and would thus change our answers to the Drake Equation. But there are other kinds of assumptions built into the equation that may be problematic. ?irkovi? notes that the equation assumes a more or less uniform physical and chemical history of our galaxy, but uniformitarianism doesn't work well in astrophysics or cosmology (think of the Steady State theory -- uniformitarian -- vs. the Big Bang, which introduced the concept of epochs...

A Hard Look at SETI and the Drake Equation

by Paul Gilster | Oct 20, 2005 | Astrobiology and SETI | 0 Comments

The famous Drake Equation was developed as a way to estimate how many technological civilizations might exist and thereby be targets for SETI research. Conceived in 1961 as astronomer Frank Drake worked at the National Radio Astronomy Observatory (Green Bank, WV), the equation exists in a variety of forms depending on which authors you consult (see, for example, this SETI Institute discussion of the equation). But all variants draw on the same idea: to study extraterrestrial civilizations, you must consider such factors as: the mean rate of star formation in the Galaxy; the fraction of stars that can support life; the fraction of stars that have planetary systems; the number of planets per system with conditions suitable for life; the number of planets where life does originate and evolve; the fraction of planets where intelligent life forms develop; the fraction of planets where intelligent life develops technology; and a final, crucial measure: the mean lifetime of a technological...

New Horizons Readied for Flight

by Paul Gilster | Oct 19, 2005 | Interstellar Medium, Missions, Outer Solar System | 0 Comments

With liftoff scheduled for January, the New Horizons mission to Pluto and Charon (and, if we are lucky, at least one flyby of a more distant Kuiper Belt object) continues to generate excitement in the scientific community. The spacecraft is now at the Kennedy Space Center and will be moved to the launch pad in December, with liftoff planned for January 11. Major testing on the science payload is complete. The next round of major instrument calibrations and testing won't occur until the early months of the journey as New Horizons moves toward a 2007 flyby of Jupiter for a gravity assist to Pluto. How do you package enough instrumentation for good science at the edge of the Solar System into a payload that draws only 28 watts of power? The science payload work was led by the Southwest Research Institute (SwRI), whose recent news release lists the seven instruments that will explore these icy worlds: Alice, an ultraviolet imaging spectrometer that will probe the atmospheric composition...

A Multi-Tiered Approach to Planetary Exploration

by Paul Gilster | Oct 18, 2005 | Autonomy and Robotics | 0 Comments

As we saw in yesterday's post on microbots, one of the problems of robotic exploration is that we put our equipment into relatively smooth terrain. That makes sense, given the time and cost of getting rovers to Mars, for example; what a shame it would be to see a priceless instrument package slam into a mountainside as it touches down. But rugged terrains, those places where water and volcanic activity have changed a landscape, may tell us much about a planet's history and the possible existence of life on it. Now a team of scientists is proposing a fundamental change to our existing paradigm of robotic exploration. In addition to orbiters, the team (scientists from the California Institute of Technology, the University of Arizona, and the U.S. Geological Survey) has focused on airborne instrument packages (think 'blimps'), complemented by the kind of small, robotic explorers that could work their way into even the most hostile landscapes. "We're not trying to take anything away from...

Surface Exploration by Microbot

by Paul Gilster | Oct 17, 2005 | Autonomy and Robotics | 0 Comments

One way to explore a planetary surface is by rover, much as we are doing now on Mars with Spirit and Opportunity. The amount of data we've received from these missions has been nothing short of sensational, but as we look to the future, a key problem looms: rovers can sample only small areas of the surface. They're a precious commodity that has to be targeted to high-value destinations, meaning they're not adaptable to broad, general surveys. But a new robotic approach may come to the rescue, and it's one that has just received Phase II funding from NASA's Institute for Advanced Concepts. Under the supervision of principal investigator Steven Dubowsky (Massachusetts Institute of Technology), the work focuses on 'microbots' to enable large-scale explorations. Microbots are spherical robots that could be dropped by the thousands, perhaps through air-bags deployed from orbiter spacecraft. They would be able to hop, bounce and roll their way to sites in the most rugged terrain, equipped...

Viewing Continents on Distant Worlds

by Paul Gilster | Oct 15, 2005 | Exoplanetary Science | 0 Comments

It was in 1999 that former NASA administrator Dan Goldin spoke to the American Astronomical Society about what future telescopes might be able to see around distant stars. He imagined a classroom filled with images of exoplanets. "When you look on the walls, you see a dozen maps detailing the features of Earth-like planets orbiting neighboring stars," Goldin said. "Schoolchildren can study the geography, oceans, and continents of other planets and imagine their exotic environments, just as we studied the Earth and wondered about exotic sounding places like Banghok and Istanbul . . . or, in my case growing up in the Bronx, exotic far-away places like Brooklyn." Is a telescope that could take such pictures remotely conceivable? The most innovative proposal I've heard to achieve these goals is Webster Cash's New Worlds Imager concept. The University of Colorado at Boulder astronomer knows how tricky the project would be. As astronomer looking at the Earth from Alpha Centauri would face...

Via Nanotechnology to the Stars

by Paul Gilster | Oct 14, 2005 | Breakthrough Propulsion | 2 Comments

What a pleasure to discover that Robert Freitas' Kinematic Self-Replicating Machines is now available online. The 2004 book (from Landes Bioscience of Georgetown TX) is the most comprehensive study of nanotechnology yet written, a compendium of information on self-replicating systems both proposed and experimentally studied. Moreover, it contains a survey of the historical development of nanotechnology, 200 illustrations and over 3000 references to the technical literature. That nanotechnology (and self-replicating systems in particular) could change our ideas of interstellar flight now seems obvious, but not so long ago ago the concept of one machine building another was studied only at the macro-level. Thus Freitas' previous work on a self-reproducing spacecraft he called REPRO. The scientist wrote the concept up in a 1980 issue of the Journal of the British Interplanetary Society, conceiving of a mammoth Daedalus-style spacecraft built in orbit around Jupiter and, like Daedalus,...

Changes at Centauri Dreams

by Paul Gilster | Oct 12, 2005 | Administrative | 0 Comments

When I began the Centauri Dreams site in August of 2004, the motivation was utilitarian. I was looking for a way to keep up with ongoing research into deep space exploration, figuring it would be helpful to establish a site that followed news day by day and maintained it in a searchable archive. Centauri Dreams the Web site actually preceded my book of the same name by several months, and it was in the back of my mind to use research collected at the site in future writing projects. That motivation still exists. But something else happened in the intervening months. As readership grew, I found I was making new contacts in the research community, not just in the government agencies like NASA and ESA, but also in academic environments and commercial companies. Those contacts have been priceless, and have led to some fine friendships. And they've kept my eye on the main prize, which in my judgment is to put deep space research into the broader context of society's awareness of time. To...

Life’s Origins in the Cosmos

by Paul Gilster | Oct 12, 2005 | Astrobiology and SETI | 4 Comments

To make life happen you need organic molecules that contain nitrogen. Now new work at NASA's Ames Research Center, to be reported in the October 10 issue of the Astrophysical Journal, reveals that organic molecules found throughout the galaxy do, in fact, contain nitrogen. "Our work shows a class of compounds that is critical to biochemistry is prevalent throughout the universe," said Douglas Hudgins, an astronomer at NASA Ames and principal author of the study. The studies combined laboratory experiments and computer simulations. We already knew, thanks to the Spitzer Space Telescope, that complex organic molecules called polycyclic aromatic hydrocarbons (PAHs) are all but ubiquitous. Learning that PAHs contain nitrogen implies that the building blocks of life are seeded everywhere in the universe. From a NASA Ames news release, quoting astrochemist and team member Louis Allamandola: "Chlorophyll, the substance that enables photosynthesis in plants, is a good example of this class...

Studying the Atmosphere of Terrestrial Exoplanets

by Paul Gilster | Oct 11, 2005 | Exoplanetary Science | 0 Comments

Of the 161 planets so far detected around other stars, eight have been discovered by the transit method as they moved between that star and the line of sight to Earth. Such transits, effective as planet finders in themselves, are also useful because they allow scientists to study the properties of the atmospheres around these worlds. The first planet found by transit methods orbits the star HD 209458 and is the object of intense atmospheric study. Can such methods be applied to transiting Earth-size planets? A new paper studies the question in terms of the kind of signatures that might be expected, and the near-term technologies that could make such detections possible. The paper focuses on terrestrial worlds orbiting K, G or F-type stars, and notes that the best targets will be K-type stars, which are in any case more abundant than the other types as well as smaller. According to the analysis, the strongest signatures in the atmosphere of such worlds could be water, ozone and carbon...

Refining the Tools for Life Detection

by Paul Gilster | Oct 10, 2005 | Astrobiology and SETI | 3 Comments

If you're looking for a terrestrial analogue to one part of the Martian environment, you could do worse than the ice vents inside a frozen volcano on the Norwegian island of Svalbard. There, in a one million year old volcano called Sverrefjell, a team of researchers has found a community of microbes both living and fossilized. Ice-filled volcanic vents are believed to occur on Mars and may well be a potential habitat for life on the planet. Behind the Svalbard investigations is AMASE, the Arctic Mars Analog Svalbard Expedition, which is designing devices and techniques that may one day be used by automated landers to search for life on Mars. And thus far the findings are promising. The team has been able to perform its tests while maintaining scrupulous sterility, a key factor in ensuring that 'life' detections on another planet aren't simply the result of Earthly microorganisms being introduced into the local ecology. Examining 780-million year old sedinmentary rocks, the team also...

Bright Spot on Titan Still a Mystery

by Paul Gilster | Oct 7, 2005 | Outer Solar System | 0 Comments

What is that bright 300-mile wide patch on Xanadu, the continent-sized region on Titan, that Cassini noted last March? The area outshines everything else on the moon in long infrared wavelengths (it's described as "...spectacularly bright at 5-micron wavelengths..."), and after considerable investigation does not appear to be a cloud, a mountain or a geologically active hot spot. In visible light, Cassini saw a bright arc-shaped feature of approximately the same size in late 2004 and again in 2005. Image: Combined VIMS and ISS images of Titan's mysterious bright red spot gives researchers more information about the feature than either single view. (Credit: NASA/JPL/University of Arizona/Space Science Institute). That quotation above comes from a University of Arizona news release, one that goes on to note that subsequent radar imaging found no real temperature variation between the spot and the terrain around it. That rules out the possibility of an active ice volcano, and quickly...

A Source for Gamma-Ray Bursts

by Paul Gilster | Oct 5, 2005 | Deep Sky Astronomy & Telescopes | 0 Comments

Imagine two neutron stars colliding, or even worse, a neutron star and a black hole. The release of energy would be catastrophic, and has apparently now led to the first detection in visible light from a short gamma-ray burst. Thus we're beginning to get a handle on the most powerful explosions in the known universe, whose identity has bedeviled astronomers for thirty years. There are actually two different kinds of gamma-ray bursts. The longer ones have been linked to the explosion of a massive star as it collapses into a black hole. It's the short-duration bursts that have proven the greater challenge. The new work, performed at La Silla (Chile) and at the European Southern Observatory's Very Large Telescope, used data from NASA's HETE-2 satellite to guide the observations, and the fading source was found. "That was the clue we were waiting for," said Garrett Jernigan, a research physicist at the Berkeley Space Sciences Laboratory. "Bursts seem to come mainly in two varieties - the...

1991 VG: Natural or Artificial?

by Paul Gilster | Oct 4, 2005 | Astrobiology and SETI | 2 Comments

The search for extraterrestrial intelligence (SETI) has seen a great deal of publicity, from television programs interviewing involved scientists to blockbuster movies like Contact. But the idea that there might be signs of extraterrestrial life closer to home has received relatively short shrift. Nonetheless, SETA (the search for extraterrestrial artifacts) has spawned interesting work, from Gregory Matloff's examinations of anomalous Kuiper Belt objects to Robert Freitas' surveys of 'halo orbits' around the Lagrangian points. So far both kinds of search -- SETI and SETA -- have come up short, but a few curious things have been observed on each side. One interesting SETA investigation involved an object called 1991 VG, which made a close approach to Earth in 1991 (thanks to Adam Crowl for bringing this one to my attention). Discovered by Jim Scotti using the University of Arizona's Spacewatch telescope (normally used to detect small asteroids near the Earth), 1991 VG seemed to be...

A Correction on Adaptive Optics

by Paul Gilster | Oct 3, 2005 | Deep Sky Astronomy & Telescopes | 0 Comments

The sharp-eyed Jon Lomberg writes with a correction to today's story on Xena and its moon Gabrielle. Specifically, my statement that adaptive optics 'bounces' the light of a laser off the atmosphere to create an artificial star used in refining the telescope's images. Lomberg rightly points out that what the laser actually does is to excite sodium atoms at a specific height. The glow from this excitation is then tracked and used to adjust for atmospheric distortion. The results, as we have seen, are nothing short of spectacular. What's ahead for adaptive optics? "A future improvement of the technique," writes Lomberg, "would use different lasers to excite other elements at other altitudes, thus giving a more detailed profile of distortion in the atmosphere resulting in more precise adjustments."

A Moon for Xena

by Paul Gilster | Oct 3, 2005 | Outer Solar System | 0 Comments

Everyone is calling 2003 UB313, the Solar System's 10th planet, Xena. The name comes from a TV warrior princess of whom the curmudgeonly Centauri Dreams, never one for television, was utterly unaware. Now Xena has been found to have a moon, inevitably named Gabrielle after an equally incrutable character on the series (apparently the sidekick of Xena herself). One-tenth the size of Xena, Gabrielle is slated for further observations with the Hubble Space Telescope that will allow more accurate determination of its mass. The advent of Gabrielle is good news for those wishing to learn more about Xena. From a California Institute of Technology press release quoting Michael Brown, the 10th planet's discoverer: "A combination of the distance of the moon from the planet and the speed it goes around the planet tells you very precisely what the mass of the planet is," explains Brown. "If the planet is very massive, the moon will go around very fast; if it is less massive, the moon will travel...

Finding Planets in the Starshine

by Paul Gilster | Sep 30, 2005 | Exoplanetary Science, Missions | 1 Comment

Finding planets around other stars is hampered by a key fact: the light from the primary star effectively masks the far dimmer reflected light from any planets. But NASA engineers at the Keck Observatory (Mauna Kea, HI) have used the Keck Interferometer in conjunction with a light-blocking device to suppress the starlight around three stars, one of which is Vega. The procedure may be used to detect dust disks of planetary systems in formation. "We have proven that the Keck Interferometer can block light from nearby stars, which will allow us to survey the amount of dust around them," said Dr. James Fanson, project manager for the Keck Interferometer at NASA's Jet Propulsion Laboratory. Keck's interferometer links its two 10-meter telescopes to provide the resolving power of a much larger instrument (in Keck's case, one the size of a football field). Examining dust disks in greater and greater detail is crucial, because NASA needs to select targets for its Terrestrial Planet Finder...

Saving the Dark Matter

by Paul Gilster | Sep 29, 2005 | Deep Sky Astronomy & Telescopes | 0 Comments

Are elliptical galaxies influenced by a halo of dark matter? The theory has been accepted until recently through observation of the gravitational effects apparently caused by such matter. But 2003 findings (Romanowsky et al., Science 301, pp. 1696-1698) turned up little evidence for dark matter in such galaxies. Now a different explanation for those observations has surfaced, one that seems to rescue the dark matter concept. That's good news, because dark matter ought to be there. From a University of California at Santa Cruz press release: "A dearth of dark matter in elliptical galaxies is especially puzzling in the context of the standard theory of galaxy formation, which assumes that ellipticals originate from mergers of disk galaxies," added Avishai Dekel, professor of physics at the Hebrew University of Jerusalem and first author of the Nature paper. "Massive dark matter halos are clearly detected in disk galaxies, so where did they disappear to during the mergers?" The dark...

New Horizons Arrives in Florida

by Paul Gilster | Sep 29, 2005 | Missions, Outer Solar System | 0 Comments

The New Horizons spacecraft, slated for a January launch and a decade-long journey to Pluto and Charon, has arrived at Kennedy Space Center for final preparations and testing. This follows a four-month series of tests at Goddard Space Flight Center and the John Hopkins University Applied Physics Laboratory, where the craft was designed and built. What's in the immediate future for New Horizons? The October testing period includes readiness checks, tests of instrument functionality and checks on communications via NASA's Deep Space Network. Hydrazine fuel for attitude control and course correction maneuvers will be loaded in November, and the craft will then undergo a final spin-balance test. A launch countdown rehearsal will be held in November, and in December the spacecraft will be loaded onto the Atlas V rocket that will carry it aloft. Launch is now scheduled for January 11, 2006, with later launch windows available daily between January 12 and February 14.

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In Centauri Dreams, Paul Gilster looks at peer-reviewed research on deep space exploration, with an eye toward interstellar possibilities. For many years this site coordinated its efforts with the Tau Zero Foundation. It now serves as an independent forum for deep space news and ideas. In the logo above, the leftmost star is Alpha Centauri, a triple system closer than any other star, and a primary target for early interstellar probes. To its right is Beta Centauri (not a part of the Alpha Centauri system), with Beta, Gamma, Delta and Epsilon Crucis, stars in the Southern Cross, visible at the far right (image courtesy of Marco Lorenzi).

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