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Microwave Beaming and the Cosmos Sail

by Paul Gilster | May 31, 2005 | Sail Concepts | 0 Comments

We're closing in on the launch of the Cosmos 1 solar sail, the first free-flying spacecraft to be powered by the momentum of solar photons. Yes, there have been deployment experiments before this, such as the Russian Znamya missions and the Japanese deployment of a thin film just last summer. But Cosmos 1 will be a functioning spacecraft capable of returning data, and its launch thus marks an important first in sail development. The launch window opens on June 21. The spacecraft is to be launched into a near polar and circular 800 kilometer orbit, with sail deployment four days later. Cosmos 1 has been moved from the test facility in Moscow to Severomorsk; the plan calls for it to be launched by a converted Russian ICBM from a submerged submarine. If successful, the mission will be a landmark not only for sail propulsion but also for commercial space development. The vehicle was funded by Cosmos Studios, with donations from members of the Planetary Society, whose latest update on the...

How to Observe a Wormhole

by Paul Gilster | May 30, 2005 | Breakthrough Propulsion | 0 Comments

If wormholes exist, is it possible to observe one? A fascinating, decade-old paper argues for the possibility, based on the observed phenomenon of mass curving space, which shows up in numerous instances of gravitational lensing. Just as the image of a background object like a distant galaxy can be bent by an intervening mass to produce a magnified image, so wormholes might be detected through their visual effects. But wormholes, remember, are odd beasts. They should display negative mass. The upshot: instead of focusing light like a gravitational lens, a wormhole should diffuse it in all directions. I discussed the possibilities with Geoffrey Landis at Glenn Research Center a couple of years ago. Landis, who worked on the paper "Natural Wormholes as Gravitational Lenses" (Physical Review D, March 15, 1995: pp. 3124-27) with a remarkable team (John Cramer, Robert Forward, Gregory Benford et al.) pointed out that an actual wormhole would not be visible. But if a wormhole passed in...

On Shielding a Starship

by Paul Gilster | May 26, 2005 | Interstellar Medium, Missions | 0 Comments

Just how empty is interstellar space? We know that atoms of hydrogen and helium are the primary elements found there, but widely scattered atoms of every other element also show up in greater or lesser densities, along with grains of dust that are pushed into deep space by the pressure of stellar winds. You can also figure on cosmic rays -- ionized atoms accelerated to extremely high energy states. So energetic are galactic cosmic rays that they correspond to the energy of protons moving anywhere from 43 to 99.6 percent of the speed of light. And let's not forget magnetic fields -- a weak interstellar field aligns with our galaxy -- and high-energy gamma rays that emerge from stellar events that are still poorly understood. Granted, the density of material in the nearby interstellar medium is far lower than the best vacuums we can create on Earth. The average in the Sun's vicinity seems to be .01 atoms of hydrogen for every cubic centimeter of space, a number that is lower than the...

Voyager at the Edge

by Paul Gilster | May 25, 2005 | Interstellar Medium, Missions | 0 Comments

NASA is now confirming that Voyager 1 has entered the heliosheath, where the solar wind and interstellar materials begin to mix. The heliosheath is the outermost layer of the heliosphere, beyond which the spacecraft passes into interstellar space. Among the confirmatory data noted by the Voyager team: the magnetic field carried by the solar wind has increased by a factor of two and a half, which is the natural result of the solar wind slowing down. These readings have remained high ever since mid-December 2004, when the spacecraft crossed the termination shock at 94 AU. The issue, controversial ever since, now seems resolved. "The consensus of the team now is that Voyager 1, at 8.7 billion miles from the Sun, has at last entered the heliosheath, the region beyond the termination shock," said Dr. John Richardson from MIT, Principal Investigator of the Voyager plasma science investigation. Analogies are always useful in explaining such matters, and NASA offers the following in relation...

Microlensing Finds Distant Planet

by Paul Gilster | May 24, 2005 | Deep Sky Astronomy & Telescopes, Exoplanetary Science | 0 Comments

One of the most distant planets ever discovered has been found 15,000 light years from Earth by an international team of astronomers helped by two amateurs from New Zealand. The method of discovery was gravitational microlensing, which occurs when a massive object like a star crosses in front of a star shining in the background. Light from the more distant object is bent and magnified as if by a lens. From astronmers' perspective here on Earth, the background star gets brighter as the lens crosses in front of it, and then fades as the lens moves away. Which is what happened on March 17, 2005 when Andrzej Udalski, professor of astronomy at Warsaw University and leader of the Optical Gravitational Lensing Experiment (OGLE) realized that a star he was observing was moving in front of a much more distant star. The brightening of the distant star was significant -- almost a hundred-fold -- and it was then that OGLE astronomers (and a team from the Microlensing Follow Up Network (MicroFUN)...

Webb Telescope Joins Voyagers on Endangered List

by Paul Gilster | May 23, 2005 | Deep Sky Astronomy & Telescopes, Exoplanetary Science | 0 Comments

The mundane facts of finance continue to threaten our far-flung Voyager spacecraft as NASA looks for dollars to keep the missions alive. Adding further significance to the issue is the upcoming news conference on May 24, in which Voyager scientists will present information that has led them to conclude Voyager 1 has reached the heliosheath -- that area between 80 and 100 AU from the Sun just inside the boundaries of the heliosphere. The heliosphere is that region carved out by the solar wind from the Sun within the larger interstellar medium. The 'termination shock' is the zone where the solar wind is slowed by interstellar gas, dropping abruptly from its 300 to 700 kilometer per second velocity (the solar wind seems to change in speed and pressure, causing the termination shock to expand and contract). Having apparently exited the termination shock, Voyager 1 is in the heliosheath, on its way to the outer boundary of the Sun's magnetic field and solar wind. What tells us that...

On ‘Central Projects’ for a Civilization

by Paul Gilster | May 21, 2005 | Culture and Society | 0 Comments

"The space program stands with the cathedrals and pyramids as one of the great 'central projects' of history, epic social feats embodying the worldview of a culture and the spirit of an age. On the launch pads, the rockets point heavenward like Gothic spires. Searchlights intersect on a waiting ship to form a great candescent pyramid, ablaze on the black horizon like some alien encounter, radiating light to the heavens. To reach for the heavens seems almost the signature of the central project. The pyramid was called the 'stairway to heaven,' the cathedral the 'gate of heaven.' The archetype is in Genesis: 'let us build us a city and a tower, whose top may reach unto heaven.' "Literature on the pyramids, cathedrals and moon shots has tended to miss the significance not only of great height as the signal feature of central projects, but also their function as means through which whole cultures have found symbolic expression. Writers often pay lip service to the official rationales --...

Space Technology Viewing Itself

by Paul Gilster | May 20, 2005 | Autonomy and Robotics, Culture and Society | 0 Comments

Sometimes the fuzziest image carries a sense of awe that later, far more detailed photographs do not quite convey. Such were the early photographs from the Palomar Observatory showing planetary images that forever fixed in my mind the dream of seeing these places up close; even Cassini's extraordinary views can't eclipse the memory of Palomar's Saturn as seen through a boy's eyes forty-five years ago. And it may be that the image below carries a bit of the same awe. Fuzzy it may be, but you're looking at an image of the Mars Odyssey spacecraft as seen by another craft, the Mars Global Surveyor using its Mars Orbiter Camera. This and another Mars Orbiter Camera image, that one of the European Space Agency's Mars Express spacecraft, mark the first time a spacecraft in orbit around another planet has taken pictures of another spacecraft orbiting that planet. You can compare the actual image of Mars Odyssey with the computer-generated view of the spacecraft below to interpret what you're...

Is Dark Energy Real?

by Paul Gilster | May 19, 2005 | Breakthrough Propulsion, Deep Sky Astronomy & Telescopes | 0 Comments

The expansion of the universe ought to be slowing down -- gravitational attraction working on the ordinary matter of the cosmos should see to that. So evidence produced during the last eight years that the universe's expansion seems to be speeding up continues to confound astrophysicists. To explain it, a provocative notion has been introduced: two-thirds of the entire energy density of the universe consists of a new kind of energy. This 'dark energy' has the opposite effect of gravity, pushing away rather than attracting. But is there such a thing as dark energy, or is it just a way to explain something so baffling that we have no other models to describe it? "We don't know," comments Professor David Spergel of Princeton University. "It could be a whole new form of energy or the observational signature of the failure of Einstein's theory of General Relativity. Either way, its existence will have profound impact on our understanding of space and time. Our goal is to be able to...

Fine-Tuning the Interstellar Lightsail

by Paul Gilster | May 18, 2005 | Sail Concepts | 0 Comments

Robert Forward's early work on the beamed-energy lightsail, exemplified by the 1984 paper "Round-trip Interstellar Travel Using Laser-Pushed Lightsails," came to grips with the central challenges of interstellar travel. As described in a recent paper on beamed energy requirements for laser sails, these are: How to reach a nearby star within a human lifetime? How to achieve this with known physics? How to hold down the cost, which also means minimizing the energy requirements? How to return the crew to Earth at the end of their explorations? Forward's methods involved huge laser installations near the Sun, lenses fully 1000-kilometers in diameter in the outer Solar System, and a vast sail constructed in three parts so it could be separated (staged), with the outer ring projecting light back on the inner two for deceleration at destination, using the still powerful laser beam from the Sol system. The method is complicated, ingenious and extraordinarily creative. But can we improve on...

New Work on ‘Hot Jupiters’

by Paul Gilster | May 17, 2005 | Exoplanetary Science | 2 Comments

The first of the giant, close-in exoplanets (widely known as 'hot Jupiters') was discovered a decade ago around 51 Pegasi. Since then, we've found numerous other examples of such objects, challenging our theories of planetary formation and revising estimates of how common habitable worlds may be. Now a team of Canadian astronomers using the MOST (Microvariability & Oscillations of STars) space telescope has found yet another interesting anomaly: a planet that seems to force its star to rotate in synchrony with the planet's orbit. The planet is in orbit around the star tau Bootis. MOST has revealed that the star varies in light output in relation to the orbit of the planet around it. The explanation offered by the team studying tau Bootis b is that the planet has forced the outer envelope of the star to rotate so it always keeps the same face toward the planet. The effect is probably limited to the outer layers of gas in the star, in much the same way the Moon can cause a tidal bulge...

Detection of Three Nearby Stars

by Paul Gilster | May 16, 2005 | Exoplanetary Science | 0 Comments

Many stars close to the Sun have familiar names, like the Centauri triple-star system, Barnard's Star, Epsilon Eridani and Tau Ceti. But the catalog of nearby stars is by no means complete, as we are reminded periodically by the discovery of stars showing large proper motion as observed from Earth. That motion flags the object as close, but the fact that so many of the galaxy's stars are M-class red dwarfs (up to 70 percent in some estimates) makes detecting them tricky. These are small, dim stars; some may have been in our catalogs for years before astronomers realized how close they were. Some scientists, in fact, measure the number of missing stellar systems at 25 percent or more, even so close as 10 parsecs from the Sun. Now an international team of researchers has found three of the missing stars. Using data from the Two-Micron All Sky Survey (2MASS), the Deep Near Infrared Survey (DENIS) and the SuperCOSMOS Sky Survey (SSS), the team uncovered the three close neighbors by...

Landfall on Titan: Two Mosaics

by Paul Gilster | May 14, 2005 | Outer Solar System | 0 Comments

Huygens' Descent Imager Spectral Radiometer (DISR) team has now produced mosaic images of the probe's descent to Titan's surface. These were created by combining images taken by Huygens as it rotated on its axis, the first image showing the view from approximately 20 kilometers altitude. The photos were taken in groups of three as the probe descended through the atmosphere last January. Image: (click to see enlargement): This stereographic projection of DISR images from ESA's Huygens probe combines 60 images in 31 triplets, projected from a height of 3000 metres above the black 'lakebed' surface. The bright area to the north (top of the image) and west is higher than the rest of the terrain, and covered in dark lines that appear to be drainage channels. Credits: ESA/NASA/JPL/University of Arizona. The stereoscopic image shown above is intriguing because of what appears to be going on in the north and west (top and top left of the image). Be sure to click on the image to see it in...

Processes in Titan’s Atmosphere Similar to Earth

by Paul Gilster | May 13, 2005 | Outer Solar System | 0 Comments

Titan continues to live up to its billing as a model of the early Earth. Recent observations by Cassini tell us much about the moon's atmosphere, about 98 percent nitrogen (with most of the remainder being methane), and laden with organic molecules. Sunlight appears to break these molecules apart as they rise in the atmosphere, where their fragments form heavier organic molecules -- propane, ethane, acetylene, hydrogen cyanide. Cold air over the winter pole then causes this material to sink, with the result that heavy organics build up in the stratosphere over the course of the winter. Supplying the data is Cassini's Composite Infrared Spectrometer instrument (CIRS); a paper on its findings is scheduled to appear in the May 13 issue of Science. The polar vortex phenomenon is similar to what occurs on Earth; strong winds circulating around Titan's north pole isolate the atmosphere over the pole during the polar night, inhibiting mixing with the lower regions of the atmosphere....

Of Robots and Reproduction

by Paul Gilster | May 12, 2005 | Autonomy and Robotics | 1 Comment

Even in best-case scenarios, a probe to Alpha Centauri or other nearby stars will take decades to reach its target, perhaps centuries. That puts the premium on spacecraft autonomy, an interesting take on which is the ability of machinery to repair itself. Cornell researchers have just announced a milestone in this regard, the creation of a robot that makes copies of itself. Previous self-replicating designs have existed only as computer simulations or were much simpler than Cornell's new devices. As reported in the May 12 issue of Nature, the university's Hod Lipson and colleagues have created machines made up of modular cubes called 'molecubes.' Each is identical and contains the computer program that allows it to reproduce. Using electromagnets on their faces, the cubes can adhere to one another selectively; a complete robot is made up of an assembly of such molecubes. And because the cubes are divided, robots composed of them can bend to various angles or manipulate other cubes....

Plasma Propulsion Under Scrutiny at MSFC

by Paul Gilster | May 11, 2005 | Advanced Rocketry, Breakthrough Propulsion | 1 Comment

A team of NASA and university-based investigators is studying the physics of magnetic nozzles, devices that could be used in plasma-based propulsion systems that would sharply reduce the length of journeys within the Solar System. The project began in April and is led by the University of Texas, with support from Marshall Space Flight Center in Huntsville (AL), along with the University of Alabama at Huntsville and NASA's Johnson Space Center in Houston. "The technology we're pursuing could play an important role in NASA's exploration of the Moon, Mars and the rest of the Solar System," said Dr. Greg Chavers, a plasma physicist at Marshall and co-investigator for the new project. "Magnetic nozzles enable a new type of plasma-based propulsion system that could significantly reduce travel times to different planetary destinations, providing a new means of exploring space." Plasma forms when a hot gas is ionized, causing the atoms to lose their electrons and take on a positive charge....

Pluto Mission in Flight Simulations

by Paul Gilster | May 10, 2005 | Missions, Outer Solar System | 0 Comments

The New Horizons mission to Pluto and Charon is on schedule. The spacecraft is now completely assembled and has undergone a comprehensive performance test of its own systems and its seven instruments, according to principal investigator Alan Stern. The first of the major flight mission simulations began at the end of April; this will be followed by another run of performance tests, with environmental testing beginning in mid-May. Eying the January 2006 launch window, NASA plans a readiness review at the end of May. Image: Pluto and Charon are primary targets for this first targeted Kuiper Belt mission. Credit: Johns Hopkins University Applied Physics Laboratory. Stern's contributions to the New Horizons site at Johns Hopkins University's Applied Physics Laboratory are a great way to keep up with the mission's progress. In the latest, Stern recalls how New Horizons got its name: ...as I waited for a streetlight to change near the intersection of Foothills and Arapahoe and looked west...

The Roadmap to Epsilon Eridani

by Paul Gilster | May 9, 2005 | Advanced Rocketry, Breakthrough Propulsion | 1 Comment

Sending a probe to another star would be NASA's greatest adventure, but how do we lay the groundwork for such a mission? The agency likes 'roadmaps,' spelling out clear and specific objectives and beginning with missions not so far beyond those we could fly today. NASA's Interstellar Probe Science and Technology Definition Team (IPSTDT) recently prepared studies on a solar sail mission into nearby interstellar space, reaching approximately 400 AU from the Sun in 20 years of flight time. Think of it as a logical follow-on to the Voyager probes. But Ralph McNutt and colleagues at Johns Hopkins' Applied Physics Laboratory have been defining a more ambitious mission. As worked out in several recent papers, McNutt's probe would approach the Sun to within 4 solar radii before a fifteen minute engine burn would establish its high-speed escape trajectory from the Solar System. At this point all acceleration would end; unlike the IPSTDT design, no sail would be deployed. The McNutt mission...

Why SETI Matters

by Paul Gilster | May 8, 2005 | Astrobiology and SETI, Culture and Society | 0 Comments

"MacDonald paused outside the long, low concrete building which housed the offices and laboratories and computers. It was twilight. The sun had descended below the green hills, but orange and purpling wisps of cirrus trailed down the western sky. "Between MacDonald and the sky was a giant dish held aloft by skeleton metal fingers -- held high as if to catch the stardust that drifted down at night from the Milky Way. Go and catch a falling star, Get with child a mandrake root, Tell me where all past years are, Or who cleft the Devil's foot; Teach me to hear mermaids singing, Or to keep off envy's stinging, And find What wind Serves to advance an honest mind. "Then the dish began to turn, noiselessly, incredibly, and to tip. And it was not a dish any more but an ear, a listening ear cupped by the surrounding hills to overhear the whispering universe. "Perhaps this was what kept them at their jobs, MacDonald thought. In spite of all disappointments, in spite of all vain efforts, perhaps...

Saturn Moon a Kuiper Belt Object

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

The Kuiper Belt yields up its secrets grudgingly, but sometimes we get help from objects much closer to the Sun. Cassini's flyby of Saturn's moon Phoebe on June 11, 2004 has provided all the information scientists needed to declare the ancient object a relic from the outer Solar System, much like Pluto and other Kuiper Belt members. Two papers in Nature provide our best look yet at Phoebe. Determining a planetary object's origin isn't easy, but Phoebe can be analyzed in terms of its density, which is calculated on the basis of the moon's mass studied in relation to volume estimates from the Cassini images. The resulting figure is 1.6 grams per cubic centimeter, lighter than most rocks but heavier than pure ice, and suggesting an ice/rock composition similar to Pluto and Neptune's moon Triton. "Cassini is showing us that Phoebe is quite different from Saturn's other icy satellites, not just in its orbit but in the relative proportions of rock and ice. It resembles Pluto in this regard...

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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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