Archives

Nudging an Earth-bound Asteroid

by Paul Gilster | Nov 15, 2005 | Asteroid and Comet Deflection, Outer Solar System | 4 Comments

The Discovery Channel's news site offers a brief story about changing the course of an Earth-threatening asteroid. Specifically, the story focuses on a paper in the November 10 issue of Nature by Edward Lu and Stanley Love that offers a new method of avoiding an impact without even touching the asteroid. Previous options had included docking a spacecraft to the asteroid and applying steady thrust to change its course, but that method seems like a long-shot considering how tricky it is to get a conventional rocket to such an object with fuel to spare for an extended burn. What Lu and Love discuss is a 20-ton spacecraft that would actually use the weak gravitational force between asteroid and ship to effect a change in the asteroid's orbit. In essence, the spacecraft would use nuclear-electric thrusters to maintain a fixed position above the asteroid. If such a mission were flown years in advance of an asteroid impact, the force exerted should be enough to change the expected impact...

Surprise on Barnard’s Star

by Paul Gilster | Nov 14, 2005 | Exoplanetary Science | 0 Comments

M-class red dwarf stars are of increasing interest in terms of astrobiology. If we can devise weather models that allow for regions of relative stability, a planet locked tidally to its star at a fraction of the distance from Mercury to the Sun could produce conditions suitable for life. The National Geographic show 'Extraterrestrial,' shown again the other night, projects just such an environment, and imagines life forms that might evolve there. But red dwarfs are tricky because they're flare stars. In their early lives, they spin more quickly than they will when they enter their dotage; the rapid spin can produce magnetic fields that, in turn, create flares. Life on a planet circling a younger red dwarf would have to adapt to flares that can double the star's brightness within a matter of seconds. Some believe this makes Proxima Centauri an unlikely candidate for life-bearing planets. And what about Barnard's Star, so tantalizingly close (5.9 light years) to our own Sun? Study a...

Extraterrestrial Life Examined on TV

by Paul Gilster | Nov 12, 2005 | Astrobiology and SETI, Exoplanetary Science | 0 Comments

Two shows catch the eye tonight [Saturday] on the National Geographic Channel: Naked Science: "Alien Contact" at 9P et/pt Are we the only intelligent species alive in the universe? Join the quest to separate scientific fact from science fiction in the search for extraterrestrials. "Extraterrestrial" at 10P et/pt A dazzling galactic journey brings you face-to-face with fantastic alien life-forms that scientists believe could exist in our own galaxy. I haven't seen the former, but "Extraterrestrial" is quite good, with sound extrapolations about life forms that could develop in such interesting environments as a planet circling an M-class red dwarf, and interviews with scientists involved in the exoplanetary hunt. For more information (and alternate program times) look here. Thanks to Larry Klaes for the tip on the re-broadcast of these shows.

Tracking Cosmic Ray Origins

by Paul Gilster | Nov 11, 2005 | Deep Sky Astronomy & Telescopes | 2 Comments

What can you do with 1600 detectors spread out over 3000 kilometers surrounded by an array of 24 telescopes? If you're in Argentina's Mendoza Province, the answer is that you can witness the arrival of high-energy cosmic rays. The 'Cherenkov' detectors, each containing 3000 gallons of water, detect the passage of the particles while the telescopes examine the ultraviolet fluorescence produced by their arrival in the atmosphere. The detector array covers an area roughly the size of Rhode Island. All this is occurring at the Pierre Auger Observatory, just east of the Andes on the Argentine Pampas. Auger was the first scientist to observe the interactions between Earth's atmosphere and cosmic rays back in 1938. The observatory named for him draws on the talent of 60 institutions in 16 countries. The presentation of the first physics results from the site took place this week in the Argentine town of Malargüe. Image: The Andes Mountains form a snow-capped backdrop to the west of the...

Attending Scientific Meetings Online

by Paul Gilster | Nov 10, 2005 | Research Tools | 2 Comments

Centauri Dreams sometimes laments the status of our research tools. Bibliographic coverage of the major journals online is spotty; some offer full text but only for recent issues, others are confined to abstracts, and access even at university libraries depends upon the services to which the library has subscribed. Pre-1995 items are rare online. People sometimes call the Internet a 'digital library,' but building the tools to make it a true library will clearly take a generation. Nonetheless, exciting developments in spreading the news about research are happening in the digital arena, such as the heartening trend toward recording and disseminating scientific lectures in MP3 format. And even more promising is a new tool for creating audio and image slideshows to distribute conference presentations in PowerPoint and PDF format. QCShow, a freely downloadable player from AICS Research in Las Cruces, NM, synchronizes slides with audio to produce a low-bandwidth way to 'attend' key...

Centauri Dreams Update

by Paul Gilster | Nov 9, 2005 | Administrative | 0 Comments

Centauri Dreams was launched with the idea of providing the occasional commentary on space research with interstellar flight implications. What surprised this writer in the past fifteen months has been the fact that an 'occasional' schedule just doesn't work. The news coming in, from exoplanetary discoveries to new research directions in propulsion and robotics, has kept the publication schedule fast and furious. Centauri Dreams now publishes six days a week except for rare periods when I'm traveling (I don't carry a laptop). The recent hosting change went much more smoothly than I had anticipated, having read horror stories from other writers who had attempted such things. In fact, it was more or less glitch-free, and by now Google has combed out many of the duplicate entries still pointing to the old pages. Only two major issues remain to be addressed. Status of the archives. For a variety of reasons, I am transferring the articles from the old site's archives one at a time (this...

Target Stars for Terrestrial Planet Hunting

by Paul Gilster | Nov 8, 2005 | Astrobiology and SETI, Exoplanetary Science | 2 Comments

If you're looking for life similar to Earth's -- based, that is, on carbon chemistry and water -- you have to determine what kind of stars might have produced such planets. Certain factors weigh heavily in this analysis. The star must be a long-lived, solar-type star with constraints on its luminosity; it must offer an environment within which a planet with liquid water at its surface can exist. This Continuously Habitable Zone (CHZ) is defined this way in a new paper called "Astrobiologically Interesting Stars within 10 parsecs of the Sun," now available on the arXiv site: The inner edge of habitability is the region where water is lost through photolysis and hydrogen escape; the oceans simply evaporate; The outer edge of habitability is the region where C02 clouds form, cooling the planet by lowering its albedo. Also critical is planetary mass. A reasonable upper limit on mass seems to be a few Earth masses; planets larger than this are likely to be entirely covered with oceans,...

FTL Technologies and Inflation Theory

by Paul Gilster | Nov 7, 2005 | Breakthrough Propulsion | 3 Comments

What could inflation theory have to do with the Fermi paradox? Quite a lot, if at least one recent paper is to be believed. The question 'where are they' about extraterrestrial visitation becomes even more pointed when faster-than-light technologies move out of the realm of the impossible to something that may be seriously investigated by physicists. Inflation theory, which holds that the early universe underwent a vast expansion as spacetime itself stretched far beyond the velocity of light, opens the door to technologies that might use this effect to create spacefaring civilizations spanning entire galaxies. Just how fast did inflation occur? In a space of time lasting about 10-35 seconds, the universe could have expanded by a factor of 1030 to 10100. As Brian Greene puts it in The Fabric of the Cosmos: An expansion factor of 1030 -- a conservative estimate -- would be like scaling up a molecule of DNA to roughly the size of the Milky Way galaxy, and in a time interval that's much...

A Fusion Runway to Nearby Stars

by Paul Gilster | Nov 5, 2005 | Breakthrough Propulsion | 11 Comments

When physicist Geoffrey Landis reviewed interstellar concepts at the American Association for the Advancement of Science's 2002 meeting, his wide-ranging presentation considered where we stand on nuclear propulsion, solar and lightsail technologies, and particle-pushed sails. He also addressed the question of the Bussard ramjet, which would use an electromagnetic scoop to collect atoms from the interstellar medium to fuel a fusion reactor. Finding serious problems here (he cites, among other things, the fact that the scoop technology acts more like a brake than an accelerator), Landis went on to consider an alternative: "These problems can be alleviated if, instead of using the ambient interstellar medium, fuel is deliberately emplaced in the path of the spacecraft before flight. In this way, the fuel (probably in the form of small 'pellets') can be chosen to be the optimum composition... The 'runway' of fuel pellets could be emplaced, for example, by a dedicated craft which drops...

The Distance to Alpha Centauri

by Paul Gilster | Nov 4, 2005 | Deep Sky Astronomy & Telescopes | 3 Comments

We can measure interstellar distances, but can we really grasp them? The distance to the nearest stars is so immense that even the scientists who study such things have resorted to homely comparisons. The most charming to my mind is that of the English astronomer Sir John Herschel (1792-1871), the son of the famous William Herschel who discovered Uranus. A wizard at mathematics, Herschel became a leading expert on double stars and the measurement of stellar distances through parallax (the apparent change in position of a nearby star against background stars due to the Earth's changing orbit around the Sun). When it came to the distance to the Alpha Centauri stars, Herschel saw things in terms of ocean voyaging, thinking himself standing on shipboard dropping peas into the water. As he once wrote, ". . . to drop a pea at the end of every mile of a voyage on a limitless ocean to the nearest fixed star, would require a fleet of 10,000 ships of 600 tons burthen, each starting with a full...

The Light of Ancient Stars

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

The Spitzer Space Telescope once again dazzles us with its capabilities at infrared wavelengths. Now it's the detection of what may be some of the earliest objects in the universe, the hypothetical Population III stars that would have formed a mere 200 million years after the Big Bang itself. These short-lived objects were probably over a hundred times more massive than our Sun. If the scientists investigating the recent Spitzer data are right, they are looking at the redshifted ultraviolet light of these ancient stars, stretched to lower energy levels by the expansion of the universe and now detected as a diffuse glow of infrared light. Image: The top panel is an image from NASA's Spitzer Space Telescope of stars and galaxies in the constellation Draco, covering about 50 by 100 million light-years (6 to 12 arcminutes). This is an infrared image showing wavelengths of 3.6 microns, below what the human eye can detect. The bottom panel is the resulting image after all the stars,...

‘Alien’ Life on Earth?

by Paul Gilster | Nov 2, 2005 | Astrobiology and SETI | 0 Comments

"We may never find other life away from Earth, but we have already made aliens on this planet and we will continue to do so at an increasing pace," says Peter Ward, author of Life As We Do Not Know It: The NASA Search for (and Synthesis of) Alien Life (Viking, 2005). "In the last five years we've come to realize that we can make microbial life in a lot more ways than Mother Earth did." Aliens on this planet? Ward is talking about laboratory work here on Earth that has modified life as we commonly understand it. That includes creating microbes with at least one amino acid beyond the 20 found in the DNA of native Earth life. Genetic modification also constitutes, in Ward's view, the creation of an alien lifeform, as does modifying a lifeform to reduce its complexity. Ward, a paleontologist who studies these matters within the University of Washington's astrobiology program, is perhaps best known to Centauri Dreams readers as the co-author (with Donald Brownlee) of Rare Earth: Why...

New Moons for Pluto

by Paul Gilster | Nov 1, 2005 | Outer Solar System | 0 Comments

The Hubble Space Telescope, in operations designed to support the upcoming New Horizons mission to Pluto, has discovered two new Plutonian moons. It's too early to speak with confidence about their size because we don't yet know to what extent light reflects from their surfaces, but the early estimates are for diameters of 32 kilometers (20 miles) and 70 kilometers (45 miles). Charon, at 1200 kilometers, dwarfs these tiny objects, provisionally designated S/2005 P1 and S/2005 P2. Their faintness makes it clear why they weren't spotted before: the new moons are roughly 5000 times fainter than Pluto itself. For more, see this Southwest Research Institute news release. "Our result also suggests that other bodies in the Kuiper Belt may have more than one satellite. We planetary scientists will have to take these new moons into account when modeling the formation of the Pluto system," says co-leader Dr. Alan Stern, executive director of the SwRI Space Science and Engineering Division. And...

On Deflecting Near Earth Objects

by Paul Gilster | Oct 31, 2005 | Asteroid and Comet Deflection, Missions, Outer Solar System | 0 Comments

The B612 Foundation continues to examine the danger of near-Earth objects (NEOs). As noted earlier in these pages, B612 points to the continuing evidence for asteroid and comet impacts and their role in shaping the planet's history; the much discussed demise of the dinosaurs, due to a likely asteroid strike in the Yucatan, is but one of the instances where the planetary ecology has been altered. We know that the Earth orbits in a swarm of near-Earth asteroids, with a probability of collision in this century that the Foundation pegs at an unacceptably high 2 percent. Given these concerns, and the possible dangers posed by the object called NEO 99942 Apophis, the Foundation has engaged in a dialogue with NASA about possible missions to this asteroid. Apophis (also known as 2004 MN4) is on course for a near-miss in 2029 , with the 400-meter asteroid approaching to within 32,000 kilometers. What happens afterwards as the near-miss itself disrupts the orbit of this object remains a...

Robert Goddard on Interstellar Migration

by Paul Gilster | Oct 29, 2005 | Culture and Society | 0 Comments

"A manuscript I wrote on January 14, 1918 ... and deposited in a friend's safe ... speculated as to the last migration of the human race, as consisting of a number of expeditions sent out into the regions of thickly distributed stars, taking in a condensed form all the knowledge of the race, using either atomic energy or hydrogen, oxygen and solar energy... [It] was contained in an inner envelope which suggested that the writing inside should be read only by an optimist." -- Robert Goddard, "Material for an Autobiography," (1927), available in Pendray, G. E. and Goddard, E. C. (Eds.), The Papers of Robert H. Goddard (New York: McGraw Hill, 1970).

Photon Pressure Affects Japanese Spacecraft

by Paul Gilster | Oct 28, 2005 | Advanced Rocketry, Autonomy and Robotics, Sail Concepts | 0 Comments

The Japanese spacecraft Hayabusa, now in a 'parking orbit' above the asteroid Itokawa, is providing good evidence of just how useful the pressure of solar photons can be. Japan's Institute of Space and Aeronautical Science (ISAS) reports that the force being experienced by the spacecraft is 1/100th of the thrust produced by its ion engines, but fully ten times larger than the gravity of Itokawa itself. The effect is consequential enough that it must be factored into Hayabusa's descent close to Itokawa's surface; the spacecraft will deploy a small surface 'hopper' called MINERVA to take measurements on the asteroid. Hayabusa (once known as MUSES-C and renamed for a Japanese rocket pioneer) thus becomes both a testbed for current technologies and a reminder of a future one. Its electric propulsion or ion drive engines have met the challenge of asteroid rendezvous, although their performance was degraded by solar panel damage from solar flares in 2003. The spacecraft also carries an...

A Gravitational Lens at Work

by Paul Gilster | Oct 27, 2005 | Deep Sky Astronomy & Telescopes, Missions | 0 Comments

Gravitational lenses of the sort discussed in yesterday's post are now widely discussed. The idea that gravity can bend light may seem counterintuitive but we've seen numerous demonstrations of the effect, starting with the famous eclipse studied by Arthur Eddington in 1919. Hoping to test Einstein's general theory of relativity, Eddington traveled to the island of Principe, off the coast of West Africa. There, despite initially cloudy skies, he was able to take the crucial photograph that verified Einstein. Stars in the Hyades Cluster that should have been blocked by the Sun were revealed in the image, offset by an amount close to that predicted by Einstein. Some have questioned whether Eddington's equipment was sufficiently precise to make accurate readings, but whatever the case, the bending of light as a result of gravity has stood up. Among the various images that show this effect in deep space, none is as dramatic as the one below. Here we're looking at multiple bluish images...

A Mission to the Gravity Focus

by Paul Gilster | Oct 26, 2005 | Astrobiology and SETI, Missions | 1 Comment

Voyager 1 is, in a sense, our first interstellar spacecraft, with evidence mounting that it has reached the heliopause, that area marking the boundary between the Sun's outward-flowing particles and the true interstellar medium. The New Horizons mission, scheduled for launch in January, will go on to explore at least part of the Kuiper Belt. But what will our first true interstellar mission be; i.e., when will we launch a spacecraft designed from top down to studying nearby interstellar space? The answer may well be a mission to the Sun's gravity focus. Located at 550 AU (3.17 light days), some 14 times farther from the Sun than Pluto, the focus is that point to which the Sun's gravity bends the light from objects on the other side of it. The effect is to magnify distant images in ways that could be observed using the proper equipment. The effect of gravitational focus, first studied by Einstein in 1936, had already borne observational fruit by 1978 in the discovery of a 'twin...

Deep Space Transmission Strategies

by Paul Gilster | Oct 25, 2005 | Communications and Navigation | 8 Comments

One reason we need to re-think our communications strategies is that our resources are so limited. The Interplanetary Internet Project, for example, points out as a major justification for its work that if we can network spacecraft in distant planetary environments, we can sharply cut back on the amount of antenna time needed. After all, having a trio of spacecraft (including an orbiter, perhaps, and two rovers) linking their data to a single relay would mean a unified data download to Earth. The IPN idea would create new networking protocols that could make these things happen. But research continues on other fronts, including the technology we use to transmit signals. An upcoming paper discusses phased arrays, wherein a large number of mini-transmitters could send a combined beam into the sky. Systems like these are familiar to those working with military radar but have been hitherto unavailable for cost reasons for civilian uses. The paper, by Louis Scheffer at Cadence Design...

The Best Way to View Terrestrial Worlds

by Paul Gilster | Oct 24, 2005 | Exoplanetary Science | 0 Comments

Centauri Dreams has been a champion of Webster Cash's New Worlds Imager for several years now. The proposal, whose initial study was funded by NASA's Institute for Advanced Concepts, offered a way to find terrestrial planets around other stars and, in its most fully developed configuration, to create startlingly sharp images of such worlds down to the level of continents and weather patterns moving across their surfaces. Now two new developments -- related in a phone call from Cash last week -- bring New Worlds Imager to the fore as NASA weighs strategies for its Terrestrial Planet Finder mission. First, Cash has changed the basic design of New Worlds Imager to move away from the enormous 'pinhole camera' concept discussed earlier in these pages to an occulter -- a design that blocks the starlight from the central star to allow its planetary companions to be visible. The problem with occulters has always been that no matter how scientists worked with their design, they could not get...

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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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