Paul Gilster | Centauri Dreams

Sailing Messenger to a Mercury Encounter

by Paul Gilster | Sep 9, 2008 | Sail Concepts | 9 Comments

Who would have thought the planet Mercury would prove so useful in explaining how solar sails work? The Messenger spacecraft's recent course adjustment maneuvers have proven unnecessary because controllers have been able to use its solar panels creatively, harnessing solar radiation pressure (SRP). And what better place to shake out such methods but on your way to a Sun-drenched planet that moves in an environment where SRP can be eleven times higher than that near Earth? It may come as a surprise that we are already using solar sailing techniques on operational missions, but Messenger is not the first. In fact, we can go back to another Mercury mission, Mariner 10, which took advantage of the effect of solar photons on its twin solar panels, each about nine feet in length and three feet in width, a highly usable 55 square feet that not only generated power but got the spacecraft out of serious trouble. Launched in 1973, Mariner 10 ran into problems with its stabilizing gyroscopes...

Cepheid Variables: A Galactic Internet?

by Paul Gilster | Sep 8, 2008 | Astrobiology and SETI | 21 Comments

Making contact with an extraterrestrial civilization, whether by microwave, laser or neutrino, highlights the problem of time. Suppose you are looking for a newly emerging technological culture around another star. When do you transmit? After all, even the most powerful signal sent to Earth a million years ago would have no listeners, which is why some have suggested putting actual artifacts in promising solar systems. Rather than transmitting over time-scales measured in eons, you leave an object that can be decoded and activated for communications. All kinds of interesting science and science fictional scenarios flow from that idea. But what if you want to contact not just a few highly targeted systems, but instead send a signal intended for everyone in the galaxy with the means to receive it? As John Learned (University of Hawaii) and team speculate in a new paper, one way to do that would be to select highly visible and important stars to carry your message. Cepheid variables are...

First Images from Steins Flyby

by Paul Gilster | Sep 7, 2008 | Outer Solar System | 5 Comments

Fine work by Rosetta on the Steins flyby. Check here for more imagery of the 'diamond in the sky,' with cratering suggesting extreme age. Image: Asteroid Steins seen from a distance of 800 km, taken by the OSIRIS imaging system from two different perspectives. The effective diameter of the asteroid is 5 km, approximately as predicted. At the top of the asteroid (as shown in this image), a large crater, approximately 1.5-km in size, can be seen. Scientists were amazed that the asteroid survived the impact that was responsible for the crater. Credits: ESA ©2008 MPS for OSIRIS Team MPS/UPM/LAM/IAA/RSSD/INTA/UPM/DASP/IDA.

Open Courseware: Self-Study and Space

by Paul Gilster | Sep 6, 2008 | Research Tools | 8 Comments

I'm a great believer in the open courseware concept that MIT has done so much to promote. The idea is to do away with the password-protected gatekeeper function that so many university and college Web sites impose, opening access to those course materials an instructor chooses to put online. Some 1800 courses in 33 different disciplines have made their way to the Web via MIT's gateway, their offerings ranging from audio of lectures, lecture notes and exams to PDFs and video files. It's a pleasure to see that Bruce Irving is tracking MIT's venture on his Music of the Spheres site, a post I've chosen to highlight from this week's Carnival of Space collection. Bruce notes one recent addition to the MIT catalog, a course called Space Systems Engineering that looks at design challenges in both ground and space-based telescopes, ultimately attempting to choose the top-rated architectures for a lunar telescope facility. But the MIT offerings are wide ranging. I'm seeing courses on aerospace...

Solar Sails: The Interstellar Prospect

by Paul Gilster | Sep 4, 2008 | Sail Concepts | 23 Comments

The vast laser-driven sails envisioned by Robert Forward have always fired my imagination. Hundreds of kilometers in diameter, they would rely upon a gigantic Fresnel lens in the outer Solar System to keep the critical laser beam tightly collimated over interstellar distances. Forward conceived of mission designs to stars as far away as Epsilon Eridani, journeys that could be achieved within a human lifetime. He even provided return capability through the use of a multi-part sail. You can read a fictional treatment of this in his novel Rocheworld. But how do we get from here to there? As of today, we're close enough to having an operational space sail that if we can talk SpaceX into lofting the NanoSail-D duplicate, we could be shaking out our first space sail within months. Assuming we do go operational before too many months (or years!) pass, the question then becomes, what kind of missions are possible between the laser-beamed lightsail of science fictional imagining and the...

Cosmic Dust from the Main Belt

by Paul Gilster | Sep 3, 2008 | Outer Solar System | 2 Comments

With the Steins encounter looming, let's keep the focus on the asteroid belt, in this case by examining a connection between that distant region and our own planet. Cosmic dust particles -- tiny bits of pulverized rock up to a tenth of a millimeter in size -- move continuously through the Solar System, a kind of micro-thin fog of micrometeorites that contributes hundreds of billions of particles to Earth's atmosphere. New research into the makeup of some 600 of these particles now reveals their chemical and mineral content, allowing an overview that points to their origin. The suspected source: A group of asteroids between Mars and Jupiter. You can see one of the Koronis asteroids in the image at left, which shows 243 Ida as photographed by the Galileo probe. What we now believe about the Koronis asteroids is that they were formed some two billion years ago by the breakup of a much larger asteroid. Within the Koronis family are the ninety or so Karin asteroids, which seem to be in a...

Rosetta Closes on Asteroid

by Paul Gilster | Sep 2, 2008 | Outer Solar System | 0 Comments

Get out to about 2.4 AU from the Sun (2.41 AU, to be precise) and your radio signals have a long travel time. It takes 20 minutes to cross the 360 million kilometers between Earth and the Rosetta spacecraft, and that, of course, is one-way. As we've learned from all our deep space missions, spacecraft are largely on their own for the brief and critical window of an encounter, like the one with asteroid Steins that is coming up for Rosetta. Opportunities for possible trajectory correction maneuvers exist both on September 4 and 5th, but it's on the 4th that Rosetta's controllers will have their last chance to acquire optical images for navigation. Uplink commands for asteroid fly-by mode will be sent on the morning of the 5th and then we wait for results as the vehicle flips for observation and tracking. Rosetta will close to within 800 kilometers of the asteroid, passing it at a speed (relative to Steins) of 8.6 kilometers per second. Image: The approach of Rosetta's spacecraft to...

Dark Matter’s ‘Building Blocks’

by Paul Gilster | Sep 1, 2008 | Deep Sky Astronomy & Telescopes | 5 Comments

Although we often talk about the Magellanic Clouds as satellites of the Milky Way, recent research seems to point to a different conclusion. The dwarf galaxies may be moving too fast to be bound to our own, cities of stars simply flowing past us in the night. Be that as it may, the Milky Way still has over twenty other dwarf galaxies in orbit around it, eighteen of which have been the subject of recent work aimed at calculating their masses. The odd results have striking implications for dark matter. For the dwarf galaxies around us vary greatly in brightness, from a thousand times the luminosity of the Sun to a billion times that amount. You would assume that the brightest dwarf galaxy would have the greatest mass, while the faintest would show the least. The surprise is that all the dwarf galaxies have roughly the same mass, some ten million times the mass of the Sun within their central 300 parsecs. Here's Manoj Kaplinghat (University of California at Irvine) with a helpful...

Preserving Future History

by Paul Gilster | Aug 29, 2008 | Culture and Society | 26 Comments

With our eyes on a proposed interstellar future, we don't want to neglect the real challenges of preserving the steps taken along the way. I'm thinking about this because of a post on an astronomy list (thanks to Larry Klaes for the pointer) by Richard Sanderson, who is curator of physical science at the Springfield Science Museum (MA). Sanderson is worried about the media upon which we store our information, and for good reason. Here's the issue in a nutshell: The difficulties that future historians may encounter are related to the ephemeral nature of digital information and the media used to store it. I can visit an old monastery in Europe, find a giant leather-bound astronomy book from the 17th century, blow off the dust, open it, and read the pages (provided I can read Latin). The only tools required are my eyes and hands. But imagine someone living in the 23rd or 24th century who finds an old box of computer diskettes or CDs. Even if the diskettes haven't been corrupted and the...

Dark Matter and Its Interactions

by Paul Gilster | Aug 28, 2008 | Deep Sky Astronomy & Telescopes | 2 Comments

Keeping our eyes open over a whole range of wavelengths makes priceless science possible. Thus the new data on dark matter, culled from observations of the galactic cluster known as MACSJ0025.4-1222. The Hubble Space Telescope offered up images in the visual light range, sufficient to provide astronomers (thanks to the effects of gravitational lensing) with a map of dark matter associated with the cluster. The Chandra X-Ray Observatory provided a balancing map of ordinary matter by showing us the distribution of hot gas in the cluster, the latter readily visible in the X-ray wavelengths Chandra works at. The result is the beautiful, if color-coded, image at the left. Here the dark matter is shown in blue, the ordinary matter in pink. The assumption is this: The two galactic clusters that formed MACSJ0025.4-1222 (each a quadrillion times the mass of the Sun) merged at titanic speeds, causing the hot gas (ordinary matter) within each to collide and slow. The dark matter, however, seems...

Fermi’s Whole-Sky Portrait

by Paul Gilster | Aug 27, 2008 | Deep Sky Astronomy & Telescopes | 8 Comments

I like the logo for the Fermi Gamma-Ray Space Telescope, shown at the right. It's appropriately stylish and, with that 'beamed' F emerging out of a galactic core, reminds us that the instrument will be opening a data window on the supermassive black holes found in such places. Fermi was until yesterday known as GLAST (Gamma-Ray Large Area Space Telescope), so the change of name moves us out of acronym territory and personalizes the instrument in favor of one of the true pioneers of high-energy physics, as well as the author of the ever intriguing Fermi paradox. We've talked about the latter in the context of the search for extraterrestrial life, wondering how Fermi's famous 'where are they?' question might be answered. But the Fermi telescope, in space for just two and a half months, is giving signs of being quite a newsmaker itself, if perhaps less controversial. The image below presents a map put together from 95 hours of observation, an all-sky view showing the glow of gas and...

Advanced Propulsion: The Next Steps

by Paul Gilster | Aug 26, 2008 | Exotic Physics | 31 Comments

by Kimberly Trent Here we depart briefly from the norm by looking at the work of Kimberly Trent, a graduate student in the Applied Physics Program at the University of Michigan. Working as an intern with Marc Millis at NASA's Glenn Research Center, Trent examined the broad issues of advanced propulsion and focused on a research topic that takes off on a Robert Forward idea from the 1960s. The goal: To develop a propulsion concept involving non-Newtonian frame-dragging effects, which Trent studies in relation to the work of Martin Tajmar. The details follow, in an article designed to show one student's involvement in the kind of studies Tau Zero hopes to encourage at other institutions. This past summer, I interned at the NASA Glenn Research Center in Cleveland, OH through the NASA Academy program. My individual research project was in theoretical spacecraft propulsion. This area involves research into devices and concepts such as space drives, warp drives, gravity control, and...

Twisting the Copernican Tail

by Paul Gilster | Aug 25, 2008 | Culture and Society | 11 Comments

The latest Carnival of Space offers several posts with an interstellar bent in addition to our own discussion, linked to from the Carnival, about antimatter rocketry and the recent thinking of JPL's Robert Frisbee. I notice that Gerald Cleaver and Richard Obousy's ideas about warp drive continue to get play, with particular reference to the amount of energy that this purely theoretical construct might demand. As with Alcubierre's own warp drive speculations, the energy levels are daunting, in Cleaver and Obousy's case the equivalent of converting the planet Jupiter into energy (that actually beats many Alcubierre demands!). Thus NextBigFuture's comment, rising naturally from this conundrum: ...it makes no sense to assume being able to convert a planetary mass into energy without having increased control of technology and information and increased economy. It is like assuming a group of cavemen get the designs for a supersonic plane but only have the economy of their tribe of six to...

Rosetta and the Language of Hope

by Paul Gilster | Aug 22, 2008 | Culture and Society | 15 Comments

There are several reasons to keep an eye on Rosetta, the European Space Agency's mission to comet 67P/Churyumov-Gerasimenko. In 2014, the spacecraft will go into orbit around the comet before deploying a lander to the nucleus. Watching changes as the comet heads toward the Sun should prove interesting indeed, but these short term effects take place within a provocative longer-term context. For aboard Rosetta is a 2.8-inch diameter disc inside a small glass sphere containing some 6000 pages of information. The subject: The languages of planet Earth, many of which will disappear before century's end. The synergy here is fascinating. The Rosetta Stone, one of the most impressive objects in the British Museum when you realize what you're looking at, contains inscriptions that include Egyptian hieroglyphics, Demotic and classical Greek. The Greek, readily understood by linguists, helped researchers unravel the meaning of the hieroglyphics, a pioneering task performed 200 years ago at the...

Star Formation Near Black Holes

by Paul Gilster | Aug 21, 2008 | Deep Sky Astronomy & Telescopes | 3 Comments

Simulations showing how giant gas clouds evolve -- clouds as large as 100,000 times the mass of the Sun -- have demonstrated that stars can form in the neighborhood of supermassive black holes, the kind of black holes found at the center of galaxies. As you would expect, the clouds are disrupted when they move close to the black hole, but only part of the cloud is captured, with the rest contributing to the formation of massive stars that move about the black hole in eccentric orbits. Usefully, the results match what we see near the center of the Milky Way. These are short-lived stars, says Ian Bonnell (St Andrews University), which in itself may be telling us something: "That the stars currently present around the Galaxy's supermassive black hole have relatively short lifetimes of ~10 million years, suggests that this process is likely to be repetitive. Such a steady supply of stars into the vicinity of the black hole, and a diet of gas directly accreted by the black hole, may...

The Interstellar Conundrum Reconsidered

by Paul Gilster | Aug 20, 2008 | Antimatter | 32 Comments

Just how hard would it be to build a true interstellar craft? I'm not talking about a spacecraft that might, in tens of thousands of years, drift past a star by happenstance, but about a true, dedicated interstellar mission. Those of you who've been following my bet with Tibor Pacher on Long Bets (now active, with terms available for scrutiny on the site) know that I think such a mission will happen, but not any time soon. And the proceedings of the Joint Propulsion Conference, held last month in Hartford, go a long way toward explaining why the problem is so difficult. Wired looked at the conference results in a just published article, the most interesting part of which contained Robert Frisbee's speculations about antimatter rocketry. Two things have been clear about antimatter for a long time. The first is that producing sufficient antimatter is a problem in and of itself, one that may keep us working with tiny amounts of the stuff for some time to come. Even so, interesting...

NanoSail-D: Duplicate Exists, Needs to Fly

by Paul Gilster | Aug 19, 2008 | Sail Concepts | 0 Comments

Remember the great scene in Contact, when the fabulously rich S. R. Hadden (John Hurt), who funded the stargate device that has been destroyed by sabotage, says "Why build one when you can build two for twice the price?" He then reveals the existence of a second facility off the coast of Japan, which is what Ellie Arroway uses on her interstellar trip. So is solar sail expert Greg Matloff a ringer for S. R. Hadden? Read on. Greg's recent phone call may not have been as dramatic as that scene in Contact, but he was able to tell me that although NanoSail-D did perish in the SpaceX Falcon explosion, there is a second sail. Marshall Space Flight Center built two. So now we're in the energizing position of having a second chance at a sail deployment in space, and it could be done soon via the next Falcon launch, if SpaceX will cooperate in the enterprise. And here's why they should: Launching a payload on the Space Shuttle costs approximately $10,000 per pound. That's pricey, and the...

An Icy Wanderer from the Oort Cloud

by Paul Gilster | Aug 18, 2008 | Outer Solar System | 8 Comments

A symposium called Sloan Digital Sky Survey:Asteroids to Cosmology, held in Chicago this past weekend, is producing interesting news, not the least of which is the discovery of a 'minor planet' that is currently inside the orbit of Neptune. 2006 SQ372 is only in the neighborhood briefly, already setting out on a journey that will take it 150 billion miles from the Sun. Its orbit is an ellipse four times longer than it is wide, not dissimilar from the dwarf world called Sedna, which was discovered in 2003. But SQ372 strays even further out and takes twice as long to complete its orbit. You'll need to click to enlarge the image below to see the details. Image (click to enlarge): The orbit of the newly discovered solar system object SQ372 (blue), in comparison to the orbits of Neptune, Pluto, and Sedna (white, green, red). The location of the Sun is marked by the yellow dot at the center. The inset panel shows an expanded view, including the orbits of Uranus, Saturn, and Jupiter inside...

On Science and Public Scrutiny

by Paul Gilster | Aug 16, 2008 | Culture and Society | 5 Comments

Hanny's Voorwerp, that odd object discovered by Dutch school teacher Hanny van Arkel via the Galaxy Zoo project, has provoked press reaction all over the world. And Chris Lintott, a key player in the Galaxy Zoo's ongoing survey of galaxies, notes the uneasiness he feels in discussing theories about the object before the paper that attempts to explain it has even gone through peer review. The speed with which the Internet allows science to be discussed can be disconcerting, as Lintott makes clear in the latest edition of the Space Carnival, conducted this week by David Chandler at his Next Generation site. Now the Galaxy Zoo is doing good science in an obviously public fashion. Anyone can sign up to participate in the classification of the images of one million galaxies drawn from the Sloan Digital Sky Survey, and that makes participating computer users scientific collaborators. Seeing this, the Galaxy Zoo blogs about its work out of a sense of obligation to its contributors, but...

‘Arabian Nights’ on Enceladus

by Paul Gilster | Aug 15, 2008 | Outer Solar System | 2 Comments

As someone who has always been interested in how we name things, the choices on Enceladus have been particularly pleasing. On the remote Saturnian moon, place names are chosen from the The Arabian Nights, which is how we wind up with Damascus Sulcus, as seen in the photo below. A sulcus is a large fracture, a 'tiger stripe,' as they're called on Enceladus. The four most prominent are named Alexandria, Cairo, Baghdad and Damascus, adding yet a further tinge of exotica to a tiny world that has already shown itself to be highly unusual. Cassini's August 11 flyby is, as the photo shows, paying off big. The intent was to focus in on sources for the jets that spew water vapor, ice and trace organics into space -- the yellow circles in the image show two particular sources of jets. What we're after, of course, is a closer look at geological activity in the sulci, in hopes of determining whether liquid water exists beneath the surface. The new details show that the fractures are some 300...

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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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