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Remembering Robert Bussard

by Paul Gilster | Oct 9, 2007 | Culture and Society | 19 Comments

A note from James Benford, soon to be followed by e-mail from other interstellar advocates, tells me of the death of Robert Bussard. The creator of the Bussard ramjet concept, Bussard (1928-2007) died of cancer in Santa Fe just a few days ago. Benford, who knew Bussard for forty years, recalls his open attitudes and deep technical insight, adding "He was still sharp as a pin into old age." We should all be so lucky. Recently we've seen a lot of discussion about Bussard's fusion ideas, but it's the ramjet that I return to as I think about him. If you collect classic papers, as I do, here's one for you: Bussard's "Galactic Matter and Interstellar Spaceflight" in Acta Astronautica 6 (1960), pp. 179-94. Imagine a scoop created by a magnetic field that sucks in interstellar hydrogen ionized by a forward-firing laser. The result is fed into a fusion reactor. Get the vehicle up to about six percent of light speed and you could light that engine, with presumably amazing results. At least,...

Orion Measurements Change Stellar Ages

by Paul Gilster | Oct 9, 2007 | Deep Sky Astronomy & Telescopes | 6 Comments

Following up on our recent discussion of interstellar distances and how they are determined comes word of a reassessment of the distance to the Orion Nebula. The star forming region is famous not only for its beauty but for the opportunity it gives us to assess young stars as they emerge from the interstellar gases around them. Their distance tells us something about their intrinsic brightness and thus their ages. The change in distance revealed in the new studies is considerable. Whereas the previous best estimate to the Nebula was 1565 light years, the new one, drawn with an uncertainty of six percent, is 1270 light years, a twenty percent adjustment. The Very Long Baseline Array was behind this work, using familiar parallax methods to observe a star called GMR A from opposite sides of Earth's orbit. "This measurement is four times more precise than previous distance estimates," says Geoff Bower (UC-Berkeley). "Because our measurement reduces the distance to this region, it tells...

Practical Positron Rocket Overflow Thread #2

by Paul Gilster | Oct 8, 2007 | Advanced Rocketry | 265 Comments

Please use this post for further comments in the above thread, which originally appeared under the title "A Practical Positron Rocket?"

Amateur Network Bags a Transit

by Paul Gilster | Oct 8, 2007 | Exoplanetary Science | 7 Comments

The news from Transitsearch couldn't be better. Long a champion of amateur involvement in the exoplanet hunt, I was delighted to see, via Greg Laughlin's systemic site, that this globally dispersed team of amateur astronomers is behind the confirmed transit observation of the planet HD 17156 b. Amateurs in Italy, the Canary Islands and California made key observations in early September, with confirmatory data coming in from Massachusetts and California on the night of September 30/October 1 as observers heeded Laughlin's online call to participate. Greg has the details and more about the individual observers at his site. The Transitsearch mode is to look at known planet-bearing stars during those times transits might conceivably occur. And it makes stunningly good sense because of two facts: 1) The tools available to dedicated amateurs today are fully capable of this kind of high-quality work; and 2) Telescope time at the major observatories around the world is obviously limited....

Laurentide Strike Discussed on Radio, TV

by Paul Gilster | Oct 8, 2007 | Asteroid and Comet Deflection | 6 Comments

A possible impact in the Laurentide ice sheet in northeastern North America some 13,000 years ago is the subject of a new National Geographic special. Called "Mammoth Mystery," the show ran yesterday and will replay multiple times this week. A clip from the show is available online. This is the impact (discussed in these pages in late May) that is implicated, some believe, in the extinction of the mammoth and mastodon, with presumably devastating effects on local human populations. A press conference on this event is now available on YouTube, while National Public Radio's Science Friday show offers its coverage here. The paper is Firestone et al., "Evidence for an extraterrestrial impact 12,900 years ago that contributed to the megafaunal extinctions and the Younger Dryas," Proceedings of the National Academy of Sciences 10.1073/pnas.0706977104 (27 September, 2007). Abstract online.

Arecibo’s Closure and a New/Old Comet

by Paul Gilster | Oct 6, 2007 | Asteroid and Comet Deflection | 6 Comments

The return of 6344 P-L won't light up network switchboards over the weekend, but it's something to ponder, particularly in light of recent Arecibo happenings. 6344 P-L was first found in 1960 on photographic plates made with the 48-inch Schmidt instrument at Palomar Observatory. The discovery team, working at Leiden Observatory in the Netherlands, had found several thousand asteroids, but this one, recognized as a potential danger to Earth, had not been re-identified until now. Under its new name of 2007 RR9, the object remains curious. It is one of almost 900 asteroids bigger than 150 meters in diameter that close within 0.05 AU of Earth's orbit, and observations now indicate it may not be an asteroid at all. SETI Institute astronomer Peter Jenniskens, whose re-discovery of the object was recently confirmed, thinks we're dealing with something else, a dormant comet. Says Jenniskens: "This is a now-dormant comet nucleus, a fragment of a bigger object that, after breaking up in the...

Notes & Queries 10/6/07

by Paul Gilster | Oct 5, 2007 | Culture and Society | 16 Comments

What better way to represent the gorgeous clouds of the Orion Nebula than with hibiscus flowers? Or how about our Sun as a small jewel on the speckled leaf of a gold-dust croton plant? If this sounds surreal, it is, but it's also a description of part of the Galaxy Garden, a 100-foot in diameter map of the galaxy on the grounds of the Paleaku Peace Gardens Sanctuary on Hawaii's Big Island. Astronomy artist Jon Lomberg used galactic maps from Leo Blitz (UC Berkeley) to design the project, a leafy, immersive experience accurate enough to satisfy the most demanding. A collaborator of Carl Sagan, illustrator of most of his books and articles, and designer of the cover for the Voyager Interstellar Record, Jon's accuracy shows through in every botanical detail. Image: Dracaena trees represent globular star clusters, spherical groups of "only" hundreds of thousands of stars, making them too small to be called galaxies. Most of the clusters have orbits that carry them far above and far below...

Terrestrial Planet Forming?

by Paul Gilster | Oct 4, 2007 | Exoplanetary Science | 16 Comments

Are we seeing an Earth -- or at least a Mars-sized world -- in the making? Look no further than HD 113766, a binary system perhaps ten million years old some 424 light years away, for the story. One of its stars contains a warm dust belt that may be undergoing planetary formation. If that's the case, the emerging planet will orbit in the classical habitable zone, defined as that region where liquid water can exist on the surface. What counts here is the composition of the dusty materials making up its interesting disk. The Spitzer Space Telescope performs its usual yeoman service at this task, its infrared spectrometer flagging the material as a step up from the pristine building blocks of comets. The latter contain interesting organic materials like polycyclic aromatic hydrocarbons (PAHs), along with their water ice and carbonates. But HD 113766's disk contains no water ice, carbonates or fragile organic materials. Image: This artist's conception shows a binary-, or two-star,...

Carnival of Space #22 Online

by Paul Gilster | Oct 4, 2007 | Culture and Society | 0 Comments

A Carnival of Space essential, from the 22nd iteration of the weekly roundup, is Universe Today's look at color in astrophotography. Is space really the gorgeous place suggested by many images from both terrestrial and space-based telescopes? Sometimes yes, sometimes no. A revealing quote on Hubble imagery from Zolt Levay (Space Telescope Science Institute): "For one thing [color] is somewhat meaningless in the case of most of the images, since we generally couldn't see these objects anyway because they are so faint, and our eyes react differently to colors of very faint light." How images passed through various filters are produced is a fascinating topic that brings a needed reality adjustment after viewing some spectacular scenes. The Carnival always offers good material, but Universe Today's piece makes for prime late week reading.

ChipSat: To the Stars via Magnetic Fields

by Paul Gilster | Oct 3, 2007 | Outer Solar System | 9 Comments

by Larry Klaes Tau Zero's Larry Klaes returns with more details on a novel form of propulsion that just might, in the long term, have interstellar implications. One of the most vital - and difficult - parts of a spacecraft is the type of propulsion it requires to move about in space. Most current forms of space propulsion, such as chemical fueled rockets, are both expensively heavy and explosively dangerous. Dr. Mason Peck and his team at Cornell University may have found a solution to this problem by utilizing the natural magnetic fields generated by our planet Earth and other worlds in space. "If our research is successful, we will have devised a new way of propelling spacecraft," declares Peck, who is an assistant professor of mechanical and aerospace engineering at Cornell, and the director of the Space Systems Design Studio. "We think of it as doing more with less. Instead of using rocket fuel, which is expensive, heavy, and often toxic, this technique allows spacecraft to...

Chance Pass Through a Cometary Tail

by Paul Gilster | Oct 2, 2007 | Outer Solar System | 3 Comments

Chance favors the prepared mind. So goes the old saying, never vindicated as clearly as in the encounter between Comet McNaught and the spacecraft called Ulysses. Thomas Zurbuchen (University of Michigan) notes that having a spacecraft on a mission to study the polar regions of the Sun pass through a cometary tail is chancy enough -- he likens it to putting your hand in Lake Michigan and pulling out a fish -- but having Ulysses already equipped with the needed instruments to study the solar wind means we had an unexpected chance to study the interactions between cold cometary materials from the Solar System's infancy and hot solar plasmas. Talk about being in the right place at the right time... Complex chemistry emerged from the serendipitous encounter, with O3+ oxygen ions showing the effects of cometary materials on the outgoing stream of solar wind ions. O3+ ions are oxygen atoms with a positive charge, resulting from the presence of five electrons instead of eight. Solar wind...

Hipparcos: Filling In the Galactic Map

by Paul Gilster | Oct 1, 2007 | Deep Sky Astronomy & Telescopes | 2 Comments

From the Cape of Good Hope, Alpha Centauri is a beacon in the sky, the third brightest star after Sirius and Canopus. The combined light of Centauri A and B (and Proxima as well, though at 11th magnitude, its contribution is minimal) caught the eye of Scottish lawyer Thomas Henderson, who in the course of a varied career found himself director of the Royal Observatory in South Africa. Cursed with poor eyesight, Henderson fixed on a mathematical approach to astronomy and chose to subject the Centauri stars to distance measurements, observing the system from both sides of Earth's orbit to look for apparent motion. And find it he did, a movement of three quarters of a second of arc that, using some basic math, gave him a distance of 41 trillion kilometers. This stellar parallax method has since been used on countless stars, but it's really suitable only within 200 light years or so. Which is why older astronomy texts show such variation in stellar distances. One estimate of the distance...

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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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