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Hard Evidence for Exoplanetary Image

by Paul Gilster | Apr 30, 2005 | Exoplanetary Science | 0 Comments

The race to confirm the first image of an exoplanet takes yet another turn with the announcement that a young brown dwarf some 200 light years from Earth really is orbited by a planet that is five times the mass of Jupiter. We looked at this brown dwarf, called 2M1207A, in an entry last September. When the object visually near it was first discovered about a year ago, there remained the possibility that the apparent planet was a background star. But new observations seem to rule this out. "Our new images show convincingly that this really is a planet, the first planet that has ever been imaged outside of our solar system," says Gael Chauvin, astronomer at ESO and leader of the team of astronomers who conducted the study. And Benjamin Zuckerman, UCLA professor of physics and astronomy and a member of the international team working on 2M1207A, adds this: "The two objects - the giant planet and the young brown dwarf - are moving together; we have observed them for a year, and the new...

Remembering ‘Proxima Centauri’

by Paul Gilster | Apr 29, 2005 | Culture and Society | 1 Comment

The possible asteroid belt around the star HD69830, covered here in a recent entry, caused several days of pondering and a scouring of the Centauri Dreams library. This exoplanetary belt seems to be 25 times as dense as our own, and as close to its parent star as the orbit of Venus is to ours. That would make for an unforgettable celestial display every night, a belt of light cutting across the sky. The idea of a 'ringed star' finally drew forth the memory: an old Murray Leinster story called "Proxima Centauri." Published in the March 1935 issue of Astounding Stories (an issue in which future Astounding editor John Campbell would have two stories, one of them under his pseudonym Don A. Stuart), "Proxima Centauri" tells the story of the Adastra, a vast starship a mile in diameter as it makes the first interstellar crossing. Ahead in the viewfinders, Proxima Centauri reveals itself to be surrounded by a glowing ring that comes into view long before the planets in the Proxima system....

An Asteroid-Based Technical Civilization

by Paul Gilster | Apr 28, 2005 | Astrobiology and SETI | 0 Comments

Is biology as much a driver for interstellar travel as technology? Hungarian engineer Csaba Kecskes argues that it may be so; indeed, biology may hold the answer to Enrico Fermi's famous 'where are they?' question about extraterrestrials. While most scenarios for the growth of technological civilizations assume a 'galactic empire' model -- colonization modeled after 16th Century explorers, or the spread of Polynesian cultures through the islands of the Pacific -- Kecskes uses a different analogy: the migration of life from water to land. As he writes in a 2002 paper in Acta Astronautica: Using this analogy, the [Fermi] paradox simply disappears; fishes never meet lizards or rats. (In the Earth's biosphere there are large groups of animals which live in a mixed water/land environment, but every analogy has its limits. Man's adaptation to the space environment, especially to weightlessness, probably will create a very effective and final barrier). In other words, technical...

Cassini Finds Organic Chemistry High Above Titan

by Paul Gilster | Apr 27, 2005 | Outer Solar System | 0 Comments

Scientists anticipated that Titan would be a model laboratory for studying the organic chemistry that eventually led to life on the primitive Earth. So the discovery of complex mixtures of hydrocarbons and carbon-nitrogen compounds came as no surprise. What was unusual was where they found them: in Titan's upper atmosphere. Organic materials were expected on Titan because nitrogen and methane, the two primary components of its atmosphere, should form complex hydrocarbons when exposed to sunlight or energetic particle radiation from Saturn's magnetosphere. But the frigid temperatures on the Saturnian moon led most researchers to believe such hydrocarbons would condense and eventually wind up on the moon's surface. Instead, Cassini's ion and neutral mass spectrometer helped them find hydrocarbons galore in Titan's outer atmosphere. Image: This natural color composite (taken during the April 16 flyby) shows approximately what Titan would look like to the human eye: a hazy orange globe...

Quasar Studies Confirm Einstein Prediction

by Paul Gilster | Apr 26, 2005 | Deep Sky Astronomy & Telescopes | 0 Comments

When theories aren't borne out by observation, the problem just may be the size of the dataset. As witness recent work on gravitational lensing, that phenomenon where light is distorted and magnified by the gravitational pull of galaxies and other matter as it makes its immense journey from distant quasars to the Earth. Such lensing has been observed for over a decade, but just how the light is magnified, and on what scale, has until now been an elusive question. And answers to it haven't seemed to fit the standard model of cosmology, one in which visible galaxies represent only a small part of the mass of a universe seemingly filled with dark matter. Now researchers from the Sloan Digital Sky Survey (SDSS) have been able to perform a large-scale study of such magnification, and their theories do gibe with the standard model. The team was able to measure the brightness of some 200,000 quasar sources and determine the precise magnification caused by gravitational lensing. The new...

A Star Sculpture on Hubble’s Anniversary

by Paul Gilster | Apr 25, 2005 | Deep Sky Astronomy & Telescopes | 0 Comments

Hard to believe that it was fully fifteen years ago today that the Hubble Space Telescope was placed into orbit from the Space Shuttle Discovery. Hubble's list of achievements has been outstanding, from detecting proto-galaxies whose light was emitted less than a billion years after the Big Bang to providing data that helped astronomers confirm the age of the universe, now calculated at some 13.7 billion years. And don't forget the extraordinary moments closer to home, such as the space telescope's views of comet Shoemaker-Levy 9, the famous 'string of pearls,' hitting Jupiter in 1994. Hubble's 700,000 images have provided views up to ten times sharper than any previous telescope could offer. The image above, a part of the Eagle Nebula, shows a tower of cold gas and dust being shaped by the light of hot new stars. It was taken with Hubble's Advanced Camera for Surveys (ACS), providing a picture so sharp that, at full resolution, the image could be blown up to the size of a billboard...

Virtual Reality Over a Galactic Network

by Paul Gilster | Apr 23, 2005 | Astrobiology and SETI | 0 Comments

"The prospect of distributing realistic simulations of alien environments throughout the galaxy sheds light on 'Fermi's question,' named after the physicist Enrico Fermi, who is said to have inquired of intelligent extraterrestrials, 'Where are they?' The point of Fermi's question, much elaborated by later thinkers, is that a technically advanced civilization could set up colonies on the planets of nearby stars, which in turn could colonize other star systems, until their race had populated the entire galaxy. Since they are not here, the argument concludes, perforce they are not anywhere, and we are alone in the galaxy. "Interstellar colonization, however, is arduous and expensive by just about any imaginable standard. It can hardly be justified in terms of population pressure or a need for raw materials: Our Sun, for instance, has enough energy, and the solar system enough space, to accomodate the most vigorous forseeable expansion of our species for many millions of years into the...

Asteroid Belt Around a Sun-like Star?

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

Finding solar systems similar to our own is a continuing quest for planet hunters. Now a star called HD69830, some 41 light years from Earth, has been found to contain a thick band of warm dust that may be an asteroid belt. Although planets have yet to be detected around the star, the find is exciting because HD69830 is similar to the Sun in age and size. And just as Jupiter seems to provide an outer limit to our own asteroid belt, there are suspicions that the asteroid belt around this star may be contained by the gravitational influence of a gas giant planet. If such planets exist around HD69830, they'll likely be spotted by future planet-hunting missions like SIM, the Space Interferometry Mission, which is scheduled for a 2011 launch. But exoplanetary systems continue to confound our expectations. The newly discovered belt is not only 25 times as dense as our own, it's also much closer to its star. Imagine a thick belt of primordial debris located inside the orbit of Venus,...

Near Term Technologies II: SailBeam

by Paul Gilster | Apr 21, 2005 | Sail Concepts | 0 Comments

Centauri Dreams first ran across Jordin Kare's remarkable SailBeam concept in a report called "High-Acceleration Micro-Scale Laser Sails for Interstellar Propulsion" that the astrophysicist prepared for NASA's Institute for Advanced Concepts (NIAC). The idea seemed outrageously simple: if you accelerate vast numbers of tiny sails rather than one enormous one, you can bring the same amount of mass to high speeds with a less complex optical system. Using dielectric rather than metal sails, you can accelerate the sails much closer to their power source. The stream of microsails then becomes a source of propulsion as it is vaporized into plasma behind a departing starship. Dana Andrews, who has worked with Kare on magsail concepts, notes that a SailBeam Boosted Magsail (SBBM) solves a key problem of particle beam propulsion. A neutral particle beam will disperse as it travels, but a stream of low-mass microsails is not limited by such diffraction. Andrews' MagOrion concept explored some...

Interstellar Flight Using Near-Term Technologies

by Paul Gilster | Apr 20, 2005 | Sail Concepts | 0 Comments

In a paper called "Interstellar Propulsion Opportunities Using Near-Term Technologies," Dana G. Andrews (Andrews Space, Seattle) sees two criteria for an interstellar mission. First, it must return results within the lifetime of its principal investigator or the average colonist. Second, it must find cost-effective ways to generate energy and to convert raw energy into directed momentum. These are steep requirements -- we're talking 15 to 20 percent of the speed of light, or 45,000 to 60,000 kilometers per second. Centauri Dreams questions the first criterion, but the need for efficient and effective propulsion is true no matter how fast a mission we manage to design. Robert Forward's massive Fresnel lenses (1000 kilometers in diameter 15 AU from the laser source) are one of those 'small problems in engineering' that the irrepressible Forward managed to concoct while not violating known physics. And Andrews points to a lightsail alternative -- building solar-pumped or...

Physical Constant Unchanged After All?

by Paul Gilster | Apr 19, 2005 | Deep Sky Astronomy & Telescopes | 0 Comments

More on the 'fine structure constant,' that fundamental number that seems to be crucial to our understanding of electromagnetism, and therefore the way the universe works. Our recent story on Michael Murphy and his Cambridge team discussed findings from the Keck I telescope on Mauna Kea that suggested subtle changes to the value of the fine structure constant since the earliest era of the universe. But those findings remain highly controversial, as was apparent on Monday the 18th. That was the day that astronomer Jeffrey Newman (Lawrence Berkeley National Laboratory) presented data from the DEEP2 redshift project, a five-year survey of galaxies more than seven light years away. Speaking at the annual meeting of the American Physical Society (APS) in Tampa, Newman said his team's results showed no change to the constant within one part in 30,000. "The fine structure constant sets the strength of the electromagnetic force, which affects how atoms hold together and the energy levels...

Interstellar Flight by Particle Beam Revisited

by Paul Gilster | Apr 18, 2005 | Sail Concepts | 5 Comments

Beamed propulsion is the classic solution to the mass ratio problem in interstellar flight. Rather than pushing more and more fuel to get your payload to another star system, you leave the fuel behind. Robert Forward's vast lightsail proposals come immediately to mind, but in 2001 physicist Geoffrey Landis proposed propulsion by particle beam, with energy delivered from the Solar System to the departing spacecraft. The notion is this: a charged particle beam is accelerated and focused, then neutralized in charge to prevent the beam from expanding as it travels due to electrostatic repulsion. When the particles reach their target, they are re-ionized and reflected by a magnetic sail, which Landis originally conceived as 'a large superconducing loop with a diameter of many tens of kilometers.' The particle-beam idea seems to solve two problems with lightsails: First, a light beam provides a relatively inefficient energy source, demanding huge power facilities and thus driving up the...

SETI? Here’s Why We Need to Keep Looking

by Paul Gilster | Apr 16, 2005 | Astrobiology and SETI | 0 Comments

"A recent book by the mathematician Amir Aczel makes the case for the probability of extraterrestrial life being 1. The physicist Lee Smolin wrote that 'the argument for the non-existence of intelligent life is one of the most curious I have ever encountered; it seems a bit like a ten-year-old child deciding that sex is a myth because he has yet to encounter it.' The late Stephen Jay Gould, referring to Tipler's contention that ETCs would deploy probe technology to colonize the Galaxy, wrote that 'I must confess that I simply don't know how to react to such arguments. I have enough trouble predicting the plans and reactions of people closest to me. I am usually baffled by the thoughts and accomplishments of humans in different cultures. I'll be damned if I can state with certainty what some extraterrestrial source of intelligence might do.' "It is easy to sympathize with this outlook. When considering the type of reasoning employed with the Fermi paradox, I cannot help but think of...

Tuning Up Terrestrial Planet Finder

by Paul Gilster | Apr 15, 2005 | Culture and Society, Exoplanetary Science | 4 Comments

We've recently discussed habitable zones, normally defined as the area around a star where liquid water can exist on the surface. Thoughts on just how far the habitable zone around our own star extends vary, but the Carnegie Institution's Maggie Turnbull pegs it at between .7 AU and 1.5 AU. To adjust the notion of habitable zone to other stars, Turnbull says, the same relationship can be scaled as the square root of the luminosity of the star. Turnbull thinks about such things because she has created a database of stars that could have terrestial-type planets around them. This is clearly of significance to future missions like Terrestrial Planet Finder and makes me wish I had been able to attend the NASA Forum for Astrobiology Research in March, where Turnbull gave a talk called "Remote Sensing of Life and Habitable Worlds: Habstars, Earthshine and TPF." The next best thing is an edited transcript of the lecture in Astrobiology Magazine, which is running it in a series of four parts...

Oort Cloud Explorer: Fast Mission to the Comets

by Paul Gilster | Apr 14, 2005 | Missions, Outer Solar System, Sail Concepts | 1 Comment

How do you build an interstellar solar sail? Back in the 1980s, two studies of sail design set parameters that before then had remained largely unanalyzed. Gregory Matloff and Eugene Mallove were able to show in their papers "Solar Sail Starships: Clipper Ships of the Galaxy" and the later "The Interstellar Solar Sail: Optimization and Further Analysis," that a so-called 'sundiver' trajectory coud produce exit velocities from the Solar System on the order of 1000 kilometers per second, even for large payloads. Both papers appeared in the Journal of the British Interplanetary Society, which remains the leading venue for interstellar studies. A sundiver maneuver is tricky stuff; the spacecraft is established on a hyperbolic solar orbit that swings close to the Sun; at perihelion (closest approach), the sail is exposed to sunlight (having, perhaps, been shielded until now by an occulting object, such as a small asteroid). Make the sail reflective enough and the accompanying linkages to...

Extremely Large Telescopes and the Hunt for Terrestrial Worlds

by Paul Gilster | Apr 13, 2005 | Deep Sky Astronomy & Telescopes, Exoplanetary Science | 0 Comments

How large can a telescope get? Today's largest optical telescopes boast 10-meter mirrors (33 feet across). But the recent Royal Astronomical Society meeting in Birmingham (UK) heard the case for much larger instruments, on the order of 50 to 100 meters (165-330 feet) in diameter, optical instruments the size of the Deep Space Network's largest antennae. Moreover, such instruments would have as much as forty times the spatial resolution of the Hubble Space Telescope, though operating deep within Earth's atmospheric well. European astronomers have been engaged in this study for the past four years; you can see a synopsis of their work in an online brochure called "Extremely Large Telescopes: The Next Step In Mankind's Quest For The Universe" (PDF warning). The conclusions of their report are remarkable: The vast improvement in sensitivity and precision allowed by the next step in technological capabilities, from today's 6-10 m telescopes to the new generation of 50-100 m telescopes...

Voyager and the Benefits of ‘Slow Science’

by Paul Gilster | Apr 12, 2005 | Culture and Society, Outer Solar System | 0 Comments

The Washington Post takes note of the possible suspension of funding for the two Voyager spacecraft in a story by Rick Weiss called Our Incredible Shrinking Curiosity. As discussed here in a previous entry, NASA is eying the Voyager budget of $4.2 million per year as it ponders cutbacks. Such news, says Weiss, leaves him "...depressingly convinced that these 8 billion-mile-long extensions of human curiosity are indeed now smarter, or at least more enlightened, than the mortals who made them." In Weiss' view, "...the U.S. scientific enterprise is riddled with evidence that Americans have lost sight of the value of non-applied, curiosity-driven research -- the open-ended sort of exploration that doesn't know exactly where it's going but so often leads to big payoffs." But is it a lack of curiosity that motivates such cuts, or something more temporal? Isn't the real culprit our inability to think in the longer time frames required of what Stewart Brand calls 'slow science'? The Voyagers...

Fundamental Constant May Need Tweaking

by Paul Gilster | Apr 11, 2005 | Deep Sky Astronomy & Telescopes | 1 Comment

Michael Murphy has been studying the fundamental constants of nature -- numbers that are key to any given theory of how the universe works -- for the past five years. His work at the Institute of Astronomy at Cambridge University has particularly foused on possible changes to the fine structure constant, a number central to electromagnetism, and therefore crucial to the interaction between light and matter. If its value were slightly different, life could not exist, although tiny changes over time could be tolerated. Normally denoted by the Greek letter α (alpha), the fine structure constant can be worked out through experiment to great precision. According to Murphy, the numbers come to 1/alpha = 137.03599958, with an experimental uncertainty of a mere 0.00000052. But as the astronomer told the Physics 2005 conference at the University of Warwick (UK) today, the fine structure constant may have had a slightly different value in the early universe. Murphy bases his conclusion...

GQ Lupi B: Exoplanet or Brown Dwarf?

by Paul Gilster | Apr 9, 2005 | Exoplanetary Science | 1 Comment

The recent image of a possible planet around the star GQ Lupi has met with understandable enthusiasm in the press, but we still don't know whether the small object just to the right of the star in the image below is a planet or a brown dwarf. The boundary between brown dwarf and planet is tricky terrain, but the European Southern Observatory fixes it at roughly 13 Jupiter masses, which is the critical mass needed to ignite deuterium. Brown dwarfs, then, are objects heavier than that. But the observations of Ralph Neuhäuser and colleagues do not provide a direct estimate of the smaller object's mass. Because GQ Lupi and its companion presumably formed at the same time, then the new object is young, and traditional models for such calculations may not apply. But using them, according to a press release from the ESO, implies that the object is somewhere between 3 and 42 Jupiter masses. In other words, based on what we can determine so far, GQ Lupi b is either a planet or a brown dwarf....

Emergence of the ‘Dark Energy Star’

by Paul Gilster | Apr 8, 2005 | Deep Sky Astronomy & Telescopes | 0 Comments

"It's a near certainty that black holes don't exist," says George Chapline. A physicist at the Lawrence Livermore National Laboratory, Chapline has an alternative explanation: when a massive star collapses, what remains is not a black hole but a star that's filled with dark energy. Some 70 percent of the universe seems to be composed of dark energy, though no one knows precisely what it is. Chapline's work may lead to new insights into the stuff. A preprint of Chapline's paper "Dark Energy Stars" appears at the ArXiv site, where the author lays down the gauntlet early on: In the 1950s a consensus was reached, partly as a result of meetings such as a famous meeting at Chapel Hill in 1957, that although quantum effects might be important below some very small distance, on any macroscopic scale the predictions of classical general relativity (GR) should be taken seriously. In the summer of 2000 Bob Laughlin and I realized that this cannot possibly be correct. Indeed I am sure it will be...

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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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