Paul Gilster | Centauri Dreams

A New Look at Near Earth Asteroids

by Paul Gilster | Aug 14, 2008 | Asteroid and Comet Deflection | 3 Comments

We could do with as much information as possible about near-Earth asteroids. A manned mission is a natural step, both for investigating a class of object that could one day hit our planet, and also for continuing to develop technologies in directions that will be useful for our future infrastructure in space. You would think we would know much of what we needed from examining meteorites, which generally are chunks of asteroid material, but that assumption turns out to be erroneous. A recent paper in Nature has the story. Richard Binzel (MIT) and colleagues have been considering the properties of asteroids for a long time, looking at the spectral signatures of near-Earth asteroids and comparing them to spectra obtained from meteorites. And it turns out that most of the meteorites that fall to Earth represent types of asteroid that are different from the great bulk of near-Earth asteroids. In fact, the varied types of meteorites we find here generally resemble the mix of asteroids...

Online Research: Narrowing the Possibilities?

by Paul Gilster | Aug 13, 2008 | Culture and Society, Research Tools | 5 Comments

I want to take a momentary detour from interstellar topics to talk about how we go about doing research, astronomical and otherwise. Some years back I debated the then new trend of online peer review with an opponent who argued for the virtues of traditional print journals and their methods. At the time, what would become the arXiv pre-print site was just beginning to grow, and the benefits of having a wide audience able to examine a scientific paper before it achieved print seemed manifest. Much good research, I reasoned, would become available for scrutiny, some of it unable to get past academic referees at a specific journal but now able to be included in a broadened scientific discussion. Even so, certain trends did worry me, some of them now manifest again in a presidential report recently cited by James Evans, a University of Chicago sociologist. The report makes a jaw-dropping claim: "All citizens anywhere anytime can use any Internet-connected digital device to search all of...

Enceladus Flyby Data Streaming In

by Paul Gilster | Aug 12, 2008 | Outer Solar System | 1 Comment

Although the Cassini spacecraft has just passed no more than fifty kilometers from the surface of Saturn's moon Enceladus, the investigation of the intriguing object will only intensify in October, when Cassini moves to within half that distance. With astrobiological interest high, Enceladus is a hot place to be. Data from the most recent flyby began streaming in to the Deep Space Network station in Canberra last night, with the downlink scheduled to continue into the afternoon of the 12th (EST). The prime target, using every camera resource available and covering infrared, visible light and ultraviolet, is the area of the moon's southern pole that houses the fissures now known as 'tiger stripes.' Under intense scrutiny will be the terrain of the fissures as well as the composition of the ice grains inside, and tuning up our data on temperature should provide a better idea of whether or not liquid water lies close to the surface. Cassini will be looking for other elements -- oxygen,...

VASIMR and the Nuclear Question

by Paul Gilster | Aug 11, 2008 | Advanced Rocketry | 26 Comments

It's safe to say that Franklin Chang-Diaz knows what he's talking about when he discusses the space experience. An astronaut who has logged seven flights and over 1600 hours in space (a period that includes three spacewalks), Chang-Diaz has been making even more impressive news in recent times with his Ad Astra Rocket Company, where the VASIMR (Variable Specific Impulse Magnetoplasma Rocket) is under development. It's heartening to think of VASIMR undergoing space-based tests, a future that is now in the cards with the news that NASA has plans to test the VASIMR engine aboard the International Space Station. We naturally think long-term here, but VASIMR's uses in potential missions to Mars (Chang-Diaz talks about a 39-day trip to the planet!) and beyond will first have to be shaken out in near-Earth orbit. But ponder a VASIMR gradually becoming operational, mounting missions to communications satellites that are now economically all but unreachable. Indeed, VASIMR sets up the...

Radiation Shielding and Jupiter’s Moons

by Paul Gilster | Aug 9, 2008 | Culture and Society | 11 Comments

The latest Carnival of Space is now available at the Mars Odyssey blog, where Nancy Houser has gathered space-themed materials from the past week, many of them dealing with the question of perchlorates on Mars and the implications of that possible discovery. I'll send you straight to the Carnival for the perchlorate story, where many bloggers dissect it. My usual practice is to focus on Carnival items that connect to our theme here on Centauri Dreams -- articles about deep space starting with the outer planets and moving to regions beyond. This week the entry that fits that bill is Brian Wang's article in NextBigFuture on radiation shielding. Although Brian couches this work in the context of solutions to radiation exposure following nuclear attacks, it's also true that a drug that is 5000 times more effective at reducing the effects of radiation injury than the drugs we currently use has interesting space implications. The experimental drug, intriguingly named Nanovector Trojan...

Anomalies, Chance Finds and SETI

by Paul Gilster | Aug 8, 2008 | Astrobiology and SETI | 10 Comments

'Hanny's Voorwerp' may soon enter the astronomical lexicon as a reference to anomalous objects in deep space. 'Hanny' is Hanny van Arkel, a 25-year old Dutch school teacher and participant in the Galaxy Zoo project, where she and 150,000 other volunteers worldwide help to scan galaxy images online. 'Voorwerp' is the Dutch word for 'object,' in this case a conglomeration of gas heated to about 10,000 degrees Celsius and marked by a hole in its center. The suspicion grows that van Arkel has stumbled upon an entirely new class of astronomical object. Out of such finds does the work of a computer-armed volunteer become fodder for the Hubble Space Telescope, which will soon have 'Hanny's Voorwerp' under observation. The object is apparently being illuminated by a source we cannot see, leading the Galaxy Zoo team to look at the nearby galaxy IC 2497. The quasar at the heart of this galaxy seems to have shut down some time in the past 100,000 years -- at least, that's the theory -- while...

A ‘Rare Earth’ After All?

by Paul Gilster | Aug 7, 2008 | Exoplanetary Science | 42 Comments

A supercomputing cluster operated by a team at Northwestern University is giving us fresh simulations of the birth of planetary systems, with results that may dismay terrestrial planet hunters. For if this work is correct, the 'rare Earth' hypothesis is back, this time bolstered by computer models that are the first to simulate the formation of planetary systems all the way from earliest dust disk to full-fledged solar system. More than a hundred simulations using exoplanet data collected over the last fifteen years went into the modeling of dust, gases and the effects of gravity. Planetary systems do seem to have a few things in common, among them a violent birth. The Northwestern team found that the dynamics of the early gas disk push nascent planets inexorably toward their central star. There they may be consumed in the star or subjected to collisions with other objects as each accumulates mass. Dynamical resonances can occur that produce increasing orbital eccentricity, with...

‘Slow Life’ and its Implications

by Paul Gilster | Aug 6, 2008 | Astrobiology and SETI | 12 Comments

Imagine a form of life so unusual that we cannot figure out how it dies. That's exactly what researchers are finding beneath the floor of the sea off Peru. The microbes being studied there -- single-celled organisms called Archaea -- live in time frames that can perhaps best be described as geological. Consider: A bacterium like Escherichia Coli divides and reproduces every twenty minutes or so. But the microbes in the so-called Peruvian Margin take hundreds or thousands of years to divide. "In essence, these microbes are almost, practically dead by our normal standards," says Christopher H. House (Penn State). "They metabolize a little, but not much." House goes on to discuss what a slow metabolism may imply about environments outside our own planet. Imagine hydrothermal vents on Europa, where the energy ration may be slim. For that matter, with Phoenix still working its magic at the Martian pole, imagine subsurface aquifers on that planet whose energy resources may be just enough...

Of Solar Sails, Bets and Optimism

by Paul Gilster | Aug 5, 2008 | Culture and Society, Sail Concepts | 22 Comments

I've been surprised by the sizable reaction to my bet with Tibor Pacher, not just in terms of comments here but in related e-mails. For those of you who missed the original post, I found Tibor's prediction that the first interstellar mission would be launched by 2025 to be an irresistible target. Tibor posted the prediction on the Long Bets site, and the way this works is that someone willing to make a bet on the prediction puts down the money upfront and challenges the predictor to match it. Negotiations follow, the outcome being that if the terms are worked out and the bet is accepted, it is finalized. Both parties send in their money, and the money grows over the years in a long-term investment portfolio called the Farsight Fund. Ultimately, either the Tau Zero Foundation or (Tibor's choice) the SOS-Kinderdorf International, will enjoy the result. Now that Tibor and I have finalized the terms, the details will go up on Long Bets as soon as our funds arrive (which should be in a...

Two Telescopic Anniversaries

by Paul Gilster | Aug 4, 2008 | Deep Sky Astronomy & Telescopes | 24 Comments

by Larry Klaes It's been a tough weekend, not only with the loss of the SpaceX Falcon booster but also the NanoSail-D sail experiment that flew aboard it. I'll have more on the loss of the sail tomorrow, but this may be a good day to look back and reflect on some of the titans of astronomical history, including the Hale instrument whose views of the heavens gave so many of us early inspiration. Tau Zero journalist Larry Klaes has been pondering these matters, and offers us a look at some of the people and instruments that proved essential in changing our view of the universe. Sixty years ago, on June 3, 1948, the most massive astronomical tool of the era was dedicated on Palomar Mountain near Pasadena, California. Known as the Hale Telescope, this instrument was much bigger than any telescope that had ever come before it. In its nearly three decades as the reigning largest telescope on Earth, the "Giant Eye" of the Palomar Observatory revealed new vistas of the heavens ranging from...

Exotic Particles from Galactic Center?

by Paul Gilster | Aug 2, 2008 | Exotic Physics | 15 Comments

What could be causing gamma-ray photons to be streaming from the galactic core with a precise energy of 511 keV (8 X 10-14 joules)? It's an interesting question, one tackled by Ian O'Neill on his astroENGINE site, as posted by 21st Century Waves in this week's Carnival of Space. O'Neill notes the defining nature of this energy level, which turns out to be the exact rest mass energy of a positron, the antimatter equivalent of an electron. That fact suggests the annihilation of positrons in the galactic center, but what's causing it? The usual suspects just don't fit, as O'Neill is quick to note: The first thing that comes to mind is a gamma-ray burst, produced when a massive star dies and collapses as a supernova. But this is short-lived and not sustained. How about the supermassive black hole sitting in the middle of the Milky Way's galactic nucleus? This theory was recently discussed on Astroengine, but the production of antimatter (i.e. positrons) is more of a slow leak than...

Simulating the First Stars

by Paul Gilster | Aug 1, 2008 | Astrobiology and SETI | 3 Comments

Without the explosions of supernovae, the heavy elements so essential to life itself would be unavailable, and stars would lack the raw materials to form planets. Thus Carl Sagan's famous "We are star-stuff" quotation, an idea validated by our extrasolar studies, which allow us to correlate the presence of planets with the existence of heavy elements in their stars. Much remains to be done here, but stars with higher metallicity and more heavy elements do appear more likely to have planets. Volker Bromm (now at the University of Texas) puts it this way: "We're now just beginning to investigate the metallicity threshold for planet formation, so it's hard to say when exactly the window for life opened. But clearly, we're fortunate that the metallicity of the matter that birthed our solar system was high enough for the Earth to form. We owe our existence in a very direct way to all the stars whose life and death preceded the formation of our Sun. And this process began right after the...

Ontario Lacus: Awash on Titan

by Paul Gilster | Jul 31, 2008 | Outer Solar System | 6 Comments

Remember those oceans of methane we thought might exist on Titan? They were an exciting thought (I recall hypothetical images of the Huygens probe bobbing in such an ocean at the end of its journey, before we knew what it would actually land on). It's exciting to confirm that liquid does exist on Titan's surface in the form of liquid hydrocarbons, with a positive identification of ethane. At least one of the large lakes the Cassini orbiter has found there contains the substance, but we also know that numerous other lake-like areas exist beneath the smog. Image: The Imaging Science System aboard NASA's Cassini orbiter took the image, left, of Ontario Lacus in June 2005. (Image credit: NASA/JPL/Space Science Institute.) Cassini's Visual and Infrared Mapping Spectrometer took the image, right, of Ontario Lacus in December 2007. This view, taken at 5-micron wavelengths from 1,100 kilometers (680 miles) away, shows the part of the lake that is visible on Titan's sunlit side. What appears...

Possible Evidence for Dark Energy

by Paul Gilster | Jul 30, 2008 | Deep Sky Astronomy & Telescopes | 6 Comments

If dark energy is accelerating the expansion of the universe, how can we identify its signature? Researchers at the University of Hawaii have been using microwaves to detect what they believe to be dark energy at work. If their work stands up, it will be a useful step for cosmology, but also a potential boon for those of us with interstellar travel in mind. We obviously want to understand a force that may one day have propulsion implications, and it's possible that the universe is offering a set of useful clues. Here cosmology and propulsion science share a common interest. Led by István Szapudi, the researchers zeroed in on galactic superclusters -- the largest structures in the universe -- and so-called 'supervoids,' vast areas with few galaxies in them. Remember the prefix 'super' here, for conventional galactic clusters are some ten times smaller and held together by gravity, while the Hawaii team believes galaxies in the supervoids and superclusters are more affected by dark...

Detection Method for Binary Star Planets

by Paul Gilster | Jul 29, 2008 | Exoplanetary Science | 12 Comments

Astrometry, using the position and motion of celestial objects to further astronomical research, is ever more useful in the study of extrasolar planets. If you can measure how much a given star is displaced by the presence of a planet, you have a valuable adjunct to existing radial velocity and transit methods. Now a new study has examined astrometry's uses with binary stars, using the Hale telescope on Mt. Palomar and the Keck II instruments on Mauna Kea. And with certain restrictions, adaptive optics may allow us to detect binary star planets. The targets were seventeen binary or multiple star systems, most of them M-dwarf binaries closer than 20 parsecs from the Sun. Observations were conducted in the near infrared, with relative separations and position angles carefully measured. Study authors Krzysztof Helminiak and Maciej Konacki (Nicolaus Copernicus Astronomical Center, Poland) note the advantage of close systems: The closure of companions allows one to observe visual binaries...

Betting on an Interstellar Future

by Paul Gilster | Jul 28, 2008 | Culture and Society | 30 Comments

Tibor Pacher has gone out on a limb. The founder of peregrinus interstellar and an active supporter of interstellar research, the Heidelberg-trained physicist (now a freelance software consultant) has made a wager on the Long Bets site that should raise eyebrows: "The first true interstellar mission, targeted at the closest star to the Sun or even farther, will be launched before or on December 6, 2025 and will be widely supported by the public." Note that no crew is assumed, the vehicle presumably being an unmanned flyby probe. We must also assume it will be targeted at the nearest star system, Alpha Centauri. Even so, to pull off the attempt in a mere seventeen years? But my friend Tibor is a gadfly as well as an optimist. He knows as well as anyone that the time frame is outrageous, but he wants to inspire discussion and keep people thinking about interstellar issues. In the same spirit, he notes the motivations that exist, from the challenge of a seemingly impossible destination...

What Makes Us Explore?

by Paul Gilster | Jul 26, 2008 | Culture and Society | 13 Comments

Is the urge for exploration innate to our species, or is it a vestigial disorder? Rand Simberg takes on the question at The Space Review this week, an article I came across thanks to a link at Music of the Spheres, which hosts the latest Carnival of Space this week. If you have an interest in simulators and flying (and as a now inactive but still interested CFII, I can relate to that!), you'll want to be reading Music of the Spheres regularly. It's a fine and enthusiastic blog frequently updated with space-related software discussions, and one I've been reading for years to follow Bruce's adventures with the ORBITER simulator. But back to exploration: Simberg questions whether the exploratory impulse isn't disruptive in modern society, pointing out that most people in the world live out their lives within miles of the place where they were born, and suggesting that those who want to push a human agenda in space need a better justification than this. The candidates? Fear is one, as in...

New Planet: CoRoT’s Interesting Find

by Paul Gilster | Jul 25, 2008 | Exoplanetary Science | 9 Comments

Finding transiting planets is no longer a surprise, and we can expect a host of transits from the CoRoT mission, which has the advantage of observing from a space-based platform. Moreover, CoRoT will, in the course of its lifetime, survey as many as 120,000 stars for up to five months. Driving home the advantage is the announcement of a new CoRoT planet known as CoRoT-Exo-4b. We're dealing with another Jupiter-sized planet orbiting in close proximity to its star, but this one has a unique claim to distinction: Its host star is rotating at the same pace as the planet's orbit. Image: Fixated upon a star: An artists impression of the satellite CoRoT in orbit around the Earth. Credit: CNES. Moreover, for a transiting world, CoRoT-Exo-4b is a relatively long-period planet, orbiting its F-class primary in 9.2 days. Thus far most transiting worlds have had orbits below about five days, two major exceptions being HD 147506b and HD 17156b, the latter with a period of 21.2 days -- both of...

A New Take on Warping Spacetime

by Paul Gilster | Jul 24, 2008 | Exotic Physics | 18 Comments

For those of you who don't see Spaceflight, a magazine published by the British Interplanetary Society, it may be useful to know that an article by Richard Obousy and Gerald Cleaver (Baylor University) on warp drive theory from the April issue is now available on the arXiv server. This material was presented at the November, 2007 symposium held by the BIS in London. Kelvin Long, who organized the session, had earlier passed along several documents from the proceedings that we looked at here, and also wrote up the duo's ideas in the same issue of Spaceflight. But let's backtrack a minute to Miguel Alcubierre's 1994 paper, which demonstrated that it would be possible -- within the context of General Relativity -- to envision a space drive that could get you to your destination in a time shorter than it would take light itself to get there. Contracting space in front of the craft while inflating it behind, the drive is permissible because the starship itself would not be going faster...

Overlooked Nova Challenges Amateurs

by Paul Gilster | Jul 23, 2008 | Deep Sky Astronomy & Telescopes | 1 Comment

How does a planet full of amateur and professional astronomers miss an exploding star that was one of the brightest novae in the past ten years? The fact that the event called V598 Puppis (the brightening of the star USNO-A2.0 0450-03360039) was only spotted days after its explosive appearance by an orbiting space observatory that was turning from one target to another seems remarkable, but maybe it's a salutary reminder that with resources limited on the professional level, amateurs are still needed to track such interesting events. The observatory in question was ESA's XMM-Newton, an X-ray observatory whose data is recorded even as the satellite moves between different objects. That 'slewing' data revealed that the star in question had brightened by more than 600 times, as verified by later observers at Las Campanas Observatory in Chile. The evident cause: A white dwarf drawing off gas from a companion star, building sufficient quantities that a nuclear reaction released the...

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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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