Archives

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...

Notes & Queries 9/29/07

by Paul Gilster | Sep 29, 2007 | Culture and Society | 5 Comments

Franklin Chang-Diaz, astronaut and CEO of Ad Astra Rocket Company, intends to test the VX-200 VASIMIR prototype in January. VASIMIR (Variable Specific Impulse Magnetoplasma Rocket) offers much greater fuel efficiency than conventional chemical rockets, working with hot plasma heated by radio waves and controlled by a magnetic field. Technology Review talks to Chang-Diaz about the prototype and the flight version to follow in this interview. And here's where Chang-Diaz see us going in the long-term: I think lots of people are going to be moving into space. I think we will be populating the moon, building enclaves of research and even money-making ventures there. Just last month, Ad Astra signed an agreement with Excalibur Exploration Ltd., a British company, to mine asteroids [when the time is right]. I believe there will be a huge demand for resources, particularly water, from asteroids and comets, because taking water from the earth is going to be very expensive. We're probably...

Ion Propulsion Flies Again — When Will Sails?

by Paul Gilster | Sep 28, 2007 | Missions | 10 Comments

The launch of the Dawn mission to the asteroids makes me think about solar sails. I realize that Dawn uses ion propulsion, about which more in a moment, but watching ion methods as they mature makes an emphatic point: We need to bring solar sail technologies up to the same readiness level that ion propulsion currently enjoys. And we need to be shaking out sail ideas in space. The Russian Znamya attempts at a 'space mirror' were attached to a Progress supply ship, and interesting mostly in terms of their deployment problems, leaving the 2004 Japanese test of reflective sails in space as the only free-flying experiments I know about. Which is not to say I'm a skeptic about ion propulsion. It will be fascinating to follow the performance of Dawn's engines as the mission progresses. 54 feet of solar array produce the needed power to ionize their onboard xenon gas, which is four times heavier than air. The ions are then electrically acccelerated and emitted as exhaust from the spacecraft....

Radio Burst Flags Celestial Oddity

by Paul Gilster | Sep 27, 2007 | Deep Sky Astronomy & Telescopes | 8 Comments

An odd radio burst that seems to signal a previously undiscovered astrophysical phenomenon is now on the scene. Culled out of archival data gathered from the Parkes radio telescope in Australia, the burst may signal something exotic indeed, the last stages of the evaporation of a black hole. Another candidate: A collision between two neutron stars. And while the data in question come from a survey that included 480 hours of observation of the Magellanic Clouds, some 200,000 light years from Earth, the phenomenon they've uncovered is far more distant. Drawing the attention of astronomers was the fact that no radio burst yet found shows the same characteristics. Despite its strength, the signal lasted less than five milliseconds. Dispersion effects caused by its passage through ionized gas in deep space caused higher frequencies to arrive at the telescope before lower frequencies. Image: Visible-light (negative greyscale) and radio (contours) image of Small Magellanic Cloud and area...

Dawn Mission Launched to Asteroids

by Paul Gilster | Sep 27, 2007 | Missions | 4 Comments

Great to see Dawn on its way. The spacecraft lifted off at 11:34 UTC, with signal acquisition just over one hour into the flight. The spacecraft will begin its exploration of Vesta in 2011 and Ceres in 2015, two asteroids that between them have much to tell us about the history of the Solar System. Measurements of shape, surface topography, tectonic history, elemental and mineral composition will be included in a full data acquisition package. Image credit: NASA.

Planets of Iron, Planets of Ice

by Paul Gilster | Sep 26, 2007 | Exoplanetary Science | 14 Comments

How large a planet is depends upon its composition and mass. Earth is largely made of silicates, with a diameter of 7,926 miles at the equator. Imagine an Earth mass planet made of iron and you're looking at a diameter of a scant 3000 miles. Interestingly, the relationship between mass and diameter follows a similar pattern no matter what material makes up the planet. Running the numbers, an Earth mass planet made of pure water will be 9500 miles across. Sara Seager (Massachusetts Institute of Technology) has been studying these things as part of a project to model the kind of Earth-size planets we're likely to find around nearby stars. About the mass/diameter pattern, she says this: "All materials compress in a similar way because of the structure of solids. If you squeeze a rock, nothing much happens until you reach some critical pressure, then it crushes. Planets behave the same way, but they react at different pressures depending on the composition. This is a big step forward in...

Exploring the Submillimeter Universe

by Paul Gilster | Sep 25, 2007 | Deep Sky Astronomy & Telescopes | 22 Comments

By Larry Klaes Tau Zero journalist Larry Klaes here offers a look at a revolutionary telescope that will soon take our vision of the universe into new domains. In the early half of the next decade, an instrument called the Cornell Caltech Atacama Telescope (CCAT) is planned to examine the Universe through a less-studied region of the electromagnetic spectrum from an observatory in the remote deserts of Chile higher than any current major ground-based facility. CCAT is the culmination of plans by Cornell University and the California Institute of Technology (Caltech) initiated in 2004 to jointly conduct submillimeter astronomy with the largest telescope ever conceived for such an endeavor. The 25-meter (82-foot) wide mirror of the CCAT will allow astronomers to see the Cosmos in the area between the infrared and radio realms of the electromagnetic spectrum, an area well beyond the region that is visible to human eyes. The moisture in Earth's atmosphere normally blocks light waves...

Habitable Planets: A Splendid Isolation?

by Paul Gilster | Sep 24, 2007 | Exoplanetary Science | 14 Comments

Our assumptions about terrestrial planets seem pretty straightforward. We're only now reaching the level where detecting such worlds becomes a possibility, with advances in ground- and space-based telescopes imminent that will begin to give us an idea how common such planets are. Hoping for the best, we assume Earth-sized worlds in relatively comfortable places are common and even extend our search from G and K-type stars to the much dimmer (and more numerous) M-dwarfs. But what do we mean by a terrestrial planet? Size is an obvious criterion, but so is placement in the kind of habitable zone we would find conducive to our kind of life. That means liquid water at the surface. So far so good, but keep a sharp eye on the wild card in all this: Orbital ecccentricity. It's a measure of how far the orbit of a planet deviates from a circle, and we need to know more about it. Obviously a highly eccentric orbit could swing a planet through the habitable zone and right back out again, never...

Notes & Queries 9/22/07

by Paul Gilster | Sep 22, 2007 | Culture and Society | 1 Comment

Apropos of our recent speculations about planets without stars, this short podcast from Earth & Sky discusses dark planets within our galaxy able to sustain life, at least for a while. The scenario, developed by John Debes (Carnegie Institution) and Steinn Sigurðsson (Pennsylvania State): A planet with a large moon passes near a giant world like Jupiter. The team's simulations show the Earth-moon system ejected into interstellar space, with the possibility of a thick atmosphere and large tidal forces keeping the place warm for more than a hundred million years. ------- ESA's latest backgrounder on the Don Quijote candidate mission lays out a plan to rendezvous with an asteroid and orbit it, monitoring its shape, mass and gravitational field. A second spacecraft would then be sent to impact the asteroid at about 10 km/s, while the first vehicle monitors the result, looking for changes in the asteroid's trajectory. Mission planners have considered oft-mentioned Apophis as one of...

The View from an Intergalactic Straggler

by Paul Gilster | Sep 21, 2007 | Deep Sky Astronomy & Telescopes | 11 Comments

Speaking of absorbing views from a planetary surface, as we've been doing recently when discussing the Magellanic Clouds and what an observer there might see of the Milky Way, consider a much darker scenario. A galaxy called ESO 137-001 is in headlong flight toward the center of the galactic cluster Abell 3627. It is leaving in its wake a trail of gas that extends for more than 200,000 light years and is forming stars. Bear in mind that the Milky Way itself is 100,000 light years across and you'll get an idea of the magnitude of this tail, which Michigan State's Ming Sun calls one of the longest of its kind his team has ever seen. Millions of stars have now come to life in the tail, apparently forming within the last ten million years. Adding to optical studies are Chandra X-ray data that show additional regions thought to be star-bearing. Give these stars a few billion years to produce planets bearing intelligent life and you have a civilization coming into its own with skies that...

Tau Ceti: Life Amidst Catastrophe?

by Paul Gilster | Sep 20, 2007 | Astrobiology and SETI | 11 Comments

Tau Ceti has always been an interesting star, one of two (the other being Epsilon Eridani) that Frank Drake chose as targets for his pioneering Project Ozma SETI observations. The astrobiological interest is understandable. We're dealing with a Sun-like star relatively close (11.9 light years) to Earth. But recent thinking downplays Tau Ceti as a potential home for life. Ponder this: The dust disk around the star seems vastly larger than what we find in our own Kuiper Belt, with deadly implications. Or are they? Let's look more closely. A model of Tau Ceti's disk shows that the mass of small objects up to ten kilometers in size may total 1.2 Earth masses. Compared to our Kuiper Belt's 0.1 Earth masses, this is one massive disk, with ten times the amount of cometary and asteroidal material found in our own system. This despite the fact that Tau Ceti seems to be twice the age of Sol. You might reasonably assume that any Earth-like planet in this system has been bombarded far more often...

Neon: Unexpected Find May Flag Planets

by Paul Gilster | Sep 19, 2007 | Exoplanetary Science | 7 Comments

Neon isn't an unusual find in spectroscopic studies of massive stars or, for that matter, in observations of novae or the galactic core. Energetic X-ray or ultraviolet emissions can ionize the gas, at which point it produces infrared light at characteristic wavelengths. Not expecting to find it around low-mass stars like our Sun, researchers have been surprised to find four Sun-like stars showing neon in their disks as measured by a Spitzer Space Telescope project run by the University of Arizona. That project, called Formation and Evolution of Planetary Systems (FEPS) is run out of Steward Observatory. The idea is to study planet-forming gas around 35 young, solar-type stars. Before this work, none of these stars would have been thought energetic enough to radiate the amount of X-ray and ultraviolet light needed to ionize neon. Unexpected though they might be, the observations are useful because neon, while hardly abundant, offers a precise spectral signature that makes it easier...

Re-Thinking the Magellanic Clouds

by Paul Gilster | Sep 18, 2007 | Deep Sky Astronomy & Telescopes | 10 Comments

Centauri Dreams has always been captivated with the Magellanic Clouds, two galaxies that are the Milky Way's nearest neighbors in space. The fascination is in many respects visual. Knowing that they're a beautiful sight to those below the equator, the counter-thought came quickly to mind -- what would the Milky Way look like from one of these small satellite galaxies? How bright would it be, how much of the sky would it fill? While pondering such questions, have a look at the Large Magellanic Cloud below, and be sure to click to enlarge this gorgeous image. Pondering such things, I wrote a story called "Magellanic," a sort of Weird Tales-era fantasy (I realize that Weird Tales still exists, but I refer to the fabled issues of the 20's and 30's). Mixing in a first contact scenario in 1920's Tibet, a mountain-climbing adventurer at the end of his career, a bit of intelligence agency intrigue and throwing in Edwin Hubble for good measure, I thought I had a winner, but the story remained...

« Older Entries

Next Entries »

Charter

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).

Now Reading

On Comments

If you'd like to submit a comment for possible publication on Centauri Dreams, I will be glad to consider it. The primary criterion is that comments contribute meaningfully to the debate. Among other criteria for selection: Comments must be on topic, directly related to the post in question, must use appropriate language, and must not be abusive to others. Civility counts. In addition, a valid email address is required for a comment to be considered. Centauri Dreams is emphatically not a soapbox for political or religious views submitted by individuals or organizations. A long form of the policy can be viewed on the Administrative page. The short form is this: If your comment is not on topic and respectful to others, I'm probably not going to run it.

Follow by E-Mail

Advanced Propulsion Research