Archives

Using the Transit Method for SETI Detections

by Paul Gilster | Mar 31, 2005 | Astrobiology and SETI | 2 Comments

Every study using transit methods to detect objects around other stars is looking for planets. But a paper by Luc Arnold (Observatoire de Haute-Provence, France), soon to be published in The Astrophysical Journal, suggests that the same methods could be employed to find artificial planet-sized objects in orbit around stars. Arnold sees this as a possible SETI ploy, for transits of multiple objects could be used to emit signals that might be detected by other civilizations. What would such objects be? Giant solar sails, perhaps, or huge low-density structures of other configuration built purposely as a means of interstellar communication. Arnold's work inevitably recalls Freeman Dyson's 1960 Science article "Search for Artificial Stellar Sources of Infrared Radiation," which developed the idea that would later be known as a Dyson Sphere, an artificial cluster of rotating objects the size of a planetary orbit that would collect almost all the solar energy available and create a vast...

A New Take on Artificial Intelligence

by Paul Gilster | Mar 30, 2005 | Autonomy and Robotics | 0 Comments

An intelligent computer that can operate autonomously is the heart of any interstellar robotic probe. In an important sense, it would be the probe, running its systems, adjusting its course, repairing damage, conducting experiments and choosing the future direction of its own research. We're a long way from such autonomy, but a new company called Numenta may be laying some of the groundwork. The firm plans to use the theories of Jeff Hawkins, inventor of the PalmPilot and co-founder of Palm Computing and Handspring, to create hardware that can think and learn like a human brain. Hawkins' theories appeared in his recent book On Intelligence, and surfaced again at the PC Forum conference in Scottsdale AZ, where he explained his plans in some detail, as discussed in a recent story by Erick Schonfeld in Business 2.0. Hawkins believes the brain's basic function is to store patterns, creating a model of the world that is constantly being used as a reference that can predict what will...

Looking for Life Around Red Giants

by Paul Gilster | Mar 29, 2005 | Astrobiology and SETI, Exoplanetary Science | 3 Comments

Should we narrow the search for life-bearing planets to Sun-like stars? The answer may be 'no' if we take age into account, according to a new study from an international team of astronomers. Stars well into their red-giant phase may have actually revived outer, icy planets to offer them a chance at developing living ecosystems of their own. This happens because stars become brighter as they get older, pushing their habitable zones deeper into any planetary system they possess. The study considered the aging process of stars having the same mass as the Sun, and also considered stars with 1.5 and 2 times its mass. "Our result indicates that searches for life-giving worlds outside our solar system should include planets around old stars," said Dr. Bruno Lopez of the Observatoire de la Cote d'Azur, Nice, France. Lopez is lead author of a paper on this research that is to appear in The Astrophysical Journal. That puts more than 150 red giants within 100 light years on a list of possible...

‘Deep Impact’ Mission in Cruise Phase

by Paul Gilster | Mar 28, 2005 | Outer Solar System | 0 Comments

NASA's Hubble, Spitzer and Chandra space telescopes will all be watching in July when the Deep Impact spacecraft releases its impactor module (about the size of a coffee table) into the path of onrushing comet Tempel 1. Deep Impact's flyby module will be watching, too, as the impactor creates a crater that may be anywhere from two to fourteen stories deep, releasing cometary dust and ice and exposing underlying materials that have remained unchanged since the formation of the Solar System. Now in the cruise phase of its flight, Deep Impact has been through a test of its autonomous navigation system, and its high gain antenna is operating nominally. A mission status report provides some details about the early stages of the flight, when critical subsystems were put through their paces: Another event during commissioning phase was the bake-out heating of the spacecraft's High Resolution Instrument (HRI) to remove normal residual moisture from its barrel. The moisture was a result of...

Out onto the Wine-Dark Sea

by Paul Gilster | Mar 26, 2005 | Culture and Society | 0 Comments

"From time to time, alarm has been expressed at the danger of a 'sensory deprivation' in space. Astronauts on long journeys, it has been suggested, will suffer the symptoms that afflict men who are cut off from their environment by being shut up in darkened, soundproofed rooms. "I would reverse this argument: our culture will suffer from sensory deprivation if it does not go into space. There is striking evidence of this in what has already happened to the astronomers and physicists. As soon as they were able to rise above the atmosphere, a new and often surprising universe was opened up to them, far richer and more complex than had ever been suspected from ground observations. Even the most enthusiastic proponents of space research never imagined just how valuable satellites would actually turn out to be, and there is a profound symbolism in this. "But the facts and statistics of science, priceless as they are, tell only a part of the story. Across the seas of space lie the new raw...

Survey Finds Mysterious ‘Dark Accelerators’

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

The central part of the Milky Way has never been surveyed in gamma ray wavelengths with the sensitivity offered by HESS, the High Energy Stereoscopic System. And as announced in the March 25th issue of Science, the HESS team has not only found eight new very high energy (VHE) gamma ray sources in the galactic disk, thus doubling the number of known sources, but has also discovered two 'dark accelerators,' objects that emit energetic particles but have no known optical or x-ray counterpart. It takes a particle accelerator of cosmic proportions to produce gamma rays, such as the explosion of a supernova. But such sources should be visible in other wavelengths. Says Dr. Paula Chadwick of the University of Durham (UK): "Many of the new objects seem to be known categories of sources, such as supernova remnants and pulsar wind nebulae. Data on these objects will help us to understand particle acceleration in our galaxy in more detail; but finding these 'dark accelerators' was a surprise....

Defining Habitable Zones in the Galaxy

by Paul Gilster | Mar 24, 2005 | Astrobiology and SETI | 0 Comments

When is a planet habitable? The assumption, in studies of the 'circumstellar habitable zone' (CHZ) ranging back as far as 150 years, is that a planet is habitable if liquid water can be maintained on its surface. That this is a 'life as we know it' scenario is obvious: it works best if you assume a planetary system not so different from our own, one with roughly the same configuration of planets (gas giants in outer orbits, rocky worlds in close). Venus and Mars have served as test cases of the boundaries of habitable zones. But our view of habitable zones is evolving. I relied on Stephen Dole's groundbreaking study Habitable Planets for Man (New York: Blaisdell Publishing Company 1964) in Centauri Dreams. Dole's work was prepared for the RAND Corporation, and was released in popularized form as Planets for Man, in collaboration with Isaac Asimov (New York: Random House, 1964). Dole defined a stellar ecosphere as ". . . a region in space, in the vicinity of a star, in which suitable...

The Light of Distant Worlds

by Paul Gilster | Mar 23, 2005 | Exoplanetary Science | 1 Comment

As discussed in yesterday's entry, being able to work with actual light from distant planets is a major breakthrough. It opens the possibility of studying characteristics like temperature and atmospheric composition, further fusing astronomy with the nascent science of astrobiology. And with the Spitzer Space Telescope's proven ability to make such observations, we can expect a whirlwind of exoplanetary data ahead. A few further details from yesterday's announcements: A study of the work on HD 209458b, a 'hot Jupiter' that orbits its parent star in 3.5 days, ran in today's online edition of Nature. The paper is Deming, D., Seager, S. et al., "Infrared radiation from an extrasolar planet." Dr. Sara Seager of the Carnegie Institution, a co-author of the study, provided more about HD 209458b: "This planet was discovered indirectly in 1999 and was later found to transit its star--the star dims as the planet moves in front of it during the course of the planet's orbit. With Spitzer, we...

Confirmed Detection of Extrasolar Planets’ Light

by Paul Gilster | Mar 22, 2005 | Exoplanetary Science | 0 Comments

Light from two planets orbiting other stars has now been directly detected by the Spitzer Space Telescope, in findings announced today at a NASA news conference. Spitzer scrutinized both planets using the 'transit' method, in which a planet eclipses its star and blocks a small fraction of its light. The space-based telescope has been able to detect not only the primary transit but the secondary eclipse, occurring when a planet comes out from behind its star on the far side of its orbit. It thus became possible for astronomers to subtract the planetary 'signal' from the otherwise overwhelming light of the parent star, the first confirmed detection of the light from extrasolar worlds. Both planets fall into the category of 'hot Jupiters' -- massive worlds that orbit at extremely close distances from their primaries. The first (studied with Spitzer's Infrared Array Camera) is TrES-1, orbiting its star at a distance of four million miles and boasting a temperature of 1340 degrees...

Extrasolar Planet Announcement Moved to Today

by Paul Gilster | Mar 22, 2005 | Exoplanetary Science | 0 Comments

"Astronomers will announce major findings about planets outside our solar system, known as extrasolar planets, at a NASA Science Update at 3 p.m. EST today." So says a media advisory just out from the agency. NASA TV plans to carry the event, which will discuss discoveries made by the Spitzer Space Telescope. The panelists: Dr. Drake Deming, chief, planetary systems laboratory, NASA's Goddard Space Flight Center, Greenbelt, Md. Dr. David Charbonneau, assistant professor of astronomy, Harvard-Smithsonian Center for Astrophysics, Cambridge, Mass. Dr. Alan Boss, staff research astronomer, Department of Terrestrial Magnetism, Carnegie Institution of Washington Dr. Kim Weaver, moderator; Spitzer program scientist, NASA's Science Mission Directorate, Washington.

Tweaking Einstein on the Nature of Light

by Paul Gilster | Mar 22, 2005 | Breakthrough Propulsion | 2 Comments

It makes sense to this former Midwesterner that Alan Kostelecky can compare light to waves propagating across a field of grain. After all, Kostelecky works at Indiana University, in a state where fields of grain are not so far from view. The theoretical physicist argues in research published online today in Physical Review D that we could consider light as the result of small violations of relativity, which compare not only to waving wheat but to "...a shimmering of ever-present vectors in empty space." Having seen my share of winds rippling across wheat fields, I know one thing: a propagating wave in a nearby crop comes with a sense of directionality. You know which way the wind is coming from, and how it's affecting the local environment. Thinking of light in such terms is a far cry from a view with a much longer pedigree, that light depends upon an an underlying symmetry that is built into nature itself. Think of symmetry this way: Spacetime in the Einstein model has no preferred...

Puzzling Stars in Omega Centauri

by Paul Gilster | Mar 21, 2005 | Deep Sky Astronomy & Telescopes, Exoplanetary Science | 6 Comments

Globular clusters are vast cities of tens of thousands of stars, traditionally thought to have been formed from a single interstellar cloud at roughly the same time. But Omega Centauri is different. As viewed by Hubble, this southern cluster (15,000 light years away in the direction of the constellation Centaurus) contains two separate stellar populations. Its blue stars, about one quarter of the total, are well outnumbered by a second hydrogen-burning population of redder stars. Now the European Southern Observatory's Very Large Telescope has collected data that show the blue stars, contrary to expectation, are metal-rich when compared to their red counterparts, meaning they include elements heavier than hydrogen and helium. Astronomers call elements heavier than helium 'metals' -- the Sun, for example, is made up of 70 percent hydrogen and 28 percent helium, with the remaining two percent being classed as metals. Current theories of star formation suggest that as metallicity...

Surprise at Enceladus

by Paul Gilster | Mar 19, 2005 | Outer Solar System | 0 Comments

How does a moon that would fit within the state boundaries of Arizona manage to hold an atmosphere? That's the question following Cassini's most recent flyby of Enceladus. The spacecraft found magnetic field oscillations that scientists now attribute to ionized water vapor. The odd magnetic field signature has shown up on both Cassini flybys, the second of which, on March 9, came to within 500 kilometers of the Saturnian moon's surface. Image: This artist conception shows the detection of an atmosphere on Saturn's icy moon Enceladus. The Cassini magnetometer instrument is designed to measure the magnitude and direction of the magnetic fields of Saturn and its moons. During Cassini's two close flybys of Enceladus -- Feb. 17 and March 9 -- the instrument detected a bending of the magnetic field around Enceladus. Credit: NASA/JPL. Because Enceladus is too small to hold an atmosphere for long, a continuous source of replenishment is suspected. The most likely candidate: volcanoes or...

On Propulsion, Dark Energy, and Humility

by Paul Gilster | Mar 18, 2005 | Breakthrough Propulsion, Deep Sky Astronomy & Telescopes | 1 Comment

Exotic forms of propulsion like warp drives or journeys through wormholes often seem like pure fantasy. It was Harvard's Edward Purcell, no stranger to the study of the cosmos through his work as a radio astronomer, who made the classic negative case: "All this stuff about traveling around the universe in space suits -- except for local exploration which I have not discussed -- belongs back where it came from, on the cereal box." But then humility returns and we realize how little we know. It would have astounded Purcell, as it astounds Centauri Dreams, to think that 70 percent of the universe is now considered to be 'dark energy,' the exact nature of which mystifies our greatest thinkers other than to say that without it, the universe would not be continuing to expand -- and accelerating its expansion, at that. And, of course, another 25 percent of the universe is equally bizarre, the so-called 'dark matter' that seems to pervade the cosmos. So our notions of interstellar flight...

New Exoplanet Findings Promised for Next Week

by Paul Gilster | Mar 17, 2005 | Exoplanetary Science | 0 Comments

NASA will announce "... major findings about planets outside our solar system..." in a press conference to be held at 1 PM EST on Wednesday March 23. NASA TV is planning to cover the event live. The new data come from the Spitzer Space Telescope, which works in the infrared and most recently made the news with its findings of remarkably bright galaxies hidden by dust some 11 billion light years away. The NASA press release can be read here.

Using Desktop PCs to Find Planets

by Paul Gilster | Mar 17, 2005 | Exoplanetary Science | 0 Comments

PlanetQuest is a distributed computing project aimed at using spare computer cycles to search for extrasolar planets. The search will use the transit method, in which a planet is detected when it crosses the face of its primary as seen from Earth. That requires subjecting the data from thousand of stellar images to analysis, a job that would tax the largest supercomputer, but perhaps not the kind of distributed network that SETI@Home has already put to work in its search for extraterrestrial intelligence. Nobody knows for sure how many stars have planets that line up edge-on to our own line of sight, but estimates run between 0.5 and 10 percent. Instead of studying a single star for long periods, as is done in the radial velocity method that has found most extrasolar planets so far, the transit approach has to rely on images of highly crowded star regions, where tens of thousands of stars can be viewed at once. The best area, then, is in the plane of the Milky Way. Stars captured in...

Autonomy and the Hunt for Life

by Paul Gilster | Mar 16, 2005 | Astrobiology and SETI, Autonomy and Robotics | 0 Comments

As our space probes go deeper into the Solar System and beyond, they'll be required to become fully autonomous, making decisions about courses of action in space or on distant planetary surfaces. Each time we test a technology in a nearby environment, we're building toward such autonomy. Consider the announcement that Carnegie Mellon scientists have discovered life with an automated rover -- life here on Earth, that is. The scene is Chile's Atacama Desert, a harsh, dry region that acts as a surrogate for the even more hostile Martian terrain. "Life in the Atacama" is a three-year program designed to develop techniques for life detection via remote sensing. The group chose the region because it is one of the most arid on Earth, where rain is so rare that it is measured in millimeters per decade, and the high elevation makes solar radiation intense. Here, a rover named Zoë is deploying new technologies in the hunt for life. Carnegie Mellon's Alan Waggoner has been presenting...

European Space Agency Eyes Europa

by Paul Gilster | Mar 15, 2005 | Missions, Outer Solar System | 1 Comment

With the Jupiter Icy Moons Orbiter (JIMO) on hold, NASA is talking to the European Space Agency about a possible joint mission to Europa. A BBC story reports that a prime driver for ESA is the need to use radioisotope thermal generators (RTGs) on the mission, a power source with which the Europeans have little experience. RTGs are needed on missions to the outer planets because they increase the power available to the spacecraft, allowing for a wider range of experiments with more sophisticated instruments. Solar panels remain an option in Jupiter space, but aren't nearly as effective. The other driver, of course, is the recent success of the Cassini/Huygens combined mission, whose stunning images of the Saturnian system and data from the Titan descent and landing have many scientists now thinking of Europa. The moon's cracked ice seems to have been shaped by tidal forces from Jupiter, with reason to believe that an ocean of liquid water might be found beneath an ice crust tens of...

Pluto/Charon Mission Taking Shape

by Paul Gilster | Mar 14, 2005 | Missions, Outer Solar System | 0 Comments

January 11 to February 14, 2006 marks the launch window for NASA's New Horizons mission to Pluto and the Kuiper Belt. At the moment, New Horizons is in pieces, or as principal investigator Alan Stern puts it in an update on the mission, it's in "...boards, boxes and a spacecraft bus on the cleanroom floor at the Johns Hopkins Applied Physics Laboratory..." The high-gain antenna is being checked, and the main computer system installed. According to Stern: The bird also received a guidance, navigation and control software load, and the first testing of the autonomy system (that provides for fault protection) has taken place. Coming soon to the spacecraft are the redundant flight computer, the gyros and the Ralph remote-sensing package. We are now approaching the time - only weeks away - when the last avionics box goes on the spacecraft and New Horizons is dressed in thermal blankets for environmental testing in a large vacuum chamber at NASA Goddard Space Flight Center. New Horizons...

Finding Dark Energy in the Data

by Paul Gilster | Mar 12, 2005 | Deep Sky Astronomy & Telescopes | 0 Comments

We always thought that the real impetus to the theory of 'dark energy' came from the discovery that the expansion of the universe seems to be accelerating. But an article in New Scientist points out that Allan Sandage (Carnegie Observatories, Pasadena) had studied evidence that might have led to the theory of dark energy way back in 1972. Sandage was working with 'peculiar velocities,' deviations in the normal rate of cosmic expansion caused by the gravitational pull between groups and clusters of galaxies. And he had seen that galaxies just outside the Local Group showed velocities that were below what was expected. Fabio Governato of the University of Washington has now plugged dark energy into a computer model of galaxy formation and finds that this force matches nicely with the peculiar velocities for galaxies in regions like the Local Group. The Sandage data plus the new computer model, it can be argued, point to dark energy. You can find an abstract of Governato's study, "The...

« Older 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