Archives

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...

Voyager Interstellar Mission in Jeopardy

by Paul Gilster | Mar 11, 2005 | Missions | 0 Comments

Nature is reporting that the two Voyager missions -- recently discussed here as our first active probes of the interstellar medium, if they live long enough to cross the heliospheric boundary -- may be terminated in October. The decision is not yet final, and there is always the hope that it will spur enough reaction among space scientists and others to force a reprieve. But if these missions end (along with six others, including Ulysses), the loss to science would be severe. Voyager 1 is the fastest man-made object, now leaving the Sun behind at over 17 kilometers per second, at a current distance of approximately 94 AU (14 billion kilometers from Earth). Voyager 2 is roughly 76 AU out. Both spacecraft should be able to continue transmitting until 2020 or later. At $4.2 million per year, the Voyager program catches NASA's eye as the agency ponders budgetary cutbacks. But to shut down two operational spacecraft as they approach the interstellar medium for the first time in history is...

Titan’s Complex Surface Analyzed

by Paul Gilster | Mar 10, 2005 | Outer Solar System | 0 Comments

The Cassini Imaging Team has published its first findings about Titan in the journal Nature. The complexity of Titan's surface and the extent to which it is continually modified draws the most attention. Where are the craters that should have pocked its surface over the past billion years? Thanks to Cassini/Huygens, some answers are beginning to emerge. Working with the last eight months of imagery from the orbiter, the team reports that thirty percent of the satellite's surface has now been mapped with resolutions high enough to pick out features as small as one to ten kilometers. From a press release from the Cassini Imaging Central Laboratory for Operations (CICLOPS): At this scale, what has been discovered are geologically young terrains with signs of tectonic resurfacing, erosion by liquid hydrocarbons, streaking of the surface materials by winds and only a few large circular features thought to be impact craters formed in the ice 'bedrock'. (The largest of these - a...

Speaking Up to Hans Bethe: An Appreciation

by Paul Gilster | Mar 9, 2005 | Culture and Society | 0 Comments

The death of Hans Bethe has been covered by the media worldwide, and William J. Broad's obituary in the New York Times seems among the most thorough and accurate of the accounts of his life. But to me, Bethe will always be seen through Richard Feynman's eyes, and I think Broad misses the point of the one Feynman anecdote he tells. Feynman first worked with Bethe at Los Alamos during the days of the Manhattan Project, and he recalls the physicist's openness to debate, and his focus on the issue at hand rather than personality. Here, Feynman has just arrived in Los Alamos, and work had just begun, as told in the wonderful Surely You're Joking, Mr. Feynman! (New York: W.W. Norton, 1984): "Every day I would study and read, study and read. It was a very hectic time. But I had some luck. All the big shots except for Hans Bethe happened to be away at the time, and what Bethe needed was someone to talk to, to push his ideas against. Well, he comes in to this little squirt in an office and...

Charting the Boundaries of the Heliosphere

by Paul Gilster | Mar 9, 2005 | Missions, Outer Solar System | 0 Comments

Has Voyager 1 left the heliosphere? The question is a reminder that the Voyagers are our first interstellar probes; they'll still be returning data when they move into the interstellar medium. The heliosphere is a kind of bubble created by the solar wind from the Sun, that stream of high-speed charged particles constantly blowing into space at roughly 400 kilometers per second. Observing how Voyager 1 makes the transition across the boundary of the heliosphere will provide our first in situ study of interstellar space. Some scientists believe that at roughly 90 AU from the Sun, Voyager 1 has already pushed up against the 'termination shock,' that region where the speed of the solar wind drops to subsonic levels. Now new data studied by French and Finnish researchers indicate that the shape of the heliosphere may be distorted, further complicating the question of just where the true interstellar medium begins. Rosine Lallement and colleagues used data collected by the Solar and...

Plasma in a Bubble

by Paul Gilster | Mar 8, 2005 | Advanced Rocketry | 0 Comments

Sonoluminescence -- the emission of light from bubbles in a liquid that has been excited by sound -- is a mystery. How does a sound wave put enough energy into such a small volume as to cause light to be emitted? The concentration of energy needed is something like a factor of one trillion, according to this Los Alamos National Laboratory introduction to the phenomenon. And not only that; the spectrum of the emitted light implies extremely high temperatures. Fusion, anyone? Well, not yet. But the slang term for sonoluminescence, 'star in a jar,' seems a little closer to reality now that the first direct measurements of the phenomenon are in. They show that the temperature inside a collapsing bubble can reach 20,000 degrees Kelvin, which is four times the temperature of the surface of the Sun. This work, by Ken Suslick and David Flannigan (University of Illinois at Urbana-Champaign), comes two years after controversial findings by an Oak Ridge National Laboratory team that found...

Toward an Active SETI

by Paul Gilster | Mar 7, 2005 | Astrobiology and SETI | 3 Comments

The search for extraterrestrial intelligence is, some would say, too passive -- it's pure listening, monitoring radio and, in some cases, optical wavelengths in hopes of intercepting either a message from another civilization or, perhaps, catching a snippet of its internal communications. But is there a place for an active SETI, one that is just as anxious to send a human message to the stars as to listen for the broadcasts of others? Not that there haven't been previous attempts to send signals, the most famous of which was the 1974 Arecibo message beamed in the direction of M13, a globular cluster in the constellation Hercules. The Hercules message, containing binary representations of the human form, the solar system, and other mathematical and chemical information, pushes us into the domain of long-term thinking, for it will take 25,000 years to reach its target (and, obviously, another 25,000 years for any reply). But M13 is also an interesting place to send a signal, for it is...

In Search of the Mad Rocketeer

by Paul Gilster | Mar 5, 2005 | Culture and Society | 0 Comments

It seems fitting that the crater named Parsons is on the Moon's dark side. It's named after John W. Parsons, a youthful rocket builder who joined Texan Frank Malina in the early experiments that would lead to the creation of the Jet Propulsion Laboratory. Parsons, Malina and a childhood friend named Ed Forman patched together equipment from junkyards and at one point tried to script a movie about going to the Moon, hoping that selling it to Hollywood would fund their idea of launching a rocket to Earth's upper atmosphere. The three formed the Rocket Research Group at the Guggenheim Aeronautical Laboratory at Caltech, where Theodore von Kármán, the Laboratory's director, gave them lab space and campus equipment to pursue their dreams. This was back in the 1930's, when the group's rocket motors were being tested at the Arroyo Seco near Pasadena. Around that time, Chinese graduate student Tsien Hsue-shen (who would go on to become the father of Chinese rocketry) joined the team,...

Tiny Star Complicates Search for Exoplanets

by Paul Gilster | Mar 4, 2005 | Exoplanetary Science | 1 Comment

Can a star look like a planet? Evidently so, to judge from observations of the star OGLE-TR-122. Astronomers working at the European Southern Observatory's Paranal Observatory in Chile have discovered that the star experiences a drop in brightness every 7 days 6 hours and 27 minutes, a strong indication (when combined with radial velocity measurements) that a low-mass star is regularly moving in front of its larger companion as seen from Earth. Measuring radial velocity allows scientists to discriminate between stars and planets as the cause of the brightness variations. The OGLE (Optical Gravitational Lensing Experiment) survey has been studying changes in the brightness of stars that could be caused by the transit of such unseen companions. And this one, christened OGLE-TR-122b, turns out to be a rarity indeed. It adds up to one-eleventh of the Sun's mass, making it the smallest known star, only 16 percent larger than Jupiter though 96 times as massive as that planet. "This result...

Hunting for Planets Around Epsilon Eridani

by Paul Gilster | Mar 3, 2005 | Deep Sky Astronomy & Telescopes, Exoplanetary Science | 0 Comments

The image below is Epsilon Eridani, some 10.5 light years from Earth, as seen in the infrared by the Spitzer Space Telescope. We have evidence of the existence of at least one planet around the star, orbiting at 3.4 AU, but subsequent attempts to detect other planets have thus far failed. However, a debris disk, detected at radio frequencies, is known to exist, and it provides evidence of other planets based on perturbations in the dust and rocks of the disk itself. Epsilon Eridani is a comparatively young star (730 million years old), and so provides a useful case study of a solar system in formation. The Spitzer photograph comes courtesy of Massimo Marengo, who heads a team that is using the Spitzer instrument to detect Epsilon Eridani's unseen companions. In this ongoing study, working especially with Spitzer's Infrared Array Camera (IRAC), the team has developed methods of light subtraction that can suppress most of the light from the central star, allowing the detection of...

Of Brown Dwarfs and Habitable Worlds

by Paul Gilster | Mar 2, 2005 | Exoplanetary Science | 0 Comments

A story in a recent issue of New Scientist covers the possibility of planets around brown dwarfs, focusing on the work of Kevin Luhman of the Harvard-Smithsonian Center for Astrophysics. Centauri Dreams looked at this study in a previous posting, but writer Hazel Muir adds a further comment on habitability around such worlds based on Luhman's work: It is conceivable that such planets, if they form, could be habitable. The surface temperature of the mini brown dwarf is 2300 kelvin, so a planet 1.5 to 7 million kilometres away could host liquid water. Planets very close to a brown dwarf would be scorched at first, but would become hospitable as the star cooled. Brown dwarfs take a long time to cool, so the planet could remain habitable long enough for life to evolve. Another thought, from Andrew Collier Cameron at the University of St. Andrews in the UK, who is quoted in the article: brown dwarfs might be useful hunting grounds for exoplanets, given the faintness of the brown dwarf...

Kurt Gödel and the Spacetime Continuum

by Paul Gilster | Mar 2, 2005 | Culture and Society | 0 Comments

Be aware of Time Bandits, an article by Jim Holt in the March 2 New Yorker, which studies the relationship between Albert Einstein and mathematician Kurt Gödel, now best known for his incompleteness theorems. The first of these, as Holt writes, "...demonstrates that no logical system can capture all the truths of mathematics." Here's a sample from this fascinating piece, discussing what happened when Gödel took on the relationship of space and time: What Gödel found was the possibility of a hitherto unimaginable kind of universe. The equations of general relativity can be solved in a variety of ways. Each solution is, in effect, a model of how the universe might be. Einstein, who believed on philosophical grounds that the universe was eternal and unchanging, had tinkered with his equations so that they would yield such a model—a move he later called "my greatest blunder." Another physicist (a Jesuit priest, as it happens) found a solution corresponding to an expanding universe...

« 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