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Yet Another Puzzle from Enceladus

by Paul Gilster | May 31, 2006 | Outer Solar System | 2 Comments

Enceladus continues to be an unlikely story, a tiny Saturnian moon jetting icy plumes of what seems to be water vapor from the surface of its south pole. Some believe there is even the potential for life here. But how did the 'hot spot' that produces this activity wind up precisely at the pole? We'll know more through future Cassini measurements, but a new study suggests that such a low-density region could cause the moon to roll over, thus moving this material to the polar area while repositioning excess mass at the equator. What's more, the bizarre Uranian moon Miranda may bear witness to the same phenomenon. The theory seems to gibe with other aspects of Enceladus including the surface features Cassini has so vividly imaged. The famous 'tiger stripe' pattern gives evidence of being made up of fault lines caused by tectonic stress. And the temperature variation at the pole also reinforces the reorientation concept. "The whole area is hotter than the rest of the moon, and the...

Science at the Edge of the Solar System

by Paul Gilster | May 30, 2006 | Interstellar Medium, Missions | 1 Comment

The Interstellar Boundary Explorer is clearly a mission whose time has come. Scheduled for launch in 2008 and recently confirmed for mission implementation, IBEX will provide global maps of the distant interactions where the heliosphere (the 'bubble' of space carved out by the solar wind) meets the interstellar medium. All of this at a time when Voyager 1 is thought in some quarters to have already crossed the 'termination shock,' that region where the solar wind is slowed as it encounters interstellar gases; some evidence suggests that the spacecraft then moved back into the supersonic solar wind. Image: The Sun's movement through the local interstellar medium. IBEX should tell us much about the boundary separating the heliosphere from this region. Credit: Southwest Research Institute. The Voyager findings remain controversial thanks to magnetic field and cosmic ray measurements that suggest different interpretations, but it's clear that Voyager is at the very edge of the...

Astrobiology Lectures Available Online

by Paul Gilster | May 29, 2006 | Research Tools | 0 Comments

Centauri Dreams continues to champion innovative tools that get scientific findings out to a broader audience. On that score, be aware of QCShow, a freely downloadable player that synchronizes PowerPoint and PDF presentation materials with audio. We've discussed this software before, when QCShow's parent company, New Mexico-based AICS Research, made sessions from NASA's Institute for Advanced Concepts meeting in 2005 available. Now a weekly series of recorded lectures on astrobiology has launched in this format. Short of attending a conference on astrobiology yourself, it would be hard to top the list of participants here. Planet hunter extraordinaire Geoff Marcy (University of California, Berkeley) leads off with a 52 minute talk entitled "Exoplanets, Yellowstone & the Prospects for Alien Life." As the discoverer of roughly 70 of the first 100 exoplanets to be found, Marcy's thoughts on planetary diversity and its implications for life are well worth hearing, but he's followed up in...

Two Thoughts for the Weekend

by Paul Gilster | May 27, 2006 | Culture and Society | 9 Comments

"Advanced societies throughout the galaxy probably are in contact with one another, such contact being one of their chief interests. They have already probed the life histories of the stars and other of nature's secrets. The only novelty left would be to delve into the experience of others. What are the novels? What are the art histories? What are the anthropological problems of those distant stars? This is the kind of material that these remote philosophers have been chewing over for a long time..." -- Philip Morrison (1961) "Will we be able to understand the science of another civilization?... Our science has concentrated on asking certain questions at the expense of others, although this is so woven into the fabric of our knowledge that we are generally unaware of it. In another world, the basic questions may have been asked differently." -- J. Robert Oppenheimer (1962)

Of ‘Braneworlds’ and Nearby Black Holes

by Paul Gilster | May 26, 2006 | Deep Sky Astronomy & Telescopes, Exotic Physics | 26 Comments

We're familiar with four dimensions, three spatial and one temporal. But is there a fourth dimension to space? If so, it implies a new way of looking at gravity. So say physicists Lisa Randall (Harvard University) and Raman Sundrum (Johns Hopkins), who have offered a mathematical description of how gravity's actual effects might differ from those predicted by Einstein's General Theory of Relativity. That fourth spatial dimension follows from the theory these two have developed called the type II Randall-Sundrum braneworld gravity model. It suggests that the universe is a membrane, or 'braneworld,' embedded within a much larger universe. Centauri Dreams admires robust theorizing but has always hoped to see solid observational clues that would make such hypotheses testable. And it may be that one has now emerged, in the hands of Charles Keeton (Rutgers) and Arlie Petters (Duke University), who used the Randall-Sundrum model to predict certain cosmological effects that could provide...

Gravitational Lensing Writ Large

by Paul Gilster | May 25, 2006 | Deep Sky Astronomy & Telescopes, Missions | 2 Comments

Here's gravitational lensing with an exclamation point. A single quasar is shown in the Hubble photograph below as five star-like points. Gravitational lensing occurs when the gravitational field of a massive object bends and amplifies the light from a much further object behind it. And although we've had numerous examples of such lensing, this is the first time the intervening object was an entire galactic cluster. Image: Five star-like images are actually a single distant quasar. Credit: ESA, NASA, K. Sharon (Tel Aviv University) and E. Ofek (Caltech). The cluster in question is SDSS J1004+4112, some seven billion light years away; the quaser is roughly ten billion light years distant. It took spectral data from the Keck I 10-meter telescope to demonstrate that these images were all of the same quasar. The quasar itself is the core of a galaxy, with a black hole at its center creating its intense light by interactions with nearby gas and dust. Note too in this picture the images of...

A Provocative Antimatter Strategy

by Paul Gilster | May 23, 2006 | Antimatter | 5 Comments

Ponder how difficult current antimatter work is. We produce the stuff in our particle accelerators and rely on extracting antiparticles from collision debris. One in about 105 proton collisions actually produces an antiproton that can be collected. This is why we see figures like $62.5 trillion per gram (some estimates are even higher) for antiproton production costs. Not only that, but once we have created antimatter, we have to store it in a vacuum in magnetic/electric fields to keep it from any contact with normal matter. All these are problems with using antimatter for propulsion. After all, it's one thing to store tiny amounts of antimatter in bulky Earth-based traps, and quite another to scale storage up to protect the antimatter from annihilation for a period of months or years, not to mention the need to transport it into orbit for uses in space. But as James Bickford (Draper Laboratory, Cambridge MA) and team point out, antimatter creation and storage in space seems more...

An All But Invisible Supernova

by Paul Gilster | May 22, 2006 | Deep Sky Astronomy & Telescopes | 0 Comments

What exactly is the object astronomers have discovered 30,000 light years away in the constellation Cepheus? The Spitzer Space Telescope found it, but the source only shows up in mid-infrared images as a re-orange blob. Scan the same region of sky in visible light or near-infrared and you see absolutely nothing, and x-ray and radio views of the same region have never betrayed the object. A stealth supernova? Apparently so, in the eyes of Patrick Morris (California Institute of Technology), who is lead author of a paper on the discovery in the April Astrophysical Journal Letters. And it's a fascinating find, because the average supernova (if there is such a thing) makes itself known by lighting up surrounding areas of dust. The new object is far from the galaxy's most crowded and dusty regions, so the gas and radiation it would have spewed into space had little to interact with. Image (click to enlarge): Unlike most supernova remnants, which are detectable at a variety of wavelengths...

New Collaboration Bags First Planet

by Paul Gilster | May 20, 2006 | Exoplanetary Science | 0 Comments

One of the most exciting things about the exoplanet hunt is that it isn't confined to huge observatories, nor does it demand bankrolling by billionaires. Consider the news that a team of professional and amateur astronomers has collaborated on a new planetary find, using off-the-shelf equipment and modest telescopes. The Jupiter-sized world orbits a Sun-like star some 600 light years away in the constellation Corona Borealis. The work is significant not just for the planet it discovered but for its implications for future collaborative work. Four amateurs worked with Peter McCullough of the Space Telescope Science Institute (Baltimore) to nail down the discovery. McCullough used a 200-millimeter telephoto camera lens mounted on an inexpensive device called the XO telescope on the summit of the Haleakala volcano in Hawaii (total cost for the equipment: roughly $60,000), while the amateurs contributed their own telescopes. Here's the search method: McCullough's XO telescope makes...

Kerala’s Unusual Rain

by Paul Gilster | May 19, 2006 | Astrobiology and SETI | 8 Comments

The red rain that fell in the Indian state of Kerala continues to create interest. Are the particles found suspended within it extraterrestrial in nature? The rain first fell on the 25th of July, 2001, but red rain phenomena continued to occur for two months thereafter, although in some cases other colors appeared, and there are reports of colored hailstones. This was no one-shot event. I've held off on this story hoping to get further information, but enough readers have asked for details that I'll go with what we now have. We know this much: The red color is caused by the mixing of microscopic red particles with the water, the characteristics of which are unusual. As noted by Godfrey Louis and Santhosh Kumar (Mahatma Gandhi University) in their paper on the subject, the particles vary from 4 to 10 microns in size and appear under magnification as red-colored glass beads. Electron microscope work shows them to have "...a fine structure similar to biological cells." And although they...

A Triple Planetary System and More

by Paul Gilster | May 18, 2006 | Exoplanetary Science | 5 Comments

Finding three planets around a single star is newsworthy in itself, but when the planets are Neptune-class things get more interesting. And when one of these worlds is found to be in the star's habitable zone, Centauri Dreams definitely drops everything for a closer look. Not only that, but the system around HD 69830, a Sun-like star some 41 light years away, is also the home of an asteroid belt, making the comparison with our Solar System that much closer. Here's what we know, as reported in a paper in the May 18 Nature: The orbital periods of the three planets are 8.67, 31.6 and 197 days, with that outer world located near the inner edge of the zone where liquid water could exist. In terms of mass, this planet is not Earth-like; in fact, the measurements show the new planets to be between 10 and 18 times the mass of Earth. So what we're probably detecting in the habitable zone is a planet with a rocky/icy core surrounded by a dense atmosphere. We know nothing, of course, about...

A Clear View of Distant Worlds

by Paul Gilster | May 17, 2006 | Exoplanetary Science | 4 Comments

Yesterday's post on UMBRAS and occulter technology focuses attention on the characteristics of light, some of them counter-intuitive but well demonstrated. And since we've also been talking recently about the nearby star Epsilon Eridani, I've chosen an image of that star to illustrate some of the problems with planetary detections. What you see below is via Massimo Marengo (Harvard-Smithsonian Center for Astrophysics), who has done such outstanding recent work on untangling the riddle of Epsilon Eridani's debris disk. This is a false color image with red, yellow, green and blue representing different infrared wavelengths. I ran the same image last summer, when Marengo posted it on his own weblog (he had used it to illustrate his team's work in a presentation at the American Astronomical Society meeting in San Diego). Image: A false-color infrared image of Epsilon Eridani. Credit: Massimo Marengo (CfA). What I want to single out here are the artifacts in the image. The red/orange...

Occulters and Their Uses: A Helpful Resource

by Paul Gilster | May 16, 2006 | Exoplanetary Science, Research Tools | 4 Comments

'Umbras' is Latin for 'shadows,' and it becomes a fitting acronym for projects to block the light of stars so that astronomers can see the planets around them. The unwound acronym is Umbral Missions Blocking Radiating Astronomical Sources, which refers to both an imaging technique and a class of space missions. The basic idea is this: deploy a space telescope flying in formation with a second, distant companion spacecraft that carries an occulting screen. We're looking for direct pictures of planets by reducing a star's glare, and there are a number of projects aimed at making them, including one we've discussed here many times, the New Worlds Imager mission championed by Webster Cash. I pulled both images in this post from the UMBRAS Web site, where these ideas are explored as a way of pooling talent in the disparate occulter community. Remember, almost everything we know about exoplanets has come from radial velocity studies, microlensing and planetary transits. At best, we are...

Probing the Epsilon Eridani System

by Paul Gilster | May 15, 2006 | Exoplanetary Science | 3 Comments

In Centauri Dreams' imagination, the name Epsilon Eridani is magic. Like many of us, my earliest speculations about life on other worlds always came back to the nearby, Sun-like stars like Tau Ceti, Epsilon Eridani and Centauri A and B. Frank Drake used the first two as his targets for Project Ozma in 1960, an effort that continues to inspire SETI work today. And Epsilon Eridani is joined by Vega, Fomalhaut and Beta Pictoris as the first stars found by the Infrared Astronomical Satellite (IRAS) to have a cool debris disk somewhat analogous to our own Kuiper Belt. The fact that this K2 star is likely to be orbited by the closest exoplanet to our Sun is also exciting. Its planet seems to be slightly larger than Jupiter, with estimates ranging from 0.8 to 1.6 Jupiter masses, and an eccentric orbit varying from 5.3 to 1.3 AU (here again we see how important it is to establish the effect of gas giants on terrestrial worlds in the habitable zone). At 10.5 light years from us, Epsilon...

A Universe Before the Big Bang

by Paul Gilster | May 13, 2006 | Exotic Physics | 4 Comments

We seem to be awash in exotic physics, an administrative category I created on this site only a couple of days ago to house the trillion-year crunch story and the 'light in reverse' work at the University of Rochester. It seems an appropriate time, then, to look at an investigation reported in the Physical Review Letters that takes us, like Alice through the looking glass, into the universe before the Big Bang. Penn State researchers are behind this study, combining quantum physics tools that Einstein didn't have with general relativity to punch through to a universe on the other side. So let's talk again about what might have been there before the Big Bang. This analysis says the previous universe had a spacetime geometry much like our own expanding universe, except that it was a contracting universe. Gravititational forces were pulling the previous universe together until the quantum properties of spacetime caused gravity itself to become repulsive. What follows is aptly described...

Faster than Light in Reverse?

by Paul Gilster | May 12, 2006 | Exotic Physics | 7 Comments

If you thought the trillion-year crunch was mind-boggling, how about light that moves backwards, and does so at speeds faster than c? From the University of Rochester comes word that Robert Boyd, a professor of optics there, has slowed light to negative speeds. To do this, the experimenter sent a pulse of laser light through an optical fiber laced with the element erbium. Leaving the laser, the light pulse was split, with one pulse going into the fiber and the other left undisturbed for reference. The remarkable result: The peak of the pulse emerged from the other end of the fiber before it entered the front of the fiber, and ahead of the reference pulse. "Through experiments we were able to see that the pulse inside the fiber was actually moving backward, linking the input and output pulses," says Boyd, who acknowledges "I've had some of the world's experts scratching their heads over this one." Centauri Dreams hardly qualifies as an expert, but head-scratching does seem in order...

Trillion Year Crunch

by Paul Gilster | May 11, 2006 | Exotic Physics | 10 Comments

How to explain dark energy, which is pushing distant galaxies away at an accelerating rate? The cosmological constant that would account for the phenomenon -- originally conceived but then rejected by Einstein -- is far smaller than one would expect from conventional Big Bang scenarios. In fact, the observed vacuum energy (a possible explanation for the repulsive force) is smaller by a factor of 10120 than it would need to be to do the job. But if the universe were older than today's estimate of 13.7 billion years, and I mean a lot older, then this tiny value might make sense. So say Paul Steinhardt (Princeton) and Neil Turok (Cambridge, UK), who put forward a startling concept: there was indeed a time before the Big Bang. There is remarkable solace in this for all of us who grew up asking what happened before the Big Bang, only to be told that the question made no sense because it was unanswerable. So said a kindly astronomy professor in a long-ago college course, raising his shaggy...

Organic Particles from the Early Solar System

by Paul Gilster | May 10, 2006 | Interstellar Medium | 3 Comments

Can we say anything definitive about organic materials in the early Solar System? Perhaps so, judging from recent news from the Carnegie Institution. Researchers there have found organic particles from the days of Solar System formation inside meteorites. The material is similar to what is found in interplanetary dust particles believed to have come from comets, and gives us a view of the complexity of the organic mix that may have been available as the planets formed. Studying six carbonaceous chondrite meteorites, the researchers looked at different isotopes of hydrogen and nitrogen associated with insoluble organic materials, which are extremely difficult to break down chemically. The relative proportion of these isotopes can reveal much about how the carbon was formed, and the meteorite samples show in some cases even higher amounts of the relevant isotopes than those found in interstellar dust. "We have known for some time, for instance, that interplanetary dust particles (IDP),...

Habitable Worlds and the Gas Giant Problem

by Paul Gilster | May 9, 2006 | Exoplanetary Science | 1 Comment

I remember wondering, while still getting acclimated to the odd existence of 'hot Jupiters' in those amazing first years of exoplanet discovery, what the view from a terrestrial world in one of those systems might be like. After all, a Jupiter-sized mass in close solar orbit must make for some unusual visual effects. Do terrestrial worlds exist around these stars? For that matter, what are the constraints on terrestrial planet formation in systems where gas giants orbit farther out, well past the habitable zone? These questions are occasioned by the work of Sean Raymond (University of Colorado), whose paper on the subject will soon run in the Astrophysical Journal Letters. Raymond looks at how the presence of gas giants would affect the late stages of terrestrial world formation and presents the results of his simulations on same. Bear this in mind: gas giants, it is now thought, must form within the first few million years of the early protoplanetary disk. Whereas terrestrial worlds...

Of Lightsails and Solar Arrays

by Paul Gilster | May 8, 2006 | Sail Concepts | 14 Comments

Rudolph Meyer's work on solar arrays and ion propulsion elicited quite a few e-mails asking for further information. I don't yet have the Acta Astronautica paper that spells out the details -- nor do I know just how detailed Meyer gets -- but I'll try to provide some answers soon. In the interim, I was startled to realize that Geoffrey Landis, who commented on the Meyer design for New Scientist, had actually gone into this concept at some length as long ago as 1989. In fact, Landis' key paper "Optics and Materials Considerations for a Laser-propelled Lightsail" (available here) was presented at the 40th International Astronautical Federation Congress in that year. Landis speculated on a lightweight sail that focuses power on a small solar array, noting that a basic problem with laser-propelled lightsails is their low energy efficiency: The energy efficiency may be greatly improved, at the cost of a reduction in specific impulse, by combining the laser sail with a photovoltaic powered...

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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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