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‘Island-Hopping’ to the Stars

by Paul Gilster | Feb 13, 2012 | Outer Solar System | 88 Comments

We tend to think of interstellar journeys as leaps into the void, leaving the security of one solar system to travel non-stop to another. But a number of alternatives exist, a fact that becomes clear when we ponder that our own cloud of comets -- the Oort Cloud -- is thought to extend a light year out and perhaps a good deal further. There may be ways, in other words, to take advantage of resources like comets and other icy objects for a good part of an interstellar trip. That scenario is not as dramatic as a starship journey, but it opens up possibilities. Let’s say, for example, that we only manage to get up to about 1 percent of lightspeed (3000 kilometers per second) before we run into technical challenges that are at least temporarily insurmountable. Speeds like that take well over 400 years to get a payload to Centauri A and B, but they make movement between planets and out into the Kuiper Belt and Oort Cloud a straightforward proposition. A civilization content to create...

Of Ice and the Planetesimal

by Paul Gilster | Feb 10, 2012 | Outer Solar System | 11 Comments

Mindful of the recent work on axial tilt I've reported in these pages, I was interested to learn that Vesta's axial tilt is just a bit greater than the Earth's, about 27 degrees. We've been pondering the consequences of such obliquity on planets in the habitable zone, but in Vesta's case, the issue isn't habitability but water ice. For spurred by the Dawn mission, scientists are looking at whether permanently shadowed craters on the asteroid's surface would allow water to stay frozen all year long. Unlike the situation on the Moon, the answer on Vesta (on the surface at least) seems to be no. Earth's axial tilt is 23.5 degrees, but the Moon's is a scant 1.5 degrees, making the shadow in some lunar craters permanent, a fact that has led to speculation that ice in these locations could be of use to future manned missions there. In contrast, Vesta's obliquity means that it has seasons, so that every part of the surface becomes exposed to sunlight at some point in the year. Even so, says...

A ‘Super-Oort’ Cloud at Galactic Center?

by Paul Gilster | Feb 9, 2012 | Deep Sky Astronomy & Telescopes | 3 Comments

Not long ago we looked at comet C/2011 N3 (SOHO), discovered last July just two days before it plunged into the Sun, evaporating some 100,000 kilometers above the solar surface. It was startling to learn that the SOHO observatory is tracking numerous ‘Sun-grazers,’ comets whose fatal encounters with our star are occurring roughly once every three days. Now comes news that Sagittarius A*, the supermassive black hole at the center of the Milky Way, is producing X-ray flares about once a day, thought by some to be the result of similar debris in the process of destruction. The flares last just a few hours, according to researchers working with data from the Chandra X-Ray Observatory, and can reach brightness levels up to 100 times what is normally observed in the black hole region. Kastytis Zubovas (University of Leicester) thinks we’re seeing asteroids and comets passing within 160 million kilometers of the black hole (roughly 1 AU), at which point they would likely be broken apart by...

Two Takes on Extraterrestrial Life

by Paul Gilster | Feb 8, 2012 | Astrobiology and SETI | 58 Comments

"With exoplanets we are entering new territory," says René Heller (Leibniz Institute for Astrophysics, Potsdam), talking about recent studies looking at axial tilt as a parameter for habitability on a planet. Heller is getting at the fact that while we've studied the axis of a planet's spin relative to the plane of its orbit rather thoroughly here in our own Solar System, we are a long way from being able to discern the axial tilt of exoplanets, much less make definitive statements about its effect on habitability. Right now we can say something about the size, mass and orbital period of many distant planets (and in a few cases, some of the components of their atmosphere) and that's about where our knowledge stops. Heller imagines the Earth with an axial tilt something akin to that of Uranus, whose equator and ring system run almost perpendicular to the plane of its orbit. Introduce such high obliquity to the Earth and the north pole would point at the Sun for a quarter of the...

Untangling a Lensed Galaxy

by Paul Gilster | Feb 7, 2012 | Deep Sky Astronomy & Telescopes | 3 Comments

Gravitational lensing always gets my attention not only because of its growing use in astronomy but because of its potential for deep space missions like FOCAL, Claudio Maccone's concept for a deep space probe that would be sent beyond the Sun's 550 AU gravitational lensing distance to make observations of astronomical targets. FOCAL is an interstellar precursor mission that could give us detailed information about any system to which we might send a future probe. And, as Maccone has shown, lensing could also be used to create the kind of robust communications relay that would function with little data loss over huge distances. But we don't have to wait for FOCAL to exploit the potential of lensing for studying distant exoplanets. As Centauri Dreams readers know, gravitational microlensing has developed into a potent tool. A foreground star distorts the light from a background object when the alignment is right, and that magnification is likewise affected by planets orbiting the...

Targeting Primitive Asteroids

by Paul Gilster | Feb 6, 2012 | Asteroid and Comet Deflection | 4 Comments

I see that there is a symposium on the MarcoPolo-R mission coming up in late March, which reminds me that at a time when asteroid missions are increasingly in the news, I have yet to cover this one. It was about a year ago that the European Space Agency selected MarcoPolo-R as one of four candidates for a medium-class mission that would launch between 2020 and 2024. The selection doesn't mean the mission has been finalized by any means, only that the four missions chosen will undergo a down-selection process to choose the one to implement. Thus this mission to return a sample of material from a near-Earth asteroid for analysis in ground laboratories will have to prove itself against some formidable competition, including another particularly interesting concept called the Exoplanet Characterisation Observatory (EChO), which would orbit around the L2 Lagrange point and study exoplanet atmospheres. Exoplanets are obviously hot property right now, but asteroids are also having their...

SETI in the News

by Paul Gilster | Feb 3, 2012 | Astrobiology and SETI | 125 Comments

Let me draw your attention to two interesting stories this morning, one harking back to the night in August of 1977 when the Big Ear radio telescope at Ohio State University recorded the famous 'Wow!' signal. For those unfamiliar with it, the 'Wow!' signal gets its name from Big Ear volunteer Jerry Ehman's annotation (several days later) on the signal's printout. 'Wow!' seemed appropriate for a signal that was 30 times stronger in volume than the background noise and took up a single 10 kilohertz-wide band on the receiver, an enigmatic 70-second narrow-band burst at almost precisely 1420 megahertz, the emission frequency of hydrogen. A message from an extraterrestrial civilization? 'Wow!' seemed to fit the bill, but it disappeared and despite more than 50 repeated searches by the Big Ear team, it never recurred. In this article for The Planetary Society, Amir Alexander calls the signal "...the single most intriguing result ever produced by the Search for Extraterrestrial...

‘Super-Earth’ in a Triple Star System

by Paul Gilster | Feb 2, 2012 | Exoplanetary Science | 81 Comments

GJ 667C is an M-class dwarf, part of a triple star system some 22 light years from Earth. Hearing rumors that a 'super-Earth' -- and one in the habitable zone to boot -- has been detected around a nearby triple star system might cause the pulse to quicken, but this is not Alpha Centauri, about which we continue to await news from the three teams studying the prospect of planets there. Nonetheless, GJ 667C is fascinating in its own right, the M-dwarf being accompanied by a pair of orange K-class stars much lower in metal content than the Sun. The super-Earth that orbits the M-dwarf raises questions about theories of planet formation. Thus Steven Vogt (UC Santa Cruz), who puts the find into context, noting that heavy elements like iron, carbon and silicon are considered the building blocks of terrestrial planets: "This was expected to be a rather unlikely star to host planets. Yet there they are, around a very nearby, metal-poor example of the most common type of star in our galaxy....

IBEX: The Heliosphere in Motion

by Paul Gilster | Feb 1, 2012 | Interstellar Medium | 9 Comments

The beauty of having spacecraft that far outlive their expected lives is that they can corroborate and supplement data coming in from much newer missions. That's the case with our Voyager spacecraft as they continue their progress at system's edge. The Voyagers will be moving outside the heliopause in not so many years, and when they do, they will tell us much about the behavior of charged particles in the interstellar medium. This will bulk up incoming results from IBEX, the Interstellar Boundary Explorer spacecraft, as it studies the neutral particles that routinely penetrate the heliosphere. Our knowledge of true interstellar space is growing. It's at the heliopause that we see the boundary between the area defined by the solar wind flowing outward from the Sun and the interstellar medium that surrounds it. Racing outward at an average of 440 kilometers per second, the solar wind is pushing into a region of dust and ionized gas, inflating the bubble we know as the heliosphere. The...

Cloud Cover’s Role in Exoplanet Studies

by Paul Gilster | Jan 31, 2012 | Exoplanetary Science | 5 Comments

I confess it had never occurred to me to consider cloud cover on exoplanets in quite the same light that a new study does. But two Spanish astronomers from the Astrophysical Institute of the Canary Islands (IAC) are taking a look at how clouds operate over different kinds of surfaces, in the process figuring out what our Earth would have looked like from space in different eras. It’s an interesting thought: Given the movement of Earth’s continents in the past 500 million years, what would cloud patterns have been like over land and sea as landforms changed? The researchers chose several times to study, from 90, 230, 340 to 500 million years ago, pondering how changes in light reflected from the Sun would have operated here and, by extension, how they might operate on distant exoplanets. We’ll need to keep these things in mind when we get the capability of studying the atmospheres of terrestrial planets around other stars. And it turns out that, according to the researchers, cloud...

Toward a New ‘Prime Directive’

by Paul Gilster | Jan 30, 2012 | Culture and Society | 47 Comments

The Italian contribution to the interstellar effort has been substantial, and I'm pleased to know three of its principal practitioners: Claudio Maccone, Giancarlo Genta, and Giovanni Vulpetti. It was with great pleasure, then, that I took Roberto Flaibani up on his offer of appearing in his excellent blog Il Tredicesimo Cavaliere (The Thirteenth Knight). Roberto had translated several Centauri Dreams articles into Italian in the previous year and was now looking for comments on the ramifications of human contact with extraterrestrials as we push into interstellar space. This article on Star Trek's Prime Directive grew out of our talks and became part of a broader discussion of related articles on Roberto's site. I thank him for continuing to translate my work into Italian, and now offer the original essay to Centauri Dreams readers. I should probably throw in a qualifier -- I've always enjoyed Star Trek but am hardly a rabid fan, getting most of my science fiction not from film or TV...

New Multiple Planet Systems Verified

by Paul Gilster | Jan 27, 2012 | Exoplanetary Science | 18 Comments

Confirming Kepler's planet candidates is a crucial part of the process, because no matter how tantalizing a candidate appears to be, its existence needs to be verified. We have more than 60 confirmed Kepler planets and over 2300 candidates, many of which will eventually get confirmed, but it's interesting to see that the mission's latest announcements relate to multiple planet systems and how their presence can itself speed up the verification process. In today's focus are the eleven new planetary systems just announced, 26 confirmed planets in all, which actually triples the number of stars known to have more than one transiting planet. One of the systems, Kepler-33, has been demonstrated to have five planets. We also have five systems (Kepler-25, Kepler-27, Kepler-30, Kepler-31 and Kepler-33) showing a 1:2 orbital resonance -- the outer planet orbits the star once for every two orbits of the inner planet -- and four systems with a 2:3 resonance, with the outer planet orbiting twice...

Project Bifrost: Return to Nuclear Rocketry

by Paul Gilster | Jan 26, 2012 | Advanced Rocketry | 54 Comments

Back in the days when I was studying Old Icelandic (this was a long time ago, well before Centauri Dreams), I took a bus out of Reykjavik for the short journey to Þingvellir, where the Icelandic parliament was established in the 10th Century. It was an unusually sunny day but that afternoon the storms rolled in, and just before sunset I remember looking out from the small hotel where I was staying to a rainbow that had formed over the lava-ridden landscape. It inevitably brought to mind Bifröst, the multi-colored bridge that in Norse mythology connected our world with Asgard, where the gods lived. The idea may have been inspired by the Milky Way. In the world of rocketry, a new Bifröst has emerged, one designed to link the nuclear rocket technologies that were brought to a high level of development in the NERVA program with our present-day propulsion needs. For despite a serious interest that resulted in a total of $1.4 billion in research and the testing of a nuclear engine, NERVA...

The Dunes of Titan

by Paul Gilster | Jan 25, 2012 | Outer Solar System | 7 Comments

The methane/ethane cycle we see on Titan is reminiscent of the water cycle on Earth, which is what people are really talking about when they refer to this frigid place as vaguely 'Earth-like' -- this is not exactly a temperate climate! But we have a long way to go in understanding just how the cycle operates on the distant moon, which is why new work on Titan's sand dunes is drawing interest. By studying the dune fields, we can learn about the climatic and geological history they depict and perhaps get clues about other issues, such as why Titan's lakes of liquid ethane and methane are found mostly in the northern hemisphere. What Cassini is showing us are regional variations among Titan's dunes, a landscape feature that covers some 13 percent of the surface in an area roughly equivalent to that of Canada. But every time we run into an Earth analogue on Titan, we're confronted with major differences. Titan's dunes are made not of silicates but of solid hydrocarbons that wind up as...

Eternal Monuments Among the Stars

by Paul Gilster | Jan 24, 2012 | Astrobiology and SETI | 93 Comments

Yesterday’s post looked at SETI and its assumptions, using the lens of a new paper on how the discipline might be enlarged. The paper’s authors, Robert Bradbury, Milan ?irkovi? and George Dvorsky, are not looking to supplant older SETI methods, but rather to broaden their scope by bringing into play what we are learning about astrobiology and artificial intelligence. It is perilous, obviously, to speculate on how an alien civilization might behave, yet to some extent we’re forced to do it in choosing SETI targets, and that being the case, why not add into the mix methods that go beyond our current radio and optical searches, methods that may have a better chance of success? The Engima of Contact A key to extending SETI’s reach is to question the very idea of contact. One assumption many of SETI’s pioneers had in common was that there was an inherent need to communicate with other species, and that this need would take the form of intentional radio beacons or optical messages. What...

Rethinking SETI’s Targets

by Paul Gilster | Jan 23, 2012 | Astrobiology and SETI | 51 Comments

Have you ever given any thought to intergalactic SETI? On the face of it, the idea seems absurd -- we have been doing SETI in one form or another since the days of Project Ozma and without result. If we can’t pick up radio signals from nearby stars that tell us of extraterrestrial civilizations, how could we expect to do so at distances like M31’s 2.573 million light years, not to mention even the closest galaxies beyond? Herein lies a tale, for what intergalactic SETI exposes us to is the baldness of our assumptions about the overall SETI attempt, that it is most likely to succeed using radio wavelengths, and that it may open up two-way communications with extraterrestrials. It’s the nature of these assumptions that we need to explore today. The Visibility of a Galactic Culture Let’s suppose, for example, that Nikolai Kardashev’s thoughts about types of civilizations are compelling enough to put to the test. A Kardashev Type III civilization is one that is able to exploit the energy...

Dawn Explores Vesta’s Chemistry

by Paul Gilster | Jan 20, 2012 | Asteroid and Comet Deflection | 30 Comments

The Dawn spacecraft, orbiting Vesta since July of last year, reached its lowest altitude orbit in December, now averaging 210 kilometers from the asteroid's surface. Ceres is Dawn's next stop, but that journey won't begin until the close-in work at Vesta is complete, with the craft in its low altitude mapping orbit for at least ten weeks and then another period at higher altitudes before Dawn leaves Vesta in late July. The spacecraft's Gamma Ray and Neutron Detector (GRaND) instrument is already telling us much about the giant asteroid's surface composition. In fact, the five weeks of mapping at low-altitude have provided the first look at global-scale variations on Vesta. GRaND measures the abundance of elements found in planetary surfaces, and while its investigations are still in the early stages of analysis, it's clear that Vesta's surface varies widely as opposed to the mostly uniform composition of smaller asteroids. We know that Vesta developed a core, mantle and crust, making...

A Comet Consumed by the Sun

by Paul Gilster | Jan 19, 2012 | Deep Sky Astronomy & Telescopes | 13 Comments

Imagine what we could do if we could attain speeds of 640 kilometers per second. That's the velocity of a comet recently tracked just before passing across the face of the Sun and apparently disintegrating in the low solar corona. I'm just musing here, but it's always fun to muse about such things. 640 kilometers per second drops the Alpha Centauri trip from 74,600 years-plus (Voyager-class speeds) to less than 2000 years. A long journey, to be sure, but moving in the right direction, and in any case, these are speeds that would allow exploration deep into the outer system. We're a long way from such capabilities, but they're a rational goal. But back to the comet. The object was discovered on July 4, 2011 and designated C/2011 N3 (SOHO), the latter a reference to the ESA/NASA Solar and Heliospheric Observatory, whose Large Angle and Spectrometric Coronagraph made the catch. On July 6, NASA's Solar Dynamics Observatory was able to pick up the comet some 0.2 solar radii off the Sun,...

NIAC Looking for New Proposals

by Paul Gilster | Jan 18, 2012 | Advanced Rocketry | 11 Comments

NASA’s Innovative Advanced Concepts program has issued a second call for proposals, following the selection of its first round of Phase I concepts in 2011. NIAC (formerly the NASA Institute for Advanced Concepts) ran from 1998 to 2007 in the capable hands of Robert Cassanova, who is now external council chair for the new organization. After a four year interregnum, the program returned in 2011 with the goal of funding “early studies of visionary, long term concepts – aerospace architectures, systems, or missions (not focused technologies).” The 2011 effort resulted in funding for 30 advanced technology proposals, each of them receiving $100,000 for one year of study. The new call for proposals continues the NIAC theme of looking for ideas that are both innovative and visionary, while remaining at an early stage of development, considered as being ten years or more from actual use on a mission. Approximately fifteen proposals are likely to win funding in the 2012 selection, with short...

Exoplanetary Ring Systems and Their Uses

by Paul Gilster | Jan 17, 2012 | Exoplanetary Science | 5 Comments

What to say about an extrasolar ring system that has already had its four distinct rings named? Rochester, Sutherland, Campanas and Tololo are the Earth-bound sites where the unusual system was first detected and analyzed, and the international team of researchers involved thought them suitable monickers for the four rings thus far detected. The light curve of the young, Sun-like star they’ve been studying in the Scorpius-Centaurus association -- a region of massive star formation -- shows what appears to be a dust ring system orbiting a smaller companion occulting the star. The data here come from SuperWASP (Wide Angle Search for Planets) and the All Sky Automated Survey (ASAS) project. The star in question is 1SWASP J140747.93-394542.6, which displays a complex eclipse event with, at some points, 95 percent of the light from the star being blocked by dust. Similar in mass to the Sun, the star is only about 16 million years old, and lies about 420 light years away from the Solar...

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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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