Yesterday's story on IBEX is now complemented by images from the Ion and Neutral Camera, part of the Magnetospheric Imaging Instrument on the Cassini orbiter. The Cassini data confirm the fact that the heliosphere isn't shaped the way we've always thought. The assumption up to now has been that the collision of the solar wind with the interstellar medium would create a foreshortened nose in the direction of the Solar System's motion, and an elongated tail in the opposite direction. Both IBEX and Cassini argue otherwise. Stamatios Krimigis (Applied Physics Lab, Laurel, MD) notes the import of these findings: "These images have revolutionized what we thought we knew for the past 50 years; the sun travels through the galaxy not like a comet but more like a big, round bubble. It's amazing how a single new observation can change an entire concept that most scientists had taken as true for nearly fifty years." Amazing and invigorating, for we're opening up serious new ground here. Put...

Findings that are outside our expectations seem par for the course as we explore the Solar System. From the volcanoes of Io to the geysers of Enceladus, unusual things show up with each new mission. Why should IBEX be any different? The Interstellar Boundary Explorer is the first spacecraft expressly designed to study what happens at the edge of the Solar System, where nearby space meets the interstellar medium. The 'bubble' around the Sun called the heliosphere comes about as charged particles in the solar wind move continuously away from the Sun. Although IBEX is far from the heliopause (it's orbiting the Earth with an apogee of 322,000 kilometers and a perigee of 16,000 kilometers), its instruments are tuned to study energetic neutral particles (ENAs) swept up by the solar wind in the boundary between the edge of the heliosphere and interstellar space beyond. IBEX has been mapping this area since last October. And here comes the surprise, as explained by IBEX principal...

Below you'll see that I'm running Mike Brown's sketch of the 'new' Solar System, one I originally ran with our discussion of Joel Poncy's Haumea orbiter paper, which was presented at Aosta in July. The sketch is germane on a slightly different level today because as we look at how our views of the Solar System have changed over the years, we've learned how many factors come into play, including one Brown's sketch doesn't show. For surrounding the planets and nearer regions of the Kuiper Belt is the heliosphere, that bubble of solar wind materials whose magnetic effects help protect the inner system. Image: Our view of the Solar System has gone from relatively straightforward to one of exceeding complexity. Credit: Mike Brown/Caltech. Look at the heliosphere diagram below and you'll see that while the eight planets are comfortably within it, our Pioneers and Voyagers are pushing toward or through the termination shock on their way to the heliopause. Galactic cosmic rays are shown...

"Interstellar travel may still be in its infancy," write Gregory Matloff and Eugene Mallove in The Starflight Handbook (Wiley, 1989), "but adulthood is fast approaching, and our descendants will someday see childhood's end." The echo of Arthur C. Clarke is surely deliberate, a sign that one or both authors are familiar with Clarke's 1953 novel about the end of human 'childhood' as we learn about the true destiny of our species in the universe. But becoming a mature species isn't easy, nor is figuring out interstellar flight. Awash in Hard Radiation Consider just one layer of complexity. Suppose we somehow discover a propulsion system that gets us to relativistic speeds in the range of 0.3 c. That seems a minimum for regular manned starflight given the times and distances involved, but suddenly attaining it doesn't end our problems. Interstellar space isn't empty, and when we accelerate to cruising speed at a substantial percentage of the speed of light, our encounter with...

Almost four years ago I wrote a Centauri Dreams entry about Dana Andrews' views on shielding an interstellar spaceship. The paper is so directly relevant to our recent discussion on the matter that I want to return to it here. Andrews (Andrews Space, Seattle) believes that speeds of 0.2 to 0.3 c are attainable using beamed momentum propulsion. That being the case, he turns in his "Things to Do While Coasting Through Interstellar Space" paper to questions of human survival. Particles with a Punch Collision with interstellar dust becomes a major issue when you're traveling at speeds like these, a fact Andrews is quick to quantify. For a starship moving at 0.3 c, a typical grain of carbonaceous dust about a tenth of a micron in diameter should have a relative kinetic energy of 37,500,000 GeV. Our hypothetical star mission with human crew moving at a substantial fraction of light speed will run into about thirteen of these dust particles every second over every square meter of frontal...

It would be helpful if space were a bit more empty. A key problem facing an interstellar probe would be encounters with dust in the planetary system it leaves and, as it reaches cruising speed, dust impact in space between the stars. Although our Solar System seems to be in an unusually sparse pocket of space, the galaxy-wide distribution of hydrogen is roughly one atom per cubic centimeter. Dust -- bits of carbon, ice, iron compounds, and silicates -- is far rarer still, but enough of a factor to a ship moving at a significant fraction of the speed of light that the designers of the Project Daedalus craft built in a payload shield 32-meters in radius to protect their starship. Then again, much depends on your location. Have a look at the image below. It's an area called the Red Rectangle some 2300 light years from Earth in the constellation Monoceros. Although the center of the image seems to be a single star, it's actually the double star system HD 44179. The Red Rectangle is a...

My wife is the most gifted poet I know. I often marvel at her ability to see things with new eyes, to take experiences we have shared and look at them with such a fresh and uncluttered view that the events are transformed and new meaning extracted from them. All of which came to mind this morning in a far different context as I pondered how good science does much the same thing. A case in point in this 'poetry of science' is offered by a view of the edge of the Solar System made not with photons but with neutral atoms, in data gathered by the twin STEREO spacecraft. It's a new kind of astronomy that draws on a different way of looking at the unexplored frontiers of the heliosphere. Our Voyager spacecraft, of course, are in this region, so we're getting new data all the time, but from an optical perspective, the outer heliosphere is invisible. This is where the solar wind -- that stream of charged particles moving outward from the Sun -- reaches the limits of the Sun's influence, a...

We think about our interstellar neighborhood in terms of stars, like Alpha Centauri and Tau Ceti, but the medium through which our relative systems move is itself a dynamic and interesting place. The Sun is currently passing through a shell of material known as the Local Interstellar Cloud. And that cloud is, in turn, located at the edge of a vast region known as the Local Bubble, scoured of material by supernova explosions in the nearby Scorpius-Centaurus and Orion Association star-forming regions. Within the past 105 years, the Sun emerged from the interior of the Local Bubble; it now moves obliquely in the direction of the high-density molecular clouds of the Aquila Rift, a star-forming region that itself reminds us how energetic 'empty' space really is. If we're ever going to send fast missions outside the Solar System, we're going to need plenty of data about the materials through which our vehicles move, particular as velocities mount to the point where collision with even...

I don't want today to pass without noting that it is the thirtieth anniversary of the launch of Voyager 2. Both Voyagers remain healthy, continuing studies of the solar wind, magnetic fields and energetic particles with their five functioning science instruments. As this JPL news release notes, the Voyagers run on less than 300 watts of power, which they tap from radioisotope thermoelectric generators. At 15.5 billion kilometers (Voyager 1) and 12.5 billion (Voyager 2), the vehicles are the farthest human-made objects, unable to use the power of distant Sol. Image: Artist concept of the two Voyager spacecraft as they approach interstellar space. Image credit: NASA/JPL. So our first mission into nearby interstellar space continues to go quite well, with both spacecraft reporting home despite one-way radio travel times of fourteen and twelve hours respectively. Voyager 1 seems to have encountered the heliosheath -- where the solar wind slows as it encounters the thin gas between the...

Scientists studying the chemistry of interstellar space have identified around 130 neutral molecules along with perhaps a dozen positively charged molecules, but it was only late last year that the first negatively charged molecule -- anion -- was found, consisting of six carbon atoms and one hydrogen atom. It was a significant find because logic seemed to suggest that molecules would have a hard time retaining extra electrons, and thus a negative charge, in a star-rich environment. Now we have a new anion, found using data from the Green Bank Telescope in West Virginia. The molecule is negatively-charged octatetraynyl, consisting of eight carbon atoms and one hydrogen atom, and it's been located in the envelope of gas around an old, evolved star known as IRC +10 216, about 550 light-years from Earth. That makes three anions found in less than a year and in a range of environments. Image: Astronomers using the Robert C. Byrd Green Bank Telescope found the negatively-charged form of...

Carbonados, also known as 'black diamonds,' are a far cry from the kind of diamonds that adorn a wedding ring. They're gray to black in color, lack the beautiful crystaline structure of standard diamonds, and usually wind up being used in industrial settings for their abrasive qualities. And now we're learning why these somewhat nondescript objects aren't found in the usual places for diamond mining. Their origin may lie not within the Earth but in interstellar space. Or so say Jozsef Garai and Stephen Haggerty (Florida International University) in a recently published paper. Working with researchers from Case Western, the team used infrared synchrotron radiation at Brookhaven National Laboratory to analyze carbonado samples, finding enough hydrogen to indicate an origin in hydrogen-rich interstellar space. Haggerty has, in fact, conducted earlier research showing that these diamonds are the result of supernovae explosions, and that they arrived on Earth as objects originally a...

It's always good to see Green Bank in the news. The West Virginia facility was the site of Frank Drake's pioneering SETI attempt called Project Ozma back in 1960. Now Green Bank's newest dish has been used to discover the first negatively charged molecule in space, a useful building block in our understanding of how interstellar matter turns into planets that can eventually produce life. The molecule in question is called C6H-, described as a chain of six carbon atoms with one hydrogen atom at the end and an extra electron. That makes it a molecular 'anion' -- a molecule with a negative charge because of the extra electron -- and it's a bit of an anomaly. You would think that ultraviolet light would dislodge that spare electron, but this molecule survives. In fact, it's larger than most neutral and all positive molecules known in space. Image: The Green Bank Telescope at dusk. Courtesy of NRAO/AUI. Astronomer Michael McCarthy (Harvard-Smithsonian Center for Astrophysics) calls it 'a...

40,000 tons of extraterrestrial matter are believed to hit the Earth every year. This from the current issue of Science, where researchers from New York (Columbia University) and Bremerhaven (Alfred-Wegener-Institut) present a study of helium isotopes found in Antarctic ice cores. Over the last 30,000 years, the scientists believe, the amount of 3He, a rare isotope found in cosmic dust, exceeds that found in terrestrial dust in ice by a factor of 5000. We have, the investigation indicates, been subject to a constant rain of cosmic dust particles over this period. Which is interesting in its own right, but becomes more pointed when you look at the measurements of the helium isotope 4He, which is much more common on Earth. Indications point to a change of origins in terrestrial dust between the last Ice Age and the current interglacial warm period. Says Gisela Winckler (Lamont-Doherty Earth Observatory, Columbia University): "The terrestrial dust coming down on Antarctica during the...

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),...