Interstellar Medium | Centauri Dreams

Briefing on Stardust Results

by Paul Gilster | Mar 7, 2006 | Interstellar Medium, Outer Solar System | 1 Comment

A number of readers have been asking about results from the Stardust mission, particularly as pertains to any interstellar materials returned by the craft. We'll know a good deal more on March 13, when NASA holds a news conference at 3 PM EST (1800 GMT). The briefing will be available both on the Web and on NASA TV, with participation by, among others, principal investigator Donald Brownlee and JPL's Peter Tsou. My understanding is that the team will largely confine its report to cometary samples, but these too may yield surprises.

Cosmic Ray Science from Voyager

by Paul Gilster | Feb 27, 2006 | Interstellar Medium | 0 Comments

Are the Voyager spacecraft still doing good science? You bet, as witness the passage of Voyager 1 through the termination shock at the edge of interstellar space. Scientists had assumed the craft's crossing of this boundary, where the solar wind abruptly slows, would confirm previous theories about anomalous, energetic cosmic rays that were thought to be produced in the region. But Voyager did anything but, finding the cosmic ray count to be far lower than predicted during its passage. New work by David McComas (Southwest Research Institute) and Nathan Schwadron (Boston University), published recently in the Geophysical Research Letters, offers a theory why. They base their thinking on the shape of the shock itself, previously thought to be circular. The duo showed that a more realistic shape made sense. "In fact, the termination shock couldn't be circular because the solar system is moving through the galaxy, which would create more of a flattened egg shape," says Schwadron. "A...

Stardust Update

by Paul Gilster | Jan 15, 2006 | Interstellar Medium, Outer Solar System | 0 Comments

The return capsule from the Stardust probe landed successfully in the Utah desert at 1012 GMT. More on Monday; for now, this BBC story contains the details, and provides video of the landing. From the story: "'I'm very confident we will have samples in there that are the first returned from beyond the Moon,' former Stardust project manager, Ken Atkins, told the BBC News website." Well done!

Stardust Just Hours from Earth

by Paul Gilster | Jan 14, 2006 | Interstellar Medium, Outer Solar System | 0 Comments

The Stardust spacecraft crossed the Moon's orbit at 1730 GMT on Saturday and will close the distance to Earth in sixteen and a half hours (an indication of how fast the vehicle is moving). The craft performed a final burn for course adjustment before passing the Moon's orbit. Approaching the Earth, it will deploy its return capsule for a scheduled landing at the Utah Test and Training Range on Sunday (the primary spacecraft will enter a Solar orbit after release). The capsule is scheduled to enter Earth's atmosphere over northern California at an altitude of 125 kilometers, traveling some 46,440 kilometers per hour (28,860 miles per hour). This is the fastest return of any man-made object on record. Landing is now expected at 1012 GMT on Sunday, after which the capsule will be taken to the U.S. Army Dugway Proving Ground (Utah); the collector grid (containing cometary and interstellar samples) will then be moved to NASA's Johnson Space Center in Houston. You can follow events at the...

Stardust@Home

by Paul Gilster | Jan 9, 2006 | Interstellar Medium, Outer Solar System | 0 Comments

As the return of the Stardust cometary samples approaches, it's encouraging to learn of a Stardust-related project with interstellar implications. Stardust@Home is an Internet-based search for interstellar dust in the Stardust materials, one that relies, like SETI@Home before it, on the combined computing resources of those who volunteer to assist. Unlike the latter project, however, Stardust@Home requires a Web-based training session and subsequent test, after which those who pass will be able to download a virtual microscope and images from the Stardust collector. It will take personal scrutiny rather than just computing cycles to try to locate interstellar materials. Although most attention has focused on Stardust's cometary samples, its aerogel collector was also designed to catch the first interstellar dust ever collected. The number of dust grains found may number in the low dozens, but even one would be a breakthrough, marking the first time such materials were studied in a...

Stardust Approaching

by Paul Gilster | Jan 4, 2006 | Interstellar Medium, Outer Solar System | 0 Comments

The return of the Stardust mission draws near. The spacecraft should jettison its return capsule around 5 AM EST on January 15; the latter is to plunge into Earth's atmosphere at the highest return speed ever recorded, some 29,000 miles per hour. A parachute will bring the capsule to the ground at the Utah Testing and Training Range southwest of Salt Lake City, and at that point we should have our first samples of primordial cometary dust, captured two years ago near Comet Wild 2. Even more intriguing, we should have particles of interstellar dust collected during the long approach to the comet. This has been a remarkable mission, and at times a scary one. Stardust was launched in February of 1999 and began collecting interstellar dust in 2000. 2.88 billion miles have accumulated during this voyage, including a gravity assist from Earth and an encounter with asteroid 5535 Annefrank. In November of 2000, a vast solar flare skewed the spacecraft's navigation system by creating false...

Measuring Outer System Dust

by Paul Gilster | Jan 2, 2006 | Interstellar Medium | 0 Comments

With the New Horizons mission to Pluto set to launch on January 17, the eyes of interstellar mission advocates turn to something seemingly mundane: the size, makeup and distribution of dust particles in the outer Solar System. In an ideal universe, each mission pushes and extends our knowledge, and if we are to build true star-faring probes one day, we'll need to do a great deal of incremental, almost prosaic study along the way. Such as learning more about the medium through which fast spacecraft will have to fly. Image: The team and the rocket. The New Horizons researchers gathered in November at the Kennedy Space Center to see New Horizons and the Atlas V that will launch it. Credit: Johns Hopkins University Applied Physics Laboratory. On that score, I see that the University of Colorado has contributed a space dust instrument that will fly on New Horizons. The first student-built instrument ever to fly on a planetary mission, the Student Dust Counter (SDC) will make observations...

New Horizons Readied for Flight

by Paul Gilster | Oct 19, 2005 | Interstellar Medium, Missions, Outer Solar System | 0 Comments

With liftoff scheduled for January, the New Horizons mission to Pluto and Charon (and, if we are lucky, at least one flyby of a more distant Kuiper Belt object) continues to generate excitement in the scientific community. The spacecraft is now at the Kennedy Space Center and will be moved to the launch pad in December, with liftoff planned for January 11. Major testing on the science payload is complete. The next round of major instrument calibrations and testing won't occur until the early months of the journey as New Horizons moves toward a 2007 flyby of Jupiter for a gravity assist to Pluto. How do you package enough instrumentation for good science at the edge of the Solar System into a payload that draws only 28 watts of power? The science payload work was led by the Southwest Research Institute (SwRI), whose recent news release lists the seven instruments that will explore these icy worlds: Alice, an ultraviolet imaging spectrometer that will probe the atmospheric composition...

A Stunning View of Interstellar Dust

by Paul Gilster | Aug 27, 2005 | Deep Sky Astronomy & Telescopes, Interstellar Medium | 0 Comments

Centauri Dreams has discussed the problem of interstellar dust for fast-moving probes before. Here the issue is highlighted in a Gemini Observatory image of NGC 6559, part of the large star-forming region in the southern constellation Sagittarius. The dark structure -- Gemini likens it to a Chinese dragon -- is the result of cool dust that absorbs background radiation from the surrounding hydrogen gas. The region, some 5000 light years away toward the center of the Milky Way, is a reminder that in many areas, space is anything but empty. Image credit: Gemini Observatory (using the Gemini South telescope at Cerro Pachón in the Chilean Andes).

Protoplanetary Disks Apparently Common

by Paul Gilster | Jun 21, 2005 | Exoplanetary Science, Interstellar Medium | 0 Comments

How can a planetary disk form in a region as chaotic as the Orion Nebula? Ponder the disruptive force of stellar winds in the range of two million miles per hour and temperatures above 18,000 degrees Fahrenheit. The assumption would naturally be that until a place like this settles down, material trying to form into a new solar system would simply be scattered into space. Not so, according to new findings from the Submillimeter Array (SMA), a telescope on Mauna Kea which works at millimeter and submillimeter wavelengths, and can therefore study interstellar material like gas, dust and small rocks the likes of which ultimately form planetary systems. SMA actually sees into dense interstellar clouds to examine the birthing process of stars. What the array has found is that protoplanetary disks are more tenacious than first thought. In fact, many of the objects called "proplyds" -- first seen by Hubble in the 1990s as silhouettes on the nebular background -- already have clustered...

Supernova Remnants and Star Formation

by Paul Gilster | Jun 9, 2005 | Interstellar Medium | 1 Comment

Apropos to our earlier discussion about shielding an interstellar probe comes this new image from the Hubble Space Telescope (click to enlarge). This chaotic and expanding mass of gas and dust, known as LMC N 63A, is the result of the explosion of a massive star. It's found in the N 63 region of the Large Magellanic Cloud, an irregular galaxy 160,000 light years from the Milky Way that is visible in the southern hemisphere. Numerous studies have been made of star formation and supernova remnants in this region. Imagine the shielding requirements that would be needed to penetrate such a active patch of sky! Fortunately, the interstellar medium is rarely so dense, but images like these remind us that space is anything but empty. Instead, it houses to a greater or lesser extent gas and dust particles that have to be reckoned with. We've also looked recently at the growing evidence that Voyager 1 is at the edge of the heliosphere, that 'bubble' of relatively clear space blown by the...

Inside the Carina Nebula

by Paul Gilster | Jun 1, 2005 | Deep Sky Astronomy & Telescopes, Interstellar Medium | 2 Comments

Panoramas this stunning deserve a lingering look (and be sure to click the image for a higher resolution view). You're looking at more of the fruits of the Spitzer Space Telescope's remarkable labors, this time a false-color image showing a part of the star-forming region known as the Carina Nebula. Using infrared, Spitzer was able to penetrate the so-called 'South Pillar' region of the nebula to reveal yellow and white stars in their infancy, wrapped up inside pillars of thick pink dust. The hottest gases here are green; the foreground stars are blue, which shows up better in the enlargement. And note the bright area at the top of the frame, which is what this story is all about. The glow is caused by the massive star Eta Carinae, which is too bright to be observed by infrared telescopes. Stellar winds and ultraviolet radiation from this star are what have torn the gas cloud, leaving the tendrils and pillars visible here. It is this 'shredding' process that triggers the birth of the...

On Shielding a Starship

by Paul Gilster | May 26, 2005 | Interstellar Medium, Missions | 0 Comments

Just how empty is interstellar space? We know that atoms of hydrogen and helium are the primary elements found there, but widely scattered atoms of every other element also show up in greater or lesser densities, along with grains of dust that are pushed into deep space by the pressure of stellar winds. You can also figure on cosmic rays -- ionized atoms accelerated to extremely high energy states. So energetic are galactic cosmic rays that they correspond to the energy of protons moving anywhere from 43 to 99.6 percent of the speed of light. And let's not forget magnetic fields -- a weak interstellar field aligns with our galaxy -- and high-energy gamma rays that emerge from stellar events that are still poorly understood. Granted, the density of material in the nearby interstellar medium is far lower than the best vacuums we can create on Earth. The average in the Sun's vicinity seems to be .01 atoms of hydrogen for every cubic centimeter of space, a number that is lower than the...

Voyager at the Edge

by Paul Gilster | May 25, 2005 | Interstellar Medium, Missions | 0 Comments

NASA is now confirming that Voyager 1 has entered the heliosheath, where the solar wind and interstellar materials begin to mix. The heliosheath is the outermost layer of the heliosphere, beyond which the spacecraft passes into interstellar space. Among the confirmatory data noted by the Voyager team: the magnetic field carried by the solar wind has increased by a factor of two and a half, which is the natural result of the solar wind slowing down. These readings have remained high ever since mid-December 2004, when the spacecraft crossed the termination shock at 94 AU. The issue, controversial ever since, now seems resolved. "The consensus of the team now is that Voyager 1, at 8.7 billion miles from the Sun, has at last entered the heliosheath, the region beyond the termination shock," said Dr. John Richardson from MIT, Principal Investigator of the Voyager plasma science investigation. Analogies are always useful in explaining such matters, and NASA offers the following in relation...

Shielding an Interstellar Probe

by Paul Gilster | Apr 1, 2005 | Interstellar Medium, Missions | 0 Comments

Project Daedalus, a probe to Barnard's Star that was the first complete design study of a starship, included among its other innovations a dust shield made of beryllium. Driven by a nuclear-pulse engine using internal confinement fusion, Daedalus was so large that its 50 ton shield (nine millimeters thick over a radius of 32 meters) represented only a fraction of its enormous payload. But it was a critical part of the design. For the Daedalus team realized that at 12 percent of the speed of light, an encounter with even a tiny object could destroy their vehicle. Working in the 1970's and made up of members of the British Interplanetary Society, the starship designers knew that most of the interstellar medium is gaseous, primarily hydrogen and about 25 percent helium. Dust is rare, no more than one dust particle for every trillion atoms, but the faster a spacecraft moves, the more stray protons and electrons it will encounter. At a significant percentage of the speed of light, such...

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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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