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Helium: Speed Brake for the Solar Wind?

by Paul Gilster | May 21, 2007 | Sail Concepts | 5 Comments

Someday fleets of interplanetary craft powered by the solar wind may cross the Solar System, using huge magnetic fields as their 'sails.' The concept is increasingly well understood, and I notice that researchers like Robert Winglee (University of Washington) have been extending it to include beamed propulsion methods as well (Winglee's concept is called MagBeam), useful if your goal is to move deeper still into nearby space. But for all this to happen, we'll need to learn much more about the solar wind itself and how we might ride it. Image: Artist's impression of a mini-magnetosphere deployed around a spacecraft. Plasma or ionized gas is trapped on the magnetic field lines generated onboard, and this plasma inflates the magnetic field much like hot air inflates a balloon. The mini-magnetosphere is then blown by the plasma wind from the Sun called the solar wind which has a speed of between about 350 to 800 km/s. Credit: Robert Winglee/University of Washington. Enter NASA's Solar...

A Galactic Collision, and the Sun’s Future

by Paul Gilster | May 19, 2007 | Deep Sky Astronomy & Telescopes | 49 Comments

I remember a startling painting from an astronomy book I once had when I was a kid. It showed two spiral galaxies much like the Milky Way in the process of collision, and I recall the caption saying that the stars in galaxies were so widely spaced that even in an event like this, few if any stars would collide individually. The galaxies, so the writer surmised, would simply pass through each other, leaving both relatively unscathed. What made the picture interesting was reading in the same volume that the Milky Way is eventually going to collide with the Andromeda galaxy, so that I had the vivid image of a vast galaxy getting ever closer in the night sky until the entire view was consumed by cities of stars. It was a lovely image, but the idea of galaxies merging without notable disruptive effect is long gone. And new work from the Harvard-Smithsonian Center for Astrophysics has implications for our Solar System as well. In two billion years, with the Sun still firmly on the main...

Amateur Bags GJ 436 b Transit

by Paul Gilster | May 18, 2007 | Exoplanetary Science | 4 Comments

One of the most exciting aspects of the exoplanet hunt is that it is not confined to huge telescopes and professional astronomers. Timothy Ferris described the remarkable advances in amateur equipment and observing techniques in Seeing In the Dark (Simon & Schuster, 2002), but he'll need a whole new chapter to cover what's happening not only with distributed computing (as via the systemic collaboration, for example) and the software and hardware advances that let amateurs observe exoplanet transits from sites around the world. Last night Tonny Vanmunster observed the transiting 'hot Neptune' GJ 436 b from his CBA Belgium Observatory in Landen, reporting his results over the Net and this morning on his Web site. Ponder this: GJ 436 b orbits an M-class red dwarf that is 33 light years away. The planet itself has a mass roughly 23 times that of Earth, with a radius approximately that of Neptune. There was a time when Neptune itself would have been a tricky catch for the average amateur,...

Plumes on Enceladus: A Tidal Squeeze

by Paul Gilster | May 17, 2007 | Outer Solar System | 3 Comments

An object in an elliptical, egg-shaped orbit experiences interesting gravitational stresses. Enough so that the changing forces it endures may be the cause of the plumes of water vapor that Cassini found on Saturn's moon Enceladus in 2005. In essence, the tiny moon is being alternately squeezed and stretched as it makes its way around the planet. These tidal forces cause existing fault lines to rub against each other, producing enough heat to turn ice into water vapor and ice crystals. That's the conclusion of new work by Francis Nimmo (University of California -- Santa Cruz) and team, who note the warmer surface of Enceladus' southern pole and the presence of the famous 'tiger stripes,' which appear to be tectonic fault lines. "We think the Tiger Stripes are the source of the plumes," says Nimmo, "and we made predictions of where the Tiger Stripes should be hottest that can be tested by future measurements." Image: This is a mosaic of Enceladus compiled from 21 images taken by the...

Transiting ‘Hot Neptune’ Found

by Paul Gilster | May 16, 2007 | Exoplanetary Science | 11 Comments

Whether or not Gliese 581 c, that intriguing world that may or may not offer temperatures conducive to life, will make a transit of its star is not yet known. But the principle that radial-velocity searches can identify a planet that is subsequently studied via transit received further validation today with the detected transit of a Neptune-class world around GJ 436. This is the smallest and least massive planet ever examined through transit methods, and it bodes well for future such studies of M-class stars. The new transit comes courtesy of the Swiss team that includes Michel Mayor and Didier Queloz, recently in the news due to their work on Gliese 581 c -- do these guys ever get any sleep? As Andy noted in a comment this morning, this 'hot Neptune' orbits closer to its star than the innermost planet of Gliese 581. GJ 436 is an M-class red dwarf, a type of star whose small radius makes the detection of such worlds by transit methods easier than would be the case for solar-type...

A Ring of Dark Matter

by Paul Gilster | May 15, 2007 | Deep Sky Astronomy & Telescopes | 6 Comments

Dark matter has to be made up of some sort of elementary particle, but we know astoundingly little about it. Its existence can be inferred from its necessary effects -- something we can 't see seems to be holding galaxy clusters together, because the gravity from the stars we do observe in them isn't sufficient to do the job. That makes gathering any evidence for dark matter's behavior -- indeed, for its very existence -- a crucial goal for astrophysicists. And today we have the strongest supporting evidence yet that dark matter is real. The work comes via the Hubble Space Telescope, used by a team of astronomers to locate what appears to be a ring of dark matter in the cluster ZwCl0024+1652, some five billion light years from our Solar system. The ring is 2.6 million light years across, and this detection appears to be unique. Says M. James Jee (Johns Hopkins): "This is the first time we have detected dark matter as having a unique structure that is different from the gas and...

Looking Hard at Gliese 581

by Paul Gilster | May 14, 2007 | Exoplanetary Science | 6 Comments

We'd all like to know more about Gliese 581 c, the most talked about exoplanet of them all because of the possibility -- however controversial -- that it may be habitable. One way to learn more would be to observe a transit, which is what the Canadian space telescope called MOST is now attempting to do. The odds are roughly one in thirty, according to MOST principal investigator Jaymie Mark Matthews, but even the few observations ahead for MOST will tell us more about the star in question. Matthews' thoughts are reported in an article in the British Columbian alternative daily The Tyee, along with a nice backgrounder on the planet by writer Monte Paulsen. Evidently the Swiss team behind the Gliese 581 c announcement, which includes Michel Mayor and Didier Queloz (the first to identify an exoplanet, in 1995), had contacted the MOST controllers at the University of British Columbia before going public with their latest work. They hoped a transit could verify the existence of the new...

The Search for Vulcan

by Paul Gilster | May 12, 2007 | Exoplanetary Science | 15 Comments

40 Eridani is a triple-star system some 16 light years from Earth. If it rings a faint bell, that's probably because of its association with Star Trek. In the universe of the show, 40 Eridani is home to Vulcan, birthplace of the inscrutable Mr. Spock (Gene Roddenberry himself signed off on the idea). Not so long ago, the existence of planets would have been doubted in such a system, but we're learning that double and even triple star systems can and do support planets. So maybe there is a 'Vulcan' out there after all, though doubtless sans humanoids with pointy ears. In any case, the elements of this system are widely spaced, and 40 Eridani A is a K-class star not so different from Centauri B, a star that could well support Earth-mass planets. Recently Angelle Tanner (Caltech) embarked on simulations designed to show whether or not the Space Interferometery Mission (known as SIM PlanetQuest) might be able to detect such a world. Tanner's work confirmed that a planet like this in the...

In Search of Ancient Stars

by Paul Gilster | May 11, 2007 | Deep Sky Astronomy & Telescopes | 3 Comments

We've seen recently how difficult it can be to pin down the age of a star. Even the Alpha Centauri system is problematic, with age ranges for Centauri A and B varying from slightly less than four billion years to as many as eleven (depending on which star we're talking about, and which of several methods was used for the calculation). But one thing that helps with stars that are older than the ordinary is the chemical composition of the star in question. "Surprisingly, it is very hard to pin down the age of a star," says Anna Frebel (University of Texas), "although we can generally infer that chemically primitive stars have to be very old." Frebel's work has led her to a star that is old indeed. It is HE 1523-0901, now pegged thanks to the work of Frebel's team at the astounding age of 13.2 billion years, meaning it would have formed not all that long after the Big Bang. The researchers were able to study radioactive elements in the star to create a precise calculation. A...

Titan’s Tholins: Precursors of Life?

by Paul Gilster | May 10, 2007 | Outer Solar System | 2 Comments

Tholins are interesting molecules, large and complex. They're organic aerosols -- particles small enough to remain suspended in the atmosphere for some time -- formed from methane and nitrogen. Their presence on Titan is intriguing because they're thought to contain some of the chemical precursors of life. That makes studying how they form there a preoccupation with those wanting insight into how life appears. Titan is a wonderful laboratory for such studies. We already knew that nitrogen and methane dominated its atmosphere. New measurements from Cassini now show that tholins form much higher in that atmosphere than was previously believed. The most recent Cassini flybys, though, have also demonstrated the presence of benzene, a key component in the formation of aromatic hydrocarbon compounds. Moreover, Cassini's Ion Beam Spectrometer (IBS) and Electron Spectrometer (ELS) have picked up the presence of large positive and negative ions. Here's Andrew Coates (University College,...

An Exoplanetary Weather Map

by Paul Gilster | May 9, 2007 | Exoplanetary Science | 11 Comments

Impressive results released today show just how much we're learning about the 'hot Jupiters' that comprise about a quarter of known exoplanets. The first concern HD 149026b, a distant world which the infrared Spitzer instrument has shown to be the hottest planet ever studied. It's somewhat smaller than Saturn but more massive, and is thought to contain more heavy elements than could be found in our entire Solar System outside the Sun itself, with a core as much as 90 times the mass of the Earth. And the odd thing about HD 149026b is that for it to reach the measured temperature -- a smoking 3,700 degrees Fahrenheit, or 2,300 degrees Kelvin -- it would have to be absorbing just about all the starlight reaching it. The upshot is a planet whose surface is blacker than charcoal, re-radiating incoming energy in the infrared. What a view for the nearby traveler: "The high heat would make the planet glow slightly, so it would look like an ember in space, absorbing all incoming light but...

Twilight of a Supernova

by Paul Gilster | May 8, 2007 | Deep Sky Astronomy & Telescopes | 22 Comments

The thought that Eta Carinae, a star at least 100 times more massive than the Sun, is a ticking time bomb seems to infuse much of the coverage about the huge supernova recently observed by the Chandra X-ray Observatory. And you can see why. Big explosions are marketable, which is why it sometimes seems that one way to categorize many of today's movies is by how many cars were blown up during the making of them. When you're talking about something a hundred times larger than the typical supernova, you're going to get attention. What if a star 100 times the size of the Sun -- or larger -- goes off in our neighborhood? Adding to the comparison is the fact that the supernova, known as SN 2006gy, seems to have expelled a large amount of material before the catastrophe. Eta Carina also shows signs of expelling mass, and it's 7500 light years away, vs. the 240 million light years of SN 2006gy. Close enough to cause us problems? I don't know the answer, but it does seem clear that one result...

A New Vision for Space

by Paul Gilster | May 7, 2007 | Culture and Society | 25 Comments

History teaches that when big operations falter, small upstarts often rise to the challenge. In the case of NASA, the process may already be at work, and the upstarts are emerging: SpaceX, Blue Origin, Virgin Galactic. Out in the wilds of Las Cruces, New Mexico is building a spaceport. In fact, says Russell Saunders, Jr., the time has come to consider contingency plans. 'Saunders' is a pseudonym for a space scientist who works for a major aerospace organization. His essay appeared this afternoon on the NASA Watch site. Saunders believes NASA is fixated on an iconography that's half a century old, referring back to the spectacular space series that ran in Collier's magazine in the early 1950's. These were glorous, von Braunian visions of enormous rockets and flotillas of spacecraft pushing outward to Mars, but they're an uncomfortable fit with today's realities. Here's what Saunders is talking about: Imagine what the artists and pioneers behind the Colliers vision might have done with...

NIAC’s Contributions and the Future

by Paul Gilster | May 7, 2007 | Culture and Society | 2 Comments

The news that NASA intends to close its Institute for Advanced Concepts has many in the space community concerned, and Centauri Dreams' comment on the matter was but one of many to fill the Net when the news broke in March. Now, however, there appears to be at least an attempt to keep the Institute alive. People who have had some connection with NIAC are being asked to step in with demonstrated benefits from its activities. That news comes via this post on the Space Elevator Blog, as passed along by Joseph Mahaney. I've just confirmed it with sources inside NIAC. Here are the areas for which contributions are solicited: Subsequent investment by NASA, other government agencies, or the private sector. Intellectual contributions that have resulted in an agency putting resources into its own studies of a concept. For example, prompted by the success of a Phase I or Phase II concept, an agency convenes panels to study the work or otherwise funds studies of its own. Unexpected spin-off...

On Wally Schirra

by Paul Gilster | May 5, 2007 | Culture and Society | 6 Comments

I wish I had something profound to say about Wally Schirra. But when I think about him, what I get instead are moments. Great moments. I remember watching Schirra's Atlas booster muscling Sigma 7 downrange that day in 1962. A space-struck kid, I thought the astronaut was as cool and unflappable as any man who would ever ride a rocket. His sense of humor was irrepressible, especially in the context of hazardous early space missions. Thus the 'Jingle Bells' moment on the harmonica, and his sighting of the 'UFO' -- Santa Claus and his reindeer. "We have an object, looks like a satellite going from north to south, probably in polar orbit... I see a command module and eight smaller modules in front. The pilot of the command module is wearing a red suit..." Tom Stafford was in on that gag on Gemini 6 (he would later go on to command Apollo 10). I was in college when Apollo 7 flew and recall the squabbles with controllers on the ground. To be fair, Schirra had a cold, a famous one that he...

COROT’s First Exoplanet

by Paul Gilster | May 4, 2007 | Exoplanetary Science | 2 Comments

The early news from COROT couldn't be more encouraging. Just sixty days into its science mission, the spacecraft has found its first transiting exoplanet and has returned information about the interior of a star. The latter findings point to COROT's role in asteroseismology, the study of stellar interiors through analysis of the star's light curves. What has mission scientists smiling is that in both cases, the instruments they're watching show signs of working even better than planned. True, the data carrying these results are still noisy and in need of plenty of analysis, but COROT project scientist Malcolm Fridlund sounds quite an optimistic note: "The data we are presenting today is still raw but exceptional. It shows that the on-board systems are working better than expected in some cases - up to ten times the expectation before launch. This will have an enormous impact on the results of the mission." One would think so. It raises the stakes for COROT from detecting...

HAT-P-2b: ‘A Really Weird Planet’

by Paul Gilster | May 3, 2007 | Exoplanetary Science | 12 Comments

Last night I was thinking that the day would come when all the planets we've been discovering have proper names instead of stark designations in catalogs. Then I realized that this is unlikely. As the rate of planetary discoveries accelerates through space-borne missions and ever more precise detection methods here on Earth, it may be that we'll keep generating new finds faster than the naming process can catch up with them. So I guess we should get used to designations like Gliese 581 c. Of course, a planet can have multiple designations, depending on how it's catalogued or found. The recently announced gas giant HAT-P-2b (a very strange place indeed) is called this not for its place in a catalog but its discovery method, the HAT network of automated telescopes. HAT stands for Hungarian-made Automated Telescope, but the project is headquartered at the Harvard-Smithsonian Center for Astrophysics (CfA) and works with instruments in Arizona, Hawaii and in this case, Israel. Its focus:...

Calculating How Stars Age

by Paul Gilster | May 2, 2007 | Exoplanetary Science | 2 Comments

We need to know more about how stars age. Ponder this: Centauri A and B are perhaps 2.5 billion years older than our Sun. If we're interested in the development of intelligent life, older is clearly better -- who knows what Earth might develop in the next two billion years? But are there planets around either of the primary Centauri stars? And if there are, how have their planetary systems changed over the course of those milennia? Addendum: See the comments below -- my figure of 2.5 billion years older than the Sun is in the middle of more extreme age estimates in both directions, and even these are questioned by the work we discuss in the following paragraphs. One way to study these things is by looking at how stars rotate. A recently announced method called gyrochronology works with the premise that a star's age is tightly bound up with both its rotation and its color. Syndey Barnes, who developed the technique at Lowell Observatory, explains it this way: "If you know the...

Death of an Astrophysicist

by Paul Gilster | May 1, 2007 | Culture and Society | 0 Comments

Bohdan Paczynski, the Princeton astrophysicist who died April 19, was a major contributor to the exoplanet hunt, fine-tuning the techniques used in gravitational microlensing. Coming to Princeton in 1982 after twenty years at Warsaw's Copernicus Astronomical Center, Paczynski understood early on that the bending of light by foreground objects, predicted by Einstein, could be applied to surveying stars in our own galaxy. A star passing directly in front of another can focus the light from the background star, producing a natural lens that allows investigation of objects otherwise impossible to observe. The consortium of scientists that Paczynski led would go on to found the Optical Gravitational Lensing Experiment (OGLE), now active at Chile's Las Campanas Observatory. Says Michael Strauss, a professor of astrophysical sciences and a colleague of Paczynski's: "The next thing Bohdan realized was that when you observe lensing that often, you can do other clever things, such as use it to...

‘Asia Emerging’: The Director’s Cut

by Paul Gilster | May 1, 2007 | Culture and Society | 0 Comments

Having had time to decompress from their exhausting Asian trip, Gregory and Elisabeth Benford have revised and enlarged the account of their travels that Centauri Dreams published in late March. The text contains numerous additional insights, but what makes this revision truly stand out from the original post are the photographs, fully seven times the number first published, each illustrating a unique facet of their journey. I've inserted the new Asia Emerging in the archives. Don't miss its unforgettable images and insights into a part of the world that will have much to say about our future on this planet. I told Gregory that my favorite photograph is the one of him at the Raffles Hotel in Singapore, Singapore Sling in hand. Shades of Somerset Maugham...

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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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