Posted on by Fraser Cain

Audio: Binary Wolf-Rayet Stars

Wolf-Rayet stars are big, violent and living on borrowed time. Put two of these stars destined to explode as supernovae in a binary system, and you’ve got an extreme environment, to say the least. Sean Dougherty, an astronomer at the Herzberg Institute for Astrophysics in Canada has used the Very Long Baseline Array radio telescope to track a binary Wolf-Rayet system. The two stars are blasting each other with ferocious stellar winds. This is one fight we’re going to stay well away from.

Listen to the interview: Wolf Rayat Binary Stars (4.2 mb)

Or subscribe to the Podcast: universetoday.com/audio.xml

Posted on by Mark Mortimer

Book Review: Stargazing with a Telescope

Stargazing can be as easy as lying flat on the back in a field and using the ‘Mark 1 eyeball’. Curving paths make planets out of dots, patterned specks transform into constellations and smears might just be a new comet portending an event of some occasion. Some people, satisfied at this level, happily return indoors into the warm embrace of artificial light. Yet others drive onwards. Bringing the moon’s mountains and valleys into stark relief on the terminator make this satellite seem somehow closer and more obtainable. With a bit more effort, the cloud bands of Jupiter transfigure a dot to a swirling artwork while the rings of Saturn unmistakenly add a dimension to the velvet darkness of night. And once heading down this path, it’s easy to become hooked. A little bit more power, a little bit more focus and the Mark 1 eyeball, aided by lens and mirrors, sees more and more.

Yet starting from square one without knowledge of lenses or manufacturers makes choosing an optical aid seem perhaps too mystical. This is where Scagell’s book excels, as within it he removes the mystery and aids those wanting to satiate their first cravings for power. The text contains about equal parts concerning the acquisition and usage of telescopes. He makes no assumptions about prior knowledge or geographical location and takes the reader on the typical learning curve of how viewing aids work and what types are available. He covers challenges of light pollution in cities, effects of mass marketing and actions for shoddy workmanship. A comparative description of 12 telescopes allows the reader to quickly determine the best type for their desires and resources. Case studies exemplify the pro’s and con’s of various types, making this a particularly good section for those thinking of purchasing a telescope as a gift. A large quantity of pictures leaves little to the imagination. Many telescopes are shown, as well as mounts and attachments. Skimming through this book or reading cover to cover removes a lot of mystery when contemplating a telescope purchase.

But Scagell doesn’t leave the reader hanging by just describing the telescopes and ancillary gear. He ably describes and depicts their usage and provides some honest appraisals of their results. In truth, he admits that most of these telescopes make little dots appear bigger or makes dots appear where none had been before. Glowing multi-coloured clouds as generated by the Hubble space telescope shouldn’t be an expectation to the backyard enthusiast. With this acknowledgement in mind, Scagell leads the reader on a possible progression of viewing targets which, though no more than dots, still result from photons that started on their journey millions to billions of years ago. From planispheres providing orientation and familiarization with seasonal variations to advanced GO TO telescopes that align far away stars in the centre of view finder at the simple push of a button, he presents the description of dials, buttons and techniques. On reading through this, there will be little doubt as to which telescope to purchase and what to expect to see through the new viewfinder.

There may seem to be a lot covered in this book and this appearance is valid. From attending Star Parties, to building your own Dobsonian mount, through to using hair dryers to keep dew off of lenses, it’s here. This volume of material is well covered as there is little superfluous material and the text is very tightly written in a well organized, well laid out reference. However, much of the enjoyment of a hobby is in sharing the pleasure and there are few hints or directions on identifying local or fellow enthusiasts. Also, there is little written on steps a typical hobbyist would make (e.g. smaller to larger aperture, multiple scopes or ancillary equipment). But these are small issues for an otherwise great text.

No one can help but pause for a moments reflection on seeing the plethora of stars seen in a clear night sky. Those who want to stick around and learn more about the universe in which we live immediately think of acquiring a telescope. Yet without clear information and advice, purchasing and using a telescope may lead to needless frustration. So, read Stargazing with a Telescope by Robin Scagell to avoid the frustration and start on a fantastic journey of discovery.

Read more reviews, or purchase a copy online from Amazon.com.

Review by Mark Mortimer.

Posted on by Fraser Cain

Audio: Dark Energy Stars

Black holes… you know. Cosmic singularities that can contain the mass of billions of stars like our Sun. Where the pull of gravity is so strong, nothing, not even light can escape their fearsome grasp. They’re the source of much discussion, indirect observation and science fiction speculation. But according to George Chapline from Lawrence Livermore National Laboratory in California, they don’t exist. Instead we have dark energy stars, which are connected to that mysterious force accelerating the expansion of the Universe.

Listen to the interview: Dark Energy Stars (5.1 mb)

Or subscribe to the Podcast: universetoday.com/audio.xml

Posted on by Fraser Cain

Is There a “Fountain of Youth” in the Galactic Core?

Most Milky Way stars – such as our own Sun – move in millions-of-years-long near-circular orbits unperturbed by the super-massive black hole (SMBH) in the midst of the galaxy. But at Milky Way Central stars can display unusually frenetic and highly eccentric motions. Those closest to the SMBH spend most of their time near aphelion – well away from its event horizon. But the SMBH’s relentless gravitational grip soon draws them inward again toward perihelion. As these stars lose their footing in the SMBH’s gravity well, they accelerate rapidly – only escaping total dissolution due to their extremely high orbital angular momentum.

Such “S-stars” were first identified by two independent teams of astronomers (one led by Reinhard Genzel at the Max Planck Institute in Garching, Germany, and the other by Andrea Ghez at UCLA) in 2002. Due to high concentrations of gas and dust enshrouding the galactic core, the teams had to detect these highly mobile sources using infrared light. By looking for shifts in the spectra of the stars and determining how fast they moved in relationship to other objects, precise orbits could be obtained. In the three years since their discovery one S-star (S2) has nearly finished a complete orbit of the Milky Way’s SMBH.

But there is something very peculiar about S-stars. Based on current models of stellar evolution, these stars should be very old – but have somehow managed to retain all the characteristics of youth.

Theoretical astronomers Melvyn Davies of Lund Observatory, Sweden and Andrew King of the University of Leicester, United Kingdom have an answer: “Our picture simultaneously explains why S-stars have tightly-bound orbits, and the observed depletion of red giants in the very center of the Galaxy.” Most stars seen around us (outside Milky Way Central) have well understood life cycles. These stars pass through a “main sequence” of development – originating as large, low-temperature bodies with smoldering central fusion furnaces and ending as small white dwarves radiating “heat” as visible light while quietly chilling out in the twilight of their celestial careers.

A star’s destiny is primarily determined by its mass. Super-massive stars, (as great as 150 Suns) live very fast lives and survive for as little as fifty thousand years. During their youth, these stars exult as brilliant blue giants with surface temperatures as high as 30,000 degrees C. Meanwhile more modest stars such as the Sun live much longer, glowing temperately for 5 to 15 billion years at lower surface temperatures (5,000 – 10,000 degrees C). Within all stars nuclear furnaces provide the energy needed to create visible light. As a star matures, its nuclear furnace grows in surface area and it gives off more and more radiation. At a certain point core radiation pressure becomes so intense that the outer atmosphere of the star swells many times over. This diffuse low- temperature gaseous envelope tells astronomers that a star is well-advanced in age and is approaching the end of its life-cycle.

But there are no such “red-giants” among the S-stars at Milky Way Central.

All stars are birthed in clusters and form associations. This should include S-stars near the SMBH. Star clusters precipitate as a group out of large regions of nebular dust and primordial gas. Although cluster stars are bound together gravitationally, tidal forces from the center of the galaxy can tear them apart over millions of years. Individual stars within such clusters then spiral inward toward the core of the galaxy. As this occurs, these stars should age to become “stars within stars” – highly radiant blue stellar cores enshrouded by hugely swollen gaseous red-giant envelopes. In their paper “The Stars of the Galactic Center” (published March 21, 2005) the authors go on to say: “S stars orbit in a region where tidal forces from the central super-massive black hole prevent star formation.”

According to current astronomical thinking S-stars should also form in clusters, and these clusters must originate well away from tidal forces near the galaxy core. It is possible, of course, for S-stars to have a different birth cycle from other stars. One idea explored by theorists is that core S-stars form as a result of recent collisions between dense molecular clouds near Milky Way Central. Another notion is that they may be spun out of the accretion disk surrounding the SMBH itself. To account for their luminosity, and high temperatures (30K degrees C), S-stars must have intermediate masses (~10 solar) and live relatively short life cycles (~10 Myrs). Because of these constraints core S-stars must all be relatively young and new ones must form constantly.

“A plausible alternative picture is that S-stars result from the sinking of massive stellar clusters toward the black hole by dynamical friction. However tides disrupt such clusters at distances much further out than the region of the observed S-stars. To supply the S-stars requires scattering into near radial orbits by gravitational interactions with other stars. However this process occurs on a timescale which would considerably exceed the main-sequence lifetime of such stars of the observed temperatures.” writes the pair.

Effectively, core S-stars must either be very youthful and delivered into the region of the SMBH by some unknown mechanism, or they must be much older than thought and somehow rendered “youthful” by interacting with the black hole and its immediate environs. Could there be a “fountain of stellar youth” at the center of the Milky Way Galaxy?

“Stripping stars solves the birth problem.”, says the authors. “… the only stars potentially identifiable as Galactic Center red giants lose their envelopes and turn into S stars instead.” Core S-stars have gone through a process of cluster birth and maturation similar to our Sun. Because they may be less massive than once thought (~ 1-4 solar masses), they’ve had more time to move toward the core.

Driven inward by gravitational scattering from more massive stars, these aging red giants receive a cosmic “face-lift” – as black hole tidal forces strip away their outer shrouds to join other gases fueling the SMBH itself. Because of greater than once thought longevity, these lower mass stars have had ample time to arrive at the galactic core from more distant clusters. The fact that they have lost their shrouds explains their relative brilliance, high temperatures, and apparent youth.

Does our own Sun have such a future before it?

According to Melvyn Davies, “No, the sun won’t suffer the same fate. We are too far from the galactic center. We are about 30000 light years from the black hole; the stars getting scattered in have come from much closer in, certainly no further than about 3000 light years.” Professor Andrew King adds, “The Sun has no close companion which could disturb its normal evolution. So it will eventually become a red giant and evolve into a run-of-the-mill white dwarf.”

Well, it would appear that there is no fountain of youth in the center of the galaxy for Sol after all.

Written by Jeff Barbour

Posted on by Fraser Cain

NASA May Silence Voyagers on April 15

Since 1958, the National Aeronautics and Space Administration (NASA) has been in service to all humankind envisioning, developing, implementing, and supporting hundreds of individual launches and missions expanding humanity’s presence in, and knowledge of, the Universe. Of the 113 probe missions NASA has undertaken, several loom extremely large in the human psyche. Of these the Pioneer and Voyager probes – now “going where no craft have gone before” – are high on the list of “vaunted-achievers”.

Pioneer 10 & 11 are now mute, the last Pioneer 10 signal was received April 27, 2002. A final attempt to receive telemetry from the debilitated craft – its nuclear power source degraded – occured on February 7, 2003. But four years earlier (on February 17, 1998) Voyager 1 surpassed Pioneer 10 as the most distant craft from the Sun in space. Today, both Voyager probes sport several fully functioning science packages (cosmic ray, plasma wave, and low-energy charged particle detectors, plus a magnetometer), healthy nuclear power sources, and operational 23 watt transmitters sending back a constant stream of data collected on conditions seen in the outermost reaches of the solar system. Despite this, NASA may be forced to say “farewell” to the Dynamic Voyager Duo – leaving their voices unheard in the night of interstellar space.

Voyager 1 took to the stars from Cape Canaveral on September 5th, 1977. Some two weeks earlier (August, 20th), Voyager 2 rode its own tail of flame skyward. Flight times and dates were scheduled to leverage a unique four-planet alignment not to recur until 2153. Voyager 1 took a short-trajectory path to make a pass at Jupiter 18 months later (March 5, 1979). Voyager 2 – on a longer route – flew by on the 8th of July. Using a wide range of instruments sensing across the lower and middle em spectrum (radio to ultraviolet), scientists and technicians at the California Institute of Technology’s Jet Propulsion Institute (JPL) soon published startling details of Sol’s largest planetary system. Unsurpassed image quality gave billion’s of human eyes extraordinary views only vaguely hinted at using earth-bound telescopes. Jupiter was found to possess a faint ring, volcanoes were seen to erupt from Io – inmost of the four galiliean satellites. Data related to Jupiter’s thermal characteristics and massive magnetic field was collected.

Even as data from Voyager 1 was being fully digested, mission specialists used emerging information to “fine-tune” Voyager 2’s upcoming view of Jupiter, its retinue of newly discovered satellites, fields, and rings. New information concerning this most dynamic of gas giants followed.

And so it went. Jupiter’s spinning globe propelled both probes further into space. Mission controllers watched as the probes scanned Saturn, then Uranus, and finally Neptune using on-board instrumentation. They resolved stunning details of Saturn’s exquisite ring system, and helped understand the role of “shepherd moons” in holding that ring together. They revealed unresolved features on the Ringed Wonder’s globe, and found surprisingly active storm systems. A ring system was discovered on Uranus too, and a large, powerful storm on distant Neptune was complete surprise. They even turned up a total of 22 new satellites. All of this at a cost of $865 million to US taxpayers.

The 1990’s saw Voyager 1 and 2 embark on a new quest – to explore the solar system’s Kuiper belt and beyond. Today with Voyager 1 traveling at the rate of 3.6 AU’s (Earth-Sun distances) per year, and located 95 AU’s from the Sun, it is poised to enter the interstellar medium. Despite 12 hour transmission delay times, these twin marvels of human imagination and creative technological genius still continue to “phone home” – garnering a wealth of data about the outermost reaches of the solar system at an annual cost of about $4 million a year.

This ongoing mission has been fruitful. Powerful solar storms caused a series of Coronal Mass Ejections (CMEs) during October 2003. By mid-April 2004, Voyager 2 had detected the resulting shock waves as they slowed to combine with matter in the Merged Interaction Regions outside the orbit of Pluto. Voyager 2 measured shock speed, composition, temperature, and magnetic flux. When included with data from spacecraft located nearer to the Sun (SOHO, Mars Odyssey, Ulysses, Cassini etc.), Voyager helped show how CMEs move through the Solar System.

From NASA’s own Voyager webpage:
“For the past two years or so, Voyager 1 has detected phenomena unlike any encountered before in all its years of exploration. These observations and what they may infer about the approach to the termination shock have been the subject of on-going scientific debates. While some of the scientist believed that the passage past the termination shock had already begun, some of the phenomena observed were not what would have been expected. So the debate continues while even more data are being returned and analyzed. However, it is certain that the spacecraft are in a new regime of space. The observed plasma wave oscillations and increased energetic particle activity may only be the long-awaited precursor to the termination shock. If we have indeed encountered the termination shock, Voyager 1 would be the first spacecraft to enter the solar system’s final frontier, a vast expanse where wind from the Sun blows hot against thin gas between the stars: interstellar space.”

NASA plans to make a final decision on continued JPL mission support for these two sturdy spacecraft by April 15.

Written by Jeff Barbour

Note from Jeff: If you are an American citizen, please call, write, email, or hand-deliver a message to your congressional representatives. Tell them that the last word sent by Voyager I and Voyager II shall not go unheard. Tell them that humanity must not orphan its children – be they human, or technological. Tell them that long-after some boondoggle project funded by taxpayer dollars in support of parochial interests has fallen by the way-side, Voyager I and II will continue to be our emissaries to the Universe.

And if you are a World citizen please petition your local government to speak plainly to the leadership of the United States telling them that all the world has entrusted its hearts and minds to the continued expansion of humankind’s presence in the Cosmos.

Voyager 1, Voyager 2 – on a mission for us all.

Posted on by Fraser Cain

What’s Up This Week – Apr 11 – Apr 17, 2005

Image credit: Sylvain Weiller
Monday, April 11 – For viewers in Alaska tonight, you will see the Moon will occult Delta Aquarii while in Chile the Moon will occult the Plieades on this universal date. Please consult the webpage for further details.

William Wallace Campbell was born today in 1862. He was a pioneer observer of stellar motions and radial velocities and served as a director of Lick Observatory. 98 years later, the first radio search for extraterrestrial civilizations was started by Frank Drake called Project Ozma and for those of us who were chasing comets in 1986, we were enjoying Halley’s closest approach to Earth on this date. Although it will be hard to best that, for northern observers, the “Magnificent Machholz” is still a large binocular or small telescope object. Skirting along the Draco – Ursa Major border, it has faded to around magnitude 8. For a nightly locator chart, please visit Heaven’s Above.

With only a slender crescent Moon, tonight would be a great time to just relax and enjoy a little skywatching. It’s the peak of the Virginid meteor shower! This shower is a very complex and tangled array of four streams with no clear radiant. While conditions are conducive, it is possible to see up to 30 faint streaks per hour, but this stream is well known for producing bolides.

Tuesday, April 12 – Today Yuri Gagarin became the first man in space making one orbit of the Earth in 1961 onboard Vostok 1. Only 20 years later, Columbia became the first space shuttle to launch. As this historic day stars, why not take the opportunity to look for a distant planet before dawn? Mars will be your guide – and you will find Neptune just slightly more than a degree north.

Let’s view the Moon tonight and locate shallow crater Cleomides just north of Mare Crisium. It is one of the most ancient features on the lunar surface and may be between 4 to 5 billion years old. Although its interior has been flooded by lava, you can still see the punctures of several young craters. For those wishing a challenge, power up to locate Rima Cleomides cutting diagonally across its northern shore.

Wednesday, April 13 – This evening will offer us an opportunity to view a crater that has long been an object of lunar transient phenomena study – Proclus. You will find this small, bright crater on the edge of Mare Crisium. It has a very high albedo (surface reflectivity) and has been known to show unusual brightenings. Depending on how far the terminator has progressed, you may get a glimpse of a highlighted rectangular feature in the shadows of its southeast wall.

Thursday, April 14 – Dutch scientist, Christian Huygens was born today in 1629. We know him as being the first to discover Saturn’s rings and large satellite Titan, but did you know Huygens held the patent for a pendulum clock? The clock ticks as the years go by on this date to reveal catastrophe. President Lincoln was shot in 1865, the Titanic sank in 1912, and who can forget that Apollo 13 met its disaster in 1970?

While today might be “bad luck” for some, it will be our good fortune to see a crater so old and ruined that it’s almost extinct. Start by identifying the three rings of Theophilus, Cyrillus and Catherina. To the south you will see the broad, bright wall of the Altai Scarp and further south a huge shallow crater on the terminator. This crater can only be seen during this particular stage of lunar sunrise and has become so dilapidated that it is unnamed. Younger craters, Lindenau and Rothman invade its northern wall and you will see a small collection of craters to the south that resemble a “paw print”. Enjoy it tonight, for it will be gone tomorrow..

Friday, April 15 – In a wide swath, the Moon will occult open cluster NGC 2331 for observers across Europe. While no specific details are listed for times, you can visit the IOTA map to see where the event will take place. For the San Francisco Bay area, the Moon will deliver a splendid graze of Epsilon Geminorum on this date. Please consult with IOTA to plan for this event. For the rest of us? We’ll see the Moon about five degrees north of Saturn.

Tonight, let’s take a quiet journey on the lunar surface as we view the area highlighted in this week’s photo – the Caucasus Mountains. Easily spotted in both binoculars and small telescopes, this mountain range towers around 5182 meters above the surrounding plains – making its peaks as high as Mount Ararat. As the shadows throw the rugged terrain into bold relief, take the time to enjoy watching the terminator move on the lunar surface. As time passes you can easily note the mountain’s shadows shortening and details emerge in Crater Cassini. It’s a very peaceful experience…

While you are waiting for the sunlight to advance, keep a watch for the “April Fireballs”. This unusual name has been given to what may be a branch of the complex Virginid stream which began earlier in the week. The absolute radiant is unclear, but keep your eyes on the southeastern skies. These bright bolides can possibly arrive in a flurry depending on how much Jupiter’s gravity has perturbed the meteoroid stream. Even if you only see one tonight, keep watching in the days ahead. The time for “April Fireballs” will last for two more weeks!

Saturday, April 16 – Tonight the Moon is furthest (apogee) from Earth at 404,304 km, but a bright star – Pollux will visually appear much closer at slightly more than a degree to the north. For viewers in the southwestern portion of North America, the Moon will occult Epsilon Geminorium on this universal date. Please check IOTA for precise times in your area.

If you explore the lunar surface this evening, you will find a very curious feature known as the Alpine Valley. Located near the terminator in the north, binocular viewers might catch a glimpse of this long, narrow scar that creases through the foothills between Mare Frigorus and Mare Ibrium. Telescopically, it is fascinating. Running a distance of 177 kilometers and ranging between 1.6 to 21 kilometers wide, this gash through the Montes Alpes will show tiny crater Trouvelot to its south and stable conditions at high power will reveal a narrow fissure on its floor. It is speculated this valley was literally carved into the lunar surface as a result of a glancing impact. Enjoy it tonight!

Sunday, April 17 – Are you ready for even more meteors? Tonight is the peak of the Sigma Leonids. The radiant is located at the Leo/Virgo border, but has migrated to Virgo in recent years. Thanks to Jupiter’s gavity, this shower may eventually become part of the Virginid Complex as well. The fall rate is very weak at around one to two per hour, and the presence of the early evening Moon will definitely hamper viewing.

Since we’ve got to deal with the Moon, why not have a look at crater Eratosthenes? Just slightly north of lunar center and on the terminator, this easily spotted feature lay at the end of the Apennine Mountain range. Its rugose walls and central peaks make for excellent viewing.

Until next week? Ask for the Moon… But keep reaching for the stars! May all your journeys be at – Light Speed… ~Tammy Plotner

Posted on by Fraser Cain

New Method Could Detect Alien Space Stations

Illustration by: Jimmy Paillet
As of February 5, we know of 136 extrasolar planets. These have been discovered in four ways: The first – called pulsar timing – allowed us to detect Earth-sized and smaller planets by studying the variations in arrival time of radiation generated by a pulsar. The next – Doppler spectroscopy – allows ground-based telescopes to measure the “shift” in a star’s spectrum caused by the gravity of an orbiting planet. The third – astrometry – is used in much the same way – looking for the periodic “wobble” in position that a possible planet could cause on its parent star. And the last? Transit photometry allows for the study of the periodic dimming of a star as a body passes in front of it from a particular viewpoint – producing a light curve.

In April 2004, Luc F. A. Arnold, (Observatoire de Haute-Provence CNRS 04870 Saint-Michel – l’Observatoire, France) was working on a transit generated by a saturn-like planet when he had an idea. Could this same principle be applied to look for transiting bodies that were artificial in nature?

“I discussed the idea with several colleagues who found it interesting,” commented Arnold. A collection of artificial bodies would produce light curves easily distinguishable from natural ones. For example, a triangular object or something shaped like our own man-made satellites would show an entirely different signature. If multiple artificial objects were detected transiting – this could possibly be a form of signaling the presence of other intelligent life – one with an effectiveness equal to the range of the laser pulse method.

A cost-effective alternative to radio SETI or optical SETI is to look for artificial planet-size bodies which may exist around other stars. Since they would always pass in front of their parent star for a given remote observer, there is a strong possibility they can be detected and characterized using the transit photometry method. A planetary transit light curve contains fine features due to the object shape – such as planet oblateness, double planets or ringed planets. As Arnold explains, “The sphere is the equilibrium shape preferred for massive and planet-size bodies to adapt to their own gravity, (but) one can consider non-spherical bodies, especially if they are small and lightweight and orbit a dwarf star. Their transits in front of a star would produce a detectable signal.” Non-spherical artificial objects – like a triangle – would produce a specific transit light curve. If multiple objects should transit, a remarkable light curve would be created by their “on again – off again” nature of light. Such an observation would clearly claim an artificial nature. To visualize this, think of a flashlight moving behind a lowered window blind, and you’ll begin to get the idea!

The bulk of Luc Arnold’s work – just accepted for publication in the “Astrophysical Journal” – has been to prove through computer simulation the effects of different and multiples shapes and show these differing light curves. To help you better understand, the screen that you are now looking at is composed of pixels – a logical rather than a physical unit. If you were to place a triangle shape over your monitor’s screen, it would cover the pixels in a specific arrangement. During a simulation, the stellar flux is zeroed out in pixels and compared to the normal flux of the star. This simulated artificial body transit is then fitted against known planetary transit using a Powell algorithm.

“But most complex artificial objects’ light curve cannot be exactly superposed by a planetary transit, and the algorithm ends with non-zero residuals, i.e. a non-zero difference between the two light curves. This difference is the ‘personal’ signature of the artificial object. Should it rotate, the residual light curves will show additional modulation. When set against a gradient, such as the limb, an artificial object would also show sudden slope variations in the light curve during ingress or egress,” explains Arnold.

The equilateral triangle produces a transit light curve different than a sphere. In fact, its light curve resembles a ringed planet transit, so an ambiguity may remain in distinguishing these objects. But more complex objects, such as clusters of shapes, for example, create very specific signatures. For an artificial satellite-like object, its symmetrical structure would be apparent – as each area would impact the light curve at specific intervals. An elongated object, would produce undulation in its longer period of ingress and egress – in effect causing multiple “transits” making detection easier. The nature of these oscillations could very well be considered a sign of intelligent device. If several objects were spatially arranged in groups to ingress a star in a mathematically constant manner, these drops in the light curve could clearly represent a type of message – the language of science.

With the computer simulations perfected, Arnold knows what a natural or artificial transiting body should look like in a light curve – but has science observed a planetary transit? “Up to now, there is only one transit light curve obtained with a very good accuracy – the transit for HD 209 458b observed with the Hubble Space Telescope. T. Brown and colleagues found the light curve could be fitted with a spherical body to within the measurement accuracy.” This type of information provides Arnold with the model he needs. In June 2006, his vision may be realized. COROT (a space mission approved by the French Space Agency CNES, with a participation of Austria, Belgium, Brazil, Germany, Spain, ESA and ESTEC) will be dedicated to stellar seismology and the study of extrasolar planets – the first approved space mission solely devoted to these subjects. The spacecraft will consist of a ~ 30 cm telescope with an array of detectors to monitor the light curves of well chosen stars through CCD. The overall potential of COROT (COnvection, ROtation and planetary Transits) is to detect several tens of Earth sized planets and more upcoming programs such as the Terrestrial Planet Finder (TPF) and Space Interferometry Mission (SIM) will change the face of all we know about extrasolar planets.

What does this kind of new technology mean to researchers like Luc Arnold? “These space missions will give a (photometric) accuracy of down to 0.01% – but 1% could be sufficient if objects are big enough.” According to his research a single transit of an artificial body would require that kind of accuracy, but a multiple transit would be much more relaxed. “1% photometry is within the capability of thousands of amateur astronomers equipped with CCD.” Chances are far greater that a communicative civilization would favour a series of objects over a single non-spherical one for signaling their presence. Transits of opaque objects are achromatic, putting them within detectability of CCD over the entire spectrum.

As Luc points out, this type of research may well be within the realm of the contributing amateur astronomer. Currently the search for signs of extra-terrestrial intelligence are limited to radio and the search for laser pulse which demands specialized equipment. “For the moment, there is no project to apply this idea. If it the idea turns into a specific (SETI) observing program, a number of collaborations would be welcome!”

The search for planetary transits is already in operation, such as the Optical Gravitational Lensing Experiment (OGLE), “and the multiple transit case could be discovered within the course of these programs – maybe tomorrow!” While tomorrow might seem like an impossible dream, Arnold knows differently. His work has already been submitted to the SETI institute. For the rest of the citizens of planet Earth, we await the results. Will tomorrow show us a possible energy collection, communication or study device put into orbit by another sentient species? If we consider what we know of astronomy to be a basic “truth” throughout the Cosmos, then a discovery of this magnitude could be the biggest news of them all… “Assuming we are sure to have detected an alien artifact in a transit light curve, my opinion is that we should consider it as a clear ‘Hello world… We are here!’ addressed to the whole Galaxy!”

Written by Tammy Plotner

Posted on by Fraser Cain

Two Massive Stars Orbiting One Another

Astronomers using the National Science Foundation’s Very Long Baseline Array (VLBA) radio telescope have tracked the motion of a violent region where the powerful winds of two giant stars slam into each other. The collision region moves as the stars, part of a binary pair, orbit each other, and the precise measurement of its motion was the key to unlocking vital new information about the stars and their winds.

Both stars are much more massive than the Sun — one about 20 times the mass of the Sun and the other about 50 times the Sun’s mass. The 20-solar-mass star is a type called a Wolf-Rayet star, characterized by a very strong wind of particles propelled outward from its surface. The more massive star also has a strong outward wind, but one less intense than that of the Wolf-Rayet star. The two stars, part of a system named WR 140, circle each other in an elliptical orbit roughly the size of our Solar System.

“The spectacular feature of this system is the region where the stars’ winds collide, producing bright radio emission. We have been able to track this collision region as it moves with the orbits of the stars,” said Sean Dougherty, an astronomer at the Herzberg Institute for Astrophysics in Canada. Dougherty and his colleagues presented their findings in the April 10 edition of the Astrophysical Journal.

The supersharp radio “vision” of the continent-wide VLBA allowed the scientists to measure the motion of the wind collision region and then to determine the details of the stars’ orbits and an accurate distance to the system.

“Our new calculations of the orbital details and the distance are vitally important to understanding the nature of these Wolf-Rayet stars and of the wind-collision region,” Dougherty said.

The stars in WR 140 complete an orbital cycle in 7.9 years. The astronomers tracked the system for a year and a half, noting dramatic changes in the wind collision region.

“People have worked out theoretical models for these collision regions, but the models don’t seem to fit what our observations have shown,” said Mark Claussen, of the National Radio Astronomy Observatory in Socorro, New Mexico. “The new data on this system should provide the theorists with much better information for refining their models of how Wolf-Rayet stars evolve and how wind-collision regions work,” Claussen added.

The scientists watched the changes in the stellar system as the star’s orbits carried them in paths that bring them nearly as close to each other as Mars is to the Sun and as far as Neptune is from the Sun. Their detailed analysis gave them new information on the Wolf-Rayet star’s strong wind. At some points in the orbit, the wind collision region strongly emitted radio waves, and at other points, the scientists could not detect the collison region.

Wolf-Rayet stars are giant stars nearing the time when they will explode as supernovae.

“No other telescope in the world can see the details revealed by the VLBA,” Claussen said. “This unmatched ability allowed us to determine the masses and other properties of the stars, and will help us answer some basic questions about the nature of Wolf-Rayet stars and how they develop.” he added.

The astronomers plan to continue observing WR 140 to follow the system’s changes as the two massive stars continue to circle each other.

Dougherty and Claussen worked with Anthony Beasley of the Atacama Large Millimeter Array office, Ashley Zauderer of the University of Maryland and Nick Bolingbroke of the University of Victoria, British Columbia.

Original Source: NRAO News Release

The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.

Posted on by Fraser Cain

Details of Xanadu Region on Titan

During a close flyby of Titan on March 31, 2005, Cassini’s cameras got their best view to date of the region east of the bright Xanadu Regio. This mosaic consists of several frames taken by the narrow-angle camera (smaller frames) put together with an image taken by the wide-angle camera filling in the background. It reveals new detail of dark expanses and the surrounding brighter terrain.

Some of the features seen here are reminiscent of those seen elsewhere on Titan, but the images also reveal new features, which Cassini scientists are working to understand.

In the center of the image (and figure A at bottom) lies a bright area completely surrounded by darker material. The northern boundary of the bright “island” is relatively sharp and has a jagged profile, resembling the now-familiar boundary on the western side of Xanadu (see PIA06159). The profile of the southern boundary is similar. However, streamers of bright material extend southeastward into the dark terrain. At the eastern end of the bright “island” lies a region with complex interconnected dark and bright regions (see figure B).

To the south, the bright terrain is cut by fairly straight dark lines. Their linearity and apparently angular intersections suggest a tectonic influence, similar to features in seen in the bright terrain west of Xanadu (see PIA06158).

The camera’s near-infrared observations cover ground that was also seen by Cassini’s synthetic aperture radar in October 2004 and February 2005. Toward the northeastern edge of the dark material a dark, circular spot in the middle of a bright feature (see figure C) is an approximately 80-kilometer-wide (50-mile) crater identified in the February 2005 radar data (see PIA07368 for the radar image).

The resolution of this new image is lower but sufficient to reveal important similarities and differences between the two observations. Part of the crater floor is quite dark compared to the surrounding material at near-infrared wavelengths. This observation is consistent with the hypothesis that the dark material consists of complex hydrocarbons that have precipitated from the atmosphere and collected in areas of low elevation. At radar wavelengths the crater floor is much more uniform and there also are brightness differences seen by these two instruments outside of the crater. Such comparisons give Cassini scientists important clues about the roughness and composition of the surface material on Titan.

Another interesting comparison is the “dark terrain” with small bright features as seen by the radar (see PIA07367) and the essentially inverted pattern (bright with small dark features) seen by the imaging science subsystem cameras. In the mosaic, this area is in the top left narrow-angle camera image.

Within the bright terrain at the top of the mosaic, just left of center, lies a very intriguing feature: a strikingly dark spot from which diffuse dark material appears to extend to the northeast. The origin of this feature is not yet known, but it, too, lies within the radar image; Cassini scientists will thus be able to study it using these complementary observations.

The mosaic is centered on a region at 1 degree north latitude, 21 degree west longitude on Titan. The Cassini spacecraft narrow-angle camera images were taken using a filter sensitive to wavelengths of polarized infrared light and were acquired at distances ranging from approximately 148,300 to 112,800 kilometers (92,100 to 70,100 miles) from Titan. Resolution in the images is about 1 to 2 kilometers (0.6 to 1.2 miles) per pixel.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA’s Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging team is based at the Space Science Institute, Boulder, Colo.

For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov . For additional images visit the Cassini imaging team homepage http://ciclops.org

Original Source: NASA/JPL/SSI News Release

Posted on by Fraser Cain

Podcast: Sedna Loses Its Moon

Remember Sedna? It’s that icy object uncovered last year in the outer reaches of the Solar System. When it was first discovered, astronomers noticed it rotated once every 20 days. The only explanation that could explain this slow rotation was a moon, but a moon never showed up in any of their observations. Scott Gaudi is a researcher with the Harvard Smithsonian Centre for Astrophysics. He and his colleagues have been watching the rotation of Sedna with a skeptical eye, and think it’s only rotating once every 10 hours or so. As for the moon? Easy come, easy go.
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