Posted on by Fraser Cain

What’s Up This Week – Nov 8 – 14, 2004

Image credit: Hubble
Monday, November 8 – Saturn turns retrograde on this date and today will be the closest approach of asteroid 4433 Goldstone to Earth at a respectable distance of 1.358 AU – or just 149,597,871 km. While asteroids of this nature are being closely monitored, they aren’t really observable to the majority of the amateur astro community. In case you’ve ever wondered just what it would be like to follow an asteroid, why not try your hand at locating and tracking one one of the brightest and easiest for beginners? Vesta!

Asteroid Vesta is considered to be a minor planet since its approximate diameter is 525 km (326 miles) wide, making it slightly smaller in size than the state of Arizona. Vesta was discovered on March 29, 1807 by Heinrich Olbers and it was the fourth such “minor planet” to be identified. Olbers discovery was fairly easy because Vesta is the only asteroid bright enough at times to be seen unaided from Earth. Why? Orbiting the Sun every 3.6 years and rotating on its axis in 5.24 hours, Vesta has an albedo (or surface reflectivity) of 42%. Although it is about 220 million miles away, pumpkin-shaped Vesta is the brightest asteroid in our solar system because it has a unique geological surface. Spectroscopic studies show it to be basaltic, which means lava once flowed on the surface. (Very interesting since most asteroids were once though to be rocky fragments left-over from our forming solar system!)

Studies by the Hubble telescope confirmed this, as well as a large meteoric impact crater which exposed Vesta’s olivine mantle. Debris from Vesta’s collision then set sail away from the parent asteroid. Some of them remained within the asteroid belt near Vesta to become asteroids themselves with the same spectral pyroxene signature, but some escaped through the “Kirkwood Gap” created by Jupiter’s gravitational pull and allowed these small fragments to be put into an orbit that would eventually bring them “down to Earth”. Did one make it? Of course! In 1960 a piece of Vesta fell to Earth and was recovered in Austrailia. Thanks to Vesta’s unique properties, the meteorite was definitely classified as once being a part of our third largest asteroid.

Now, that we’ve learned about Vesta, let’s talk about what we can see from our own backyards. As you can discern from the image, even the Hubble Space Telescope doesn’t give incredible views of this bright asteroid. What we will be able to see in our telescopes and binoculars will closely resemble a roughly magnitude 7 “star”, and it is for that reason that I strongly encourage you to visit Heaven’s Above, follow the instructions and print yourself a detailed map of the area. When you locate the proper stars and the asteroid’s probable location, mark physically on the map Vesta’s position. Keeping the same map, return to the area a night or two later and see how Vesta has moved since your original mark. Since Vesta will stay located in the constellation of Aquarius all month, your observations need not be on a particular night, but once you learn how to observe an asteroid and watch it move – you’ll be back for more!

Tuesday, November 9 – Remember last week when Jupiter and Venus did a spectacular morning dance in the sky? Well, the excitement hasn’t ended yet for now the Moon has joined the show. Before local dawn, Jupiter will be 1 degree to the lower right of the crescent Moon. For most of us, this beautiful “sky scenery” would be pleasure enough, but for those living in eastern Canada and the north-eastern United States, something just a bit more exciting is about to happen – the Moon is going to occult Jupiter during the daylight hours! Timing for such events is very critical and varies widely by location. To ensure success, please visit the International Occultation Timing Association (IOTA) for precise times in your area.

Asteroid 2000 JE5 will be performing a very near Earth fly-by today as it passes only 0.131 AU away. While that is less than the distance between Earth and the Sun, it is still 19,597,338 km or 12,177,221 miles away!

Thanks to dark skies, early tonight would be a great opportunity to use telescopes or large binoculars to study one of the finest of deep space objects, the “Ring” nebula. Located in the quickly westering constellation of Lyra and roughly halfway between bright stars Sheilak (Beta Lyrae) and Sulfat (Gamma Lyrae) this wonderful planetary nebula can be seen in small binoculars and comes to life with a telescope. But before we view the “Ring”, let’s learn a little more about the M57 and the two stars we’ll use to find it.

Beta is a variable star that averages around 3.38 magnitude at its maximum, but drops to around 4.1 at minima. This typical lyrid-type eclipsing variable is relatively easy to observe even without optical aid because nearby Gamma remains a constant magnitude 3.25. For a few days, both stars will appear to be about the same brightness, but about every 13 days, Sheilak will fade out to about half the brightness of Sulafat! For those of you aiming a telescope towards Gamma, you will find that it is a optical double star with a 10th magnitude companion.

Roughly halfway between these two interesting stars (but a bit closer to Beta) is tonight’s object. The M57 is a classic example of a planetary nebula first discovered by French astronomer Antoine Darquier in 1779 and cataloged only days later by Charles Messier. At approximately 2300 light years away, the “Ring” is basically the ejecta of a dying star. Many theories exist about the structure of the nebula itself , but popular opinion is that we may be looking through the shell, much like looking down the barrel of a gun. Its interior star has reached white dwarf stages, slowly shedding its mass and complex waves of ultra-violet radiation which fluoresce the rarefied gases of the nebula expanding at the gentle rate of around 19 km (12 miles) per second. The nebula itself exhibits many different spectral qualities as seen in photography, but what does it really look like?

To binoculars, the M57 will appear almost stellar in size, but the small disk lacks the properties of starlight. To the average telescope, the “Ring” will appear much as you see here – a softly glowing torus with a gentle grey/green color. At low power it is spectacular because the accompanying stellar field is so rich. Larger telescopes can resolve the central star under excellent sky conditions along with variances in the structure of the ring itself. Reach for the “Ring” tonight… You’ll be glad you did!

(In loving memory of Carl Sagan who was born on November 9, 1934. You were an inspiration to us all…)

Wednesday, November 10 – The early morning show continues as Jupiter, Venus, the very thin crescent Moon and Mars all appear with 20 degree of each other just before local dawn. For observers in other parts of the world, today is your day to observe an occultation as the Moon moves across Venus! The “footprint” for this occultation will be for skywatchers in Australia, New Zealand and Southern Asia. As always, timing is everything, so please visit IOTA for precise times for your locations. Observers with sense of curiousity and a large telescope might like to know that Mars will also occult an 11.8 magnitude star. (The challenge will be seeing how long you can follow the progress.) Information on this event is slim, but if you want to know where and when – here’s your clue.

This evening we are once again going to study a single star and it will help you become acquainted with the constellation of Perseus. Its formal name is Beta Persii and it is the most famous of all eclipsing variable stars. Tonight, let’s identify Algol and learn all about the “Demon Star”.

Ancient history has given this star many names. Associated with the mythological figure, Perseus, Beta was considered to be the head of Medusa the Gorgon, and was known to the Hebrews as Rosh ha Satan or “Satan’s Head”. 17th century maps labeled Beta as Caput Larvae, or the “Spectre’s Head”, but it is from the Arabic culture that the star was formally named. They knew it as Al Ra’s al Ghul, or the “Demon’s Head”, and we know it as Algol. Because these medieval astronomers and astrologers associated Algol with danger and misfortune, we are led to believe that Beta’s strange visual variable properties were noted throughout history.

Italian astronomer Geminiano Montanari was the first to note that Algol occasionally “faded” and its methodical timing was cataloged by John Goodricke in 1782, who surmised that it was being partially eclipsed by a dark companion orbiting it. Thus was born the theory of the “eclipsing binary” and it was proved spectroscopically in 1889 by H.C. Vogel. At 93 light years away, Algol is the nearest eclipsing binary of its kind and is treasured by the amateur astronomer for it requires no special equipment to easily follow its stages. Normally Beta Persii holds a magnitude of 2.1, but approximately every three days it dims to magnitude 3.4 and gradually brightens again. The entire eclipse only lasts about 10 hours!

Although Algol is known to have two additional spectroscopic companions, the true beauty of watching this variable star is not telescopic – but visual. The constellation of Perseus is well placed this month for most observers and appears like a glittering chain of stars that lay between Cassiopeia and Andromeda. To help further assist you, re-locate last week’s study star, Gamma Andromedae (Almach) east of Algol. Almach’s visual brightness is about the same as Algol’s at maxima. Tonight at 16:55 UT, Algol will be at minima and will appear approximately the same brightness of Alpha Trianguli. Depending on what time zone you live in, it would be possible for you to see Algol return to full brightness once again at 02:55 UT on November 11! If you are clouded out, don’t worry. Agol reaches minima again on November 13 at 13:44 UT, November 16 at 10:33 UT, November 19 at 7:22 UT, November 22 at 4:11 UT, November 25 at 1:00 UT, November 27 at 21:49 UT and November 30 at 18:38 UT. Just remember that it only takes 10 hours to complete its eclipse and enjoy the “Demon”!

Thursday, November 11 – Southern hemisphere viewers? You asked for it and you got it. This morning the Moon will occult Mars for East Africa and Australia! It was a bit difficult for me to find precise timing information for you, but I did locate at list of cities and times that you might find useful. Best of luck!

Uranus becomes stationary today and Comet P/1996 R2 (Lagerkvist) will make its closest approach to Earth today at a distance of 1.793 AU. At around magnitude 17, this would be one serious observing challenge!

Tonight let us take the opportunity to visit with another planetary nebula seen from a different perspective – “The Dumbbell”. You will want to start fairly early, because as with Lyra, the constellation of Vulpecula is fast declining. The M27 is challenging with small binoculars, readily apparent in larger ones and superior in even small telescopes. By using previously visited stars Altair and Albireo, look for four stars that form the constellation of Sagitta between them. On a good night, the “Arrow” is easy to recognize. By looking at this constellation, get in mind the distance between the arrow’s point, Gamma, and the first of the three stars that make the arrow’s tailfeathers. Using this as your measure, return to Gamma and move the same distance due north, and let’s learn about the M27!

The M27 was the first planetary nebula discovered by Charles Messier and cataloged on July 12, 1764. As we learned with the “Ring”, a planetary nebula is a star shedding its mass in a thin, cold field of hydrogen and helium gas illuminated by the energy of the star itself. It is the strong ultraviolet radiation that excites these rarefied gases to glow in the soft greenish-blue that our eyes can perceive in a spectral condition which can only exist in space – doubly ionized oxygen! The nebula lies about 1,000 light years away from us and is expanding at a rate of about 17 miles per second, meaning that it grows about one arc-second per century. If these figures are correct, it has taken about 50,000 years for the M57 to have reached it’s present size.

The Hubble Telescope reveals the M27 in all its glory. Instead of looking through the planetary’s shell as we did with the M57, we are looking at the entire structure itself. Larger telescopes will have no problem resolving out tenuous rifts, folds and concentrations in the lobes of the nebula, as well as embedded stars. The central star is also evident in larger telescopes and the outer shell named the Millikin 1976 is apparent in Earth based telescopes with an aperture of around 30″. But what about large binoculars and the average backyard telescope?

Don’t worry. The wonderful “dumbbell” shape first described by John Herschel is very there. The spectral qualities described above are easily seen in the most modest of instruments! The M27 is perhaps one of the finest of deep sky objects for the amateur, and tonight? It’s yours…

Friday, November 12 – This morning will mark the peak of the Southern Taurid meteor shower. The Earth will be entering the second “stream” of debris in the early morning hours. The Taurids have a predicted fall rate of 7 per hour, but thanks to their relatively slow speed (27 km or 17 miles per second) and a New Moon, they might produce spectacular results. Good luck!

Asteroid 33342 (1998 WT24) will make a near Earth fly-by as it passes on 0.097 AU away. Hey, wait a minute. That dry fact seems pretty close doesn’t it? Then let’s find out… 0.097 AU would be 14,511,006 km or 9,016,721 miles. That’s roughly 34 times further away than our Moon, yet less than half the distance to our nearest planet, Venus. In astronomical terms? That is close!

Tonight we continue with our planetary studies by finding another such nebula located within a deep-space object. The M15 is well positioned now in the constellation of Pegasus and we start by once again identifying the “Great Square”. Leading the constellation to the west of the square is bright star Epsilon Pegasi, or Enif. By focusing either small binoculars or your telescope on Epsilon, you will know if you have the correct star, for Enif appears gently red. From there, the M15 is an easy catch in binoculars about 4 degrees northwest (about one field of view) and will appear to modest powers (5X30) as a small, round fuzzy patch with a star caught on the edge. Now let’s use a telescope and learn about the M15 as we view it.

Discovered originally by Miraldi in 1746, the wonderfully compact globular cluster was rediscovered by Charles Messier in 1764. It is one of the richest of clusters with an intense, compact core region and ranks as the 12th brightest globular in the sky. Its thousands of stars are gathered in a huge ball spanning 120 light years across and approximately 40,000 light years from Earth, but the M15 has many surprises. It has well been known this particular globular cluster contains many variable stars and pulsars, as well as a planetary nebula. As a rich radio x-ray source, studies of the M15 revealed many neutron stars and made headlines when Chandra revealed the presence of a binary neutron star.

To the average telescope, is simply a beautiful compact globular cluster. Even small apertures will begin to resolve out individual stars. For those with larger telescopes, take the time to “power up” on the M15 and find the planetary amidst the awesome resolvability!

Saturday, November 13 – Double your pleasure, double your fun, as tonight we’ll view two star clusters instead of just one! It’s a Saturday night and what finer way to celebrate than to view one of the most impressive star clusters in our galaxy – the NGC869 and NGC884. This pair of rich galactic open clusters are a naked-eye object from a dark site, easily seen in the smallest of binoculars from urban locations and beyond compare when viewed with a telescope at lowest power.

The western-most of the pair is NGC869, also known as “h Perseii”. It contains at least 750 stars clustered in a brilliant mass spanning about 70 light years, and approximately 7,500 light years away from us. It’s eastern companion is NGC884, or “Chi Perseii”. The statistics are almost a match, but NGC884 only has about half as many stars – some being “super giants” over 50,000 times brighter than our own Sun! These twin clusters have only one major difference: NGC884 is approximately 10 million years old and the NGC869 is perhaps 5 million. The existance of these splendid clusters was cataloged as far back as 350 B.C. with both Ptolemy and Hipparchus noting their appearance – yet Messier never “discovered” them!

Be sure to check out Algol again tonight, it’s minima is at 13:34 UT. Mercury will also be occulted by the Moon today, but it is far to close to the Sun to observe.

Sunday, November 14 – Tonight the Moon is at perigee, or the closest in its elliptical orbit to Earth. The challenge this evening will be to spot the very slender two-day old crescent while it is at its closest – only 356,410 km (221,473 miles) away!

This would be extremely fitting as we observe the 35th anniversary of the Apollo 12 mission. At 11:20:00 a.m. EDT, from launch complex 34-A at Kennedy Space Center, Florida, the Apollo 12 left Earth on November 14, 1969 in the second manned space mission bound for the Moon.

For Southern Hemisphere observers, tonight would be a great opportunity to study the Small Magellanic Cloud. At 210,000 light years away, this near neighbor to the Milky Way will be apparent to the naked eye just north of Beta Toucanae. Easily viewed in binoculars and incredible in telescopes, the Small Magellanic Cloud is home to the rich globular cluster 47 Toucanae. As the second brightest globular cluster in the sky, 47 was once believed to be a star until the 1750’s when French astronomer Nicohlas Louis du Lacaille discovered its true nature.

Until next week? Keep looking up… I wish you clear skies and light speed!
~Tammy Plotner

Posted on by Mark Mortimer

Book Review: How NASA Leaned to Fly in Space

Three programs got the USA to the moon. The Mercury program, conceived before Kennedy’s speech, was to achieve orbital flight and the recovery of a manned satellite. The Gemini program, an indirect result of Kennedy’s speech, had quickly to teach NASA if one could travel to the moon and how best to do so. The Apollo program used all the lessons learned and had to place a human on the moon. Or, in other words, Mercury was the child, Gemini was the teacher, and Apollo was the graduate.

Harland’s book opens with a brief description of the Mercury program, its association with von Braun and the prerequisites for a manned satellite. Here we see that ocean explorers had one advantage. They could stretch and walk about their ships! The Mercury capsule was effectively a flying chair encased in a protective steel shell. Once the challenge of the Moon race began, the Gemini capsule ensued. To test rendezvous requirements, two people were needed. One flew the craft while the other confirmed the rendezvous. Much as the Gemini capsule was second generation and fit two people, it wasn’t much better than its predecessor. Or as one pilot put it, ‘it was like sitting in the front end of a Volkswagen for days’. Apparently functionality kept winning over form.

Much of the remainder of the book presents each of the Gemini launches in a chronological order. The focus is on the human aspects of the Gemini program, principally the pilots. Benign actions and casual banter are judiciously presented. The early flights assessed endurance abilities. Some experimental work occurred but you will discover that even being in orbit can be boring. For example, the astronauts were advised to bring fiction books to while away the time. You will also discover how a House investigation was convened to discuss how sandwich crumbs ended up floating around the cabin.

A typical chapter begins with a description of the mission for the flight. Often it was an extension or elaboration of a preceding flight so the chapters smoothly flow together. Sometimes outside interests arose as the Air Force wanted to know if their special backpack could allow an astronaut to ‘visit’ an orbiting USSR satellite. The launch is also covered in detail. Sometimes they were tricky; one had a launch window of two seconds (it succeeded!). The flight themselves are presented firsthand by the use of conversations between the crew and the ground controllers of the stations of the World Wide Tracking Network (WWTN). When there is lots going on, these chapters get extensive. When an endurance record is set, the topics change such as centring on the best way to sleep in space. A brief summary concludes each chapter, usually including a reference to how the results affect future Gemini missions or Apollo designs.

One of the best feelings Harland raises is the sense of urgency. Though no or little information was known about space flight, a lot had to be learned very quickly. The ten Gemini flights were launched at an average of one every two months. There was little room for error even though target satellites failed or onboard equipment performed inadequately. Just looking at the pilots’ work cycle clearly shows this. First they help define their flights mission(s). Next, they train. Then they adapt to any mission specific tasks. Their launch pad experience may transcend many countdowns and mission scrubs. Finally they go and undertake their mission. Afterward they go through debriefings. Afterward they complete a stint as communications officer at one of the WWTN sites and then they’re back training for their next mission. Nothing like a deadline set by a president to provide inspirational feelings and timeliness.

This book does not contain much technical description of the Gemini craft, its launcher or the mathematical trickeries of orbital mechanics. There are descriptions but really, this book is about the people, their actions and their emotions. Many photographs identify the astronauts and their achievements. Perhaps some will find this a trifle too casual such as reading how an astronaut’s wife gave birth while he was in orbit. Yet this vantage contributes to the depiction of these craft as for humans and controlled by humans. The empirical data can happily stay in text books, this one is for the people.

The early explorers knew how to sail but didn’t know what they would find during their voyages. NASA’s Gemini program taught the USA how to sail through space to place their feet on the ever present moon. In David Harland’s book ,’How NASA Learned to Fly in Space’ you can read what they had to learn and how they learned it so that they, like the ocean’s explorers before them, could extend the travelogue of humankind.

To get your own copy, visit Countdown Creations.

Review by Mark Mortimer

Posted on by Fraser Cain

Something Oozed on Titan’s Surface

This synthetic aperture radar image of the surface of Saturn’s moon Titan was acquired on Oct. 26, 2004, when the Cassini spacecraft flew approximately 2,500 kilometers (1,553 miles) above the surface and acquired radar data for the first time.

The radar illumination was from the south: dark regions may represent areas that are smooth, made of radar-absorbing materials, or are sloped away from the direction of illumination. A striking bright feature stretches from upper left to lower right across this image, with connected ‘arms’ to the East. The fact that the lower (southern) edges of the features are brighter is consistent with the structure being raised above the relatively featureless darker background. Comparisons with other features and data from other instruments will help to determine whether this is a cryovolcanic flow, where water-rich liquid has welled up from Titan’s warm interior.

The image covers an area about 150 kilometers (90 miles) square, and is centered at about 45 degrees north, 30 degrees west in the northern hemisphere of Titan, over a region that has not yet been imaged optically. The smallest details seen on the image are around 1 kilometer (.62 mile) across. Features are less clear at the bottom of the image where the viewing was less favorable. A faint horizontal seam between the radar beams can be seen half way up in this image.

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 Cassini-Huygens 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 radar instrument team is based at JPL, working with team members from the United States and several European countries.

For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov.

Original Source: NASA/JPL News Release

Posted on by Fraser Cain

Interview with David A. Hardy

There are few people who have astronomical bodies named after them in recognition of their hard work over the years, so TV astronomer Sir Patrick Moore and space artist David A. Hardy are true space companions: both have asteroids named after them. Their friendship goes back half a decade.

“In almost all of the books that Patrick and I have done together, he gives me a free hand – he knows that I have a good knowledge of astronomy etc., and has complete confidence in my ability (especially, after 50 years!). In the early days, if he wrote the text first, he sent it to me or we would meet to discuss which parts needed illustrating and how. But in the case of Futures – you’ll notice that my name appears first on the cover – the choice of subjects and illustrations were mine. Patrick approved them, and then wrote the text. In many cases, I wrote some notes of my own first, which he then incorporated. As his health allows him to type only slowly and inaccurately now (on his 1908 Woodstock), he sent me the typescript, which I passed to my wife Ruth to transcribe into Word on her Mac, and I then emailed it to the publisher.”

Both Sir Patrick and David A. Hardy have been keen artists in their own respect. Patrick has a talent for writing clear concise books and features on astronomy, and he’s presented the BBCs “The Sky at Night” program every month for more than 48 years. He began as a school teacher, and humbled by his mother’s artistic talent for colourful drawings of sweet looking aliens canoing down a Martian canal or driving a car around on the rings of Saturn, Sir Patrick took to writing books and continues writing today.

They’re both in a good position to have watched space exploration change over the last half century, participating in and popularizing the many discoveries that have been made. So what is the better approach, making an alien looking world or making the detail as accurate as possible?

“Where possible, I try to do both. But remember that this is astronomical art, not science fiction, and in a book like this I would not include anything that is not accurate according to current knowledge, or at least scientifically possible. This means that paintings done in the 1950s or 60s showing, say, Mars or Titan with a blue sky were accurate for our state of knowledge at the time. Where I have included alien life or signs of civilization, it is based on scientific extrapolation. My favourite of these is the alien life on a planet in a globular cluster (page 99 in Futures: 50 Years in Space), as I believe the idea to be quite original: a type of photosynthesis producing oxygen inside balloon-like organisms, which then float in a carbon dioxide atmosphere.

“I think my paintings, whether traditional or digital, are pretty realistic, aren’t they? I don’t see any need to go as far as super-realism, as that can lead to rather bland art with little character or emotion. I have painted in the styles of Mondrian, Pollock, Picasso on occasion, but only for special commissions. Romanticism, yes – the painting of Antares (page 80) was, as stated, painted deliberately in the style of the Hudson River School of artists. I’ve seen some of those (often huge) originals while in the USA, and love them! I hope that the work of space artists can help to inspire the public to further exploration, just as those artists did in the great days of the opening up of the US West, which in turn led to the creation of National Parks, like Yellowstone and Yosemite.”

The planet Saturn with its rings is now becoming visible again after its period of invisibility in the eastern sky, and is certainly at the centre of attention right now as Cassini continues to send back “postcards”; most recently of the planet’s largest moon Titan. Yet some artists still paint Saturn inaccurately.

“Saturn is beautiful, with its rings, but views of Saturn from its moons in the media are almost always incorrect,” explained David, “since they show Saturn with the rings wide open, whereas from all but one of the satellites (Iapetus) the rings appear as a straight line.”

When asked what about his favorite planet, David said, “I suppose I would have to say that my favorite is Mars. I’d need time to think about the second part, but I would comment that on a frivolous note I thought of Michael Jackson, whose face has surely changed as many times as that of Mars over the years!”

As we press on into 21st century, we have many more planetary close encounters awaiting us. And David A. Hardy and Sir Patrick Moore will be right there to help us get a sense of what it would be like to stand in distant places of the Universe, and appreciate how much is out there, waiting for us to discover.

If you’re interested in Futures: 50 Years in Space, please read Universe Today’s review. You can also visit Amazon.com to read more reviews, or purchase a copy online (or Amazon.co.uk). You can also visit David’s website at http://www.astroart.org, or the BBC’s website for Sir Patrick Moore’s “The Sky at Night”.

David A. Hardy was interviewed by Richard Pearson.

Posted on by Fraser Cain

Rover Toolkits are Still Full

All the scientific tools on NASA’s two Mars Exploration Rovers are still working well, a full 10 months after Spirit’s dramatic landing.

The ones on Spirit are adding fresh evidence about the history of layered bedrock in a hill the rover is climbing.

“Our leading hypothesis is that these rocks originated as volcanic ash that fell from the air or moved in ground-hugging ash flows, and that minerals in them were altered by water,” said Dr. Ray Arvidson of Washington University, St. Louis, deputy principal investigator for the mission.

“This is still a working hypothesis, not a firm conclusion, but all the instruments have contributed clues that fit,” he said. “However, it is important to point out that we have just begun to characterize the textures, mineralogy and chemistry of these layered rocks. Other hypotheses for their origin focus on the role of transport and deposition by water. In fact, it may turn out that volcanism, water and wind have produced the rocks that Spirit is examining. We are just beginning to put together the big picture.”

Both rovers completed three-month primary missions in April. NASA has extended their missions twice because they have remained productive longer than anticipated.

“We’re still making good progress even though Spirit has two types of problems with its wheels,” said Jim Erickson, rover project manager at NASA’s Jet Propulsion Laboratory, Pasadena, Calif. “We are working around those problems successfully, but they might be a sign of things to come, as mechanical parts wear out during our exploration of Mars.”

One question for continuing investigations as Spirit heads for rocks higher in the “Columbia Hills,” is what the environment was like when water altered the minerals. Possibilities include water in the volcanic magma mixture before the ash erupted, surface water transporting the ash while it was still loose after the eruption, and ground water soaking through the rocks that solidified from the accumulated ash.

Some clues for a volcanic-ash origin come from a layered rock dubbed “Uchben.” Researchers pointed Spirit’s microscopic imager at a spot on Uchben scoured with the rock abrasion tool. The images reveal sand-size particles, many of them sharply angular in shape and some quite rounded. The angularity is consistent with transport by an eruption. Particles carried across the surface by wind or water usually tumble together and become more rounded. Uchben’s rounded particles may be volcanic clumps, may be concretions similar to what Opportunity has found, or may be particles tumbled in a water environment.

Evidence for alteration by water comes mainly from identification of minerals and elements in the rocks by the rover’s Moessbauer spectrometer and alpha particle X-ray spectrometer.

The rovers’ principal investigator, Dr. Steve Squyres of Cornell University, Ithaca, N.Y., said, “We have really made headway just in the last several weeks in understanding these rocks. The most likely origin is debris that blasted out of a volcano, was transported by air or water to its present location, and settled out in layers.”

Opportunity, meanwhile, examined a lumpy boulder called “Wopmay” inside “Endurance Crater.” The slope of the ground and loose surface material around the rock prevented Opportunity from getting firm enough footing to use its rock abrasion tool. Evidence from the spectrometers and microscopic imager is consistent with scientists’ earlier hypothesis that rocks near the bottom of the crater were affected by water both before and after the crater formed. The evidence is still not conclusive, Squyres said.

Opportunity is heading toward the base of “Burns Cliff,” a tall exposure of layered rock in the wall of the crater. However, if the rover encounters more of the poor traction found around Wopmay, planners may change course and drive up out of the crater.

JPL, a division of the California Institute of Technology in Pasadena, manages the Mars Exploration Rover project for NASA’s Science Mission Directorate, Washington. Images and additional information about the project are available from JPL at http://marsrovers.jpl.nasa.gov and from Cornell University at http://athena.cornell.edu.

Original Source: NASA/JPL News Release

Posted on by Fraser Cain

Second Black Hole at the Heart of the Milky Way

Using archived science verification data from the Hokupa?a/QUIRC Adaptive Optics system on Gemini North, a French/US team of astronomers led by Jean-Pierre Maillard of the Institut d?Astrophysique de Paris has confirmed the physical association of a cluster of massive stars in the infrared source IRS 13 near the center of the Milky Way galaxy.

The team also used data from Hubble Space Telescope, the Chandra X-Ray Observatory, the Canada-France-Hawai?i Telescope (CFHT), and the Very Large Array to provide broad spectral coverage to complement the Gemini data. The Gemini observations consisted of deconvolved H and Kp band images that identified the existence of two formerly undetected sources within IRS 13E. In all, seven individual massive stars appear to be associated with what the team believes was once a larger cluster of massive stars held together by a central intermediate-mass black hole of about 1,300 solar masses. (This black hole is distinct from the black hole at the galactic center which has a mass of about four million solar masses.) The seven individual stars of IRS 13E seen within a diameter of about 0.5″ (or projected 0.6 light-year across) are co-moving westward with a similar velocity of about 280 kilometers per second in the plane of the sky.

The compactness of the cluster and the common proper motion of the components suggest that they are kept together by a massive source, a stellar black hole at the center of IRS 13E. The size of the cluster allow to infer a mean orbit radius. The radial velocities (+/- 30 kilometers per second) of the individual stars derived from the BEAR Fourier Transform Spectrometer (CFHT) measurements can be used to estimate the average orbital velocity. The authors then explored a range of orbital assumptions and were able to constraint the mass of the holding black hole to about 1,300 solar masses rather robustly.

The team also speculates that this cluster was once located farther from the galactic center, where the stars could form away from the extreme gravitational influence of the central supermassive black hole. IRS 13E seems to be the wreckage or remnant core of a once larger cluster of stars that is now spiraling towards Sgr A* at the galactic center.

This theory also explains the existence of other massive stars around the galactic center, which are thought to be stars stripped from the cluster due to the gravitational environment around the galaxy?s central black hole.

The Gemini data for this work were obtained by a team led by Francois Rigaut (Gemini Observatory) as part of an adaptive optics demonstration run in July 2000. The results are published in Astronomy and Astrophysics, Volume 423, pgs 155-167 (2004)

Original Source: Gemini News Release

Posted on by Fraser Cain

Triple Eclipse on Jupiter

At first glance, Jupiter looks like it has a mild case of the measles. Five spots – one colored white, one blue, and three black – are scattered across the upper half of the planet.

Closer inspection by NASA’s Hubble Space Telescope reveals that these spots are actually a rare alignment of three of Jupiter’s largest moons – Io, Ganymede, and Callisto – across the planet’s face.

In this image, the telltale signatures of this alignment are the shadows [the three black circles] cast by the moons. Io’s shadow is located just above center and to the left; Ganymede’s on the planet’s left edge; and Callisto’s near the right edge. Only two of the moons, however, are visible in this image. Io is the white circle in the center of the image, and Ganymede is the blue circle at upper right. Callisto is out of the image and to the right.

On Earth, we witness a solar eclipse when our Moon’s shadow sweeps across our planet’s face as it passes in front of our Sun. Jupiter, however, has four moons roughly the same size as Earth’s Moon. The shadows of three of them occasionally sweep simultaneously across Jupiter. The image was taken March 28, 2004, with Hubble’s Near Infrared Camera and Multi-Object Spectrometer.

Seeing three shadows on Jupiter happens only about once or twice a decade. Why is this triple eclipse so unique?

Io, Ganymede, and Callisto orbit Jupiter at different rates. Their shadows likewise cross Jupiter’s face at different rates. For example, the outermost moon Callisto orbits the slowest of the three satellites. Callisto’s shadow moves across the planet once for every 20 shadow crossings of Io. Add the crossing rate of Ganymede’s shadow and the possibility of a triple eclipse becomes even more rare. Viewing the triple shadows in 2004 was even more special, because two of the moons were crossing Jupiter’s face at the same time as the three shadows.

Jupiter appears in pastel colors in this photo because the observation was taken in near-infrared light. Astronomers combined images taken in three near-infrared wavelengths to make this color image. The photo shows sunlight reflected from Jupiter’s clouds. In the near infrared, methane gas in Jupiter’s atmosphere limits the penetration of sunlight, which causes clouds to appear in different colors depending on their altitude.

Studying clouds in near-infrared light is very useful for scientists studying the layers of clouds that make up Jupiter’s atmosphere. Yellow colors indicate high clouds; red colors lower clouds; and blue colors even lower clouds in Jupiter’s atmosphere. The green color near the poles comes from a thin haze very high in the atmosphere. Ganymede’s blue color comes from the absorption of water ice on its surface at longer wavelengths. Io’s white color is from light reflected off bright sulfur compounds on the satellite’s surface.

“I’m increasingly aware that some of the most interesting things in astronomy and astrophysics, for instance, can change the way people understand the universe, how it got started and where it’s going. I found those Voyager pictures of the moons of Jupiter incredibly exciting, these beautiful color pictures showing volcanoes on the surface”. -Robert C. Richardson, Nobel Laureate, Physics, Cornell, (1996)

In viewing this rare alignment, astronomers also tested a new imaging technique. To increase the sharpness of the near-infrared camera images, astronomers speeded up Hubble’s tracking system so that Jupiter traveled through the telescope’s field of view much faster than normal. This technique allowed scientists to take rapid-fire snapshots of the planet and its moons. They then combined the images into one single picture to show more details of the planet and its moons.

Original Source: NASA Astrobiology

Posted on by Fraser Cain

First Gamma Ray Image

A team of UK astronomers working with international partners has produced the first ever image of an astronomical object using high energy gamma rays, helping to solve a 100 year old mystery – the origin of cosmic rays. Their research, published in the Journal Nature on November 4th, was carried out using the High Energy Stereoscopic System (H.E.S.S.), an array of four telescopes, in Namibia, South-West Africa.

The astronomers studied the remnant of a supernova that exploded some 1,000 years ago, leaving behind an expanding shell of debris which, seen from the Earth, is twice the diameter of the Moon. The resulting image helps to solve a mystery that has been puzzling scientists for almost 100 years – the origin of cosmic rays. Cosmic rays are extremely energetic particles that continually bombard the Earth, thousands of them passing through our bodies every day. The production of gamma rays in this supernova shock wave tells us that it is acting like a giant particle accelerator in space, and thus a likely source of the cosmic rays in our galaxy.

Dr Paula Chadwick of the University of Durham said “This picture really is a big step forward for gamma-ray astronomy and the supernova remnant is a fascinating object. If you had gamma-ray eyes and were in the Southern Hemisphere, you could see a large, brightly glowing ring in the sky every night.”

Professor Ian Halliday, CEO of PPARC which funds UK participation in HESS said “These results provide the first unequivocal proof that supernovae are capable of producing large quantities of galactic cosmic rays – something we have long suspected, but never been able to confirm.”

Gamma rays are the most penetrating form of radiation we know, around a billion times more energetic than the X-rays produced by a hospital X-ray machine. This makes it very difficult to use them to create an image – they just pass straight through any surface which we might use to reflect them, for instance. However, luckily for life on Earth, gamma rays from objects in outer space are stopped by the atmosphere; when this happens, a faint flash of blue light is produced, lasting for a few billionths of a second. The astronomers used images of these flashes of light, called Cherenkov radiation, to make a gamma ray ‘image’ for the first time.

Original Source: PPARC News Release

Posted on by Fraser Cain

Earth Will Be Watching When Huygens Arrives

Image credit: ESA
When ESA?s Huygens probe plunges into the atmosphere of Saturn?s largest moon, Titan, on 14 January 2005, telescopes on Earth will be watching the remote world.

Observations of Titan from Earth will help to understand the global condition of the atmosphere, while Huygens is passing through a tiny section of it. As Huygens drifts down, its instruments and cameras will be collecting vital information about the atmosphere and surface.

The Cassini mothership will be listening, so that it can later transmit the results to Earth but, while Cassini is pointing its high-gain antenna at Huygens, it cannot watch Titan with its cameras. So telescopes on Earth will try to do the job.

The telescopes located around the Pacific Ocean will be used because Titan will be in view from these areas at the time of the Huygens descent. An observation from space, by the NASA/ESA Hubble Space Telescope, is also planned.

The most exciting possibility is that the observations may show a tiny, bright speck at the moment Huygens enters the atmosphere.

This point of light will be the ?fireball?, created by friction as the probe?s heatshield hurtles through the denser parts of the moon?s atmosphere and the spacecraft shoots across Titan?s sky like a giant meteor.

Although the chances of seeing the fireball are faint, the best location to be looking from happens to coincide with the largest single telescope in the world: the 10-metre Keck telescope. Situated on the summit of the dormant volcano Mauna Kea, on Hawaii, Keck will be directly in line with Titan at the moment of the Huygens descent.

In addition to optical telescopes, a string of radio telescopes across America, Australia, China and Japan will team up to listen for the faint radio signal of Huygens itself. If they hear this tiny call, they will be able to help determine, after weeks of processing the Huygens amount of data that will be collected, the precise landing location for the probe on Titan?s surface.

Jean-Pierre Lebreton, Huygens Project Scientist, will be in ESA?s European Space Operations Centre (ESOC) at Darmstadt, Germany, during the descent of the probe. As any space scientist knows, planetary descents can be risky things. However, Lebreton says that preparations for the day of descent are going well, and adds, ?We have no time to get nervous, there is too much work to do.?

Original Source: ESA News Release

Posted on by Fraser Cain

Alaskan Martian Update, Eclipse Photos, and More

It’s a bit of a slow news day today. I’m not sure why… some kind of election, or something. Anyway, I wanted to give you an update on Ray Collins, who shut himself in a greenhouse in Alaska to figure out how much space would be required to feed an astronaut. He ate the last of his potatoes, and exited Mars Base Zero on Tuesday. You can read his final update, and if you’re interested in getting involved, or sharing ideas, they’ve got some ambitious plans and I’m sure they’d love to hear from you.

Second, thanks to everyone who sent in your stories and pictures of last week’s lunar eclipse. It’s great to see how an event like this can really bring people together, and help encourage an appreciation for the beautiful night skies. So, check them out, and share your experience if you hadn’t already.

Finally, a reminder to head out in the next couple of morning and enjoy the Venus/Jupiter planetary conjunction. The two planets are already close together in the sky, and getting closer. It’s really beautiful.

Enjoy!

Fraser Cain
Publisher
Universe Today