Posted on by Fraser Cain

What’s Up This Week – Mar 14 – 20, 2005

Image credit: NOAO/AURA/ASF
Monday, March 14 – Today is the birthday of Albert Einstein. Often called the most brilliant mind of our times, I’d rather think of him as a man who never wore socks, believed that curiosity and imagination were more important than knowledge and made a math mistake when helping a student with homework. Now that’s a man you can admire!

For our friends in eastern Europe, we wish you clear skies as the Moon occults bright star, Delta Aries during the early evening hours. Please check IOTA information for precise times and locations. For the rest of us, tonight’s Moon will offer an outstanding view of Mare Crisium, easily identified with binoculars in the northeast section. Let’s turn the telescope its way to discover two small interior craters that will be near the terminator. Not far from the western wall, look for small craters Pierce in the northwest and Picard to the southwest.

Give the Moon time to wester and let’s head back out for both binocular and telescopic open cluster – M50. By drawing a mental line between Sirius and Procyon, you will find this sparkling collection of stars easy to find. Cataloged by Messier in April of 1772, this loose – and somewhat heart-shaped gathering of blue/white stars resides around 3000 light years distant and contains several red giants like the prominent one on its southern edge.

Tuesday, March 15 – Although Mercury has passed its greatest elongation, it is still possible for northern hemisphere observes to catch the elusive inner planet planet about a fist’s width above the western horizon just after sunset. Look southwest of bright Gamma Pegasus to help guide you.

For the southern hemisphere, keep watch for the Gamma-Normid meteor shower with an average fall rate of about five to eight per hour.

Tonight Mare Fecunditatis will be visible in the southeast section of the Moon to binoculars with the bright ring of Langrenus on its eastern shore. For telescopic viewers wishing a challenge, focus on the area where Mare Fecunditatis and the northern Tranquillitatis meet. The shallow bright ring is Crater Taruntius. About midway across Fecunditatis expanse to the south you will see two small pockmarks sitting side by side. Both are named for Charles Messier, crater Messier A is to the west. As you scan the sky around the Moon, be sure to check out how close the Plieades are. At 8:00 pm EST, the M45 will be only one degree away to the north.

Wednesday, March 16 – Tonight will be the peak of the Corona-Australid meteor shower. Favouring more southern observers, be on the lookout for around five to seven bright streaks per hour moving from south to north.

Today in 1926, Robert Goddard launched the first liquid fuel rocket that reached the amazing height of about twelve meters. How about if we set our sites about 20 million times higher? For binoculars, the Moon will reveal the beginnings of Mare Frigorius to the north joined by Mare Serenitatis to its south. Look for the dark floored Lacus Somniorum between them. Steady hands will reveal the ancient Crater Posidonius, but try a telescope. South of Posidonius along the eastern shore is the ruins of Le Monnier – the Luna 21 landing site. Continue south approximately the same distance and you will see a shallow crater known as Littrow. Look to the mountains just south of the edge to discover the Apollo 17 landing area.

If you’ve got a clear night, why not wait a few hours and return for the M44? If skies are still bright, form a triangle between Pollux, Regulus and Procyon and set your binoculars in the center. Known as the “Beehive”, our stellar swarm is only about 500 light years away. With a wide range of magnitudes to feast the eyes upon, look for at least a handful of orange stars in the blues and whites. Judging by these well evolved members, science concludes this cluster is about 400 million years old.

Thursday, March 17 – Happy St. Patrick’s Day! All of Europe will be favoured tonight as the Moon occults 4.6 magnitude 136 Tauri in the early evening hours. Please check IOTA for specific times in your area. For west/central and southeast Australia and New Zealand, you will fare better with brighter Beta Tauri on this universal date. Check this IOTA page to compute times for your location.

The early evening Moon will also offer up the Apollo 11 landing area, but since we’ve become familiar with Sabine and Ritter, let’s head north of the pair for a more unusual feature. Tonight use your telescope to locate the Rima Ariadaeus located on the terminator about midway along the west shore ofMare Tranquillatatis. It will appear as a fine “crack” running roughly from east to west through the bright landscape.

Friday, March 18 – The Moon will dominate the early evening hours, but why not enjoy its features as we scan the terminator in binoculars to enjoy the Caucasus Mountains and outstanding craters Aristillus and Autolycus to the north. Just south of this outstanding pair is a rather curious dark area known as Palus Putredinus, or the “Rotten Swamp”. On September 13, 1959 European observers witnessed the impact of Lunik 2 in this area.

The first “space walk” was performed by Cosmonaut Alexei Leonov on this day in 1965, but tonight let’s walk across space as we head towards the back of the lion’s head – Gamma Leonis. Known as Algieba, this magnitude 2.6 yellow star will appear to have a companion star to its south in binoculars, but a telescope is needed to see the 3.8 magnitude B star to the east/southeast. At around 100 light years away, this yellow/orange pair share an elliptical orbit about 300 AU apart. It takes about 600 years for this pair to revolve and they will reach maximum separation in just another 95 years.

Saturday, March 19 – Tonight will be central Europe’s turn for yet another occultation as the Moon covers Upsilon Geminorum. Check IOTA for times and locations. For northwestern Australia, you have Iota Geminorum on your list, but be advised this is a universal date.

As we view the Moon through binoculars tonight, we see near the terminator to the south three very prominent craters in a line. From north to south their names are Ptolemy, Alphonsus and Arzachel. Telescopically, the centermost – Alphonsus – has a wonderful history of volcanism. Its small central mountain is the only place on the Moon where photographic evidence of outgassing was verified by a spectrogram. For eastern time zones, be sure to have another look around 11:00 pm when the creamy yellow Saturn will be about five degrees south of Selene.

Sunday, March 20 – Tonight the Moon will be at apogee – the furthest from the Earth – at around 251,560 miles. Even at this incredible distance, no feature on the Moon will be more prominent to binoculars and telescopes than the dazzling class one Crater Copernicus. Thanks to the work of Shoemaker, there is no doubt this impressive impact crater bears similarities to own our terrestrial formations. The more power and aperture you add to this crater, the more details you will see.

Just because skies are bright tonight doesn’t mean that astronomy has come to an end! Take the time to visit with Saturn and note the position of Titan as well as its smaller moons. If skies cooperate, stay up a bit later and view Jupiter. With its many satellite events and transits of the “Great Red” spot, you are sure to catch something new and different each time you look.

Until next week, keep looking up and traveling at Light Speed… ~Tammy Plotner

Posted on by Fraser Cain

Rover Sees a Dust Devil on Mars

Mars is often enveloped by planet-wide dust storms – their biting winds choke the air and scour the arid surface. Tornado-like dust devils dance across the planet so frequently that their numerous tracks crisscross each other, tracing convoluted designs in the red soil. Martian dust includes magnetic, composite particles, with a mean size of one micron–the equivalent to powdered cement or flour in consistency. This size range is about five percent the width of a human hair.

By comparison to how a dust devil in Arizona might stir up uncultivated farmland, the scale on Mars is much more daunting. “These martian dust devils dwarf the five-to-10 meter terrestrial ones, can be greater than 500 meters in diameter and several thousand meters high. The track patterns are known to change from season to season, so these huge dust pipes must be a large factor in transporting dust and could be responsible for eroding landforms,” said Peter Smith of the University of Arizona (Tucson)

Mars has only a faint atmosphere [less than one percent of terrestrial pressures], yet offers up its history of dust devils as swirling tracks in a remarkable landscape of wind-swept and carved terrain. These tiny twisters tend to appear in the middle afternoon on Mars, when solar heating is maximum and when warm air rises and collides with other pressure fronts to cause circulation.

In his first press conference after the Spirit rover landed, the principal investigator for the rover’s science package, Cornell’s Steven Squyres, described one instance his team has been discussing: the intriguing possibility that at Gusev, over their mission, the rover’s camera may actually be able to animate a dust devil in action.

Squyres informally proposed a mini-series of frames, or twister movie which with some meterological luck, might offer a rare example of surface weather on another planet.

“At the Pathfinder site during its 83 sol mission, approximately thirty dust devils were either sensed by the pressure drop as they passed over the lander, or were imaged by the Pathfinder camera,” says Smith. “Based on these observations, one might expect to see several dust devils per hour from an active site on Mars between 10 am and 3 pm. Few, if any dust devils will be present at other times. Dust devils typically form during late spring and summer and can be found at all latitudes. Exactly, how their population density varies around the planet is currently unknown.”

In addition to Pathfinder’s run-in with a dust devil, previous missions to Mars have run into very dusty days. For instance, there was a dust storm covering the Viking Lander I (VL-1) site on Martian day (1742) or sol 1742 (1 Martian year=669 Earth days). In 1971, Mariner 9 and 2 USSR missions all arrived during a dust storm.

“Rovers and other robots must be carefully designed to withstand the sandblasting that they will endure from dust devils,” said Smith. “Bearing surfaces and solar panels must be protected and dust accumulation on solar panels will lower their efficiency.”

Actual mini-tornadoes of this magnetic dust, or dust devils, have been caught in the act by orbital cameras are highlighted by images below. These miniature tornadoes can span about 10 to 100 meters wide with 20- to 60-mile-per-hour (32- to 96-km/hr) winds swirling around a heated column of rising air. One might expect to see several dust devils per hour from an active site on Mars between 10 am and 3 pm, when rising afternoon air is hottest.

Original Source: Astrobiology Magazine

Posted on by Fraser Cain

Dr. Mike Griffin Chosen to Lead NASA

The US White House has announced the Dr. Mike Griffin will pick up the reins at NASA, filling the vacancy left by Sean O’Keefe. Griffin is currently the director of space at Johns Hopkins University’s Applied Physics Laboratory (APL), and is a supporter of the new Vision for Space Exploration. Once confirmed by the senate, Griffin will become the 11th Administrator for NASA.

Posted on by Fraser Cain

Atlas V Lofts Satellite for Inmarsat

An Atlas V launch vehicle carried its largest payload to date into orbit tonight, the Inmarsat 4-F1 satellite that weighs nearly 6 metric tons (5,959 kgs/13,138 pounds). This also marked the third launch of the year for International Launch Services (ILS).

The Lockheed Martin-built (NYSE: LMT) Atlas V vehicle, designated AV-004, lifted off at 4:42 p.m. EST (21:42 GMT). It placed the Inmarsat spacecraft in a supersynchronous transfer orbit 32 minutes later. Satellite controllers have confirmed that the spacecraft is functioning properly.

Tonight’s vehicle used the Atlas V “431” configuration, meaning it had a 4-meter-diameter fairing, three solid rocket boosters (SRBs) and a single-engine Centaur upper stage. Atlas V vehicles have now flown five times, three of them with SRBs.

“The Atlas series now has achieved an unprecedented string of 76 successful launches, and we’re proud to count this mission and two others for Inmarsat among them,” said ILS President Mark Albrecht.

“This is a milestone launch for us, also, in terms of the size of the payload,” Albrecht said. “Inmarsat 4-F1 is one of largest commercial communications satellites in the world, as well as the most massive satellite launched by Atlas. Yet it falls into the middle of the Atlas V capability range, demonstrating the flexibility of our design.”

The spacecraft is a Eurostar E3000 model built by EADS Astrium. It is the first in a generation of satellites that will support Inmarsat’s new Broadband Global Area Network (BGAN), delivering internet and intranet content and solutions, video-on-demand, videoconferencing, fax, e-mail, phone and LAN access at speeds up to 432kbit/s almost anywhere in the world. BGAN will also be compatible with third-generation cellular systems. The operating location for Inmarsat 4-F1 is 65 degrees East longitude.

“We thank ILS for the safe delivery of our first I-4 satellite into space,” said Andrew Sukawaty, chairman and CEO of Inmarsat. “The first two I-4 satellites will bring broadband communications to 86 percent of the world. History has been made and the world has become closer through advanced data communications.”

Antoine Bouvier, CEO of EADS Astrium, said: “This successful launch is a major event for EADS Astrium, as Inmarsat-4 is certainly one of the most sophisticated communications satellites ever built. We thank for this achievement International Launch Services, and Inmarsat for the confidence they had in EADS Astrium on this innovative and ambitious program.”

ILS is a joint venture of Lockheed Martin of Bethesda, Md., and Khrunichev State Research and Production Space Center of Moscow. ILS is the global leader in launch services, offering the industry’s two best launch systems: Atlas and Proton. With a remarkable launch rate of 73 missions since 2000, the Atlas and Proton launch vehicles have consistently demonstrated the reliability and flexibility that have made them preferred choice among satellite operators worldwide. Since the beginning of 2003, ILS has signed more new commercial contracts than all of its competitors combined.

Original Source: ILS News Release

Posted on by Fraser Cain

Probing the Large Scale Structure of the Universe

According to astrophysicist Naoki Seto of the California Institute of Technology, “Large angular CMBR fluctuations contain precious information of the largest spatial scale fluctuations, but they are also contaminated by the (less interesting) small spatial scale power. Therefore, if we can remove the small spatial scale ones, we can get a cleaner picture of the potentially anomalous features of our universe.”

It all comes down to filtering out the distractions. Say someone from another country asks you about where you live and you describe the cracks in the front driveway and the angle of the sign perched on the pole at the end of the street. Not very helpful you say – especially to someone living in an entirely different part of the world. Data from WMAP is like that. Although it reveals slight temperature related fluctuations in the CMBR across the sky, these fluctuations are mostly associated with scattering of CMBR by “nearby” matter. As a result they are “contaminated” by the expansionary influence of dark energy associated with galaxies as far off as several billions of light-years. From an astronomical point of view, CMBR fluctuations are caused by nearby cracks in the pavement. Ultimately the goal is to see the “big picture” of the entire universe. It’s all a matter of scale…

What will we learn about the Universe based on such large scale variations? “You can study interesting behaviors of the inflation that might generate seed perturbations for cosmic structure, like galaxies”, says Naoki.

Early on, a curious form of energy dominated the universe (during the so called hyper-inflationary phase). In this period the attractive influence of matter was not a factor and the universal balloon expanded incredibly fast. Later as matter dominated, gravitation put the brakes on things, the Universe decelerated and the balloon may have barely managed to keep expanding at all. After deceleration, another engine kicked in – the mysterious force called “dark energy”. The constraining influence of gravity was overcome and the Universe resumed expansion, but at a more leisurely rate. In our current epoch, studies of the light of distant supernovas have shown that the expansion of the universal balloon is accelerating again. We live in an era of universal inflation and questions about inflation, along with the possibility of dark energy driving it, can best be answered by studying previous cycles of slower expansion.

Naoki and Caltech associate Elena Pierpaoli hope to eliminate the effects of dark energy by studying the polarization of microwave radiation arriving at our solar system from the direction of older galaxy clusters. One possibility is to use a future WMAP-like probe capable of higher resolution of detail to collect microwave radiation from regions where the CMBR was once scattered by distant clouds of free electrons in space. Since electron scattering naturally occurs where matter is found, galaxy clusters make ideal candidates. The catch is that such clusters must be far enough away to provide a picture of scattering as it occured long ago. By focusing on galaxy clusters seven billion light years away, we could see the CMBR as it appeared from clusters when the universe was half its current age. Dark energy at work then would not be as strong as it is now.

The resulting picture could provide important clues related to insights coming out of the WMAP project group. There is a possibility that, at the very largest scales, the universe is quite different from what was originally thought to be true. “Very roughly speaking,?, says Naoki, ?we expected that there would be no characteristic length in the largest-scale observable universe. This includes the spatial spectrum of the fluctuations and the shape of the universe.”

Other researchers have considered the use of galaxy clusters to probe large scale structure in the universe as well. But these researchers were not convinced the approach would work. Naoki and Elena found two important factors not sufficiently emphasized in earlier studies. First, they linked the obscuring small scale fluctuations in CMBR anisotropy to the influence of dark energy associated with the current accelerating era. Second, they determined that this obscuration could be minimized by exploiting scattering effects projected from galaxy clusters 7 billion light years away. Together these two insights could make it possible to see the largest scale universal structures influencing things today.

According to Elena: “The beauty of what we showed is that the observable quantity we propose to use is a function that varies very slowly on the sky. In order to map it observationally, you don’t need a high-resolution all-sky experiment, but you need to observe targeted objects uniformly spaced on the sky. This is, observationally, a much easier task than mapping the whole sky with that resolution.”

Unfortunately it is not possible for WMAP to achieve the degree of resolution needed to bring out the largest scale structures hinted at in the original data. For this reason, it may be several years before information needed by Naoki, Elena, and other astrophysicists is collected. The next probe scheduled for launch is ESA’s Planck in 2007. Despite Planck’s increased sensitivity and resolution, the signals needed are so weak that it will be difficult to eliminate other competing signals from those polarized by distant galaxy clusters. However future high-altitude ground-based instruments, such as ACT, APEX-SZm, and SPT, may provide the aperture needed to resolve the 1 arc minute sized regions needed to bring out the largest scale structures of the Universe. The Cornell-Caltech Atacama Telescope – a 25 meter sized submillimeter-wave instrument currently undergoing feasibility study – could be sensitive to these effects. The CCAT is expected to collect first photons in the early part of the next decade. Such an instrument should be able to resolve signals separated by as little as .5 arc minutes (1/60th the diameter of the Moon).

Ah, what irony! To map the largest scale structures of 7 billion years past we still need to be able to see a few cracks in the pavement…

About The Author:
Inspired by the early 1900’s masterpiece: “The Sky Through Three, Four, and Five Inch Telescopes”, Jeff Barbour got a start in astronomy and space science at the age of seven. Currently Jeff devotes much of his time observing the heavens and maintaining the website Astro.Geekjoy.

Posted on by Fraser Cain

Astrophoto: Moon and Jupiter by Bojan Stajcar

Amateur photographer Bojan Stajcar took this picture of the lunar occulation of Jupiter on the 27th of February. This picture was taken 10 minutes after the Moon partially occulted Jupiter, at 11:04 pm local time, from Melbourne, Australia. The camera used was a mechanically modified Connectix Quickcam, with 320×240 pixel CCD sensor in the focus of the motorized (“Bartelized”) homemade 10″, f5.6 reflector. Note the difference in the surfaces brightness of the Moon and Jupiter. Despite the fact that the moon surface consists of very low reflective material (dominantly basalt), it is brighter, as Jupiter is 5 times further away from the Sun.

If you’re an amateur astrophotographer, visit the Universe Today forum and post your pictures, we might feature it in the newsletter.

Posted on by Fraser Cain

New Theory on Meteor Crater

Scientists have discovered why there isn’t much impact-melted rock at Meteor Crater in northern Arizona.

The iron meteorite that blasted out Meteor Crater almost 50,000 years ago was traveling much slower than has been assumed, University of Arizona Regents’ Professor H. Jay Melosh and Gareth Collins of the Imperial College London report in Nature (March 10).

“Meteor Crater was the first terrestrial crater identified as a meteorite impact scar, and it’s probably the most studied impact crater on Earth,” Melosh said. “We were astonished to discover something entirely unexpected about how it formed.”

The meteorite smashed into the Colorado Plateau 40 miles east of where Flagstaff and 20 miles west of where Winslow have since been built, excavating a pit 570 feet deep and 4,100 feet across – enough room for 20 football fields.

Previous research supposed that the meteorite hit the surface at a velocity between about 34,000 mph and 44,000 mph (15 km/sec and 20 km/sec).

Melosh and Collins used their sophisticated mathematical models in analyzing how the meteorite would have broken up and decelerated as it plummeted down through the atmosphere.

About half of the original 300,000 ton, 130-foot-diameter (40-meter-diameter) space rock would have fractured into pieces before it hit the ground, Melosh said. The other half would have remained intact and hit at about 26,800 mph (12 km/sec), he said.

That velocity is almost four times faster than NASA’s experimental X-43A scramjet — the fastest aircraft flown — and ten times faster than a bullet fired from the highest-velocity rifle, a 0.220 Swift cartridge rifle.

But it’s too slow to have melted much of the white Coconino formation in northern Arizona, solving a mystery that’s stumped researchers for years.

Scientists have tried to explain why there’s not more melted rock at the crater by theorizing that water in the target rocks vaporized on impact, dispersing the melted rock into tiny droplets in the process. Or they’ve theorized that carbonates in the target rock exploded, vaporizing into carbon dioxide.

“If the consequences of atmospheric entry are properly taken into account, there is no melt discrepancy at all,” the authors wrote in Nature.

“Earth’s atmosphere is an effective but selective screen that prevents smaller meteoroids from hitting Earth’s surface,” Melosh said.

When a meteorite hits the atmosphere, the pressure is like hitting a wall. Even strong iron meteorites, not just weaker stony meteorites, are affected.

“Even though iron is very strong, the meteorite had probably been cracked from collisions in space,” Melosh said. “The weakened pieces began to come apart and shower down from about eight-and-a-half miles (14 km) high. And as they came apart, atmospheric drag slowed them down, increasing the forces that crushed them so that they crumbled and slowed more.”

Melosh noted that mining engineer Daniel M. Barringer (1860-1929), for whom Meteor Crater is named, mapped chunks of the iron space rock weighing between a pound and a thousand pounds in a 6-mile-diameter circle around the crater. Those treasures have long since been hauled off and stashed in museums or private collections. But Melosh has a copy of the obscure paper and map that Barringer presented to the National Academy of Sciences in 1909.

At about 3 miles (5 km) altitude, most of the mass of the meteorite was spread in a pancake shaped debris cloud roughly 650 feet (200 meters) across.

The fragments released a total 6.5 megatons of energy between 9 miles (15 km) altitude and the surface, Melosh said, most of it in an airblast near the surface, much like the tree-flattening airblast created by a meteorite at Tunguska, Siberia, in 1908.

The intact half of the Meteor Crater meteorite exploded with at least 2.5 megatons of energy on impact, or the equivalent of 2.5 million tons of TNT.

Elisabetta Pierazzo and Natasha Artemieva of the Planetary Science Institute in Tucson, Ariz., have independently modeled the Meteor Crater impact using Artemieva’s Separated Fragment model. They find impact velocities similar to that which Melosh and Collins propose.

Melosh and Collins began analyzing the Meteor Crater impact after running the numbers in their Web-based “impact effects” calculator, an online program they developed for the general public. The program tells users how an asteroid or comet collision will affect a particular location on Earth by calculating several environmental consequences of the impact.

Original Source: University of Arizona News Release

Posted on by Fraser Cain

Hubble Helps Discover How Massive Stars Can Get

Unlike humans, stars are born with all the weight they will ever have. A human’s birth weight varies by just a few pounds, but a star’s weight ranges from less than a tenth to more than 100 times the mass of our Sun. Although astronomers know that stars come in a variety of masses, they are still stumped when it comes to figuring out if stars have a weight limit at birth.

Now astronomers have taken an important step toward establishing a weight limit for stars. Using NASA’s Hubble Space Telescope, astronomers made the first direct measurement within our Milky Way Galaxy that stars have a limit to how large they can form. Studying the densest known cluster of stars in our galaxy, the Arches cluster, astronomers determined that stars are not created any larger than about 150 times the mass of our Sun, or 150 solar masses.

The finding takes astronomers closer to understanding the complex star-formation process and gives the strongest footing yet to the idea that stars have a weight limit. Knowing how large a star can form may offer important clues to how the universe makes stars. Massive stars are the “movers and shakers” of the universe. They manufacture many of the heavier elements in the cosmos, which are the building blocks for new stars and planets. Hefty stars also may be the source of titanic gamma-ray bursts, which flood a galaxy with radiation.

“This is an incredible cluster that contains a rich collection of some of the most massive stars in the galaxy, yet it appears to be ?missing’ stars more massive than 150 times the mass of our Sun,” said astronomer Donald F. Figer of the Space Telescope Science Institute in Baltimore, Md. “Theories predict that the more massive the cluster, the more massive the stars within it. We looked at one of the most massive clusters in our galaxy and found that there is a sharp cutoff to how large a star can form.

“Standard theories predict 20 to 30 stars in the Arches cluster with masses between 130 and 1,000 solar masses. But we found none. If they had formed, we would have seen them. If the prediction was only one or two stars and we saw none, then we could claim that our result could be due to statistical errors.”

Figer is pursuing follow-up studies to determine an upper limit in other star clusters to test his result. His finding is consistent with statistical studies of smaller-mass star clusters in our galaxy and with observations of a massive star cluster known as R136 in our galactic neighbor, the Large Magellanic Cloud. In that cluster, astronomers discovered that stars were not created any larger than 150 solar masses.

Astronomers have been uncertain about how large a star can get before it cannot hold itself together and blows itself apart. Even with the advances in technology, astronomers do not know enough about the details of the star-formation process to determine an upper-mass limit for stars. Consequently, theories have predicted that stars can be anywhere between 100 to 1,000 times more massive than our Sun. Predicting a lower weight limit for stars has been easier. Objects less than one-tenth a solar mass are not hefty enough to sustain nuclear fusion in their cores and shine as stars.

Making this finding was so tricky that Figer spent seven years puzzling over the Hubble data. The results are published in the March 10th issue of the journal Nature.

“Knowing that extraordinary claims demand extraordinary proof, I scratched my head for a long time trying to figure out why the result might be wrong,” he said.

Figer used Hubble’s Near Infrared Camera and Multi-Object Spectrometer to study hundreds of stars ranging from 6 to 130 solar masses. (Although Figer did not find any stars larger than 130 solar masses, he conservatively set the upper limit at 150 solar masses.) The Arches cluster is a youngster, about 2 to 2.5 million years old, and resides 25,000 light-years away in our galaxy’s hub, a hotbed of massive star formation. In this rough-and-tumble region, huge clouds of gas collide to form behemoth stars.

Hubble’s infrared camera is well suited to analyze the Arches because it penetrates the dusty core of our galaxy and produces sharp images, allowing the telescope to see individual stars in a tightly packed cluster. Figer estimated the stars’ masses by measuring the ages of the cluster and the brightness of the individual stars. He also collaborated with Francisco Najarro of the Instituto de Estructura de la Materia in Madrid, who produced detailed models to confirm the masses, chemical abundances, and ages of the cluster’s stars.

A cluster must meet a long list of requirements for astronomers to use it for identifying an upper-mass limit. The cluster must be hefty enough, about 10,000 solar masses, to produce stars large enough to probe the upper limit. A cluster also cannot be too young or too old. Selecting an older cluster ? beyond 2.5 million years ? means that many of the massive young stars have already exploded as supernovas. In a very young cluster ? less than 2 million years old ? many of the stars are still enshrouded in their natal dust clouds, and astronomers cannot see them.

Another important factor is a cluster’s distance from Earth. Astronomers must know the cluster’s distance to reliably estimate the brightness of its stars, a key ingredient used to estimate a star’s mass. The cluster also must be close enough to see individual stars. The Arches cluster is the only cluster in the galaxy that meets all of those requirements, Figer said.

The Arches outshines almost every other star cluster in the galaxy. With a mass equivalent to more than 10,000 stars like our Sun, the monster cluster is 10 times heavier than typical young star clusters, such as the Orion cluster, scattered throughout our Milky Way. If our galactic neighborhood were as cluttered with stars, more than 100,000 stars would fill the void of space between our Sun and its nearest neighbor, the star Alpha Centauri, 4.3 light-years away. Astronomers estimate that only 1 out of every 10 million stars in the galaxy is as bright as the stars in the Arches cluster. At least a dozen of the cluster’s stars weigh about 100 times the mass of our Sun.

Figer cautions that the upper limit does not rule out the existence of stars larger than 150 solar masses. Such hefty stars, if they exist, could have gained weight by merging with another massive star. For example, the young Pistol star, located near our galactic hub, is 150 to 250 times more massive than our Sun. This behemoth star, however, seems out of place because it dwells in a neighborhood of older stars. One way to explain this apparent paradox, Figer said, is that the Pistol could be a “born-again” star, formed from the merger of two stars. His explanation is not just theory. Astronomers have found older stars that have been reborn through mergers with other stars in ancient globular star clusters.

The Pistol also could be part of a double-star system that is masquerading as a single giant star. The two stars have not been unmasked because they cannot be resolved by even the Hubble telescope.

Double-star systems, astronomers also caution, could make up some of the most massive stars in the Arches cluster. This means that the upper limit in the Arches could be lower than 150 solar masses, but not any higher.

Figer’s next step is to pinpoint more clusters to test his weight limit. Several telescopes, including the Spitzer Space Telescope, have been searching for new star clusters in our Milky Way. In the last two years, the number of known clusters in our galaxy has doubled from a few hundred to 500, Figer said. Many of the newly found clusters are compiled in the Two Micron All Sky Survey (2MASS) catalogue. Figer already has identified about 130 of these newly discovered clusters as possible candidates to study. NASA has recognized Figer’s important work by giving him a five-year Long Term Space Astrophysics award, which will support his hunt for the most massive stars in the Milky Way.

Original Source: Hubble News Release

Posted on by Fraser Cain

Galaxies in the Early Universe Came in Every Flavour

What did the universe look like when it was only 2 to 3 billion years old? Astronomers used to think it was a pretty simple place containing relatively small, young star-forming galaxies. Researchers now are realizing that the truth is not that simple. Even the early universe was a wildly complex place. Studying the universe at this early stage is important in understanding how the galaxies near us were assembled over time.

Jiasheng Huang (Harvard-Smithsonian Center for Astrophysics) said, “It looks like vegetable soup! We’re detecting galaxies we never expected to find, having a wide range of properties we never expected to see.”

“It’s becoming more and more clear that the young universe was a big zoo with animals of all sorts,” said Ivo Labb? (Observatories of the Carnegie Institution of Washington), lead author on the study announcing this result.

Using the Infrared Array Camera (IRAC) aboard NASA’s Spitzer Space Telescope, the astronomers searched for distant, red galaxies in the Hubble Deep Field South-a region of the southern sky previously observed by the Hubble Space Telescope.

Their search was successful. The IRAC images displayed about a dozen very red galaxies lurking at distances of 10 to 12 billion light-years. Those galaxies existed when the universe was only about 1/5 of its present age of 14 billion years. Analysis showed that the galaxies exhibit a large range of properties.

“Overall, we’re seeing young galaxies with lots of dust, young galaxies with no dust, old galaxies with lots of dust, and old galaxies with no dust. There’s as much variety in the early universe as we see around us today,” said Labb?.

The team was particularly surprised to find a curious breed of galaxy never seen before at such an early stage in the universe–old, red galaxies that had stopped forming new stars altogether. Those galaxies had rapidly formed large numbers of stars much earlier in the universe’s history, raising the question of what caused them to “die” so soon.

The unpredicted existence of such “red and dead” galaxies so early in time challenges theorists who model galaxy formation.

“We’re trying to understand how galaxies like the Milky Way assembled and how they got to look the way they appear today,” said Giovanni Fazio (CfA), a co-author on the study. “Spitzer offers capabilities that Hubble and other instruments don’t, giving us a unique way to study very distant galaxies that eventually became the galaxies we see around us now.”

The study will be published in an upcoming issue of The Astrophysical Journal Letters.

This press release is being issued in conjunction with the Observatories of the Carnegie Institution of Washington.

NASA’s Jet Propulsion Laboratory, Pasadena, Calif., manages the Spitzer Space Telescope mission for NASA’s Science Mission Directorate, Washington. Science operations are conducted at the Spitzer Science Center, Pasadena, Calif. JPL is a division of California Institute for Technology, Pasadena.

Headquartered in Cambridge, Mass., the Harvard-Smithsonian Center for Astrophysics (CfA) is a joint collaboration between the Smithsonian Astrophysical Observatory and the Harvard College Observatory. CfA scientists, organized into six research divisions, study the origin, evolution and ultimate fate of the universe.

Posted on by Fraser Cain

Titan is Similar to Earth in Many Ways

Saturn’s largest and hazy moon, Titan, has a surface shaped largely by Earth-like processes of tectonics, erosion, winds, and perhaps volcanism. The findings are published in this week’s issue of the journal Nature.

Titan, long held to be a frozen analog of early Earth, has liquid methane on its cold surface, unlike the water found on our home planet. Among the new discoveries is what may be a long river, roughly 1,500 kilometers long (930 miles). Scientists have also concluded that winds on Titan blow a lot faster than the moon rotates, a fact long predicted but never confirmed until now.

Tectonism (brittle fracturing and faulting) has clearly played a role in shaping Titan’s surface. “The only known planetary process that creates large-scale linear boundaries is tectonism, in which internal processes cause portions of the crust to fracture and sometimes move either up, down or sideways,” said Dr. Alfred McEwen, Cassini imaging team member from the University of Arizona, Tucson. “Erosion by fluids may accentuate the tectonic fabric by depositing dark materials in low areas and enlarging fractures. This interplay between internal forces and fluid erosion is very Earth-like.”

Cassini images collected during close flybys of the moon show dark, curving and linear patterns in various regions on Titan, but mostly concentrated near the south pole. Some extend up to 1,500 kilometers (930 miles) long. Images from the European Space Agency’s Huygens probe show clear evidence for small channels a few kilometers long, probably cut by liquid methane. Cassini imaging scientists suggest that the dark, curved and linear patterns seen in the Cassini orbiter images of Titan may also be channels, though there is no direct evidence for the presence of fluids. If these features are channels, it would make the ones near the south pole nearly as long as the Snake River, which originates in Wyoming and flows across four states.

Since most of the cloud activity observed on Titan by Cassini has occurred over the south pole, scientists believe this may be where the cycle of methane rain, channel carving, runoff, and evaporation is most active, a hypothesis that could explain the presence of the extensive channel-like features seen in this region. In analyzing clouds of Titan’s lower atmosphere, scientists have concluded that the winds on Titan blow faster than the moon rotates, a phenomenon called super-rotation. In contrast, the jet streams of Earth blow slower than the rotation rate of our planet.

“Models of Titan’s atmosphere have indicated that it should super-rotate just like the atmosphere of Venus, but until now there have been no direct wind measurements to test the prediction,” said Cassini imaging team member Dr. Tony DelGenio of NASA’s Goddard Institute for Space Studies, in New York. DelGenio made the first computer simulation predicting Titan super-rotation a decade ago.

Titan’s winds are measured by watching its clouds move. Clouds are rare on Titan, and those that can be tracked are often too small and faint to be seen from Earth. Ten clouds have been tracked by Cassini, giving wind speeds as high as 34 meters per second (about 75 miles per hour) to the east — hurricane strength — in Titan’s lower atmosphere. “This result is consistent with the predictions of Titan weather models, and it suggests that we now understand the basic features of how meteorology works on slowly rotating planets,” said Del Genio.

“We’ve only just begun exploring the surface of Titan, but what’s struck me the most so far is the variety of the surface patterns that we?bfre seeing. The surface is very complex, and shows evidence for so many different modification processes,” said Dr. Elizabeth Turtle, Cassini imaging team associate in the Lunar and Planetary Laboratory at the University of Arizona, Tucson and co-author of one of the papers in Nature.

“Throughout the solar system, we find examples of solid bodies that show tremendous geologic variation across their surfaces. One hemisphere often can bear little resemblance to the other,” said Dr. Carolyn Porco, Cassini imaging team leader, Space Science Institute, Boulder, Colo. “On Titan, it’s very likely to be this and more.”

These results are based on Cassini orbiter images of Titan collected over the last eight months during a distant flyby of the south pole and three close encounters of Titan’s equatorial region. Cassini cameras have covered 30 percent of Titan’s surface, imaging features as small as 1 to 10 kilometers (0.6 to 6 miles). Cassini is scheduled to make 41 additional close Titan flybys in the next three years.

For images and information on the Cassini mission visit http://saturn.jpl.nasa.gov and http://www.nasa.gov/cassini and http://ciclops.org .

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 was designed, developed and assembled at JPL.

Original Source: NASA/JPL News Release