Posted on by Fraser Cain

Robot Finds Life in the Desert

Image credit: CMU
Current Mars expeditions raise the tantalizing possibility that there may be life somewhere on the red planet. But just how will future missions find it? A system being developed by Carnegie Mellon scientists could provide the answer.

At the 36th Lunar and Planetary Science Conference in Houston this week (March 14-18), Carnegie Mellon scientist Alan Waggoner is presenting results of the life detection system’s recent performance in Chile’s Atacama Desert, where it found growing lichens and bacterial colonies. This marks the first time a rover-based automated technology has been used to identify life in this harsh region, which serves as a test bed for technology that could be deployed in future Mars missions.

“Our life detection system worked very well, and something like it ultimately may enable robots to look for life on Mars,” says Waggoner, a member of the “Life in the Atacama” project team and director of the Molecular Biosensor and Imaging Center at Carnegie Mellon’s Mellon College of Science.

The “Life in the Atacama” 2004 field season?from August to mid-October?was the second phase of a three-year program whose goal is to understand how life can be detected by a rover that is being controlled by a remote science team. The project is part of NASA’s Astrobiology Science and Technology Program for Exploring Planets, or ASTEP, which concentrates on pushing the limits of technology in harsh environments.

David Wettergreen, associate research professor in Carnegie Mellon’s Robotics Institute, leads rover development and field investigation. Nathalie Cabrol, a planetary scientist at NASA Ames Research Center and the SETI Institute, leads the science investigation.

Life is barely detectable over most areas of the Atacama, but the rover’s instruments were able to detect lichens and bacterial colonies in two areas: a coastal region with a more humid climate and an interior, very arid region less hospitable to life.

“We saw very clear signals from chlorophyll, DNA and protein. And we were able to visually identify biological materials from a standard image captured by the rover,” says Waggoner.

“Taken together, these four pieces of evidence are strong indicators of life. Now, our findings are being confirmed in the lab. Samples collected in the Atacama were examined, and scientists found that they contained life. The lichens and bacteria in the samples are growing and awaiting analysis.”

Waggoner and his colleagues have designed a life detection system equipped to detect fluorescence signals from sparse life forms, including those that are mere millimeters in size. Their fluorescence imager, which is located underneath the rover, detects signals from chlorophyll-based life, such as cyanobacteria in lichens, and fluorescent signals from a set of dyes designed to light up only when they bind to nucleic acid, protein, lipid or carbohydrate?all molecules of life.

“We don’t know of other remote methods capable both of detecting low levels of micro-organisms and visualizing high levels incorporated as biofilms or colonies,” says Gregory Fisher, project imaging scientist.

“Our fluorescent imager is the first imaging system to work in the daylight while in the shade of the rover. The rover uses solar energy to operate so it needs to travel during daylight hours. Many times, the images we capture may only reveal a faint signal. Any sunlight that leaks in to the camera of a conventional fluorescence imager would obscure the signal,” Waggoner says.

“To avoid this problem, we designed our system to excite dyes with high intensity flashes of light. The camera only opens during those flashes, so we are able to capture a strong fluorescence signal during daytime exploration,” says Shmuel Weinstein, project manager.

During the mission, a remote science team located in Pittsburgh instructed the rover’s operations. A ground team at the site collected samples studied by the rover to bring back for further examination in the lab. On a typical day in the field, the rover followed a path designated the previous day by the remote operations science team. The rover stopped occasionally to perform detailed surface inspection, effectively creating a “macroscopic quilt” of geologic and biological data in selected 10 by 10 centimeter panels. After the rover departed a region, the ground team collected samples examined by the rover.

“Based on the rover findings in the field and our tests in the laboratory, there is not one example of the rover giving a false positive. Every sample we tested had bacteria in it,” says Edwin Minkley, director of the Center for Biotechnology and Environmental Processes in the Department of Biological Sciences.

Minkley is conducting analyses to determine the genetic characteristics of the recovered bacteria to identify the different microbial species present in the samples. He also is testing the bacteria’s sensitivity to ultraviolet (UV) radiation. One hypothesis is that the bacteria may have greater UV resistance because they are exposed to extreme UV radiation in the desert environment. According to Minkley, this characterization also may explain why such a high proportion of the bacteria from the most arid site are pigmented?red, yellow or pink?as they grow in the laboratory.

The first phase of the project began in 2003 when a solar-powered robot named Hyperion, also developed at Carnegie Mellon, was taken to the Atacama as a research test bed. Scientists conducted experiments with Hyperion to determine the optimum design, software and instrumentation for a robot that would be used in more extensive experiments conducted in 2004 and in 2005. Zo?, the rover used in the 2004 field season, is the result of that work. In the final year of the project, plans call for Zo?, equipped with a full array of instruments, to operate autonomously as it travels 50 kilometers over a two-month period.

The science team, led by Cabrol, is made up of geologists and biologists who study both Earth and Mars at institutions including NASA’s Ames Research Center and Johnson Space Center, SETI Institute, Jet Propulsion Laboratory, the University of Tennessee, Carnegie Mellon, Universidad Catolica del Norte (Chile), the University of Arizona, UCLA, the British Antarctic Survey, and the International Research School of Planetary Sciences (Pescara, Italy).

The Life in the Atacama project is funded with a three-year, $3 million grant from NASA to Carnegie Mellon’s Robotics Institute. William “Red” Whittaker is the principal investigator. Waggoner is principal investigator for the companion project in life-detection instruments, which garnered a separate $900,000 grant from NASA.

Original Source: CMU News Release

Posted on by Fraser Cain

Helium-Richest Stars Found

On the basis of stellar spectra totalling more than 200 hours of effective exposure time with the 8.2-m VLT Kueyen telescope at Paranal (Chile), a team of astronomers [1] has made a surprising discovery about the stars in the giant southern globular cluster Omega Centauri.

It has been known for some time that, contrary to other clusters of this type, this stellar cluster harbours two different populations of stars that still burn hydrogen in their centres. One population, accounting for one quarter of its stars, is bluer than the other.

Using the FLAMES multi-object spectrograph that is particularly well suited to this kind of work, the astronomers found that the bluer stars contain more heavy elements than those of the redder population. This was exactly opposite to the expectation and they are led to the conclusion that the bluer stars have an overabundance of the light element helium of more than 50%. They are in fact the most helium rich stars ever found. But why is this so?

The team suggests that this puzzle may be explained in the following way. First, a great burst of star formation took place during which all the stars of the red population were produced. As other normal stars, these stars transformed their hydrogen into helium by nuclear burning. Some of them, with masses of 10-12 times the mass of the Sun, soon thereafter exploded as supernovae, thereby enriching the interstellar medium in the globular cluster with helium. Next, the blue population stars formed from this helium-rich medium.

This unexpected discovery provides important new insights into the way stars may form in larger stellar systems.

Two Populations
Globular clusters are large stellar clusters some of which contain hundreds of thousands of stars. It is generally believed that all stars belonging to the same globular cluster were born together, from the same interstellar cloud and at the same time. Strangely, however, this seems not to be the case for the large southern globular cluster Omega Centauri.

Omega Centauri is the galactic globular cluster with the most complex stellar population. Its large mass may represent an intermediate type of object, between globular clusters and larger stellar systems such as galaxies. In this sense, Omega Centauri is a very useful “laboratory” for better understanding the history of star formation.

However, it appears that the more information astronomers acquire about the stars in this cluster, the less they seem to understand the origin of these stars. But now, new intriguing results from the ESO Very Large Telescope (VLT) may show a possible way of resolving the present, apparently contradictory results.

Last year, an international team of astronomers [1], using data from the Hubble Space Telescope (HST), showed that Omega Centauri, unlike all other globular clusters, possesses two distinct populations of stars burning hydrogen in their centre. Even more puzzling was the discovery that the bluer population was more rare than the redder one: they accounted for only a quarter of the total number of stars still burning hydrogen in their central core. This is exactly the opposite of what the astronomers had expected, based on the observations of more evolved stars in this cluster.

Over Two Weeks of Total Exposure Time!
The same team of astronomers then went on to observe some of the stars from the two populations in this cluster by means of the FLAMES instrument on the Very Large Telescope at Paranal. They used the MEDUSA mode, allowing to obtain no less than 130 spectra simultaneously.

Twelve one-hour spectra were obtained for 17 stars of the blue population and the same number stars from the red one. These stars have magnitudes between 20 and 21, i.e., they are between 500,000 and 1 million times fainter than what can be seen with the unaided eye.

The individual spectra of stars from each population were then co-added. This produced a “mean” spectrum of a blue-population star and another of a red-population. Each of these spectra represents a total of no less than 204 hours of exposure time and accordingly provides information in unrivalled detail about these stars, especially in terms of their chemical composition.

The scientific outcome matches the technical achievement!
From a careful study of the combined spectra, the astronomers were able to establish that – contrary to all prior expectations – the bluer stars are more “metal-rich” (by a factor two) than the redder ones. “The latter were found to have an abundance of elements more massive than helium corresponding to about 1/40 the solar abundance [2] “, explains Raffaele Gratton of INAF-Osservatorio Astronomico di Padova in Italy. “This is indeed very puzzling as current models of stars predict that the more metal-rich a star is, the redder it ought to be”.

Giampaolo Piotto (University of Padova, Italy), leader of the team, thinks that there is a solution to this celestial puzzle: “The only way we can explain this discrepancy is by assuming that the two populations of stars have a different abundance of helium. We find that while the red stars have a normal helium abundance, the bluer stars must be enriched in helium by more than 50% with respect to the other population!”

These stars are thus the most helium-rich stars ever found, and not by just a few percent! It took some 8 billion years for the Milky Way Galaxy to increase its helium abundance from the primordial 24% value (created by the Big Bang) to the present solar 28% value, and yet in a globular cluster that formed only 1 or 2 billion years after the Big Bang, stars were produced with 39% of helium!

Contamination from supernovae
The obvious question is now: “Where does all this helium come from?”

Luigi Bedin (ESO), another member of the team, suggests that the solution might be connected to supernovae: “The scenario we presently favour is one in which the high helium content originates from material ejected during the supernovae explosions of massive stars. It is possible that the total mass of Omega Centauri was just right to allow the material expelled by high-mass supernovae to escape, while the matter from explosions of stars with about 10-12 times the mass of the Sun was retained.”

According to this scenario, Omega Centauri must therefore have seen two generations of stars. The first generation, with primordial helium abundance, produced the redder stars. A few tens of million years later, the most massive stars of this first generation exploded as supernovae. The helium-enriched matter that was expelled during the explosions of stars with 10-12 times the mass of the Sun “polluted” the globular cluster. Then a second population of stars, the bluer ones, formed from this helium-rich gas.

The scientists acknowledge that certain problems still remain and that the last word may not yet have been said about this unusual globular cluster. But the new results constitute an important step towards the solution of the biggest mystery of all: why is Omega Centauri the only one among the galactic globular cluster that was able to produce super helium-rich stars?

More information
The research presented here appeared in the March 10 issue of the Astrophysical Journal, Vol. 621, p. 777 (“Metallicities on the Double Main Sequence of Omega Centauri Imply Large Helium Enhancement” by G. Piotto et al.) and is available for download as astro-ph/0412016.

Notes
[1]: The team is composed of Giampaolo Piotto, Giovanni Carraro, Sandro Villanova, and Yazan Momany (University of Padova, Italy), Luigi R. Bedin (ESO, Garching), Raffaele Gratton and Sara Lucatello (INAF- Osservatorio Astronomico di Padova, Italy), Santi Cassisi (INAF- Osservatorio Astronomico di Teramo, Italy), Alejandra Recio-Blanco (Observatoire de Nice, France), Ivan R. King (University of Washington, USA), and Jay Anderson (Rice University, USA).

[2]: Helium is the second most abundant chemical element in the Universe, after hydrogen. The Sun contains about 70% hydrogen and 28% helium. The rest, about 2%, is made of all elements more heavier than helium. They are commonly referred to by astronomers as “metals”.

Original Source: ESO News Release

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