Posted on by Fraser Cain

Strange Extrasolar Planet Orbits Explained

Image credit: NWU
The peculiar orbits of three planets looping around a faraway star can be explained only if an unseen fourth planet blundered through and knocked them out of their circular orbits, according to a new study by researchers at the University of California, Berkeley, and Northwestern University.

The conclusion is based on computer extrapolations from 13 years of observations of planet motions around the star Upsilon Andromedae. It suggests that the non-circular and often highly elliptical orbits of many of the extrasolar planets discovered to date may be the result of planets scattering off one another. In such a scenario, the perturbing planet could be shot out of the system entirely or could be kicked into a far-off orbit, leaving the inner planets with eccentric orbits.

“This is probably one of the two or three extrasolar systems that have the best observations and tightest constraints, and it tells a unique story,” said Eric Ford, a Miller postdoctoral fellow at UC Berkeley. “Our explanation is that the outer planet’s original orbit was circular, but it got this sudden kick that permanently changed its orbit to being highly eccentric. To provide that kick, we’ve hypothesized that there was an additional planet that we don’t see now. We believe we now understand how this system works.”

If such a planet had caromed through our solar system early in its history, the researchers noted, the inner planets might not now have such nicely circular orbits, and, based on current assumptions about the origins of life, Earth’s climate might have fluctuated too much for life to have arisen.

“While the planets in our solar system remain stable for billions of years, that wasn’t the case for the planets orbiting Upsilon Andromedae,” Ford said. “While those planets might have formed similarly to Jupiter and Saturn, their current orbits were sculpted by a late phase of chaotic and violent interactions.”

According to Ford’s colleague, Frederic A. Rasio, associate professor of physics and astronomy at Northwestern, “Our results show that a simple mechanism, often called ‘planet-planet scattering’ – a sort of slingshot effect due to the sudden gravitational pull between two planets when they come very near each other – must be responsible for the highly eccentric orbits observed in the Upsilon Andromedae system. We believe planet-planet scattering occurred frequently in extrasolar planetary systems, not just this one, resulting from strong instabilities. So, while planetary systems around other stars may be common, the kinds of systems that could support life, which, like our solar system, presumably must remain stable over very long time scales, may not be so common.”

The computer simulations are reported in the April 14 issue of the journal Nature by Ford, Rasio and Verene Lystad, an undergraduate student majoring in physics at Northwestern. Ford was a student of Rasio’s at the Massachusetts Institute of Technology before pursuing graduate studies at Princeton University and arriving at UC Berkeley in 2004.

The planetary system around Upsilon Andromedae is one of the most studied of the 160-some systems with planets discovered so far outside our own solar system. The inner planet, a “hot Jupiter” so close to the star that its orbit is only a few days, was discovered in 1996 by UC Berkeley’s Geoff Marcy and his planet-hunting team. The two outer planets, with elongated orbits that perturb each other strongly, were discovered in 1999. These three, huge, Jupiter-like planets around Upsilon Andromedae comprised the first extrasolar multi-planet system discovered by Doppler spectroscopy.

Because of the unusual nature of the planetary orbits around Upsilon Andromedae, Marcy and his team have studied it intensely, making nearly 500 observations – 10 times more than for most other extrasolar planets that have been found. These observations, the wobbles in the star’s motion induced by the orbiting planets, allow a very precise charting of the planets’ motions around the star.

“The observations are so precise that we can watch and predict what will happen for tens of thousands of years in the future,” Ford said.

Today, while the innermost planet huddles close to the star, the two outer planets orbit in egg-shaped orbits. Computer simulations of past and future orbital changes showed, however, that the outer planets are engaged in a repetitive dance that, once every 7,000 years, brings the orbit of the middle planet to a circle.

“That property of returning to a very circular orbit is quite remarkable and generally doesn’t happen,” Ford said. “The natural explanation is that they were once both in circular orbits, and one got a big kick that caused it to become eccentric. Then, the subsequent evolution caused the other planet to grow its eccentricity, but because of the conservation of energy and angular momentum, it returns periodically to a very nearly circular orbit.”

Previously, astronomers had proposed two possible scenarios for the formation of Upsilon Andromedae’s planet system, but the observational data was not yet sufficient to distinguish the two models. Another astronomer, Renu Malhotra at the University of Arizona, had previously suggested that planet-planet scattering might have excited the eccentricities in Upsilon Andromedae. But an alternative explanation claimed that interactions among the planets and a gas disk surrounding the star could also have produced such eccentric orbits. By combining additional observational data with new computer models, Ford and his colleagues were able to show that interactions with a gas disk would not have produced the observed orbits, but that interactions with another planet would naturally produce them.

“The key distinguishing feature between those theories was that interactions with an outer disk would cause the orbits to change very slowly, and a strong interaction with a passing planet would cause the orbits to change very quickly compared to the 7,000-year time scale for the orbits to evolve,” Ford said. “Because the two hypotheses make different predictions for the evolution of the system, we can constrain the history of the system based on the current planetary orbits.”

Ford said that as the planets formed inside a disk of gas and dust, the drag on the planets would have kept their orbits circular. Once the dust and gas dissipated, however, only an interaction with a passing planet could have created the particular orbits of the two outer planets observed today. Perhaps, he noted, the perturbing planet was knocked into the inner planets by interactions with other planets far from the central star.

However it started, the resulting chaotic interactions would have created a very eccentric orbit for the third planet, which then also gradually perturbed the second planet’s orbit. Because the outer planet dominates the system, over time it perturbed the middle planet’s orbit enough to deform it slowly into an eccentric orbit as well, which is what is seen today, although every 7,000 years or so, the middle planet returns gradually to a circular orbit.

“This is what makes the system so peculiar,” said Rasio. “Ordinarily, the gravitational coupling between two elliptic orbits would never make one go back to a nearly perfect circle. A circle is very special.”

“Originally the main objective of our research was to simulate the Upsilon Andromedae planetary system, essentially in order to determine whether the outer two planets lie in the same plane like the planets in the solar system do,” said Lystad, who started working with Rasio when she was a sophomore and did many of the computer integrations as part of her senior thesis. “We were surprised to find that, for many of our simulations, it was difficult to tell whether the planets were in the same plane due to the fact that the middle planet’s orbit periodically became so very nearly circular. Once we noticed this strange behavior was present in all of our simulations, we recognized it as an earmark of a system that had undergone planet-planet scattering. We realized there was something much more interesting going on than anyone had found before.”

Understanding what happened during the formation and evolution of Upsilon Andromedae and other extrasolar planetary systems has major implications for our own solar system.

“Once you realize that most of the known extrasolar planets have highly eccentric orbits (like the planets in Upsilon Andromedae), you begin to wonder if there might be something special about our solar system,” Ford said. “Could violent planet-planet scattering be so common that few planetary systems remain calm and habitable? Fortunately, astronomers – led by Geoff Marcy, a professor of astronomy at UC Berkeley – are diligently making the observations that will eventually answer this exciting question.”

The research was supported by the National Science Foundation and UC Berkeley’s Miller Institute for Basic Research.

Original Source: Berkeley News Release

Posted on by Fraser Cain

Next Up, Mars Science Laboratory

Even before the Mars Science Lander (MSL) touches down descending from its hovering mother ship like a baby spider from an egg case the first of a slew of cameras will have started recording, capturing and storing high-resolution video of the landing area.

The MSL landing will represent a first, says Frank Palluconi, MSL project scientist. After entering the Mars atmosphere like Viking and MER but with a potential landing zone about one fourth the size he says, MSL will show its stuff. “It completes the descent down to the ten-meter [33-foot] level, or so, where the descent vehicle hovers, and it lowers the rover on a tether down to the surface. By that time, the rover has erected its wheels, so it lands on its mobility system. And then the tether is cut and the descent stage flies away and is no longer used. It crashes.”

In addition to the obvious advantages of such a soft landing, hovering and the tether drop are possible to model mathematically, unlike the airbag landing the MER vehicles used. Tethered descent is also scalable, Palluconi says, whereas the much smaller MERs were pushing the envelope of the airbag system’s capability.

Eyes on Mars
Shooting will begin as soon as the heat shield drops from the MSL descent stage. The Mars Descent Imager will take video in megapixel resolution, comparable to modern consumer digital video cameras. Aimed straight down, this camera will provide a spider’s eye view of the landing area a very wide angle at first and continue shooting until the rover touches down on Mars.

Landing videos will be transmitted to Earth by the rover when it becomes fully functional. This visual information, showing the landing area and its surroundings in fine detail, along with the fact that the rover will land on its wheels no tricky navigation off of a landing vehicle needed will allow project scientists to begin working the rover much sooner.

Once the rover’s mast rises and all systems are go, the real work will begin. As with MER, a mast-mounted, two-eyed camera system will feature prominently. The MastCam, like the descent imager and an arm-mounted close-up camera, is being designed and built by Malin Space Science Systems in San Diego, CA. All three rely on similar full-color, high-resolution subsystems. MastCam takes the basic setup found on the MERs twin cameras that will allow scientists to assemble 3D images and refines it considerably. MastCam has twin 10x optical zoom lenses, the same power as found in high-end consumer digital cameras on Earth. This will allow the camera to take not only wide-angle panoramas but also zoom in and focus on fist-sized rocks a kilometer (0.6 miles) away.

MastCam also shoots high definition video, a first for Mars. Both stills and video will be captured in full color, just like with earthbound digital cameras. In addition, MastCam will use a variety of specialized filters. Several members of the Malin Space Science Systems scientific team contributed to the various camera designs, including director James Cameron (Titanic, The Abyss, Aliens), a coinvestigator on the MastCam science team.

Photograph, Vaporize, Analyze
The MSL mast will also hold a unique hybrid optical instrument, never before flown to Mars. Called the ChemCam, this telescopic tool takes close-ups at a distance with a field of view of about 30 cm (1 foot) at ten meters (33 feet) distance. But that’s just the first step for ChemCam. In step two eerily reminiscent of the heat rays described in War of the Worlds a powerful laser will focus through the same telescope at the target. The laser can heat a spot about a millimeter (0.04 inches) in diameter to nearly ten thousand degrees Celsius (18 thousand degrees Fahrenheit). The heat blows away dust, breaks off molecules, breaks up the molecules and even breaks apart atoms in the rocky target.

As a result, the target emits a spark of light. ChemCam can analyze the spark’s spectrum, identifying what elements carbon or silicon, for example the target contained. Called Laser-Induced Breakdown Spectroscopy, or LIBS, this technique is widely used on Earth but will be a first for Mars, says Roger C. Wiens, a planetary scientist at Los Alamos National Laboratory and the principal investigator on the ChemCam project. “LIBS is being used in a number of facets on earth. For example, a company that makes aluminum uses it to check the composition of their aluminum alloy in the molten state.”

Going into space is a different story. Seven years in the making, ChemCam will make MSL much faster than MER at choosing targets, Wiens says. “The Opportunity rover landed in a small crater and here in front of us sat a rock outcrop, which is the first one we had seen on Mars up close and personal. And it was less than ten meters away. [With the ChemCam] we could have immediately analyzed that rock before actually even driving the rover off the pad, and told them that here sits a sedimentary rock outcrop right in front of you. Instead, it took a number of days, and they drove up to the rock and actually sampled it with the contact instruments before they really determined that it was a sedimentary rock outcrop.” With its long optical reach, ChemCam can analyze objects out of reach of the rover’s mechanical arm, even overhead.

In addition, ChemCam will be able to do some chemical analysis of small parts of rock samples, before they are crushed and transported to MSL’s internal analytical instruments

“I think this instrument is going to see a lot of use,” Wiens says, “because we can take a lot of data rapidly. So one of the great things is that we can get a much larger database of rock samples than some of the in-situ techniques. I think it’s going to be an exciting instrument to build and fly.”

Palluconi sees MSL as an intermediary step between MER and the direct search for life on Mars. “I would regard MSL as being kind of a transition mission between the more conventional aspects of planetary exploration, which involve geology and geophysics and, in the case of Mars because of its atmosphere, the climate and weather to ones in the future which will make direct searches for life. So the overall objective of MSL is to make a habitability assessment of the area that the vehicle lands in on Mars.”

The Near Future
Because NASA decided only in December 2004, which of many scientific instruments proposed for MSL will actually fly, all of the scientists whose projects were chosen are scrambling to put the finishing touches on their instruments. “The mission is in phase A, which is a definition phase, so it’s really the earliest formal phase of the mission,” Palluconi says. “Right now the principle work on the science side is figuring out where to place the instruments on the rover, how to meet their thermal needs, how to ensure that they have the fields of view they need and that their other requirements are met. Of course, the vehicle itself is being designed at the same time and the design is being refined. So there’s quite a bit of work to do and we’re probably just about a year away from the preliminary design review, which on the 2009 launch schedule would occur next February.”

Some aspects of the Mars Science Laboratory remain up in the air. Many of the MSL scientific instruments require plenty of power. The proposed source of that power, a radioisotope power supply, requires presidential approval, which lies in the future. And in March 2005, NASA began considering the possibility of flying two MSL rovers in 2011 instead of one in 2009.

Original Source: NASA Astrobiology Magazine

Posted on by Fraser Cain

Cassini Set for Closest Titan Flyby

This map of Titan’s surface illustrates the regions that will be imaged by Cassini during the spacecraft’s close flyby of the smog-enshrouded moon on April 16, 2005. At closest approach, the spacecraft is expected to pass approximately 1,025 kilometers (640 miles) above the moon’s surface.

The colored lines delineate the regions that will be imaged at differing resolutions.

Images from this encounter will add to those taken during the March 31, 2005, flyby and improve the moderate resolution coverage of this region. The imaging coverage will include the eastern portion of territory observed by Cassini’s radar instrument in October 2004 and February 2005, and will provide a way to compare the surface as viewed by the different instruments. Such comparisons (see PIA06222) will provide insight into the nature of Titan’s surface.

The higher-resolution (yellow boxes) have been spread out around a central mosaic in order to maximize coverage of this region by the visual and infrared mapping spectrometer which will be observing simultaneously with the cameras of the imaging science subsystem.

The map shows only brightness variations on Titan’s surface (the illumination is such that there are no shadows and no shading due to topographic variations). Previous observations indicate that, due to Titan’s thick, hazy atmosphere, the sizes of surface features that can be resolved are a few times larger than the actual pixel scale labeled on the map.

The images for this global map were obtained using a narrow band filter centered at 938 nanometers — a near-infrared wavelength (invisible to the human eye). At this wavelength, light can penetrate Titan’s atmosphere to reach the surface and return through the atmosphere to be detected by the camera. The images have been processed to enhance surface details.

It is currently northern winter on Titan, so the moon’s high northern latitudes are not illuminated, resulting in the lack of coverage north of 35 degrees north latitude.

At 5,150 kilometers (3,200 miles) across, Titan is one of the solar system’s largest moons.

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

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

Original Source: NASA/JPL/SSI News Release

Posted on by Fraser Cain

One of the Earliest Stars Found

Image credit: ANU
A new star that may be one of the first to have formed in the Universe has been discovered by an international team led by ANU researchers.

The new star ? which goes by the innocuous name HE 1327-2326 ? is of enormous importance because it provides the crucial evidence of the time when the very first stars formed after the Big Bang.

?This star?s a record breaker ? it has the lowest levels of iron ever recorded in a star so far. This is of great importance because it indicates HE 1327-2326 formed in the very early Universe,? team leader and astronomy PhD student, Ms Anna Frebel said.

In general, stars with a low iron abundance compared to the Earth?s sun are called ?metal-poor? stars.

?Elements such as iron are only synthesised in the course of the lifetime of stars during the evolution of the Universe,? Ms Frebel said.

?Thus, we believe HE 1327-2326 formed shortly after the Big Bang ? it?s about twice as iron-poor as the previous record holder, HE 0107-5240, which was discovered in 2001 by ANU and German astronomers as part of the same survey.

?HE 1327-2326 will be used to trace the very early chemical enrichment history of the Universe as well as star formation processes and will challenge astronomers around the world ? it?s a pretty exciting prospect.?

The researchers first observed HE 1327-2326 using the European Southern Observatory?s 3.6-metre telescope in Chile. High quality data taken later with Japan?s 8-metre Subaru telescope in Hawaii revealed HE 1327-2326?s extraordinarily low iron content.

The star was discovered in a sample of about 1800 ?metal-poor? stars that are being investigated as part of Ms Frebel?s PhD project and is detailed in the latest edition of Nature in the paper Nucleosynthetic signatures of the first stars.

Research collaborators included Professor John Norris from the Research School of Astronomy and Astrophysics, Dr Wako Aoki from the National Astronomical Observatories of Japan and Dr Norbert Christlieb from Hamburger Sternwarte in Germany, as well as other researchers in Sweden, the US, the UK, Japan and Australia.

?HE 1327-2326 is a very unusual object in many ways for us astronomers,? Professor Norris, Ms Frebel?s supervisor, said. ?Relative to its iron levels has abnormally high levels of several elements including carbon, nitrogen and strontium.

?Another very interesting and unusual observation is that no lithium could be detected in the relatively unevolved star. A yet unknown process must have led to depletion of that element.

?Stars that formed later in the history of the Universe tend to have more predictable ratios of these elements,? Professor Norris said.

Ms Frebel said there could be several scenarios that explain the unusual features of HE 1327-2326.

?An explanation could be that only one explosion of one of the first stars in the Universe happened, which led to pollution of the surrounding gas cloud with elements heavier than hydrogen, helium and lithium in which stars like HE 1327-2326 might have formed,? she said.

?However, it can not be excluded that HE 1327-2326 formed just after the Big Bang and there was little time for the iron content to develop and therefore is actually one of the ?first stars? itself ? although as yet no genuine ?first star? has been found.?

Original Source: ANU News Release

Posted on by Fraser Cain

Podcast: Binary Wolf-Rayet Stars

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

Posted on by Nancy Atkinson

Testing New Technologies… In Space

NASA’s New Millennium Program (NMP) was conceived as a way to accelerate the use of advanced technologies into operational science missions. “It was recognized that there were significant investments being made by the United States in advanced technologies,” said Dr. Christopher Stevens, the Program Manager for NMP, “and that they had real applications to either reducing the cost or providing new capability for science missions.” However, bringing these technologies into actual science missions in space is a high risk because of the uncertainty that comes with emerging technology. NMP reduces those risks with validating new technology by flying and testing it in space. “We take technologies that are ready to go forward from the laboratory and mature them so they are ready to go to space,” said Stevens, “but the operational missions could be 10 to 20 years in the future.”

There are two types of missions or systems that NMP undertakes. One is an integrated system validation, where the whole flight system is the subject of the investigation. The second type is a subsystem validation mission, where small, stand alone experiments are carried on a space vehicle, but the vehicle is not part of the experiments.

NMP was jointly established in 1995 by NASA’s Office of Space Science and the Office of Earth Science, and in the past, missions were usually separated as being applicable to future Earth science or space science mission needs. NMP is now managed by NASA’s Science Mission Directorate, and focuses on the needs of three science areas: the Earth-Sun System, Solar System Exploration, and the Universe.

The program began with the Deep Space 1 mission in 1998, which was a space science, integrated system validation. DS1’s defining technology was solar electric, or ion, propulsion. “It was known that this technology had a capability to reduce the mass needed for propulsion over conventional chemical propulsion, but nobody wanted to take the risk of flying it untested in space,” said Stevens. DS1 successfully proved the effectiveness of ion propulsion, and now subsequent missions will use this type of propulsion, including the upcoming Dawn mission.

Other successful NMP validations include improvements and cost reduction of LANDSAT-type satellites and the testing of an autonomous science spacecraft which has flight planning software that can be used on rovers as well as orbiting spacecraft to re-plan a robotic mission with no human intervention. Upcoming NMP missions yet to fly include a group of small satellites called nano-sats that will make simultaneous measurements from multiple places in space of Earth’s magnetosphere, and the testing of equipment to be used on the Laser Interferometer Space Antenna (LISA) mission, a joint mission between NASA and the European Space Agency. The only unsuccessful NMP mission to date was Deep Space 2, which was the Mars Microprobes that were part of the ill-fated Mars Polar Lander.

NASA recently announced the newest NMP mission, Space Technology 8, which is a subsystem validation project. It is a collection of four stand alone experiments that will travel to space on a small, low-cost, currently available spacecraft, dubbed a New Millennium carrier. The first experiment on ST8 is called Sail Mast, which is an ultra-light graphite mast. Applications for Sail Mast are spacecraft that require large membrane structures that need to be deployed, such as solar sails, telescope sunshades, large aperture optics, instrument booms, antennas or solar array assemblies. “There are a series of missions that have been identified on the NASA Roadmap for the future that could benefit from this capability,” said Stevens. “This will be a significant step forward in the mass of the structure. We are operating in a ? kg per meter mass range for a 30 or 40 meter boom that can be stowed compactly and has a reasonable stiffness.”

The second experiment is the Ultraflex Next Generation Solar Array System. This is a high power, extremely lightweight solar array. “This could be used for a mission that needs significant power in a lightweight, deployable array, such as for solar electric propulsion, or it could also be used on the surface of planetary bodies,” said Stevens. “We are looking at increasing the specific power of the array to greater than 170 watts per kilogram on an array that has at least 7 kilowatts of power.”

The third experiment is the Environmentally Adaptive Fault Tolerant Computing System. “Here the objective is to use commercial off the shelf processors configured in an architecture that is fault-tolerant to single event upsets caused by radiation,” said Stevens. “We want to show that this is a robust design that can be used in space without having to use radiation-hard parts, because you get a significant increase in processing speed and capability over currently available radiation-hard processors. We want to reduce the costs with high reliability.” This can be used for processing science data on board a spacecraft, and for autonomous control functions.

The final experiment on ST8 is the Miniature Loop Heat Pipe Small Thermal Management System. “What we want to do here is to reduce the thermal constraints on small spacecraft design and manage heat and the need for cooling without expending significant amounts of power,” said Stevens. This system proposes to efficiently manage thermal balance within the spacecraft by taking heat where it is being produced by, for example, electronics, and provide it to other places in the spacecraft that need heat. It has no moving parts and doesn’t require power.

The ST8 mission should be ready for launch in 2008.

In July of 2005 NASA plans to announce the technology providers for the next NMP mission. ST9 will be an integrated system validation mission. There are five different concepts that we are being considered, and all five are regarded as areas of high priority for NASA. They are:

– Solar Sail Flight System Technology
– Aerocapture System Technology for Planetary Missions
– Precision Formation Flying System Technology
– System Technology for Large Space Telescopes
– Terrain-Guided Automatic Landing System for Spacecraft

All five concepts will be studied over the next year. Following the completion of these studies, one of the five concepts will be selected for ST9. Launch time will depend on which concept is selected, but is tentatively in the 2008-2009 time frame.

Stevens has been with NMP since it was formed, and has been program manager for 3 years. He enjoys being able to demonstrate advanced technologies so that they can be incorporated into future missions. “It’s an exciting business, a very high risk business,” he said, “because advanced technology is so uncertain in regards to how long it will take and how much it will cost.” He said that the validation of the autonomous science spacecraft experiment has been especially rewarding. “The current Mars rovers are extremely labor-intensive, but NASA has not been willing to turn over the operation of a spacecraft to a software package, so I think this validation has been a major step.” Stevens said that his office has a technology infusion activity currently going on with the Mars program, looking at using this capability for future missions, like the Mars Science Laboratory rover, scheduled for launch in 2009.

Written by Nancy Atkinson

Posted on by Fraser Cain

Torino Scale Revised

Astronomers led by an MIT professor have revised the scale used to assess the threat of asteroids and comets colliding with Earth to better communicate those risks with the public.

The overall goal is to provide easy-to-understand information to assuage concerns about a potential doomsday collision with our planet.

The Torino scale, a risk-assessment system similar to the Richter scale used for earthquakes, was adopted by a working group of the International Astronomical Union (IAU) in 1999 at a meeting in Torino, Italy. On the scale, zero means virtually no chance of collision, while 10 means certain global catastrophe.

“The idea was to create a simple system conveying clear, consistent information about near-Earth objects [NEOs],” or asteroids and comets that appear to be heading toward the planet, said Richard Binzel, a professor in MIT’s Department of Earth, Atmospheric and Planetary Sciences and the creator of the scale.

Some critics, however, said that the original Torino scale was actually scaring people, “the opposite of what was intended,” said Binzel. Hence the revisions.

“For a newly discovered NEO, the revised scale still ranks the impact hazard from 0 to 10, and the calculations that determine the hazard level are still exactly the same,” Binzel said. The difference is that the wording for each category now better describes the attention or response merited for each.

For example, in the original scale NEOs of level 2-4 were described as “meriting concern.” The revised scale describes objects with those rankings as “meriting attention by astronomers”–not necessarily the public.

Equally important in the revisions, says Binzel, “is the emphasis on how continued tracking of an object is almost always likely to reduce the hazard level to 0, once sufficient data are obtained.” The general process of classifying NEO hazards is roughly analogous to hurricane forecasting. Predictions of a storm’s path are updated as more and more tracking data are collected.

According to Dr. Donald K. Yeomans, manager of NASA’s Near Earth Object Program Office, “The revisions in the Torino Scale should go a long way toward assuring the public that while we cannot always immediately rule out Earth impacts for recently discovered near-Earth objects, additional observations will almost certainly allow us to do so.”

The highest Torino level ever given an asteroid was a 4 last December, with a 2 percent chance of hitting Earth in 2029. And after extended tracking of the asteroid’s orbit, it was reclassified to level 1, effectively removing any chance of collision, “the outcome emphasized by level 4 as being most likely,” Binzel said.

“It is just a matter of the scale becoming more well known and understood. Just as there is little or no reason for public concern over a magnitude 3 earthquake, there is little cause for public attention for NEO close encounters having low values on the Torino scale.” He notes that an object must reach level 8 on the scale before there is a certainty of an impact capable of causing even localized destruction.

The Torino scale was developed because astronomers are spotting more and more NEOs through projects like the Lincoln Near Earth Asteroid Research project at MIT’s Lincoln Laboratory. “There’s no increase in the number of asteroids out there or how frequently they encounter our planet. What’s changed is our awareness of them,” Binzel notes.

As a result, astronomers debated whether they should keep potential NEO collisions secret or “be completely open with what we know when we know it,” Binzel said. The IAU working group, of which Binzel is secretary, resoundingly decided on the latter.

The revised wording of the scale was published last fall in a chapter of “Mitigation of Hazardous Comets and Asteroids” (Cambridge University Press). The revisions were undertaken through consultation with astronomers worldwide for nearly a year before being published.

Binzel concludes that “the chance of something hitting the Earth and having a major impact is very unlikely. But although unlikely, it is still not impossible. The only way to be certain of no asteroid impacts in the forecast is to keep looking.”

For more information on the revised Torino scale go to: neo.jpl.nasa.gov/torino_scale.html.

Original Source: MIT News Release

Posted on by Fraser Cain

Sedna Untouched for Millions of Years

Recent spectroscopic studies of infrared light reflected from the surface of Sedna reveal that it is probably unlike Pluto and Charon since Sedna’s surface does not display evidence for a large amount of either water or methane ice. Due to Sedna?s extreme distance from the Sun, the frigid surface has probably been untouched for millions of years by anything except cosmic rays and solar ultraviolet radiation.

Gemini Observatory astronomer Chad Trujillo led an effort by the same California Institute of Technology research team responsible for Sedna’s original discovery to obtain spectra of this distant planetoid using the Near Infrared Imager (NIRI) on Gemini North. Their aim was to better understand the surface of this distant world and how it has evolved since its formation. ?It is likely that Sedna has experienced an extremely isolated life in the outskirts of our solar system,? said Trujillo. ?Out there beyond what we used to think was the edge of the solar system, interactions or collisions between bodies are probably very rare. Our observations confirm what you would expect from a surface that has been so far out in our solar system for such a long time and exposed to space weathering.?

The Sedna data lack the strong spectral lines that would indicate the existence of substances like methane and water ice, but deeper studies are needed to confirm how low the levels of these ices might be on this planetoid. Sedna might be more like the minor planet Pholus (that lies just inside the orbit of Saturn), which is similar in its redness in visible light. This same ?space weathering? may also affect Pluto and Charon, but there may be other processes that replenish their water- and methane-rich surfaces, such as atmospheric effects, geological processes and collisions.

The data could reveal something of Sedna’s evolutionary history in the outer solar system. Astronomers think that objects like Sedna start out with icy surfaces. Over time cosmic rays and solar ultraviolet radiation ?bake and burn? the surfaces into black hydrocarbon-rich substances similar to asphalt, which do not reveal themselves well in infrared spectra. Such a history might explain why Sedna doesn’t exhibit traces of methane and water ice, whereas Pluto and Charon do.

?Like a sandblaster operating for several billion years, most of the objects out as far as Pluto are constantly being resurfaced by impacts and collisions which expose and supply fresh surface materials before the black stuff can get baked on,? said Michael Brown of California Institute of Technology, who is the Principle Investigator of the team that originally discovered Sedna. ?Pluto and its moon Charon provide an excellent example of this process, with Pluto displaying a strong methane ice signature in its spectrum and Charon dominated by water ice.?

The team does not rule out the possibility that longer-duration (deeper) observations might reveal evidence of methane or water ice on Sedna. However, the Gemini data indicate that if they do exist their extent is limited.

The results of these observations will appear in The Astrophysical Journal.

Original Source: Gemini News Release

Posted on by Fraser Cain

Audio: Binary Wolf-Rayet Stars

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

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

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

Posted on by Mark Mortimer

Book Review: Stargazing with a Telescope

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

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

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

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

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

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

Review by Mark Mortimer.