A green laser was used to guide the invisible infrared beam from La Palma to Tenerife as part of an experiment to test a new satellite concept for measuring atmospheric greenhouse gases and turbulence. Credits: ESA
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It may have looked like a futuristic scene from Star Wars, but ESA’s latest technique for aiding space exploration might shed some “green light” on greenhouse gases. A recent experiment involving the Spanish Canary Islands was conducted by shooting laser beams from a peak on La Palma to Tenerife. The two-week endeavor not only increased the viability of using laser pulses to track satellites, but increased our understanding of Earth’s atmosphere.
ESA runs an optical ground station in Tenerife for communications links with satellites. The facility is part of a larger astronomical installation Observatorio del Teide run by Instituto de Astrofisica de Canarias. Credit: ESAKnown as infrared differential absorption spectroscopy, the laser method is an accurate avenue to measure trace gases such as carbon dioxide and methane. It is accomplished by linking two Earth-orbiting satellites – one a transmitter and the other a receiver – and examining the atmosphere as the beam passes between the two. As satellites orbit, they both rise and set behind Earth and radio occultation occurs. It’s a time-honored way of employing microwave signals to measure Earth’s atmosphere, but new wave thinking employs shortwave infrared laser pulses. When the correct wavelength is achieved, the atmospheric molecules impact the beam and the resultant data can then be used to establish amounts of trace gases and possibly wind. By different angular repetitions, a vertical picture can be painted which stretches between the lower stratosphere to the upper troposphere.
While it all sounded good on paper – the proof of a working model is when it is tested. Enter ESA’s optical ground station on Tenerife – a facility built on a peak 2390 meters above sea level and part of a larger astronomical installation called the Observatorio del Teide run by the Instituto de Astrofisica de Canarias (IAC).With equipment placed on two islands, the Tenerife location offered the perfect setting to install receiver hardware grafted to the main telescope. The transmitter was then assigned to a nearly identical peak on La Palma. With nothing but 144 kilometers of ocean between them, the scenario was ideal for experimentation.
Over the course of fourteen days, the team of researchers from the Wegener Center of the University of Graz in Austria and the Universities of York and Manchester in the UK were poised to collect this unique data.
The Observatorio del Roque de los Muchachos on the island of La Palma housed the equipment to transmit the infrared signal and green guidance laser across the Atlantic Ocean to the receiving station in Tenerife. The experiment was carried out to test a new satellite mission concept for measuring concentrations of atmospheric carbon dioxide and methane. Credit: ESAWhile the infrared beam wasn’t visible to the unaided eye, the green guidance laser lit up the night during its runs to record atmospheric turbulence. Gottfried Kirchengast from the Wegener Center said, “The campaign has been a crucial next step towards realising infrared-laser occultation observations from space. We are excited that this pioneering inter-island demonstration for measuring carbon dioxide and methane was successful.”
Armin Loscher from ESA’s Future Mission Division added, “It was a challenging experiment to coordinate, but a real pleasure to work with the motivated teams of renowned scientists and young academics.” The experiment was completed within ESA’s Earth Observation Support to Science Element.
Cygnus X hosts many young stellar groupings, including the OB2 and OB9 associations and the cluster NGC 6910. The combined outflows and ultraviolet radiation from the region's numerous massive stars have heated and pushed gas away from the clusters, producing cavities of hot, lower-density gas. In this 8-micron infrared image, ridges of denser gas mark the boundaries of the cavities. Bright spots within these ridges show where stars are forming today. Credit: NASA/IPAC/MSX
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Situated about 4,500 light-years away in the constellation of Cygnus is a veritable star factory called Cygnus X… one estimated to have enough “raw materials” to create as many as two million suns. Caught in the womb are stellar clusters and OB associations. Of particular interest is one labeled Cygnus OB2 which is home to 65 of the hottest, largest and meanest O-type stars known – and close to 500 B members. The O boys blast out holes in the dust clouds in intense outflows, disrupting cosmic rays. Now, a study using data from NASA’s Fermi Gamma-ray Space Telescope is showing us this disturbance can be traced back to its source.
Discovered some 60 years ago in radio frequencies, the Cygnus X region has long been of interest, but dust-veiled at optical wavelengths. By employing NASA’s Fermi Gamma-ray Space Telescope, scientists are now able to peer behind the obscuration and take a look at the heart through gamma ray observations. In regions of star formation like Cygnus X, subatomic particles are produced and these cosmic rays shoot across our galaxy at light speed. When they collide with interstellar gas, they scatter – making it impossible to trace them to their point of origin. However, this same collision produces a gamma ray source… one that can be detected and pinpointed.
“The galaxy’s best candidate sites for cosmic-ray acceleration are the rapidly expanding shells of ionized gas and magnetic field associated with supernova explosions.” says the FERMI team. “For stars, mass is destiny, and the most massive ones — known as types O and B — live fast and die young.”
Because these star types aren’t very common, regions like Cygnus X become important star laboratories. Its intense outflows and huge amount of mass fills the prescription for study. Within its hollowed-out walls, stars reside in layers of thin, hot gas enveloped in ribbons of cool, dense gas. It is this specific area in which Fermi’s LAT instrumentation excels – detecting an incredible amount of gamma rays.
“We are seeing young cosmic rays, with energies comparable to those produced by the most powerful particle accelerators on Earth. They have just started their galactic voyage, zig-zagging away from their accelerator and producing gamma rays when striking gas or starlight in the cavities,” said co-author Luigi Tibaldo, a physicist at Padova University and the Italian National Institute of Nuclear Physics.
Clocked at up to 100 billion electron volts by the LAT, these highly accelerated particles are revealing the extreme origin of gamma-ray emission. For example, visible light is only two to three electron volts! But why is Cygnus X so special? It entangles its sources in complex magnetic fields and keeps the majority of them from escaping. All thanks to those high mass stars…
“These shockwaves stir the gas and twist and tangle the magnetic field in a cosmic-scale jacuzzi so the young cosmic rays, freshly ejected from their accelerators, remain trapped in this turmoil until they can leak into quieter interstellar regions, where they can stream more freely,” said co-author Isabelle Grenier, an astrophysicist at Paris Diderot University and the Atomic Energy Commission in Saclay, France.
However, there’s more to the story. The Gamma Cygni supernova remnant is also nearby and may impact the findings as well. At this point, the Fermi team considers it may have created the initial “cocoon” which holds the cosmic rays in place, but they also concede the accelerated particles may have originated through multiple interactions with stellar winds.
“Whether the particles further gain or lose energy inside this cocoon needs to be investigated, but its existence shows that cosmic-ray history is much more eventful than a random walk away from their sources,” Tibaldo added.
The Fermi Gamma-ray Space Telescope (formerly called GLAST). Credit: NASA
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A couple of years ago, the Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics, PAMELA, sent us back some curious information… an overload of anti-matter in the Milky Way. Why does this member of the cosmic ray spectrum have interesting implications to the scientific community? It could mean the proof needed to confirm the existence of dark matter.
By employing the Fermi Large Area Telescope, researchers with the Kavli Institute for Particle Astrophysics and Cosmology (KIPAC) at Stanford University were able to verify the results of PAMELA’s findings. What’s more, by being in the high energy end of the spectrum, these abundances seem to verify current thinking on dark matter behavior and how it might produce positrons.
“There are various theories, but the basic idea is that if a dark matter particle were to meet its anti-particle, both would be annihilated. And that process of annihilation would generate new particles, including positrons.” says Stephan Funk, an assistant professor at Stanford and member of KIPAC. “When the PAMELA experiment looked at the spectrum of positrons, which means sampling positrons across a range of energy levels, it found more than would be expected from already understood astrophysics processes. The reason PAMELA generated such excitement is that it’s at least possible the excess positrons are coming from annihilation of dark matter particles.”
But there has been a glitch in what might have been a smooth solution. Current thinking has the positron signal dropping off when it reaches a specific level – a finding which wasn’t verified and led the researchers to feel the results were inconclusive. But the research just didn’t end there. The team consisting of Funk, Justin Vandenbroucke, a postdoc and Kavli Fellow and avli-supported graduate student Warit Mitthumsiri, came up with some creative solutions. While the Fermi Gamma-ray Space Telescope can’t distinguish between negatively charged electrons and positively charged positrons without a magnet – the group came up with their needs just a few hundred miles away.
Earth’s own magnetic field…
This illustration shows how the electron-positron sky appears to the Large Area Telescope. The purple region contains positrons while electrons are blocked by the Earth's bulk, the orange region contains electrons but is inaccessible to positrons, and the green region is completely out of the Earth's shadow for both positrons and electrons. Image courtesy Justin Vandenbroucke, Fermi-LAT collaboration.That’s right. Our very own planet is capable of bending the paths of these highly charged particles. Now it was time for the research team to start a study on geophysics maps and figure out precisely how the Earth was sifting out the previously detected particles. It was a new way of filtering findings, but could it work?
“The thing that was most fun about this analysis for me is its interdisciplinary nature. We absolutely could not have made the measurement without this detailed map of the Earth’s magnetic field, which was provided by an international team of geophysicists. So to make this measurement, we had to understand the Earth’s magnetic field, which meant poring over work published for entirely different reasons by scientists in another discipline altogether.” said Vandenbroucke. “The big takeaway here is how valuable it is to measure and understand the world around us in as many ways as possible. Once you have this basic scientific knowledge, it’s often surprising how that knowledge can be useful.”
Oddly enough, they still came up with more than the expected amount of antimatter positrons as previously reported in Nature. But again, the findings didn’t show the theoretical drop-off that was to be expected if dark matter were involved. Despite these inconclusive results, it’s still a unique way of looking at difficult studies and making the most of what’s at hand.
“I find it to be fascinating to try to get the most out of an astrophysical instrument and I think we did that with this measurement. It was very satisfying that our approach, novel as it was, seemed to work so well. Also, you really have to go where the science takes you.” says Funk. “Our motivation was to confirm the PAMELA results because they are so exciting and unexpected. And as far as understanding what the Universe is actually trying to tell us here, I think it was important that PAMELA results were confirmed by a completely different instrument and technique.”
Mars Science Laboratory, launched three days ago on the morning of Saturday, November 26, is currently on its way to the Red Planet – a journey that will take nearly nine months. When it arrives the first week of August 2012, MSL will begin investigating the soil and atmosphere within Gale Crater, searching for the faintest hints of past life. And unlike the previous rovers which ran on solar energy, MSL will be nuclear-powered, generating its energy through the decay of nearly 8 pounds of plutonium-238. This will potentially keep the next-generation rover running for years… but what will fuel future exploration missions now that NASA may no longer be able to fund the production of plutonium?
Pu-238 is a non-weapons-grade isotope of the radioactive element, used by NASA for over 50 years to fuel exploration spacecraft. Voyagers, Galileo, Cassini… all had radioisotope thermoelectric generators (RTGs) that generated power via Pu-238. But the substance has not been in production in the US since the late 1980s; all Pu-238 has since been produced in Russia. But now there’s only enough left for one or two more missions and the 2012 budget plan does not yet allot funding for the Department of Energy to continue production.
Where will future fuel come from? How will NASA power its next lineup of robotic explorers? (And why aren’t more people concerned about this?)
Amateur astronomer, teacher and blogger David Dickinson went into detail about this conundrum in an informative article written earlier this year. Here are some excerpts from his post:
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When leaving our fair planet, mass is everything. Space being a harsh place, you must bring nearly everything you need, including fuel, with you. And yes, more fuel means more mass, means more fuel, means… well, you get the idea. One way around this is to use available solar energy for power generation, but this only works well in the inner solar system. Take a look at the solar panels on the Juno spacecraft bound for Jupiter next month… those things have to be huge in order to take advantage of the relatively feeble solar wattage available to it… this is all because of our friend the inverse square law which governs all things electromagnetic, light included.
Curiosity's MMRTG (about 15 inches high.) Credit: NASA / Frankie Martin
To operate in the environs of deep space, you need a dependable power source. To compound problems, any prospective surface operations on the Moon or Mars must be able to utilize energy for long periods of sun-less operation; a lunar outpost would face nights that are about two Earth weeks long, for example. To this end, NASA has historically used Radioisotope Thermal Generators (RTGs) as an electric “power plant” for long term space missions. These provide a lightweight, long-term source of fuel, generating from 20-300 watts of electricity. Most are about the size of a small person, and the first prototypes flew on the Transit-4A & 5BN1/2 spacecraft in the early 60’s. The Pioneer, Voyager, New Horizons, Galileo and Cassini spacecraft all sport Pu238 powered RTGs. The Viking 1 and 2 spacecraft also had RTGs, as did the long term Apollo Lunar Surface Experiments Package (ALSEP) experiments that Apollo astronauts placed on the Moon. An ambitious sample return mission to the planet Pluto was even proposed in 2003 that would have utilized a small nuclear engine.
A glowing cake of plutonium. (Department of Energy)
David goes on to mention the undeniable dangers of plutonium…
Plutonium is nasty stuff. It is a strong alpha-emitter and a highly toxic metal. If inhaled, it exposes lung tissue to a very high local radiation dose with the attending risk of cancer. If ingested, some forms of plutonium accumulate in our bones where it can damage the body’s blood-forming mechanism and wreck havoc with DNA. NASA had historically pegged a chance of a launch failure of the New Horizons spacecraft at 350-to-1 against, which even then wouldn’t necessarily rupture the RTG and release the contained 11 kilograms of plutonium dioxide into the environment. Sampling conducted around the South Pacific resting place of the aforementioned Apollo 13 LM re-entry of the ascent stage of the Lunar Module, for example, suggests that the reentry of the RTG did NOT rupture the container, as no plutonium contamination has ever been found.
Yet the dangers of nuclear power often overshadow its relative safety and unmistakable benefit:
The black swan events such as Three Mile Island, Chernobyl and Fukushima have served to demonize all things nuclear, much like the view that 19thcentury citizens had of electricity. Never mind that coal-fired plants put many times the equivalent of radioactive contamination into the atmosphere in the form of lead210, polonium214, thorium and radon gases, every day. Safety detectors at nuclear plants are often triggered during temperature inversions due to nearby coal plant emissions… radiation was part of our environment even before the Cold War and is here to stay. To quote Carl Sagan, “Space travel is one of the best uses of nuclear weapons that I can think of…”
Yet here we are, with a definite end in sight to the supply of nuclear “weapons” needed to power space travel…
Currently, NASA faces a dilemma that will put a severe damper on outer solar system exploration in the coming decade. As mentioned, current plutonium reserves stand at about enough for the Mars Science Laboratory Curiosity, which will contain 4.8kilograms of plutonium dioxide, and one last large & and perhaps one small outer solar system mission. MSL utilizes a new generation MMRTG (the “MM” stands for Multi-Mission) designed by Boeing that will produce 125 watts for up to 14 years. But the production of new plutonium would be difficult. Restart of the plutonium supply-line would be a lengthy process, and take perhaps a decade. Other nuclear based alternatives do indeed exist, but not without a penalty either in low thermal activity, volatility, expense in production, or short half life.
The implications of this factor may be grim for both manned and unmanned space travel to the outer solar system. Juxtaposed against at what the recent 2011 Decadal Survey for Planetary Exploration proposes, we’ll be lucky to see many of those ambitious “Battlestar Galactica” –style outer solar system missions come to pass.
Landers, blimps and submersibles on Europa, Titan, and Enceladus will all operate well out of the Sun’s domain and will need said nuclear power plants to get the job done… contrast this with the European Space Agency’s Huygens probe, which landed on Titan after being released from NASA’s Cassini spacecraft in 2004, which operated for scant hours on battery power before succumbing to the -179.5 C° temps that represent a nice balmy day on the Saturnian moon.
So, what’s a space-faring civilization to do? Certainly, the “not going into space” option is not one we want on the table, and warp or Faster-Than-Light drives a la every bad science fiction flick are nowhere in the immediate future. In [my] highly opinionated view, NASA has the following options:
Exploit other RTG sources at penalty. As mentioned previously, other nuclear sources in the form of Plutonium, Thorium, and Curium isotopes do exist and could be conceivably incorporated into RTGs; all, however, have problems. Some have unfavorable half-lives; others release too little energy or hazardous penetrating gamma-rays. Plutonium238 has high energy output throughout an appreciable life span, and its alpha particle emissions can be easily contained.
Design innovative new technologies. Solar cell technology has come a long way in recent years, making perhaps exploration out to the orbit of Jupiter is do-able with enough collection area. The plucky Spirit and Opportunity Mars rovers(which did contain Curium isotopes in their spectrometers!) made do well past their respective warranty dates using solar cells, and NASA’s Dawn spacecraft currently orbiting the asteroid Vesta sports an innovative ion-drive technology.
Push to restart plutonium production. Again, it is not that likely or even feasible that this will come to pass in today’s financially strapped post-Cold War environment. Other countries, such as India and China are looking to “go nuclear” to break their dependence on oil, but it would take some time for any trickle-down plutonium to reach the launch pad. Also, power reactors are not good producers of Pu238. The dedicated production of Pu238 requires either high neutron flux reactors or specialized “fast” reactors specifically designed for the production of trans-uranium isotopes…
Based on the realities of nuclear materials production the levels of funding for Pu238 production restart are frighteningly small. NASA must rely on the DOE for the infrastructure and knowledge necessary and solutions to the problem must fit the realities within both agencies.
And that’s the grim reality of a brave new plutonium-free world that faces NASA; perhaps the solution will come as a combination of some or all of the above. The next decade will be fraught with crisis and opportunity… plutonium gives us a kind of Promethean bargain with its use; we can either build weapons and kill ourselves with it, or we can inherit the stars.
Diagram of an RTG. (Source: The Encyclopedia of Science)
Thanks to David Dickinson for the use of his excellent article; be sure to read the full version on his Astro Guyz site here (and follow David on Twitter @astroguyz.) Also check out this article by Emily Lakdawalla of The Planetary Society on how the RTG unit for Curiosity was made.
“There are some people who legitimately feel like this is simply not a priority, that there’s not enough money and it’s not their problem. But I think if you try to step back and look at the forest and not just the individual trees, this is one of the things that has helped drive us to become a technological powerhouse. What we’ve done with robotic space exploration is something that people not just in the U.S., but around the world, can look up to.”
– Ralph McNutt, planetary scientist at Johns Hopkins University’s Applied Physics Laboratory (APL)
It hasn’t been a great year for Roscosmos, the Russian Federal Space Agency. In the last twelve months, it has lost four major missions on top of the aerospace industry’s failure to produce its planned number of spacecraft.
For the most part, lost missions conjure up feelings of despair for the spacecraft from a scientific or exploration perspective – what does the silent satellite or failed launch mean for the agency’s immediate and overall goals? But there’s another side to lost missions that are less common. What does a lost mission or failed launch mean for the people responsible? All four missions Roscosmos has lost in the last year have been substantial. In December 2010, a Proton-M booster failed to put three Glonass-M satellites in orbit. These were meant to enhance Russia’s Global Navigation Satellite System, the Russian counterpart to America’s GPS system, and just recently, Russia successfully launched replacements.
In February, a Rokot booster carrying the Geo-IK-2 satellite ended in failure. The satellite was designed to build on Russia’s geodesic research. Acting as a precise reference point, it would help scientists take accurate measurements of the Earth’s shape and the properties of its gravitational field and support such fields as cartography, missile guidance, study of tectonic plate movements, ocean tides, and ice conditions.
A schematic showing the loss of theProgress M-12 expendable spacecraft. Credit: RIA Novosti.
The loss of these missions was doubtless devastating for the teams who designed them, but the After the loss of Geo-IK-2, a number of senior space industry officials were fired and Roscosmos’s chief, Anatoly Perminov, was forced to resign.
In August, another Proton-M rocket failed to launch an Ekspress-AM4. The communications satellite was designed to provide digital television and secure government communications throughout the Russian Federation extending far into Siberia and the Far East.
This failure prompted further disciplinary action. A Russian State Commission of inquiry was established to determine the reasons for the failure. The International Launch Services (ILS), a joint US-Russian venture with exclusive rights to launch commercial payload from the Baikonur Cosmodrome in Kazakhstan, formed its own Failure Review Oversight Board to review Roscosmos‘ final internal report. The final verdict was both missions were lost due to negligence.
Things didn’t get better for the Russian Space Agency. Only a week after the loss of Eskpress-AM4, A Soyuz-U booster failed. Its cargo, the Progress M-12 expendable cargo spacecraft, never reached the crew waiting for its contents aboard the International Space Station.
Now, it looks like further harsh disciplinary action might befall the scientists and engineers behind the failed Phobos-Grunt. Designed to land on Mars’ larger moon and return a soil sample, the spacecraft got stuck in Earth orbit in November. Russian President Dmitry Medvedev has suggested that those responsible for the failure need to be punished. They could he fined, he said. He even went so far as to suggest criminal prosecution. The threat might be directed at Lavochkin, the company that built Phobos-Grunt.
Russian President Dmitry Medvedev. Credit: RIA Novosti
It’s possible Medvedev is protecting the Russian people who, like Americans, foot the bill of their nation’s space program. But he might not be. The failures do, after all, deal a serious blow to Russia’s technological pride and standing as a power in space.
“I am not suggesting putting them up against the wall like under Josef Vissarionovich (Stalin), but seriously punish either financially or, if the fault is obvious, it could be a disciplinary or even criminal punishment,” Medvedev said.
Surprisingly, or perhaps not, Roscosmos isn’t the only Russian industry to be target by Medvedev’s calls for disciplinary action. Similar calls have been made for disciplinary action after carelessness, corruption, and problems within Russia’s infrastructure, such as a riverboat sinking in July that killed 122. The difference is that no one dies when an unmanned spacecraft fails to complete its mission.
Ever since a study conducted back in 1993, it has been proposed that in order for a planet to support more complex life, it would be most advantageous for that planet to have a large moon orbiting it, much like the Earth’s moon. Our moon helps to stabilize the Earth’s rotational axis against perturbations caused by the gravitational influence of Jupiter. Without that stabilizing force, there would be huge climate fluctuations caused by the tilt of Earth’s axis swinging between about 0 and 85 degrees.
But now that belief is being called into question thanks to newer research, which may mean that the number of planets capable of supporting complex life could be even higher than previously thought.
Since planets with relatively large moons are thought to be fairly rare, that would mean most terrestrial-type planets like Earth would have either smaller moons or no moons at all, limiting their potential to support life. But if the new research results are right, the dependence on a large moon might not be as important after all. “There could be a lot more habitable worlds out there,” according to Jack Lissauer of NASA’s Ames Research Center in Moffett Field, California, who leads the research team.
It seems that the 1993 study did not take into account how fast the changes in tilt would occur; the impression given was that the axis fluctuations would be wild and chaotic. Lissauer and his team conducted a new experiment simulating a moonless Earth over a time period of 4 billion years. The results were surprising – the axis tilt of the Earth varied only between about 10 and 50 degrees, much less than the original study suggested. There were also long periods of time, up to 500 million years, when the tilt was only between 17 and 32 degrees, a lot more stable than previously thought possible.
So what does this mean for planets in other solar systems? According to Darren Williams of Pennsylvania State University, “Large moons are not required for a stable tilt and climate. In some circumstances, large moons can even be detrimental, depending on the arrangement of planets in a given system. Every system is going to be different.”
Apparently the assumption that a planet needs a large moon in order to be capable of supporting life was a bit premature. The results so far from the Kepler mission and other telescopes have shown that there is a wide variety of planets orbiting other stars, and so probably also moons, which we are now also on the verge of being able to detect. It’s nice to think that more of the terrestrial-type rocky planets, with or without moons, might be habitable after all.
Visible at the bottom of the image is the venting of gases, probably from the Mars Science Laboratory Centaur rocket stage, as seen from the Sir Thomas Brisbane Planetarium in Australia. The Orion Nebula is at the top. Photo by Duncan Waldron.
What does a spacecraft look like as it lights-out for another world? This incredible time-lapse video was taken by astronomers at the Sir Thomas Brisbane Planetarium in Australia. The sequence shows a plume drifting against the background stars, probably caused by venting from the Centaur rocket stage that sent the Mars Science Laboratory/Curiosity Rover on its way to the Red Planet, after it carried out a burn over the Indian Ocean on November 26, 2011.
Brisbane Planetarium Curator Mark Rigby said that he and photographer/amateur astronomer Duncan Waldron, along with another planetarium staff member were likely the only people who saw this amazing sight, as they have received no other reports of similar observations.
Rigby said they are “are over the Moon – or higher” from seeing the departure of the Mars Science Laboratory, its rocket stage and plume above Australia on Sunday. “It is a real shame that we couldn’t have woken up everyone that didn’t have clouds,” Rigby wrote on the Planetarium’s Facebook page. “Even we didn’t expect to see such a spectacle. Can you imagine the feeling if there had been a crew onboard heading for Mars?”
Rigby first saw the plume at 2:15am local time, (16:15 UT) and said it was “a one-degree elongated cloud of VERY easy naked eye brightness.” Duncan Waldron also saw it starting at about 2:30pm and began to photograph it until it faded. Nonetheless, he captured a unique timelapse covering 21 minutes until 3am.
Here is one of Waldron’s images, below:
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The coordinates of the observing site: -27.630779,152.966324, altitude 40m approx.
Congrats to the Sir Thomas Brisbane Planetarium team for capturing such an amazing and historical sight!
A brand new Carnival of Space is hosted by my pal, The Noisy Astronomer, Nicole Gugliucci from One Astronomer’s Noise, (who is recovering from a turkey coma.)
And if you’re interested in looking back, here’s an archive to all the past Carnivals of Space. If you’ve got a space-related blog, you should really join the carnival. Just email an entry to [email protected], and the next host will link to it. It will help get awareness out there about your writing, help you meet others in the space community – and community is what blogging is all about. And if you really want to help out, sign up to be a host. Send and email to the above address.
For many astronomers who are just getting started, dobsonian reflector telescopes are a popular choice. While many newcomers to Astronomy seek out computerized “go-to” telescopes, some prefer the “no-frills” setup a dobsonian telescope offers.
The Orion XT8 dobsonian is a mid-range reflector telescope. There are a few smaller and less expensive models available in Orion’s classic dobsonian series, and there are a few larger, more expensive models as well. The XT8 offers a good balance between portability, price and performance. In this review we’ll look at the build quality of the XT8, along with how it performs at planetary and “dark sky” objects.
For starters, let’s look at the raw specifications for the XT8. The XT8 features an 8″ (203mm) primary mirror. With a focal length of 1200mm, this gives a focal ratio of f/5.9. Advanced observers will enjoy the XT8’s 2″ focuser, which allows for larger eyepieces, or even a “T” adapter for short-exposure astrophotography. New observers (or those on a budget) will find the included 2″ to 1.25″ eyepiece adapter allows the use of 1.25″ eyepieces with no noticeable wiggle/slop.
The XT8 does come with a 25mm 1.25″ Plossl eyepiece which performs well as a medium-power eyepiece in the XT8. The XT8 features Orion’s EZ Finder II sight. While the EZ Finder II isn’t a terribly bad “red-dot” finder, some observers may see fit to replace the stock finder with something like a “correct image” finder scope, a laser pointer, or even a Telrad non-magnified finder.
Orion ships the XT8 in two boxes. One for the optical tube, and a second for the dobsonian mount base. The shipping box for the mount base was well thought out, minimizing potential damage to the base components. The shipping box for the optical tube was adequate, but as with any piece of delicate equipment – there can never be enough padding.
Assembling the XT8 took about half an hour by myself. With a helper, the XT8 could probably be assembled in ten minutes. Once assembled the mount base is quite sturdy and allowed for smooth rotation of the optical tube, due to the Teflon azimuth bearings. Adjusting the optical tube in altitude was equally effortless and the tension springs provided enough tension to maintain position (even pointed at the horizon) without making the tube difficult to raise or lower.
The mount base does include a carrying handle. At around 40lbs total weight, some users of the scope may prefer to carry the optical tube and base assemblies separately. Once assembled and put in place at an observing location, operation of the XT8 is fairly straight forward. Depending on what finder setup is used, aligning the finder may take just a few minutes, or slightly longer. Generally, using a very bright object (newcomers may want help with this step) in the finder makes the process of alignment easier and faster. When setting up the XT8 for this review, I aligned my Telrad finder and the telescope itself with Jupiter.
After aligning the finder, using the XT8 is simply a matter of moving the optical tube to whatever objects are desired. Once the telescope is pointed at an object, making focus and/or eyepiece adjustments are fairly trivial. The eyepiece holder features thumbscrews which do a good job of holding eyepieces in place. The focuser offers smooth operation with very little image “wobble”.
Putting the XT8 through a short observing session, I was able to obtain great views of the Moon, Jupiter, the Orion Nebula (M42), and the Andromeda Galaxy (M31). At the time of testing, the Moon was in a waning crescent phase and the XT8 brought out some great views of lunar craters near the terminator. Despite being close to the horizon, the view of lunar craters in the eyepiece were crisp and clear. Moving eastward to Jupiter revealed a delightful view of a few of Jupiter’s atmospheric bands, as well as the Galilean moons. While the view from an 8″ telescope can’t compare to the views of Jupiter from Voyager or the Hubble, the detail revealed is still quite impressive.
Saving the best for last, I pointed the XT8 at M42 (Orion Nebula) and M31 (Andromeda Galaxy). Star-hopping to M31 was fairly trivial, via Alpheratz (In Pegasus). I did switch from the stock 25mm to a lower power 40mm eyepiece, as M31 does tend to benefit from lower power eyepieces, at least visually. The view of M31 provided a fuzzy patch that clearly stood out from the background stars. Moving eastward to M42, the views were breathtaking for such a relatively small telescope. Significant detail (albeit without much color) of the gas and dust was visible, along with a bright trapezium.
In Summary, the Orion XT8 is a great mid-range telescope which balances price and performance quite well. Despite Orion classifying this telescope as an “Intermediate” telescope, the XT8 would be an excellent choice for a beginning astronomer, or even an experienced observer looking to add a new scope to their fleet.
Assembling the XT8 was a trivial task with the included wrenches, and after assembly the telescope felt very sturdy. At around 40lbs, most people will have little to no trouble carrying the XT8 from their car to their observing spot, or from the house to a spot in their backyard. The included 25mm eyepiece works well as a mid-range eyepiece, but some users may want to invest in additional eyepieces, or at the very least a 2X barlow lens.
Some users of the XT8 may choose to replace the stock finder with one of their own choosing, but the included red-dot sight is fairly adequate. With a scope as powerful as the XT8, those planning to regularly perform lunar observations may want to consider purchasing a lunar filter. Any users who choose to perform solar observations can easily obtain a glass filter lens for the XT8 at a cost of around $100.
A mosaic of nine oblique views from the MESSENGER spacecraft of Mercury's limb, looking towards the horizon. Click for larger, more amazing view. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington
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Wow — just wow! Here’s a unique, jaw-dropping, and beautiful look at Mercury from the MESSENGER spacecraft, in a mosaic created from nine images taken by the Narrow Angle Camera (NAC) of the Mercury Dual Imaging System (MDIS). The camera took a “sideways” or oblique view of Mercury’s limb, looking towards the horizon, providing a distinctive look at the rough terrain, ridges, craters and scarps of the Van Eyck Formation region, adjacent to the Caloris basin. Combining the images for a larger view not only provides a “you are there” feel, but it provides the science team with new ways to study Mercury’s geology.
Make sure you click on the image for a larger, even more amazing view. You can compare this image with a “straight-down” look of the same region, below.
Correlation of features between the limb mosaic and an overhead view. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington
Looking at any landscape in from different angles has a major impact on how terrain location and feature orientation is perceived, the MESSENGER science team explained in a detailed description of how this image was made. While single images that focus on one feature are wonderful for in-depth explorations, combining images together in a mosaic studying can provide regional or even global perspective. These mosaics are particularly important for understanding the geological context of a particular feature and for exploring Mercury’s geologic history.
The Van Eyck region was formed by ejecta from the Caloris basin. Visible in the overhead view are “ghost craters” which are impact craters that were later buried by the voluminous volcanic lavas that form the plains in this part of Mercury. What appear as rough terrain and ridges in the oblique limb view show up as lineated, distinctive features from overhead. Both views provide clues to scientists about the processes or environment that the features formed.
The ejecta blanket of Caloris basin is to the lower left of the overhead-view.
The limb mosaic is just 9 of 75,000 images the NAC has taken and will continue to take during MESSENGER’s primary mission, which goes through March of 2012. These images were taken in June of 2011, and the mosaic was released today by the imaging team.
Since planets with relatively large moons are thought to be fairly rare, that would mean most terrestrial-type planets like Earth would have either smaller moons or no moons at all, limiting their potential to support life. But if the new research results are right, the dependence on a large moon might not be as important after all. “There could be a lot more habitable worlds out there,” according to Jack Lissauer of NASA’s Ames Research Center in Moffett Field, California, who leads the research team.
