News reports of some ‘long lost’ Apollo 11 footage surfacing in Australia sounded pretty intriguing, with articles about it appearing on several websites this morning. But surely, any of the long-searched-for-and-believed-lost footage finally showing up would have received a bigger fanfare than just a few articles. I checked with NASA Headquarters about this footage, and they told me it actually is the same video that NASA restored and released in 2009 for the 40th anniversary of the Apollo 11 mission.
These restored videos include a copy of a tape recorded at NASA’s Sydney, Australia, video switching center, where down-linked television from Parkes and Honeysuckle Creek was received for transmission to the U.S., as well as original broadcast tapes from the CBS News Archive recorded via direct microwave and landline feeds from NASA’s Johnson Space Center in Houston, and kinescopes found in film vaults at Johnson that had not been viewed for over 30 years. Continue reading “‘Long Lost’ Apollo Footage Was Actually Released in 2009”
Jim Lovell with artist Marla Friedman who painted Lovell's portrait for the Abraham Lincoln Presidential Library and Museum. Image: Nancy Atkinson
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Apollo astronaut Jim Lovell was awarded the Lincoln Leadership Prize by the Abraham Lincoln Presidential Library and Museum foundation last week, and while humbled to receive the award, Lovell said he really is just an ordinary person. “I was just at the right place at the right time with the right credentials; there was nothing so extra special about me that got me where I am.”
But those in attendance at a reception to unveil a portrait of Lovell which will hang at the presidential library in Springfield, Illinois said Lovell embodies the intersection of heroism and legacy.
Lovell speaking at a reception in his honor at the Abraham Lincoln Presidential Museum. Image: Nancy Atkinson
“NASA had a leader at the exact moment they needed it,” said Richard K. Davis, Chair, President and CEO of US Bancorp, who introduced the former Apollo astronaut at the reception. “With the help of many, Lovell and his crew created the outrageous but amazing solution to plot Apollo 13 back home. NASA found they had a cool, calm, competent leader, a hero who took this crew and a nation from ‘Houston we have a problem’ to America, we have a miracle.
Davis said one of his all-time favorite quotes comes from Lovell: “There are people who make things happen, there are people who watch things happen, and there are people who wonder what happened. To be successful you need to be a person who makes things happen.”
Earlier in the week, Lovell talked with members of the media about his life and his thoughts on NASA’s current budget situation. You can read part one of the interview here, and following is the continuation of the conversation with Jim Lovell, where he talks about some of his memories of his flights to space, and what it took for him to realize that Apollo 13 was more than just a failure:
We’re coming up to almost the 40th anniversary of the last person who landed on the Moon—what are your thoughts about that?
Lovell: It is a rather sad remembrance. I think it is an end of an era. I think the anniversaries will end—we probably won’t get together much anymore. We should look ahead to have a space program that everyone can be proud of, regardless of what it ends up to be. Sometimes we live too much in the past. But the future is here.
Why did you decide to become an astronaut?
Lovell: When I was in high school I was interested in both astronomy and rockets. There was a fellow I admired, the father of modern rocketry named Robert Goddard. I really wanted to be a rocket engineer. So I wrote to the secretary of the American Rocket Society, and asked how I could become one. He told me there was no school at that time that offered that type of study specifically, but I should take mechanics and mathematics, thermodynamics and either go to MIT or CalTech.
But my father had died earlier that year and I didn’t have the money to go to either of those places, so I gave that up. But I did apply to get an ROTC scholarship and was accepted. I went to the University of Wisconsin for two years and won an appointment to the Naval Academy. I went there for four years and got into the Navy and became a naval aviator – which was a second goal for me, as my uncle had been a naval aviator and had regaled me with all his stories. Then I went to test pilot school for the Navy. And when NASA was asking for astronauts, it seemed to me to be the perfect opportunity: here was a marrying of flight and rockets all coming together for me as if I had planned it all this time.
You couldn’t have seen a more disappointed person when I wasn’t selected for the first original seven astronauts. I made it to the final 32 candidates. But then, for round two, I was selected.
Universe Today: What are your favorite memories from your four flights to space?
Lovell: Apollo 8 was the most inspirational flight to me, and I hope it brought a message back to the Earth of what we have.
The most impressive sight I saw was not the moon, not the far side that we never see, or the craters. It was Earth. The Earth was the most impressive sight. As we came around the far side of the Moon and saw the Earth come up above the horizon, we could see the only color in our part of the Universe. The blues of the oceans, the white clouds, the tans, the pinks. I could put my thumb up and hide the Earth completely. Then it dawned on me how completely insignificant we are. Everything I had ever known – my family, my country, my world – was behind my thumb.
So there in the distance was this small body orbiting a rather normal sun, — nothing so particular about it — tucked away on the outer edge of the galaxy we call the Milky Way.
I thought how fortunate we are to live on this small body, with everyone – all those ‘astronauts’ — living together like on a starship, with limited resources. So, in a way that was just like Apollo 13, and we have to learn to live and work together. And I hope we could bring that message back to the people of Earth.
But I also have to say one of my other favorite memories was from Apollo 13: the splashdown! Seeing the parachutes, feeling the capsule swaying in the ocean, and having one of the divers come to knock on the window was a great feeling. It was pretty impressive, too.
Jim Lovell speaking at the museum, in front of a replica of the White House. Image: Nancy Atkinson
What was scarier, the explosion of Apollo 13 or seeing the service module after it was jettisoned and wondering if the heat shield was still intact?
Lovell: The low point was the explosion – which we didn’t realize was an explosion until I saw the oxygen leaking outside the spacecraft, and saw from our instruments that we would be completely out of oxygen. This also meant we would be out of electrical power, and because we used the electrical power to control the rocket engine, we also lost the propulsion system. We knew we were losing the command module, but that was the only thing that had the heat shield to get us back to Earth.
As we were going through and solving all the problems one by one, when we came back towards Earth and jettisoned the Service Module and saw the explosion had blown out the entire side panel, we wondered about that heat shield which was right behind us, if the explosion had cracked it. But there was nothing we could do at that point. There was no solution. You just crossed your fingers. Once we entered the atmosphere we just had to hope the heat shield was intact. And it was.
Lovell and museum officials at the unveiling of a portrait of Lovell that will hang in the Abraham Lincoln Presidential Museum. Image: Nancy Atkinson
You went from the space program to the tugboat business. What was that like?
After I retired from NASA and the Navy, and I was looking for something to do. I went to the advanced management program at Harvard and learned enough about business to be dangerous. Some friends of ours had a tugboat company and he offered me a job leading the company. Since I was a Navy officer — which has something to do with ships and water – I thought I could handle that. I was in that about five years. Then I got into the telecommunications business, which was fortunate timing because the deregulation of AT&T was just around the corner. We sold digital systems, where AT&T had analog systems, and we could sell the systems instead of how it was done the past where customers leased equipment from the phone company.
As you sit in this museum and library, what are your thoughts about studying the past?
This library and museum is not just something to look back on the era of Lincoln, it is an education for all ages coming through here of how we can keep the country together in the future. At the various museums around the country, like at the Air and Space museum, we show what people have done in the past in spaceflight. Here, and there, we show how people are committed to do things. Lincoln was committed to preserve the country. This type of an institution gives young people the chance to learn about those who were committed to make our country strong, and it should give everyone hope about our future.
You didn’t write the book “Lost Moon” for over 20 years after the Apollo 13 mission. What took so long?
Lovell: When we first got back from Apollo 13, the three of us astronauts said, this was a pretty unusual flight, so we should write a book about this. So, we said, we’re going to get together and write something. Well, as it often happens, as time went on, we all had jobs to do and life got busy for all of us. Jack Swigert went into politics in Colorado, and then, of course, he passed away. Fred Haise went into the aerospace business with Grumman, and I went into the telephone business. But just after I retired I got a call from a young man (Jeffrey Kluger) who said he had never written a book before, but he was a science writer for the Discover Magazine.
To make a long story short, I liked the way he wrote and we got together and wrote the book about 22 years after Apollo 13. But you have to remember that Apollo 13 was a failure. I mean, the only experiment that was completed was really done by the mission control team when they maneuvered the third stage of our booster to hit the Moon so that the Apollo 12 seismometers could pick up the results of the hit to learn something about the lunar surface. So there were no other successful experiments. The only thing we were doing was trying to figure out how to get home.
So, for years after we got back, I was frustrated. I wanted to land on the Moon like the other crews had, but I didn’t. But as we started to write the book, I realized that in its initial mission, yes, the flight was a failure. But as we wrote and I found out more about how hard the mission control team worked to get us back, I realized it really was a triumph in the way people handled a crisis: good leadership at all levels at NASA, teamwork that was generated because of that leadership, the use of imagination and initiative to figure out how to get us home by using just what we had on board, the perseverance of people who kept on going when it looked like initially that we didn’t have a chance. Jules Bergman (ABC science reporter) only gave us a 10 per cent chance, and my wife never forgave him for that!
But this is why Apollo 13 went from being a failure to a triumph.
The movie is very accurate, by the way. Ron Howard followed the real story very well. All the incidents were true except for the argument between Haise and Swigert, but Ron Howard had to figure out a way to portray the tension we all felt, and decided to do it in that way.
Previous winners of the Lincoln Leadership Prize are archbishop Desmond Tutu and Supreme Court Justice Sandra Day O’Connor. For more information about the Lincoln Prize and the Presidential Museum and Library, see the ALPLM website.
Many annual meteor showers have parent bodies identified. For example, the Perseids are ejecta from the comet, Swift-Tuttle and the Leonids from Tempel-Tuttle. Most known parent bodies are active comets, but one exception is the Geminid meteor shower that peaks in mid December. The parent for this shower is 3200 Phaethon. Observations of this object have shown it to be largely inactive pegging it as either a dead comet or an asteroid. But on June 20, 2009, shortly after perihelion, 3200 Phaethon brightened by over two magnitudes indicating this object may not be as dead as previously considered. A new paper considers the causes of the brightening and concludes that it could be a new mechanism leading to what the authors deem a “rock comet”.
David Jewett and Jing Li of UCLA, the authors of this new paper, consider several potential causes. Due to the size of 3200 Phaethon, they suggest that a collision is unlikely. One clue to the reason for the sudden change in brightness was a close link of a half of a day to a brightening in the solar corona. Given a typical solar wind speed and the distance of 3200 Phaethon at the time, this would put the Geminid parent just at the right range to be feeling the effects of the increase. However, the authors conclude that this cannot be directly responsible by imparting sufficient energy on the surface of the object to cause it to fluoresce due to an insufficient solar wind flux at that distance.
Instead, Jewett and Li consider more indirect explanations. Due to the temperature at 3200 Phaethon’s perihelion (0.14 AU) the presence of ices and other volatile gasses frozen solid and then blasting away as often happens in comets was ruled out as they would have been depleted on earlier orbits. However, the blow from the increased solar wind may have been sufficient to blow off loosely bound dust particles. While this is plausible, the authors note that the amount of mass lost if this were the case would be a paltry 2.5 x 108 kg. While it’s possible that this may have been the cause of this single brightening, this amount of mass loss to the overall stream of particles responsible for the Geminid shower would be insufficient to sustain the stream and similar losses would have to occur ~10 times per orbit of the body. Since this has not been observed, it is unlikely that this event was tied to the production of the meteors. Additionally, it is somewhat unlikely that it could even be the event for this sole case since repeated perihelions would slowly deplete the reservoir of available dust until the body was left with only a bare surface. Unlike active comets which continually free dust to be ejected through sublimation of ice, 3200 Phaethon has no such process. Or does it?
The novel proposition is that this object may have an unusual mechanism by which to continually generate and liberate dust particles of the size of the Geminids. The authors propose that the heating at perihelion causes portions of the rock to decompose. This process is greatly enhanced if the rock has water molecules bonded to it and lab experiments have shown that this can lead to violent fracturing. Such processes, if present, could easily lead to the production of new dust particles that would be liberated during close approach to the sun. This would make this object a “rock comet” in which the properties of a comet’s dust ejection via gasses would be carried out by rocks.
To confirm this hypothesis, future observations would be needed to search for subsequent brightening at perihelion. Similarly, it should be expected that such a process may make a faint cometary tail with only a dust component that may be visible as well, although the lack of any such detection so far, despite studies looking for cometary tails, casts some doubt on this process.
Image from the 1951 move "The Day the Earth Stood Still." Credit: IMBD.com
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UPDATE: OK, this seemed like a cool story, reported by many news sources, but apparently, it isn’t true. The Discovery Discoblog has the details. . I guess there was a truth abduction.
If aliens ever visit Earth and actually do use the time-worn phrase, “Take me to your leader,” or if a SETI search ever finds a signal of an alien civilization saying “hello,” there may be someone ready and waiting to respond. The United Nations is considering selecting a special ambassador to be the first point of contact for aliens wishing to communicate with Earth. Mazlan Othman, a Malaysian astrophysicist and currently head of the UN’s Office for Outer Space Affairs (UNOOSA) is expected to be named to the position.
“Othman is absolutely the nearest thing we have to a ‘take me to your leader’ person,” said Richard Crowther, in an article in the UK newspaper, the Telegraph.
Crowther is an expert in space law at the UK space agency who leads delegations to the UN. Reportedly, the plan to make UNOOSA the coordinating body for dealing with alien encounters will be debated by UN scientific advisory committees and should eventually reach the body’s general assembly.
The proposal is said to have been prompted by the recent discovery of hundreds extrasolar planets, which makes the discovery of extraterrestrial life more probable than ever.
Ms. Othman said in a recent talk to fellow scientists, “The continued search for extraterrestrial communication, by several entities, sustains the hope that someday human kind will received signals from extraterrestrials. When we do, we should have in place a coordinated response that takes into account all the sensitivities related to the subject. The UN is a ready-made mechanism for such coordination.”
But will visiting ET’s be greeted with open arms, or with a conditional sterilization? Under the Outer Space Treaty written in 1967, (which UNOOSA oversees) UN members agreed to protect Earth against contamination by alien species by “sterilizing” them. Reportedly, Othman supports a more tolerant approach.
But physicist Stephen Hawking has warned that aliens should be treated with caution.
“I imagine they might exist in massive ships,” he said, “having used up all the resources from their home planet. The outcome for us would be much as when Christopher Columbus first landed in America, which didn’t turn out very well for the Native Americans.” Alien abduction would be the least of our worries.
In the meantime, US citizens wishing to be ‘ambassadors’ for space exploration should consider joining JPL’s Solar System Ambassador program. This is a great program (which I am honored to participate in) to spread the word about the wonders of excitement of space exploration and science. Find out more at the SSA website, and if interested, the program is now taking applications for new ambassadors. Hurry, as applications are being taken until September 30, 2010.
A Minotaur IV rocket launched the Space-Based Space Surveillance satellite. Image: U.S. Air Force/Senior Airman Andrew Lee
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The U.S. Air Force successfully launched the Space Based Space Surveillance spacecraft, a first-of-its-kind satellite that can detect and track orbiting space objects from space. The new satellite was blasted into orbit by a Minotaur IV rocket at 9:41 p.m. PDT, September 25th, from Vandenberg Air Force Base in California.
“SBSS will greatly enhance our existing space situational awareness capability, a capability vital to protecting our space-based assets,” said Colonel Richard Boltz from Vandenberg.
SBSS spacecraft. Image courtesy of Boeing.
There are about 500,000 known pieces of space junk – such as spent rocket boosters, failed satellites, and pieces of satellites – in Earth orbit. Of those, about 21,000 objects are larger than 10.1 cm (4 inches) in diameter. These are being tracked by the Department of Defense, as part of the Space Surveillance Network.
“This satellite is going to revolutionize the way we track objects in space by not being constrained by weather, the atmosphere or the time of day,” said Col. J.R. Jordan, vice-commander of the Space Superiority Systems Wing at the U.S. Air Force Space and Missile Systems Center, in a prelaunch briefing. “This capability will be essential to our space situational awareness architecture for the near future and beyond.”
The satellite will be fully operational and handed over to the Air Force Space Command in about 210 days. The SBSS will be able to detect, identify and tracking man-made space objects from deep space to low-earth orbit. The SBSS space vehicle uses a two-axis gimbal in order to observe in all directions. The spacecraft’s on-board mission data processor performs image processing to extract moving targets and reference star pixels to reduce the downlink data size.
This was the third launch in eight days from Vandenberg.
Artist's impression of The Milky Way Galaxy. Based on current estimates and exoplanet data, it is believed that there could be tens of billions of habitable planets out there. Credit: NASA
If you are not an astronomy enthusiast you not have thought much about what galaxy do we live in. So depending on that the answer may surprise you. If you know anything about galaxies you know that they are groupings of stars that number in the hundreds of billions. The most famous is the Milky Way. It is from this galaxy that we even have the term. The simple point is that the Earth is part of the Milky Way even though if we see it in the sky it looks like we are observing it from the outside. Why is that? To understand you need to know exactly where we live in neighborhood of the Milky Way Galaxy.
As we are part of the solar system Earth pretty much follows the path of the sun as it goes through its own orbit around the galaxy. The Milky Way is a spiral galaxy type so it has arms sort of like an octopus. The Sun is located near the outward tip of the Sagittarius arm of the Milky Way. This makes Earth about 28,000 light years from the galactic core of our home galaxy.
The Solar System also has a galactic year that it follows. It takes around 200 million to 250 million years for the solar system to orbit the Sun. Another indicator of our position is where the galactic equator. While our star system is considered to be on the outskirts of the Milky Way this is only an estimate. It is believed that the Milky Way is larger than first estimated. There is also suspicion that our galaxy is in the process of absorbing other smaller galaxies. However, there is not enough empirical evidence available to support the claim.
So what would be so important about knowing what part of the galaxy we live in? One reason is space exploration. Some time in the future mankind may find a way to achieve faster than light space travel. This can provide a new set of challenges for engineers and astronomers to tackle. For example how would an astronaut keep from getting lost in space? Detailed mapping and computer programming in the future could help galactic wayfarers know where they are going and more importantly how to get home.
The other reason is that it never hurts to know our place in the scheme of things. Just thinking of the challenge of finding earth if we were so far way helps us to understand how truly vast the universe is.
The University of Chicago's Sunyaev-Zeldovich Array - searching for the point in time when dark energy became an important force in the evolution of the universe. Credit: Erik Leitch, University of Chicago.
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A recent cosmological model seeks to get around the sticky issue of dark energy by jury-rigging the Einstein field equation so that the universe naturally expands in an accelerated fashion. In doing so, the model also eliminates the sticky issue of singularities – although this includes eliminating the singularity from which the Big Bang originated. Instead the model proposes that we just live in an eternal universe that kind of oscillates geometrically.
As other commentators have noted, this model hence fails to account for the cosmic microwave background. But hey, apart from that, the model is presented in a very readable paper that tells a good story. I am taking the writer’s word for it that the math works – and even then, as the good Professor Einstein allegedly stated: As far as the laws of mathematics refer to reality, they are not certain, and as far as they are certain, they do not refer to reality.
Like a number of alternate cosmological models, this one also requires the speed of light in a vacuum to vary over the evolution of the universe. It is argued that time is a product of universe expansion – and hence time and distance are mutually derivable – the conversion factor between the two being c – the speed of light. So, an accelerating expansion of the universe is just the result of a change in c – such that a unit of time converts to an increasing greater distance in space.
Yes, but…
The speed of light in a vacuum is the closest thing there is to an absolute in general relativity – and is really just a way of saying that electromagnetic and gravitational forces act instantaneously – at least from the frame of reference of a photon (and perhaps a graviton, if such a hypothetical particle exists).
It’s only from subluminal (non-photon) frames of reference that it becomes possible to sit back and observe, indeed even time with a stopwatch, the passage of a photon from point A to point B. Such subluminal frames of reference have only become possible as a consequence of the expansion of the universe, which has left in its wake an intriguingly strange space-time continuum in which we live out our fleetingly brief existences.
As far as a photon is concerned the passage from point A to point B is instantaneous – and it always has been. It was instantaneous around 13.7 billion years ago when the entire universe was much smaller than a breadbox – and it still is now.
But once you decide that the speed of light is variable, this whole schema unravels. Without an absolute and intrinsic speed for relatively instantaneous information transfer, the actions of fundamental forces must be intimately linked to the particular point of evolution that the universe happens to be at.
For this to work, information about the evolutionary status of the universe must be constantly relayed to all the constituents of the universe – or otherwise those constituents must have their own internal clock that refers to some absolute cosmic time – or those constituents must be influenced by a change in state of an all-pervading luminiferous ether.
In a nutshell, once you start giving up the fundamental constants of general relativity – you really have to give it all up.
The basic Einstein field equation. The left hand side of the equation describes space-time geometry (of the observable universe, for example) and the right hand side describes the associated mass-energy responsible for that curvature. If you want to add lambda (which these days we call dark energy) - you add it to the left hand side components.
The cosmological constant, lambda – which these days we call dark energy – was always Einstein’s fudge factor. He introduced it into his nicely balanced field equation to allow the modeling of a static universe – and when it became apparent the universe wasn’t static, he realized it had been a blunder. So, if you don’t like dark energy and you can do the math, this might be a better place to start.
The white dwarf in the AE Aquarii system is the first star of its type known to give off pulsar-like pulsations that are powered by its rotation and particle acceleration.
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Some satellites get all the glory. While Hubble, Chandra, and Spitzer frequently make headlines with their stunning images, many other space based observatories silently toil away. One of them, known as the Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics (PAMELA) has been in orbit since 2006, but rarely receives media attention although a stunning discovery has led to the publication of over 300 papers within a single year. A new paper in that onslaught has proposed an interesting new object: pulsars powered by white dwarfs.
PAMELA isn’t a satellite in its own right. It piggybacks on another satellite. Its mission is to observe high energy cosmic rays. Cosmic rays are particles, whether they be protons, electrons, nuclei of entire atoms, or other pieces, that are accelerated to high velocities, often from exotic sources and cosmological distances.
Among the types of particles PAMELA detects is the elusive positron. This anti-particle of the electron is quite rare due to the scarcity of anti-matter in general in our universe. However, much to the surprise of astronomers, in the range of 10 – 100 GeV, PAMELA has reported an abundance of positrons. In even higher ranges (100 GeV – 1 TeV) astronomers have found that there is a rise in both electrons and positrons. The conclusion from this is that something is able to actually create these particles in these energy ranges.
A flurry of papers went to publication to explain this unexpected finding. Explanations ranged from showers of particles created by even higher energy cosmic rays striking the interstellar medium, to the decay of dark matter, to neutron stars, pulsars, supernovae, and gamma ray bursts. Indeed, many events that produce high energies are sufficient to spontaneously produce matter from energy through the process of pair production. However, the range of these ejected particles would be limited. Effects, such as synchrotron and inverse Compton emission would drain their energy over large distances and as such, by the time they reached PAMELA’s detectors would be too low energy to account for the excesses in the observed energy ranges. From this, astronomers are presuming the culprits are in the local universe.
Joining the long list of candidates, a new paper has proposed a mundane object could be responsible for the high energy necessary to create these energetic particles, albeit with an unusual twist. Neutron stars, one of the potential objects formed in a supernova, are known to release large amounts of energies when spinning quickly while creating a strong magnetic field in the form of pulsars, but the authors propose that white dwarfs, the products of the slow death from stars not massive enough to result in a supernova, may be able to do the same thing. The difficulty in creating such a white dwarf pulsar is that, since white dwarfs don’t collapse to such a small size, they don’t “spin up” as much as they conserve angular momentum and shouldn’t have the sufficient angular velocity necessary.
The authors, led by Kazumi Kashiyama at Kyoto University propose that a white dwarf may reach the necessary rotational speed if they undergo a merger or accrete a sufficient amount of mass. This idea is not unheard of since white dwarf mergers and accretion are already implicated in Type Ia Supernovae. The combination of this with the expectation that around 10% of white dwarfs are expected to have magnetic fields of 106 Gauss, the steps necessary to produce a pulsar from a white dwarf seem to be in place. They note that since white dwarfs tend to have weaker magnetic fields, they shed their angular momentum more slowly and would last longer. Although this duration is still far longer than humans can possibly watch, this may indicate that many of the pulsars observed in our own galaxy are white dwarfs.
Next, the authors hope to conclusively identify such a star. The creation of each of these types of pulsars may provide a clue: Since neutron stars form from supernovae, they are surrounded by a shell of gas that contains a shock front from the supernova itself, which is more dense than the interstellar medium in general. As particles pass through this shock front, some of them would be lost. The same would not be said for white dwarfs which formed from a more gentle release and aren’t impeded by the relatively high density area. This shift in energy distributions may be one distinguishing characteristic.
Some stars have even been tentatively proposed as candidates for white dwarf pulsars. AE Aquarii was seen to give off some pulsar-like signals. EUVE J0317-855 is another white dwarf that appears to meet the qualifications, although no signals have been detected from this star. This new class of stars would be able to explain the excess signal in the higher energy range detected by PAMELA and will likely be the target of further observational searches in the future.
Saturn's moons Dione and Rhea appear conjoined in this optical illusion-like image taken by the Cassini spacecraft. Credit: NASA/JPL/Space Science Institute
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This latest image from the Cassini spacecraft will make you do a double-take! It is an optical illusion, but the two moons appear like conjoined, identical twins! The two moons are fairly close in size, but Dione, the smaller of the two at the top in the image, is actually closer to the spacecraft, making the two look almost identical. And because of the similar albedo, or reflectivity, of the two moons and because of the location of a particularly large crater near the south polar region of Dione, the moon appears blended seamlessly with Rhea. Double your pleasure!
Dione is 1123 kilometers (698 miles) across and Rhea is 1528 kilometers (949 miles) across.
The image was taken in visible light with the Cassini spacecraft narrow-angle camera on July 27, 2010.
Cassini crossed the radio aurora of Saturn on 17 October 2008, at a distance of 4 Saturn's radii above the atmosphere. These radio emissions, generated by fast electrons, are strongly beamed. They were characterised by simultaneous observations of three different experiments. Credit: NASA/JPL/University of Iowa/CNES/Observatoire de Paris
Saturn’s mysterious aurora has fascinated astronomers and space enthusiasts since it was first observed back in 1979. Now, the Cassini spacecraft has made the first observations from within the giant radio aurora of Saturn. The spacecraft flew through an active auroral region in 2008, and scientists say there are both similarities and contrasts between the radio auroral emissions generated at Saturn and those at Earth. Additionally, Cassini’s visual and infrared mapping spectrometer instrument (VIMS) took data to create a new movie (above) showing Saturn’s shimmering aurora over a two-day period. All this new data are helping scientists understand what drives some of the solar system’s most impressive light shows.
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“So far, this is a unique event,” said Dr. Laurent Lamy at the European Planetary Science Congress in Rome this week. “Whereas the source region of Earth’s radio aurora has been studied by many missions, this is our first opportunity to observe the equivalent region at Saturn from the inside. From this single encounter, we have been able to build up a detailed snapshot of auroral activity using three of Cassini’s instruments. This gives us a fascinating insight into the processes that are generating Saturn’s radio aurora.”
See an animation created from the radio instrument on Cassini at this link. On the left hand side are the radio sources as seen from Cassini. The right hand side shows the projection of the radio sources down onto the southern pole of the planet. Credit: NASA/JPL/University of Iowa/CNES/Observatoire de Paris
Separately, Tom Stallard, lead scientist on a joint VIMS and Cassini magnetometer collaboration, presented the VIMS movie at the conference.
In the movie, the aurora phenomenon clearly varies significantly over the course of a Saturnian day, which lasts around 10 hours 47 minutes. On the noon and midnight sides (left and right sides of the images, respectively), the aurora can be seen to brighten significantly for periods of several hours, suggesting the brightening is connected with the angle of the sun. Other features can be seen to rotate with the planet, reappearing at the same time and the same place on the second day, suggesting that these are directly controlled by the orientation of Saturn’s magnetic field.
Image of Saturn’s aurora seen at ultraviolet wavelengths. The spiral shape seen here is similar to the distorted radio aurora visualised by the team and also indicates enhanced auroral activity. Credit: ESA/NASA/Hubble
“Saturn’s auroras are very complex and we are only just beginning to understand all the factors involved,” Stallard said. “This study will provide a broader view of the wide variety of different auroral features that can be seen, and will allow us to better understand what controls these changes in appearance.”
Auroras on Saturn occur in a process similar to Earth’s northern and southern lights. Particles from the solar wind are channeled by Saturn’s magnetic field toward the planet’s poles, where they interact with electrically charged gas (plasma) in the upper atmosphere and emit light. At Saturn, however, auroral features can also be caused by electromagnetic waves generated when the planet’s moons move through the plasma that fills Saturn’s magnetosphere.
This false-color composite image shows Saturn’s rings and southern hemisphere. The composite image was made from 65 individual observations by Cassini’s visual and infrared mapping spectrometer in the near-infrared portion of the light spectrum on Nov. 1, 2008. Credit: NASA/JPL/University of Arizona
