What’s the News: An international team of researchers, led by the National Center for Atmospheric Research, has learned that large magnetic waves are partly to blame for the Sun’s immensely hot corona. The study, published in the journal Nature, also suggests that the waves could be the driving force behind the solar wind.
The twin satellites have taken their positions, and now we get to see something we’ve never seen before: the whole sun, all at once.
The pair of observers that make up NASA’s Solar Terrestrial Relations Observatory (STEREO) have been traveling since 2006 to reach opposite sides of our star, and they just beamed back the first 360-degree solar images.
The satellites are in the same orbital path as Earth, more or less, and have just taken up their final positions — one is where we’ll be in three months, and the other where we were three months ago. (The first has NASA’s least imaginative name to date: STEREO A, for “ahead.” The second is called STEREO B, for…you can probably guess.) [TIME]
Seeing the far side of the sun isn’t just a scientific curiosity. It could also helps researchers figure out the sun’s violent outbursts, like the coronal mass ejections that could endanger astronauts and foul up satellites if one headed for Earth.
Into the great unknown, into the wild blue yonder, past the second star on the right and straight on till morning: That’s where NASA’s Voyager 1 is heading. The remarkable spacecraft was launched 33 years ago, and it’s now reaching the edge of our solar system. Within a few years, NASA says, it will enter interstellar space.
Phil Plait reports on how researchers realized they’d reached a milestone in Voyager 1′s journey:
Over all those years, there has been one constant in the Voyager flight: the solar wind blowing past it. This stream of subatomic particles leaves the Sun at hundreds of kilometers per second, much faster than Voyager. But now, after 33 years, that has changed: at 17 billion kilometers (10.6 billion miles) from the Sun, the spacecraft has reached the point where the solar wind has slowed to a stop. Literally, the wind is no longer at Voyager’s back.
Read the rest of his post at Bad Astronomy.
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The edge of the solar system is not some static line on a map. The boundary between the heliosphere in which we live and the vastness of interstellar space beyond is in flux, stretching and shifting more rapidly than astronomers ever knew, according to David McComas.
McComas and colleagues work with NASA’s Interstellar Boundary Explorer (IBEX), a satellite orbiting the Earth with its eye turned to the edge of the heliosphere—the bubble inflated by the solar wind that encapsulates the solar system and protects us from many of the high-energy cosmic rays zinging across interstellar space. This week in the Journal of Geophysical Research, the team published the results of IBEX’s second map of the region, and found that its makeup has changed markedly over the span of just six months. Says McComas:
“If we’ve learned anything from IBEX so far, it is that the models that we’re using for interaction of the solar wind with the galaxy were just dead wrong.” [National Geographic]
Chalk up one more mind-blowingly beautiful Saturn image to the Cassini spacecraft. The fruitful mission beamed home this stunner as part of a video of the auroras on the sixth planet.
Auroras on Saturn form like those on Earth, when charged particles in the solar wind stream down the planet’s magnetic field towards its poles, where they excite gas in the upper atmosphere to glow. Some auroras on the ringed planet are also triggered when some of its moons, which are electrically conducting, move through the charged gas surrounding Saturn. [New Scientist]
At long last, here comes the sun (mission).
Never mind NASA’s numerous observatories; never mind the unmanned Pioneer 10 and Voyager probes careening toward the far reaches of the solar system—no craft has ever gone to the center of the solar system, the sun. This decade that will change. NASA is in the process of selecting the instruments for its Solar Probe Plus, a mission to launch by 2018 that will get closer to then sun than ever before, and hopefully find some answers to the open questions that remain about our life-giving star.
“The experiments selected for Solar Probe Plus are specifically designed to solve two key questions of solar physics: why is the Sun’s outer atmosphere so much hotter than the Sun’s visible surface, and what propels the solar wind that affects Earth and our Solar System,” said Dick Fisher, director of Nasa’s Heliophysics Division in Washington DC. [BBC News]
The probe isn’t quite setting the controls for the heart of the sun, Pink Floyd-style, but it will draw dangerously close.
Venus, meet Japan. Today the Japan Aerospace Exploration Agency (JAXA) launched a rocket carrying several different missions bound for our boiling-hot sister planet. Here’s what they want to learn.
Atmospheric Tag Team
Akatsuki, the Venus climate probe, will arrive at the second planet from the sun in December. There it will team up with the European Space Agency’s Venus Express probe, using five cameras to peer down into the turbulent atmosphere and study Venus‘ maniacal meteorology.
One of the main goals is to understand the “super-rotation” of the Venus atmosphere, where violent winds drive storms and clouds at speeds of more than 220 mph (360 kilometers per hour), 60 times faster than the planet itself rotates [MSNBC].
The Venus Express’ own findings since it reached the planet in 2006 have bolstered the idea that Venus was once alive with plate tectonics, oceans, and continents—that is, it was once much more Earth-like than its current, sweaty incarnation. In fact, Venus may still be active.
Volcanoes?
It’s alive! It’s alive! (Maybe.)
On May 18, the Japan Aerospace Exploration Agency (JAXA) says, it will launch into space a “solar yacht” called Ikaros—the Interplanetary Kite-craft Accelerated by Radiation of the Sun (named, of course, in honor of Icarus in Greek mythology). JAXA plans to control the path of Ikaros by changing the angle at which sunlight particles bounce off the silver-coloured sail [AFP].
Actually, the solar sail is a dual-purpose system, taking advantage of both the pressure and the energy of sunlight. The sail, which is less than the thickness of a human hair and 66 feet in diagonal distance, will catch the actual force of sunlight for propulsion as a sailboat’s sail catches the wind. But the solar sail is also covered in thin-film solar cells to generate electricity. And if you can make electricity, you can use it to ionize gas and emit it at high pressure, which is the propulsion systems most satellites use.
Potential velocity using a solar sailor has been theorized to be extremely high. “Eventually you’ll have these missions lasting many years, reaching speeds approaching 100,000 mph, getting out of the solar system in five years instead of 25 years,” said Louis D. Frieman, the Executive Director of the Planetary Society [Clean Technica]. The society has toyed around with its own solar sail.
For now, though, JAXA has a six-month test mission planned for Ikaros. If it works, they want to send a solar sail-powered mission to Jupiter and then the Trojan asteroids. That voyage would employ both the force of the sun and ion propulsion, and the Japanese are brimming with confidence: “Unlike the mythical Icarus, this Ikaros will not crash,” Yuichi Tsuda, an assistant professor at JAXA, said today [BusinessWeek].
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DISCOVER: Japan Stakes Its Claim in Space
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DISCOVER: Japan Sets Sail in Space
Image: JAXA
While astronomers continue to learn about peculiar phenomena in distant galaxies, our own sun’s behavior still presents a mystery. So NASA’s next mission, the Solar Dynamics Observatory, will watch every move the sun makes in the hope of fully figuring out its cycles of sunspots, solar flares, and other activity.
Set to launch next week aboard an Atlas V rocket, the SDO will snap 60 high-resolution images of the sun every minute. Using three specific science instruments, SDO will measure how much extreme ultraviolet light the Sun emits, map plasma flows in the Sun, map the surface of its magnetic field, and image the solar atmosphere [Astronomy]. Scientists hope this huge catalog of images, taken at a resolution far better than that of HDTV and measuring about 1.5 terabytes of data per day, will help them connect the flares and spots on the solar surface to what’s happening down below, inside the star.
After three-plus decades of exploring the gas giants, passing the orbit of Pluto, and reaching points beyond, Voyager 2 has found something interesting near the edge of the solar system: surprisingly magnetic fluff. Researchers document their findings in this week’s Nature.
Of course, this fluff isn’t made from the dust bunnies you find under your bed, the ‘Local Fluff’ (a nickname for the Local Interstellar Cloud) is a vast, wispy cloud of hot hydrogen and helium stretching 30 light-years across [Discovery News]. Astronomers already knew this fluff was out there near the boundary area between our solar system and interstellar space. What surprised them is that the fluff is much more magnetized than they’d expected.
It was a fitting tribute to Carl Sagan’s imagination, optimism, and starry-eyed wonder. On Monday, which would have been Sagan’s 75th birthday, the Planetary Society announced that it is pushing ahead with a plan for experimental spacecraft that will ride on sunbeams, powered by solar sails. The first small craft will be sent into orbit in 2010, if all goes well, and will be followed by two others, which may venture farther. Sagan was a founder of the Planetary Society and a big booster of solar sail plans.
Solar sail technology, which has not yet been tested in space, relies on the tiny impacts created by the light particles streaming from the sun as they hit a reflective surface. The force on a solar sail is gentle, if not feeble, but unlike a rocket, which fires for a few minutes at most, it is constant. Over days and years a big enough sail, say a mile on a side, could reach speeds of hundreds of thousands of miles an hour, fast enough to traverse the solar system in 5 years. Riding the beam from a powerful laser, a sail could even make the journey to another star system in 100 years, that is to say, a human lifespan [The New York Times].
The spacecraft that is scheduled for orbit in 2010, the LightSail-1, has been made possible by an anonymous donation to the Planetary Society. The recent donation reinvigorates the Society’s solar sail hopes, which were dashed in 2005 when the Russian Volna rocket carrying its first solar sail prototype, Cosmos 1, failed to reach orbit…. In addition to the Cosmos 1 disappointment, NASA’s NanoSail-D attempt was lost in the third failed flight of SpaceX’s Falcon 1 rocket in 2008 [SPACE.com].
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Image: The Planetary Society
Today in the innermost region of our solar system, NASA’s Messenger space probe will swoop past Mercury for the third and final time. The maneuver will give scientists a close look at the dense, iron-rich, oddball planet, and will also alter the probe’s trajectory and prepare it to begin orbiting Mercury in March 2011.
As Messenger travels within 142 miles of Mercury at 12,000 miles per hour, the spacecraft’s camera will swivel to stare at a succession of craters and other geological features…. One target will be an old 90-mile-wide crater. Another will be young 13-mile crater and a splash of light-colored soil surrounding it. A third crater of interest has materials of unusual color perhaps produced by violent volcanic eruptions [The New York Times]. When this third flyby is complete, 95 percent of the planet will have been mapped in high resolution.
The solar probe Ulysses has circled the sun for more than 18 years–almost as long as the Greek hero Odysseus, also called Ulysses, was absent from home due to the Trojan War and his prolonged journey home–but the space probe doesn’t have a homecoming in its future. Ulysses will receive its final transmission tomorrow, as researchers say the scientific findings sent home by the failing spacecraft no longer justify the mission’s costs. After shut-off, Ulysses will continue to orbit the Sun, becoming in effect a man-made ‘comet’. “Whenever any of us look up in the years to come, Ulysses will be there, silently orbiting our star, which it studied so successfully during its long and active life” [SPACE.com], says mission manager Richard Marsden.
The craft has already exceeded expectations. In February 2008, mission engineers announced with great solemnity and with heaps of praise for the orbiter that the craft would fall silent within a few months. Its power supply had grown too weak to keep the craft’s fuel lines from freezing. Not so fast: Engineers figured out that they could keep the lines warm by firing the craft’s thrusters in short bursts every couple of hours [The Christian Science Monitor]. Using that clever fix, Ulysses soldiered on for another year.
When the Messenger spacecraft swooped low past the planet Mercury on October 6 2008, it gathered up a wealth of data that will have planetary scientists puzzling for years. As researchers sort through findings regarding Mercury’s volcanic past, meteor impacts, and the effect of the solar wind on the innermost planet’s magnetosphere, one broad conclusion stands out: Mercury isn’t just a boring chunk of rock. Marilyn Lindstrom, a NASA program scientist, said the Messenger findings show that Mercury is “just an amazingly dynamic planet, both in the past and in the present” [Baltimore Sun].
Superficially, Mercury looks a lot like the moon: small, grayish-brown and pockmarked with craters. Some scientists assumed that Mercury’s surface formed the same way the moon’s did, with lighter rocks rising to the surface of a magma ocean and congealing into a brittle crust early on. But the new observations reveal that 40 percent of the surface was formed by volcanoes. “Up until before Messenger’s arrival, we weren’t even sure that volcanism existed on Mercury” [Wired], says researcher Brett Denevi. The presence of titanium oxide also suggests that the planet was hot enough in its first 100 million years to be covered in magma oceans.
A pair of solar observers known as the STEREO spacecraft have taken the first 3-D pictures of the sun‘s powerful storms, during which billions of tons of charged particles erupt from the sun’s surface. The two spacecraft have taken up two positions about 100 million miles apart: Not unlike human eyes, the satellites’ two points of view allow for combination images that render scenes in three dimensions [National Geographic News].
Solar storms can have serious repercussions here on Earth. They can disrupt GPS signals and power grids, damage satellites, and bombard astronauts with solar radiation, experts said [National Geographic News]. But with the STEREO system, researchers say they can predict when a fierce storm will hit Earth 24 hours in advance (an improvement over previous 12-hour predictions). Says researcher Chris Davies: “That’s ample time to power down a satellite until the worst of the storm has passed; and if you’re an astronaut on the space station, you would have had plenty of time to get into an area that has much better shielding” [BBC News]. While STEREO is a temporary scientific research mission, researchers say it provides an example of how a “space weather” early-warning system would work.
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