Its doom was sealed six years ago.
In 2004, UC Berkeley researchers say, this comet was tugged by Jupiter’s gravity into a path bound for destruction in the cauldron of the sun. And when its end finally came this March, astronomers captured the comet plunging deep into the sun on video (see below), watching it go farther into the light than any suicide comet seen before.
Seeing comets and other small objects approach the sun is difficult because the objects are overwhelmed by the sun’s brightness. Scientists were able to track this one closer to the sun than ever, before it it burned up in the sun’s lower atmosphere [Wired.com].
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On this Earth Day, NASA’s focused on the sun. It just released the first images from the Solar Dynamics Observatory (SDO), launched in February to study our star in breathtaking detail at a rate of 60 images per minute. The new pictures include the evolution of this loop. Known as a prominence eruption, the loop was born from a relatively cold cloud of plasma, or charged gas, tenuously tethered to the sun’s surface by magnetic forces. Such clouds can erupt dramatically when they break free of the sun’s unstable hold [National Geographic].
Scroll through the gallery for a few more blazing wonders.
Images: NASA
Astronomers keep turning up new exoplanets, and as the count rises, they keep edging closer to finding worlds like our own pale blue dot. Astronomer Jay Farihi thinks Earth-like worlds might be even more common in the universe than previously expected, based on evidence from rocky planets few astronomers are studying: The ones that don’t exist anymore.
Farihi’s research subjects are white dwarfs. In our galaxy, about 90 percent of stars will end their lives in this incredibly dense state once the star sheds its outer material and only the core remains. This is the fate of our sun. White dwarfs usually have atmospheres composed of the light elements helium and hydrogen, as the heavy elements have settled to the core. But about 20 percent of white dwarfs are different, showing heavy elements—what astronomers call “metals”—in their atmospheres. For decades, astronomers attributed this metallic pollution to the interstellar medium, the thin gas that permeates the space between stars. The idea was that white dwarfs were old stars that had been on several orbits around the Milky Way and had picked up bits of the interstellar medium as they went around [Space.com]. But Farihi thinks those elements are evidence of something else.
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The “young sun paradox” just won’t go away. For decades, scientists like Carl Sagan have tried to resolve this mystery of the early solar system—how the newborn Earth stayed warm enough to keep liquid water—but it continues to bob and weave around an answer. In the journal Nature, a team led by Minik Rosing proposes an alternate solution to the leading theory, which relies on the greenhouse effect hypothesis. But don’t expect the debate to end here.
The problem is this: The young Earth received much less heat from the sun. Four billion years ago, a lower solar luminosity should have left Earth’s oceans frozen over, but there is ample evidence in the Earth’s geological record that there was liquid water — and life — on the planet at the time [Space.com]. So what gives? The traditional explanation going back to the 1970s has been that a powerful greenhouse effect, far stronger than the one we experience today, kept the Earth basked in enough warmth to keep water sloshing around the planet’s surface as a liquid and not packed in solid ice. In 1972, Sagan and colleague George Mullen wrote that such an effect would have required intense carbon dioxide concentrations in the atmosphere during that period, the Archaen.
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Here we are drinking coffee and tweeting and otherwise going about our lives, generally not giving much thought to the protection that the Earth’s magnetic field affords us from the solar wind. But that magnetic field is crucial for our existence. Now, new findings in Science say that this protective shield originated even 200 million years earlier than scientists had previously thought, perhaps protecting the planet’s water from evaporating away and aiding the rise of life on the early Earth.
To know about the planet’s magnetic field three and a half billion years ago, you need iron, which records not only the direction but also the strength of the magnetic field when it forms. In South Africa, study leader John Tarduno and his team found quartz with iron tucked inside that had remained unchanged in all those years. Using a specially designed magnetometer and improved lab techniques, the team detected a magnetic signal in 3.45-billion-year-old rocks that was between 50 and 70 percent the strength of the present-day field, Tarduno says [Science News]. Three years ago he made a similar find in rocks 3.2 billion years old; thus, this find pushes back the Earth’s magnetic field at least another 200 million years.
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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.
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The genomes of lung and skin cancer have been decoded by scientists at the UK-based Wellcome Trust Sanger Institute near Cambridge, which is the first time an entire cancer gene map has been created.
The scientists say they have pinpointed specific DNA errors that may cause tumors in these two cancers, both of which have direct known causes—smoking for lung cancer and sun exposure for skin cancer. Researchers predict these maps will offer patients a personalized treatment option that ranges from earlier detection to the types of medication used to treat cancer. The genetic maps will also allow cancer researchers to study cells with defective DNA and produce more powerful drugs to fight the errors, according to the the study’s scientists [CNN]. News reports are heralding the new research as revolutionary, however it will be years, perhaps decades, before the full implications of the work are understood.
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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.
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The sun has been surprisingly quiet lately, and until now astronomers couldn’t figure out why. An 11-year cycle governs solar flares and sunspots, and researchers knew that we were at the end of a cycle in a “solar minimum” or quiet period–but that somnolence has continued for an extra year beyond the point at which researchers expected sunspot activity to resume. Comments Australian astronomer Phil Wilkinson: “We have had a drought of sunspots…. This is the longest period the sun has been quiet since the start of the Space Age. Seeing the sun doing nothing is really exciting,” he said, adding it made physicists wonder how little they really understood [Sydney Morning Herald].
Now, new observations announced at a meeting of the American Astronomical Society reveal a possible explanation: “sluggish” solar jet streams 4,350 miles below the surface of the sun. Every 11 years, the sun simultaneously generates twin streams of plasma at each of its poles. Unlike the jet streams on Earth, the solar versions are magnetized and travel only toward the equator. This migration takes place very slowly–at about 10 kilometers per hour. For reasons still not understood, when the streams reach 22 degrees of latitude, north and south, they touch off a new solar cycle, and the sunspots reappear [ScienceNOW Daily News].
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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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As the year 2008 draws to a close, the world’s timekeepers are giving us a little extra time to wrap up loose ends: They’re giving us one extra second, to be precise. The “leap second” must be added to keep atomic clocks ticking along in time to the planet’s rotation. So at precisely 23:59:60 at Greenwich, England, on New Year’s Eve, there will be a one-second void before the onset of midnight and the start of the New Year…. By the time the transition from 2008 to 2009 arrives in North America the Leap Second will have already been inserted into the world’s timescale [SPACE.com].
The adjustment is necessary because we have two different ways of measuring time. Traditionally, humankind has reckoned time by the spin of the Earth and its orbit around the sun. Under this astronomical arrangement, a second is one-86,400th of our planet’s daily rotation. But because of tidal friction and other natural phenomena, that rotation is slowing down by about two-thousandths of a second a day. Since the 1950s, however, atomic clocks — which are based on the unwavering motions of cesium atoms — have made it possible to measure time far more accurately, to within a billionth of a second a day [The New York Times]. To keep the two measurement systems in alignment, the atomic clocks have to add an extra second about every 500 days.
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Researchers have discovered the our planet’s atmosphere regularly expands and contracts in a short cycle of about nine days, and say that this “breathing” is caused by powerful gusts of solar wind. While researchers already knew that ultraviolet light from the sun can heat and swell the atmosphere, the discovery of short, cyclical fluctuations “was a surprising finding” that wasn’t correlated with any variation in solar UV flux [Science News], says atmospheric scientist Jeffrey Thayer.
The breathing cycle seems to reach its peak when solar features called coronal holes are facing Earth. These dark spots in the sun’s corona—a sort of solar atmosphere—are areas where the sun’s magnetic field has been blown open by pressurized solar wind, sending the “winds” toward Earth at high speed. As the fast winds streaming from coronal holes approach Earth, they cause gases in our upper atmosphere to heat up and expand, then cool down and contract, changing the upper atmosphere’s density [National Geographic News].
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A starlit sky may look serene, but those stars are actually quivering and quaking; now, researchers have recorded the stellar vibrations of distant stars for the first time. The pulsations reflect changes in temperature caused when roiling heat makes the outer surface of the star vibrate. Portions of the surface expand and cool, while others contract and get warmer [New Scientist].
The initial discovery of oscillations in our Sun in the late 1970′s led to the creation of “solar seismology,” which has since been used to measure the movement and transport of heat around the Sun. Solar seismology led to rapid progress in understanding the Sun’s internal structure, but eventually researchers hit a wall [COSMOS]. For accurate measurements, researchers need a long stretch of uninterrupted observations, which is impossible from ground-based telescopes.
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The solar wind, a steady stream of charged subatomic particles that stream out from the sun at a speed of one million miles per hour, has dwindled to its weakest state since recording began, researchers say. While researchers already knew that solar winds fluctuate in 11-year cycles, the current doldrums trump the declines seen over the past 50 years. “We know that the sun has been this cool before, this inactive before,” said [physicist] Nancy Crooker…. “But that was prior to the Space Age, so we didn’t have actual physical measurements until now” [SPACE.com].
The data was collected by the first solar explorer, the Ulysses probe, which was launched in 1990 as a joint venture between NASA and the European Space Agency. The 17-year-old space probe, which circles the sun from a distance of about 337 million miles, has been studying the environment above and below the poles of the sun. It is just months away from shutting down because of freezing fuel [AP].
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