The tiger stripes on Saturn's moon Enceladus might be active. Even today, they may be spewing ice from the moon's icy interior into space, creating a cloud of fine ice particles over the moon's South Pole and creating Saturn's mysterious E-ring. Recent evidence for this has come from the robot Cassini spacecraft now orbiting Saturn. Cassini detected a marked increase in particle collisions during its July flyby only 270 kilometers over a South Polar region of Enceladus. Pictured above, a high resolution image of Enceladus is shown from the close flyby. The unusual surface features dubbed tiger stripes are visible on the left in false-color blue. Why Enceladus is active remains a mystery, as the neighboring moon Mimas, approximately the same size, appears quite dead.
20080330
stripes and holes
20080327
mass ejection
A coronal mass ejection (CME) is an ejection of material from the solar corona, usually observed with a white-light coronagraph.
The ejected material is a plasma consisting primarily of electrons and protons (in addition to small quantities of heavier elements such as helium, oxygen, and iron), plus the entrained coronal magnetic field.
The first detection of a CME was made on December 14, 1971 by R. Tousey (1973) using the 7th Orbiting Solar Observatory (OSO-7).
The largest geomagnetic perturbation, resulting presumably from a "prehistoric" CME, coincided with the first-observed solar flare, in 1859. The flare was observed visually by Richard Christopher Carrington and the geomagnetic storm was observed with the recording magnetograph at Kew Gardens.
When the ejecta reaches the Earth as an ICME (Interplanetary CME), it may disrupt the Earth's magnetosphere, compressing it on the dayside and extending the nightside tail. When the magnetosphere reconnects on the nightside, it creates trillions of watts of powerupper atmosphere. This process can cause particularly strong aurora also known as the Northern Lights, or aurora borealis (in the Northern Hemisphere), and the Southern Lights, or aurora australis (in the Southern Hemisphere). CME events, along with solar flares, can disrupt radio transmissions, cause power outages (blackouts), and cause damage to satellites and electrical transmission lines.
20080324
the missing link
Observations from NASA’s Rossi X-ray Timing Explorer (RXTE) have revealed that the youngest known pulsing neutron star has thrown a temper tantrum. The collapsed star occasionally unleashes powerful bursts of X-rays, which are forcing astronomers to rethink the life cycle of neutron stars. "We are watching one type of neutron star literally change into another right before our very eyes. This is a long-sought missing link between different types of pulsars," says Fotis Gavriil of NASA’s Goddard Space Flight Center in Greenbelt, Md., and the University of Maryland, Baltimore. Gavriil is lead author of a paper in the February 21 issue of Sciencexpress.
A neutron star forms when a massive star explodes as a supernova, leaving behind an ultradense core. Most known neutron stars emit regular pulsations that are powered by rapid spins. Astronomers have found nearly 1,800 of these so-called pulsars in our galaxy. Pulsars have incredibly strong magnetic fields by Earthly standards, but a dozen of them — slow rotators known as magnetars — actually derive their energy from incredibly powerful magnetic fields, the strongest known in the universe. These fields can stress the neutron star’s solid crust past the breaking point, triggering starquakes that snap magnetic-field lines, producing violent and sporadic X-ray bursts. But what is the evolutionary relationship between pulsars and magnetars? Astronomers would like to know if magnetars represent a rare class of pulsars, or if some or all pulsars go through a magnetar phase during their life cycles. Gavriil and his colleagues have found an important clue by examining archival RXTE data of a young neutron star, known as PSR J1846-0258 for its sky coordinates in the constellation Aquila.
Previously, astronomers had classified PSR J1846 as a normal pulsar because of its fast spin (3.1 times per second) and pulsar-like spectrum. But RXTE caught four magnetar-like X-ray bursts on May 31, 2006, and another on July 27, 2006. Although none of these events lasted longer than 0.14 second, they all packed the wallop of at least 75,000 Suns. "Never before has a regular pulsar been observed to produce magnetar bursts," says Gavriil. "Young, fast-spinning pulsars were not thought to have enough magnetic energy to generate such powerful bursts," says coauthor Marjorie Gonzalez, who worked on this paper at McGill University in Montreal, Canada, but who is now based at the University of British Columbia in Vancouver. "Here’s a normal pulsar that’s acting like a magnetar."
Observations from NASA’s Chandra X-ray Observatory also provided key information. Chandra observed the neutron star in October 2000 and again in June 2006, around the time of the bursts. Chandra showed the object had brightened in X-rays, confirming that the bursts were from the pulsar, and that its spectrum had changed to become more magnetar-like. Astronomers know that PSR J1846 is very young for several reasons. First, it resides inside a supernova remnant known as Kes 75, an indicator that it hasn’t had time to wander from its birthplace. Second, based on the rapidity that its spin rate is slowing down, astronomers calculate that it can be no older than 884 years — an infant on the cosmic timescale. Magnetars are thought to be about 10,000 years old, whereas most pulsars are thought to be considerably older.
The fact that PSR J1846’s spin rate is slowing down relatively fast also means that it has a strong magnetic field that is braking the rotation. The implied magnetic field is trillions of times stronger than Earth’s field, but it’s 10 to 100 times weaker than typical magnetar field strengths. Coauthor Victoria Kaspi of McGill University notes, "PSR J1846’s actual magnetic field could be much stronger than the measured amount, suggesting that many young neutron stars classified as pulsars might actually be magnetars in disguise, and that the true strength of their magnetic field only reveals itself over thousands of years as they ramp up in activity."
Robert Naeye
Goddard Space Flight Center (+)
20080319
a great loss
British expatriate science fiction author, futurist, and visionary Arthur C. Clarke died on Wednesday in a hospital in his adopted hometown of Colombo, Sri Lanka. He was 90 years old.
"Sir Arthur passed away a short while ago at the Apollo Hospital. He had been in hospital for the past four days. He had been in and out of the hospital in recent weeks," said Clarke's assistant, Rohan de Silva.
Reports say that after a long 50 year battle with post-polio syndrome, Clarke died at 1:30 a.m. (local time) on Wednesday from breathing complications.
Famous for writing over 100 science fiction and science publications, including 2001: A Space Odyssey, he is also credited as the one who presented the concept of the geostationary communication satellite.
"Sometimes I am asked how I would like to be remembered. I have had a diverse career as a writer, underwater explorer and space promoter. Of all these I would like to be remembered as a writer," said Clarke not long before he died.
bird's don't fly as high
Credit & Copyright: James N. Brown
Endeavour is currently in orbit for the STS-123 mission, and is docked to the International Space Station. Launch from Kennedy Space Center took place on 2008-03-11, at 2:28:14 a.m. EDT (06:28 GMT) On board; seven astronauts, four of them being rookies.
20080313
20080310
all line up
Last week, Mercury, Venus, and the Moon all appeared close together in Earth's sky. This picturesque conjunction was caught on camera behind elements of the Australia Telescope Compact Array (ATCA) near the town of Narrabri in rural New South Wales. The ATCA consists of six radio telescopes in total, each one larger than a house. Together they form one of the highest resolution measurement devices in the world. Impressive planetary conjunctions occur every few years. Involving the brightest objects in the night sky, this alignment was easy to spot just before sunrise. In the picture, taken on the morning of March 6, Mercury is the highest of the three bright celestial beacons.
Credit & Copyright: Graeme L. White & Glen Cozens
