stripes and holes

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.

photo session: cities in flight

skylabsalyut 7

MIR

ISS

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.

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 (+)

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.

all mighty saturn

(+) ciclops

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

sandia's tunguska

The stunning amount of forest devastation at Tunguska a century ago in Siberia may have been caused by an asteroid only a fraction as large as previously published estimates, Sandia National Laboratories supercomputer simulations suggest.

“The asteroid that caused the extensive damage was much smaller than we had thought,” says Sandia principal investigator Mark Boslough of the impact that occurred June 30, 1908. “That such a small object can do this kind of destruction suggests that smaller asteroids are something to consider. Their smaller size indicates such collisions are not as improbable as we had believed.”

Because smaller asteroids approach Earth statistically more frequently than larger ones, he says, “We should be making more efforts at detecting the smaller ones than we have till now.”

The new simulation — which more closely matches the widely known facts of destruction than earlier models — shows that the center of mass of an asteroid exploding above the ground is transported downward at speeds faster than sound. It takes the form of a high-temperature jet of expanding gas called a fireball.

This causes stronger blast waves and thermal radiation pulses at the surface than would be predicted by an explosion limited to the height at which the blast was initiated.

“Our understanding was oversimplified,” says Boslough, “We no longer have to make the same simplifying assumptions, because present-day supercomputers allow us to do things with high resolution in 3-D. Everything gets clearer as you look at things with more refined tools.”

Sandia is a National Nuclear Security Administration laboratory.

The new interpretation also accounts for the fact that winds were amplified above ridgelines where trees tended to be blown down, and that the forest at the time of the explosion, according to foresters, was not healthy. Thus previous scientific estimates had overstated the devastation caused by the asteroid, since topographic and ecologic factors contributing to the result had not been taken into account.

“There’s actually less devastation than previously thought,” says Boslough, “but it was caused by a far smaller asteroid. Unfortunately, it’s not a complete wash in terms of the potential hazard, because there are more smaller asteroids than larger ones.”

Boslough and colleagues achieved fame more than a decade ago by accurately predicting that that the fireball caused by the intersection of the comet Shoemaker-Levy 9 with Jupiter would be observable from Earth.

Simulations show that the material of an incoming asteroid is compressed by the increasing resistance of Earth’s atmosphere. As it penetrates deeper, the more and more resistant atmospheric wall causes it to explode as an airburst that precipitates the downward flow of heated gas.

Because of the additional energy transported toward the surface by the fireball, what scientists had thought to be an explosion between 10 and 20 megatons was more likely only three to five megatons. The physical size of the asteroid, says Boslough, depends upon its speed and whether it is porous or nonporous, icy or waterless, and other material characteristics.

“Any strategy for defense or deflection should take into consideration this revised understanding of the mechanism of explosion,” says Boslough.

One of most prominent papers in estimating frequency of impact was published five years ago in Nature by Sandia researcher Dick Spalding and his colleagues, from satellite data on explosions in atmosphere. “They can count those events and estimate frequencies of arrival through probabilistic arguments,” says Boslough.

The work was presented at the American Geophysical Union meeting in San Francisco on Dec. 11. A paper on the phenomenon, co-authored by Sandia researcher Dave Crawford and entitled “Low–altitude airbursts and the impact threat” has been accepted for publication in the International Journal of Impact Engineering.

The research was paid for by Sandia’s Laboratory-Directed Research and Development office.

(+) Sandia.gov
(+) googlesightseeing.com

eta carinae

Eta Carinae (η Carinae or η Car) is a highly luminous hypergiant double star. Estimates of its mass range from 100–150 times the mass of the Sun, and its luminosity is about four million times that of the Sun.

Very large stars like Eta Carinae use up their fuel very quickly because of their disproportionately high luminosities. Eta Carinae is expected to explode as a supernova or hypernova some time within the next million or so years. As its current age and evolutionary path are uncertain, it could explode within the next several millennia or even in the next few years. LBVs such as Eta Carinae may be a stage in the evolution of the most massive stars; the prevailing theory now holds that they will exhibit extreme mass loss and become Wolf-Rayet Stars before they go supernova, if they are unable to hold their mass to explode as a hypernova.

More recently another possible Eta Carinae analogue was observed; namely SN 2006jc some 77 million light years away in UGC 4904, in the constellation of Lynx. It brightened on 20 October 2004 and was reported by amateur astronomer Koichi Itagaki as supernova. However, it survived and finally exploded two years later as a Mag 13.8 type Ib supernova on 9 October 2006. Its earlier brightening was a supernova impostor event; the initial explosion hurled 0.01 solar masses (~20 Jupiters) of material into space.

Due to the similarity of Eta Carinae and SN 2006jc, Stefan Immler of NASA's Goddard Space Flight Center suggests that Eta Carinae could explode in our lifetime or even in the next few years. However, Stanford Woosley of the University of California in Santa Cruz disagrees with Immler’s suggestion, and he says it is likely that Eta Carinae is at an earlier stage of evolution and that it has several kinds of material left for nuclear fusion.

the young family

The Young Family (2002-3) presents a transgenic creature. The inspiration behind this work is the expectation that we have of growing human organs in other species, especially pigs. Rather than make a didactic image that argues for or against these technologies, I want to address the reality of these possible creatures in a very compassionate way. The question I raise, that I am interested in, relates to the distinction between human and animal characteristics: Not so much her humanity, but the 'animalness' in us. Genetically, we share traits with her, but also we share the fundamental trait of looking after offspring. I am interested in the kinds of ways that we look at the many ethical issues that surround medical technologies.
There are two kinds of people who are thinking about these issues; those who are objective observers, and those that are actually affected by the issues, such as somebody who has a family member who is affected by a disease. These two viewpoints are often very different. It is impossible to be objective about these issues when you are emotionally involved, but I don't think that is a bad thing. These are not simple issues with easy answers: It is one thing to talk about an idea and another to be confronted by the emotional reality of a creature, and yet another to be in need of what that creature might provide.

Title: The Young Family 2002-3
Author: Patricia Piccinini (+)

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sky raptor

An F-22 Raptor, the world's first stealth air-to-air fighter, demonstrates combat maneuvers while participating in the 2007 Naval Air Station Oceana Air Show. The three-day air show featured demonstrations from the Blue Angels, British Red Devils and Blac