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The inside of a neutron star is superconducting as well as superfluid

The inside of a neutron star is superconducting as well as superfluid | Slash's Science & Technology Scoop | Scoop.it

The Crab Nebula and the pulsar at its center are endlessly fascinating. The pulsar is a neutron star, with the same mass as our Sun but only the size of a city. It rotates 30 times per second, flashing like a lighthouse as it does so. It is very nearly, but not quite, an ideal clock, without any outside influence to disturb it. At Jodrell Bank Observatory, astronomers have been watching the pulsar for over 40 years, timing it without missing a beat while it rotated more than 30 billion times. Putting together the results from our radio observations with data from the opposite end of the electromagnetic spectrum has proved remarkably rewarding.

 

The pulsar has slowed down from 30.2 to 29.7 rotations per second while astronomers have been watching it. This is not unexpected: the energy stored in the rapid rotation powers not only the pulses which we observe but the whole of the Crab Nebula. This little neutron star is acting as a huge electrical generator, spinning at the same speed as a dynamo in a terrestrial power station but with a magnetic field billions of times greater. So far so good, but as is often the case, it is the odd things that seem to be going wrong that we are really interested in.

 

Astronomers also discovered so-called "glitches", sudden changes in the regular sequence of pulses, showing that the rotation has suddenly sped up, then recovered and started on a new regime of slowing down. We have seen this happen a couple of dozen times. The explanation involves some very strange physics inside the star. Although it is so condensed, the whole of the inside is liquid and only a thin crust is solid. Furthermore, the inside is superfluid, which allows it to rotate independently of the crust. Some times, however, it clutches onto the crust and the whole rotation rate suddenly changes; this is what causes the glitch.

 

What researchers have found recently is less obvious, having taken the whole of the 40 years to show up. The radio pulse is actually double, like a lighthouse with two beams. These two beams are nearly, but not quite, in opposite directions; how are they formed? Fortunately the Fermi gamma-ray telescope has helped to understand the strange geometry of the atmosphere outside the star, where the beams are formed. The whole of this atmosphere is rotating with the star itself, swept round by the powerful magnetic field. It is called a magnetosphere, and it is forced to move so fast that it reaches relativistic speeds; the radiation appears to originate at a location so far outside the surface that it is moving with half the velocity of light. Now comes some more new physics.

 

The inside of a neutron star is superconducting as well as superfluid. This means that the strength and shape of the huge dipole magnetic field is fixed, or can change only very slowly. So the pattern of the magnetic field in the magnetosphere, where the radiated beams are formed, is fixed. But the star is less than 1000 years old (it was formed in a supernova explosion in the year 1054), so we have been observing it for an appreciable fraction of its lifetime. And we have indeed found a change in the pattern of the double pulse. The two parts are moving apart, at the rate of 3o in the whole lifetime of the star. What this means is that the dipole is not tidily arranged at a right angle to the rotation, as it would be in a power station dynamo, but it is tilted at around 45o and slowly moving to wards the expected orthogonal arrangement. Now the theorists have to take over and explain how that can happen!


Via Dr. Stefan Gruenwald
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Scientists 3D-print self-assembling 'living tissue' using just water and oil

Scientists 3D-print self-assembling 'living tissue' using just water and oil | Slash's Science & Technology Scoop | Scoop.it

Researchers have created networks of water droplets that mimic some properties of cells in biological tissues. Using a three-dimensional printer, a team at the University of Oxford, UK, assembled tiny water droplets into a jelly-like material that can flex like a muscle and transmit electric signals like chains of neurons. The work is published today in Science.

 

These networks, which can contain up to 35,000 droplets, could one day become a scaffold for making synthetic tissues or provide a model for organ functions, says co-author Gabriel Villar of Cambridge Consultants, a technology-transfer company in Cambridge, UK. “We want to see just how far we can push the mimicry of living tissue,” he says.

 

The network relies on each water droplet having a lipid coating, which forms when the droplets are in a finely-tuned mix of oil and a pure lipid.

The lipid molecules have a water-loving head, which sticks to the droplet's surface, and a water-fearing tail, which pokes out into the oily solution. When two lipid-coated droplets come together, each with its carpet of water-fearing tails, they stick to each other like Velcro, forming a lipid bilayer, similar to those in cell membranes. The bilayer creates a structural and functional connection between droplets.

 

Although previous studies have shown that lipid-coated droplets can form such connections, their watery composition and spherical shape made them tricky to assemble. “I already made a raft of droplets that stuck together,” says biomedical engineer David Needham of the University of Southern Denmark in Odense, who was not involved in the study. “But to print them is really an achievement.”

 


Via Dr. Stefan Gruenwald
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One small click for a man: NASA releases more than 17,000 photos from the Apollo program

One small click for a man: NASA releases more than 17,000 photos from the Apollo program | Slash's Science & Technology Scoop | Scoop.it
The archive, released through the Nasa-funded Lunar And Planetary Institute, shows both famous photos of Apollo 11 and everyday work for the astronauts in other missions.

 

This time 45 years ago, three Americans were orbiting the moon in the Apollo 8 space craft - the furthest from the Earth that any man had ever gone - and were paving the way for humanity's first successful mission to another celestial body. Astronauts Frank Borman, James Lovell and William Anders even read sections of the Book of Genesis as part of a Christmas Eve television broadcast. They were the first to photograph the Earth from far away and the moon up close - also capturing the now-famous 'Earthrise' photo while in lunar orbit.


Now Nasa has released more than 17,000 photos from the 33 Apollo astronauts who made it into space for the lunar missions, including the 12 men who set foot on the moon's surface.


Via Dr. Stefan Gruenwald
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Sharrock's curator insight, December 25, 2013 6:18 PM

pics for students and teachers to use and explore.