Wednesday 7 June 2017

Scientists discover a 2-D magnet

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For the first time, scientists have discovered magnetism in the 2-D world of monolayers, or materials that are formed by a single atomic layer. The findings demonstrate that magnetic properties can exist even in the 2-D realm -- opening a world of potential applications.
via Science Daily

Celestial Boondocks: Study Supports the Idea We Live in a Void

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A new study not only firms up the idea that we exist in one of the holes of the Swiss cheese structure of the cosmos, but helps ease the apparent disagreement between different measurements of the Hubble Constant, the unit cosmologists use to describe the rate at which the universe is expanding today.
via Science Daily
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Century-old relativity experiment used to measure a white dwarf's mass

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Astronomers have used the sharp vision of NASA’s Hubble Space Telescope to repeat a century-old test of Einstein’s general theory of relativity. The team measured the mass of white dwarf Stein 2051 B, the burned-out remnant of a normal star, by seeing how much it deflects the light from a background star. The gravitational microlensing method data provide a solid estimate of the white dwarf’s mass and yield insights into theories of the structure and composition of the burned-out star.
via Science Daily
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Mini-flares potentially jeopardize habitability of planets circling red dwarf stars

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Solar flares and associated eruptions can trigger auroras on Earth or, more ominously, damage satellites and power grids. Could flares on cool, red dwarf stars cause even more havoc to orbiting planets, even rendering them uninhabitable? To help answer that question, astronomers sought to find out how many flares such stars typically unleash.
via Science Daily
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Hubble Astronomers Develop a New Use for a Century-Old Relativity Experiment to Measure a White Dwarf’s Mass


White dwarf shows how gravity can bend starlight

Albert Einstein reshaped our understanding of the fabric of space. In his general theory of relativity in 1915, he proposed the revolutionary idea that massive objects warp space, due to the effects of gravity. Until that time, Isaac Newton's theory of gravity from two centuries earlier held sway: that space was unchanging. Einstein's theory was experimentally verified four years later when a team led by British astronomer Sir Arthur Eddington measured how much the sun's gravity deflected the image of a background star as its light grazed the sun during a solar eclipse. Astronomers had to wait a century, however, to build telescopes powerful enough to detect this gravitational warping phenomenon caused by a star outside our solar system. The amount of deflection is so small only the sharpness of the Hubble Space Telescope could measure it.

Hubble observed the nearby white dwarf star Stein 2051B as it passed in front of a background star. During the close alignment, the white dwarf's gravity bent the light from the distant star, making it appear offset by about 2 milliarcseconds from its actual position. This deviation is so small that it is equivalent to observing an ant crawl across the surface of a quarter from 1,500 miles away.


via Hubble - News feed
http://hubblesite.org/news_release/news/2017-25

Orbiting Jupiter

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What would it be like to orbit Jupiter? The dramatic featured video depicts just this and was made from images taken by NASA's Juno spacecraft currently orbiting the Jovian giant. Juno recently completed its sixth pass near Jupiter during its looping elliptical six-week orbit. As the time-lapse video starts, alternating dark and light cloud bands passed underneath the spacecraft as it approaches Jupiter's South Pole. These clouds contain complex textures involving eddies, swirls, ovals, and extended clouds that are have no direct analog from Earth. As the spacecraft passes beneath Jupiter, new cloud patterns devoid of long bands emerge but are again rich with alien swirls and ovals. Over the next few years, Juno will continue to orbit and probe Jupiter, determine atmospheric water abundance, and attempt to determine if Jupiter has a solid surface underneath these fascinating clouds.

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LHC’s objective: maximum intensity

This image shows a simulation of the electron clouds development when the proton beam passes through the vacuum chamber. (Image: CERN)

Protons are jostling for space in the Large Hadron Collider. Since the start of the physics run on 23 May, the operators of the huge accelerator have been increasing the intensity of the beams, injecting more and more protons in order to increase the number of collisions.

“Trains” of proton bunches have been circulating in the machine for the past week. Consisting of up to 288 bunches, each containing more than 100 billion protons, the trains are formed by the accelerator chain and then sent into the large ring. They are then accelerated to a speed close to that of light for around twenty minutes, before they collide with each other in the centre of each experiment. Recently, 600 bunches have been circulating in each direction. The aim is to reach 2500 bunches in each beam within a few weeks.

To achieve this, the machine specialists must first improve the surface conditions of the vacuum chambers in which the protons circulate. Obtaining the best possible vacuum is an essential prerequisite to make an accelerator work. Molecules remaining in the vacuum chamber are obstacles to the circulation of the protons – it is like sending Formula 1 cars around a track full of parked cars. Hence, before starting up the accelerator, the vacuum specialists pump the air out of the beam pipes, obtaining a high-quality vacuum, almost as good as on the surface of the moon (10-10 or even 10-11 millibar). This is enough to allow the circulation of a few hundred proton bunches, but beyond that, things get harder.

Despite the ultra-high vacuum, residual gas molecules and electrons remain trapped on the walls of the vacuum chambers. When the beam circulates, these electrons are liberated from the surface of the walls due to the impact of lost particles or photons emitted by the LHC proton beams. They are accelerated by the beam’s electrical field and hit the walls on the opposite side of the chamber, detaching trapped molecules and freeing more electrons. If the number of liberated electrons is larger than the number of impacting electrons, it may initiate an avalanche of electrons, which will destabilise the beam. This phenomenon, known as the “electron cloud”, is amplified by the large number of proton bunches and the short distance between the bunches in the beam.

To mitigate the impact of these clouds, the vacuum chamber can be conditioned with the beam itself. Increasing the number of circulating bunches frees as many molecules of gas as can be sustained and causes a massive release of electron clouds. Experience has shown that, once this operation, called "scrubbing", has been carried out, the production rate of gas molecules and electrons progressively falls. This allows the beam intensity to be increased stepwise until the LHC can be filled completely.

So it’s time for spring cleaning at the LHC. For five days, starting today, the LHC operators will carry out scrubbing of the vacuum chambers with beam. The physics run will take a short break, starting again in much better conditions mid-June.

 


via CERN: Updates for the general public
http://home.cern/about/updates/2017/06/lhcs-objective-maximum-intensity

Jackpot! Cosmic magnifying-glass effect captures universe's brightest galaxies

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Boosted by natural magnifying lenses in space, NASA's Hubble Space Telescope has captured unique close-up views of the universe's brightest infrared galaxies, which are as much as 10,000 times more luminous than our Milky Way.
via Science Daily
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Jackpot! Cosmic Magnifying-Glass Effect Captures Universe's Brightest Galaxies


Galaxies Shine with the Brilliance of up to 100 Trillion Suns

Astronomers were fascinated in the 1980s with the discovery of nearby dust-enshrouded galaxies that glowed thousands of times brighter than our Milky Way galaxy in infrared light. Dubbed ultra-luminous infrared galaxies, they were star-making factories, churning out a prodigious amount of stars every year. What wasn't initially clear was what powered these giant infrared light bulbs. Observations by the Hubble Space Telescope helped astronomers confirm the source of the galaxies' light output. Many of them reside within "nests" of galaxies engaged in multiple pile-ups of three, four or even five galaxies. The dust is produced by the firestorm of star birth, which glows fiercely in infrared light.

Now Hubble is illuminating the bright galaxies' distant dust-enshrouded cousins. Boosted by natural magnifying lenses in space, Hubble has captured unique close-up views of the universe's brightest infrared galaxies. The galaxies are ablaze with runaway star formation, pumping out more than 10,000 new stars a year. This unusually rapid star birth is occurring at the peak of the universe's star-making boom more than 8 billion years ago. The star-birth frenzy creates lots of dust, which enshrouds the galaxies, making them too faint to detect in visible light. But they glow fiercely in infrared light, shining with the brilliance of 10 trillion to 100 trillion suns.

The galaxy images, magnified through a phenomenon called gravitational lensing, reveal a tangled web of misshapen objects punctuated by exotic patterns such as rings and arcs. The odd shapes are due largely to the foreground lensing galaxies' powerful gravity distorting the images of the background galaxies. Two possibilities for the star-making frenzy are galaxy collisions or gas spilling into the galaxies.


via Hubble - News feed
http://hubblesite.org/news_release/news/2017-24