Category Archives: Science Advance & Theoretical

Prof. Stephen Hawking tells students the universe does not need a God to exist

Prof. Stephen Hawking tells students the universe does not need a God to exist (via Raw Story )

Former Cambridge Professor Stephen Hawking told students at Caltech this week that, contrary to the feelings of many God enthusiasts, the universe did not require a deity to create, nor does it require one to continue existing. Though his speech was supposed to be free of recording devices, some sly…

NASA’s NuSTAR helps solve riddle of black hole spin

This artist’s concept illustrates a supermassive black hole with millions to billions times the mass of our sun. Supermassive black holes are enormously dense objects buried at the hearts of galaxies. (Credit: NASA/JPL-Caltech)

Feb. 27, 2013 — Two X-ray space observatories, NASA’s Nuclear Spectroscopic Telescope Array (NuSTAR) and the European Space Agency’s XMM-Newton, have teamed up to measure definitively, for the first time, the spin rate of a black hole with a mass 2 million times that of our sun.

The supermassive black hole lies at the dust- and gas-filled heart of a galaxy called NGC 1365, and it is spinning almost as fast as Einstein’s theory of gravity will allow. The findings, which appear in a new study in the journal Nature, resolve a long-standing debate about similar measurements in other black holes and will lead to a better understanding of how black holes and galaxies evolve.

“This is hugely important to the field of black hole science,” said Lou Kaluzienski, a NuSTAR program scientist at NASA Headquarters in Washington.

The observations also are a powerful test of Einstein’s theory of general relativity, which says gravity can bend space-time, the fabric that shapes our universe, and the light that travels through it.

“We can trace matter as it swirls into a black hole using X-rays emitted from regions very close to the black hole,” said the coauthor of a new study, NuSTAR principal investigator Fiona Harrison of the California Institute of Technology in Pasadena. “The radiation we see is warped and distorted by the motions of particles and the black hole’s incredibly strong gravity.”

NuSTAR, an Explorer-class mission launched in June 2012, is designed to detect the highest-energy X-ray light in great detail. It complements telescopes that observe lower-energy X-ray light, such as XMM-Newton and NASA’s Chandra X-ray Observatory. Scientists use these and other telescopes to estimate the rates at which black holes spin.

Until now, these measurements were not certain because clouds of gas could have been obscuring the black holes and confusing the results. With help from XMM-Newton, NuSTAR was able to see a broader range of X-ray energies and penetrate deeper into the region around the black hole. The new data demonstrate that X-rays are not being warped by the clouds, but by the tremendous gravity of the black hole. This proves that spin rates of supermassive black holes can be determined conclusively.

“If I could have added one instrument to XMM-Newton, it would have been a telescope like NuSTAR,” said Norbert Schartel, XMM-Newton Project Scientist at the European Space Astronomy Center in Madrid. “The high-energy X-rays provided an essential missing puzzle piece for solving this problem.”

Measuring the spin of a supermassive black hole is fundamental to understanding its past history and that of its host galaxy.

“These monsters, with masses from millions to billions of times that of the sun, are formed as small seeds in the early universe and grow by swallowing stars and gas in their host galaxies, merging with other giant black holes when galaxies collide, or both,” said the study’s lead author, Guido Risaliti of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass., and the Italian National Institute for Astrophysics.

Supermassive black holes are surrounded by pancake-like accretion disks, formed as their gravity pulls matter inward. Einstein’s theory predicts the faster a black hole spins, the closer the accretion disk lies to the black hole. The closer the accretion disk is, the more gravity from the black hole will warp X-ray light streaming off the disk.

Astronomers look for these warping effects by analyzing X-ray light emitted by iron circulating in the accretion disk. In the new study, they used both XMM-Newton and NuSTAR to simultaneously observe the black hole in NGC 1365. While XMM-Newton revealed that light from the iron was being warped, NuSTAR proved that this distortion was coming from the gravity of the black hole and not gas clouds in the vicinity. NuSTAR’s higher-energy X-ray data showed that the iron was so close to the black hole that its gravity must be causing the warping effects.

With the possibility of obscuring clouds ruled out, scientists can now use the distortions in the iron signature to measure the black hole’s spin rate. The findings apply to several other black holes as well, removing the uncertainty in the previously measured spin rates.

For more information on NASA’s NuSTAR mission, visit: http://www.nasa.gov/nustar .

For more information on ESA’s XMM-Newton mission, visit: http://go.nasa.gov/YUYpI6 .

The California Institute of Technology in Pasadena manages JPL for NASA.

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Cassini sheds light on cosmic particle accelerators

This artist’s impression by the European Space Agency shows NASA’s Cassini spacecraft exploring the magnetic environment of Saturn. (Credit: ESA)

Feb. 19, 2013 — During a chance encounter with what appears to be an unusually strong blast of solar wind at Saturn, NASA’s Cassini spacecraft detected particles being accelerated to ultra-high energies. This is similar to the acceleration that takes place around distant supernovas.

Since we can’t travel out to the far-off stellar explosions right now, the shockwave that forms from the flow of solar wind around Saturn’s magnetic field provides a rare laboratory for scientists with the Cassini mission — a partnership involving NASA, the European Space Agency and the Italian Space Agency — to observe this phenomenon up-close. The findings, published this week in the journal Nature Physics, confirm that certain kinds of shocks can become considerably more effective electron accelerators than previously thought.

Shock waves are commonplace in the universe, for example in the aftermath of a stellar explosion as debris accelerate outward in a supernova remnant, or when the flow of particles from the sun — the solar wind — impinges on the magnetic field of a planet to form a bow shock. Under certain magnetic field orientations and depending on the strength of the shock, particles can be accelerated to close to the speed of light at these boundaries. These may be the dominant source of cosmic rays, high-energy particles that pervade our galaxy.

Scientists are particularly interested in “quasi-parallel” shocks, where the magnetic field and the “forward”-facing direction of the shock are almost aligned, as may be found in supernova remnants. The new study, led by Adam Masters of the Institute of Space and Astronautical Science, Sagamihara, Japan, describes the first detection of significant acceleration of electrons in a quasi-parallel shock at Saturn, coinciding with what may be the strongest shock ever encountered at the ringed planet.

“Cassini has essentially given us the capability of studying the nature of a supernova shock in situ in our own solar system, bridging the gap to distant high-energy astrophysical phenomena that are usually only studied remotely,” said Masters.

The Cassini-Huygens mission is a cooperative project of NASA, ESA and ASI, the Italian space agency. NASA’s Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA’s Science Mission Directorate, Washington.

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Higgs data indicates our universe is unstable | TG Daily

Posted February 19, 2013 – 04:28 by Kate Taylor

Our universe could one day be wiped out by a new one that bubbles up inside it and replaces it, a Fermilab scientist says.

Through a phenomenon known as vacuum instability, a quantum fluctuation could create a tiny new universe that would then expand at the speed of light.

Whether or not this happens depends on the properties of the Higgs boson, including its precise mass, which would give an indication of just how unstable out universe is. But, physicist Joseph Lykken tells Reuters, “If you use all the physics that we know now and you do what you think is a straightforward calculation, it’s bad news.”

“Many tens of billions of years from now, there’ll be a catastrophe. A little bubble of what you might think of as an ‘alternative’ universe will appear somewhere and then it will expand out and destroy us.”

Ruling this theory in or out depends on the precise mass of the Higgs boson. Frustratingly, the current best measure of the mass of the particle found at the Large Hadron Collider last summer doesn’t resolve the matter.

“Before we knew, the Higgs could have been any mass over a very wide range,” Professor Chris Hill of Ohio State University tells the BBC.

“And what’s amazing to me is that out of all those possible masses from 114 to several hundred GeV, it’s landed at 126-ish where it’s right on the critical line, and now we have to measure it more precisely to find the fate of the universe.”

Unfortunately, that’s not going to happen terribly soon. The LHC is currently shut down to allow for maintenance and repairs, and won’t be back up and running until 2015.

Scientists find weird new property of matter that breaks all the rules | The Verge

Similar eureka moments have brought us maglev trains — what’s next?

By Arikia Millikan on February 18, 2013 06:55 pm Email 156Comments

Don’t miss any stories Follow The Verge

When physicists discover new properties of matter, it usually means better technologies for the rest of us. Superconductors, liquid crystal displays like the ones found in most TVs now, medical imaging technologies that allow doctors to peer inside the human body, and magnetic levitation — which was used to create the Shanghai Maglev train — are all examples of how discoveries of new properties of matter have resulted in revolutionary products.

A quantum dot energy harvester

An array on nano energy harvesters in what the researchers call a “swiss cheese” arrangement. (Credit: Image courtesy of University of Rochester)

Feb. 14, 2013 — A new type of nanoscale engine has been proposed that would use quantum dots to generate electricity from waste heat, potentially making microcircuits more efficient.

“The system is really a simple one, which exploits certain properties of quantum dots to harvest heat,” Professor Andrew Jordan of the University of Rochester said. “Despite this simplicity, the power it could generate is still larger than any other nanoengine that has been considered until now.”

The engines would be microscopic in size, and have no moving parts. Each would only produce a tiny amount of power — a millionth or less of what a light bulb uses. But by combining millions of the engines in a layered structure, Jordan says a device that was a square inch in area could produce about a watt of power for every one degree difference in temperature. Enough of them could make a notable difference in the energy consumption of a computer.

A paper describing the new work is being published in Physical Review B by Jordan, a theoretical physics professor, and his collaborators, Björn Sothmann and Markus Buttiker from the University of Geneva, and Rafael Sánchez from the Material Sciences Institute in Madrid.

Jordan explained that each of the proposed nanoengines is based on two adjacent quantum dots, with current flowing through one and then the other. Quantum dots are manufactured systems that due to their small size act as quantum mechanical objects, or artificial atoms.

The path the electrons have to take across both quantum dots can be adjusted to have an uphill slope. To make it up this (electrical) hill, electrons need energy. They take the energy from the middle of the region, which is kept hot, and use this energy to come out the other side, higher up the hill. This removes heat from where it is being generated and converts it into electrical power with a high efficiency.

To do this, the system makes use of a quantum mechanical effect called resonant tunneling, which means the quantum dots act as perfect energy filters. When the system is in the resonant tunneling mode, electrons can only pass through the quantum dots when they have a specific energy that can be adjusted. All other electrons that do not have this energy are blocked.

Quantum dots can be grown in a self-assembling way out of semiconductor materials. This allows for a practical way to produce many of these tiny engines as part of a larger array, and in multiple layers, which the authors refer to as the Swiss Cheese Sandwich configuration (see image).

How much electrical power is produced depends on the temperature difference across the energy harvester — the higher the temperature difference, the higher the power that will be generated. This requires good insulation between the hot and cold regions, Jordan says.

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New-found prime number is 17 million digits long | TG Daily

Posted February 6, 2013 – 09:17 by Emma Woollacott

Mathematicians have discovered the largest prime number yet – two to the power of 257,885,161, minus one.

The number has 17,425,170 digits, and was found using the Great Internet Mersenne Prime Search (GIMPS) project – the longest-evercontinuously-running global ‘grassroots supercomputing’ project, involving 360,000 CPUs peaking at 150 trillion calculations per second.

The new prime number is a member of a special class of extremely rare prime numbers known as Mersenne primes, and is only the 48th of these to be discovered.

Mersenne primes were named for the French monk Marin Mersenne, who studied these numbers more than 350 years ago. All take the form 2 to the power of p – 1, where p is also a prime number – although not all numbers that take that form are prime.

Mathematicians suspect that there may be an infinite number of Mersenne primes. GIMPS, founded in 1996, has discovered all 14 of the largest known Mersenne primes – with this latest one taking 39 days of non-stop computing to establish.

To prove there were no errors in the prime discovery process, the latest one was independently verified using different programs running on different hardware.

This is the third record prime for Dr Curtis Cooper and the University of Central Missouri, the others having been discovered in 2005 and2006. Computers at UCLA broke that record in 2008 with a 12,978,189 digit prime number that was the longest until now.
Work to find more will continue – especially given the $150,000 reward promised by the Electronic Frontier Foundation to the first person to find a 100 million-digit prime.

Anyone with a reasonably powerful PC can join GIMPS and have a shot themselves, with the necessary software available free at www.mersenne.org/freesoft.htm.