Dark Matter Grows ‘Hair’ Around Stars And Planets

Dark matter may make up 27% of the Universe’s energy density, compared to just 5% of normal (atomic) matter, but in our Solar System, it’s notoriously sparse. In particular, there’s just a nanogram’s worth per cubic kilometer, which makes the fact that we’ve never directly detected it seem inevitable.
But recent work has demonstrated that Earth and all the planets leave a ‘wake’ of dark matter where the density is enhanced by a billion times or more. Time to go put those dark matter detectors where they belong: in the path of these dark matter hairs….

Read more at www.forbes.com

What statistics can tell us about strategy in tennis


Theoretical result for the probability to have a result from -7 to 7 in a tiebreak considering that the probability to win(lose) a point is 0.5. Horizontal axis is the difference of points from a given and other players. Positive values mean victories and negative losses

I. Y. Kawashima, R. S. Marques de Carvalho, O. Helene, M. T. Yamashita
In this paper we analyse tiebreak results from some tennis players in order to investigate whether we are able to identify some strategy in this crucial moment of the game. We compared the observed results with a binomial distribution considering that the probabilities of winning or losing a point are equal. Using a χ2 test we found that, excepting some players, the greatest part of the results agrees with our hypothesis that there is no hidden strategy and the points in tiebreaks are merely aleatory.

Read more at http://arxiv.org/pdf/1511.06163v1.pdf

Dark matter might cause fundamental constants to change over time

dark matter_1The fundamental constants of nature—such as the speed of light, Planck’s constant, and Newton’s gravitational constant—are thought to be constant in time, as their name suggests. But scientists have questioned this assumption as far back as 1937, when Paul Dirac hypothesized that Newton’s gravitational constant might decrease over time.

Now in a new paper published in Physical Review Letters, Yevgeny V. Stadnik and Victor V. Flambaum at the University of New South Wales in Sydney, Australia, have theoretically shown that dark matter can cause the fundamental constants of nature to slowly evolve as well as oscillate due to oscillations in the dark matter field. This idea requires that the weakly interacting dark matter particles be able to interact a small amount with standard model particles, which the scientists show is possible.
In their paper, the scientists considered a model in which dark matter is made of weakly interacting, low-mass particles. In the early Universe, according to the model, large numbers of such dark matter particles formed an oscillating field. Because these particles interact so weakly with standard model particles, they could have survived for billions of years and still exist today, forming what we know as dark matter.
Although these low-mass dark matter particles are weakly interacting, they are thought to still interact with standard model particles to some extent, but it’s unclear exactly how much. By using data from experiments that have measured the amount of helium produced during big bang nucleosynthesis, as well as measurements of the rare element dysprosium and the cosmic microwave background, Stadnik and Flambaum have derived the most stringent limits to date on how strongly such dark matter particles interact with photons, electrons, and light quarks, improving on existing constraints by up to 15 orders of magnitude.
The new limits on the dark matter interaction strength allow for the possibility that an oscillating, low-mass dark matter field coupled to standard model particles causes variations in the fundamental constants. As the scientists explain, this could have important implications for understanding life’s origins.
“The fundamental constants are ‘fine-tuned’ to be consistent with the existence of life in the Universe,” Stadnik told Phys.org. “If the physical constants were even slightly different, life could not have appeared. The discovery of varying fundamental ‘constants’ may help shed important light on how the physical constants came to have their life-sustaining values today. We simply appeared in an area of the Universe where they are consistent with our existence.”
Whether or not the fundamental constants actually do vary due to dark matter is still an open question, but the scientists hope that future experiments with atomic clocks, laser interferometers, and other devices may help test out the new idea.
“We have shown that linking dark matter and variation of the fundamental constants of Nature leads to a major breakthrough in the sensitivity of dark matter searches,” Flambaum said. “We plan to continue searching for other novel signatures of dark matter that may lead to the direct detection of dark matter for the first time.”

Read more at: phys.org – arxiv.org

A supermassive black hole in action

Copyright NASA, ESA, S. Baum & C. O’Dea (RIT), R. Perley & W. Cotton (NRAO/AUI/NSF), and the Hubble Heritage Team (STScI/AURA)

Copyright NASA, ESA, S. Baum & C. O’Dea (RIT), R. Perley & W. Cotton (NRAO/AUI/NSF), and the Hubble Heritage Team (STScI/AURA)

Scientists often use the combined power of multiple telescopes to reveal the secrets of the Universe – and this image is a prime example of when this technique is strikingly effective.

The yellow-hued object at the centre of the frame is an elliptical galaxy known as Hercules A, seen by the Earth-orbiting NASA/ESA Hubble Space Telescope. In normal light, an observer would only see this object floating in the inky blackness of space.

However, view Hercules A with a radio telescope, and the entire region is completely transformed. Stunning red–pink jets of material can be seen billowing outwards from the galaxy – jets that are completely invisible in visible light. They are shown here as seen by the Karl G. Jansky Very Large Array radio observatory in New Mexico, USA. These radio observations were combined with the Hubble visible-light data obtained with the Wide Field Camera 3 to create this striking composite.

The two jets are composed of hot, high-energy plasma that has been flung from the centre of Hercules A, a process that is driven by a supermassive black hole lurking at the galaxy’s heart. This black hole is some 2.5 billion times the mass of the Sun, and around a thousand times more massive than the black hole at the centre of our Milky Way galaxy.

Hercules A’s black hole heats material and accelerates it to nearly the speed of light, sending it flying out into space at phenomenally high speeds. These highly focused jets lose energy as they travel, eventually slowing down and spreading out to form the cloud-like lobes seen here.

The multiple bright rings and knots seen within these lobes suggest that the black hole has sent out numerous successive bursts of material over the course of its history. The jets stretch for around 1.5 million light-years – roughly 15 times the size of the Milky Way.

Hercules A, also known as 3C 348, lies around two billion light-years away. It is one of the brightest sources of radio emission outside our Galaxy.

This image was originally published in November 2012.

Read more at www.esa.int