19 Οκτωβρίου 2017  ---  S. Chandrasekhar’s 107th Birthday

Freeman Dyson: Once the astrophysics community had come to grips with a calculation performed by a 19-year-old student sailing off to graduate school, the heavens could never again be seen as a perfect and tranquil dominion.

Physics Today 63, 12, 44 (2010); doi: http://dx.doi.org/10.1063/1.3529001

In 1946 Subrahmanyan Chandrasekhar gave a talk at the University of Chicago entitled “The Scientist.” 1 He was then 35 years old, less than halfway through his life and less than a third of the way through his career as a scientist, but already he was reflecting deeply on the meaning and purpose of his work. His talk was one of a series of public lectures organized by Robert Hutchins, then the chancellor of the university. The list of speakers is impressive, and included Frank Lloyd Wright, Arnold Schoenberg, and Marc Chagall. That list proves two things. It shows that Hutchins was an impresario with remarkable powers of persuasion, and that he already recognized Chandra as a world-class artist whose medium happened to be theories of the universe rather than music or paint. I say “Chandra” because that is the name his friends used for him when he was alive.

BASIC SCIENCE AND DERIVED SCIENCE

Chandra began his talk with a description of two kinds of scientific inquiry. “I want to draw your attention to one broad division of the physical sciences which has to be kept in mind, the division into a basic science and a derived science. Basic science seeks to analyze the ultimate constitution of matter and the basic concepts of space and time. Derived science, on the other hand, is concerned with the rational ordering of the multifarious aspects of natural phenomena in terms of the basic concepts.”

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LYING IN WAIT Huge tubs of water (one shown) at the Pierre Auger Observatory in Argentina reveal the tracks left as cosmic particles zip through them.

Huge experiment is trying to track the particles back to their sources
BY LISA GROSSMAN 2:00PM, SEPTEMBER 21, 2017

The largest study yet of the most energetic particles to slam into Earth provides the first solid clues to where the particles come from. Using a giant array of tubs of water, scientists found that these ultrahigh energy cosmic rays mostly originate outside the Milky Way.

An international team analyzed about 12 years of data to show that particles with energies above 8 billion billion electron volts generally come from a particular direction in the sky, and it’s not the galaxy’s center. The researchers report their findings in the Sept. 22 Science.

“It’s the first clear experimental indication that the sources of these high-energy particles are located outside of our own galaxy, probably somewhere in the nearby universe,” says Karl-Heinz Kampert of the University of Wuppertal in Germany, a spokesperson for the Pierre Auger Collaboration, which made the discovery.

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The stars within and beyond the Pillars of Creation are revealed in the infrared. 

Ethan Siegel, Contributor

While Hubble extends its view out to 1.6 microns, more than twice the limit of visible light, James Webb will go out to 30 microns: nearly 20 times as far again.

It's been a staple of science throughout the centuries: the arrogant thinking that we've almost arrived at the ultimate answers to our deepest questions. Scientists thought that Newton's mechanics described everything, until they discovered the wave nature of light. Physicists thought we were almost there when Maxwell unified electromagnetism, and then relativity and quantum mechanics came along. And many thought the nature of matter was complete when we discovered the proton, neutron and electron, until high-energy particle physics revealed an entire Universe of fundamental particles. In just the past 25 years, five incredible discoveries have changed our understanding of the Universe, and each one holds the promise of an even bigger revolution. There's never been a better time to look into the deepest mysteries of existence.

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NASA's Kepler mission has verified 1,284 new planets – the single largest finding of planets to date.

“This announcement more than doubles the number of confirmed planets from Kepler,” said Ellen Stofan, chief scientist at NASA Headquarters in Washington. “This gives us hope that somewhere out there, around a star much like ours, we can eventually discover another Earth.”

Analysis was performed on the Kepler space telescope’s July 2015 planet candidate catalog, which identified 4,302 potential planets. For 1,284 of the candidates, the probability of being a planet is greater than 99 percent – the minimum required to earn the status of “planet.” An additional 1,327 candidates are more likely than not to be actual planets, but they do not meet the 99 percent threshold and will require additional study. The remaining 707 are more likely to be some other astrophysical phenomena. This analysis also validated 984 candidates previously verified by other techniques.

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Findings by University of Cape Town, University of Western Cape offer glimpse of early universe to be revealed when SKA is operational

By Alexis Haden - April 11, 2016

Deep radio imaging by researchers in the University of Cape Town and University of the Western Cape has revealed that supermassive black holes in a region of the distant universe are all spinning out radio jets in the same direction – most likely a result of primordial mass fluctuations in the early universe, a new paper in MNRAS reports today.

The new result is the discovery – for the first time – of an alignment of the jets of radio galaxies over a large volume of space, a finding made possible by a three-year deep radio imaging survey of the radio waves coming from a region called ELAIS-N1 using the Giant Metrewave Radio Telescope (GMRT).

The radio jets are produced by the supermassive black holes at the centres of these galaxies, and the only way for this alignment to exist is if supermassive black holes are all spinning in the same direction, says Prof Andrew Russ Taylor, joint UWC/UCT SKA Chair, Director of the recently-launched Inter-University Institute for Data Intensive Astronomy and principal-author of the study.

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Comet 67P and Rosetta are now just over 400 million km from the Sun, and receding

Perfectly backlit by our star. This is how Comet 67P was pictured this week by the Rosetta spacecraft.

The European Space Agency (Esa) probe was a few hundred km "downstream" of all the vapour and dust being vented from the icy dirt-ball.
Even though the duck-shaped object is heading out of the inner Solar System, it remains classically active.
Rosetta will continue to study the comet until controllers direct it to make a "landing" in September.
Mission officials will endeavour to make this touchdown a gentle one, to ensure data is returned for as long as possible. But it will bring the whole venture to an end.

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Artist’s impression of a quasar. In the quasar OJ 287, a secondary supermassive black hole orbits the primary, occasionally punching through the accretion disk surrounding the primary. [ESO/M. Kornmesser]

This past December, researchers all over the world watched an outburst from the enormous black hole in OJ 287 — an outburst that had been predicted years ago using the general theory of relativity.

Outbursts from Black-Hole Orbits

OJ 287 is one of the largest supermassive black holes known, weighing in at 18 billion solar masses. Located about 3.5 billion light-years away, this monster quasar is bright enough that it was first observed as early as the 1890s. What makes OJ 287 especially interesting, however, is that its light curve exhibits prominent outbursts roughly every 12 years.

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Researchers have finally witnessed, in visible light wavelengths, the “shock breakout” of a supernova—the exact moment when the expanding blast wave from a vanishing star lastly explodes the outer stellar layers and makes its outstanding entry onto the cosmic stage. The recent supernova results signify the proverbial needle in a haystack—an international group of researcher examined 3 years’ worth of data, in which Kepler taken pictures every other 30 minutes of some 50 trillion stars dispersed amid 500 remote galaxies.

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Paris, 16 March 2016
"A source accelerating Galactic cosmic rays to unprecedented energy discovered at the centre of the Milky Way"

For more than ten years the H.E.S.S. observatory in Namibia, run by an international collaboration of 42 institutions in 12 countries, has been mapping the centre of our galaxy in very-high-energy gamma rays. These gamma rays are produced by cosmic rays from the innermost region of the Galaxy. A detailed analysis of the latest H.E.S.S. data, published on 16th March 2016 in Nature, reveals for the first time a source of this cosmic radiation at energies never observed before in the Milky Way: the supermassive black hole at the centre of the Galaxy, likely to accelerate cosmic rays to energies 100 times larger than those achieved at the largest terrestrial particle accelerator, the LHC at CERN.

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Louie Psihoyos / Corbis

The Arecibo Observatory in Puerto Rico, which has spotted the first example of a repeating fast radio burst.

One paper suggests that fast radio bursts can repeat, but a finding on the origin of another burst is in doubt.

Mark Zastrow
02 March 2016

Three reports within a week have astronomers aflutter about the puzzling origins of short, bright pulses of radio waves called fast radio bursts (FRBs).

Last week, astronomers said that they had1 identified the origins of an FRB for the first time — pinpointing the signal to a distant galaxy. And a paper published today3 offers a different clue to the origins of FRBs, which have baffled astronomers since they were first observed nine years ago. It reports the discovery of a repeating signal: a surprise because all 17 known bursts so far have been one-off blips.

But sceptics have questioned the first work, recording telescope observations within days of the announcement that cast doubt on the finding2.

Origin story

On 24 February, astronomers announced that they had identified the origin of an FRB in a galaxy 1.9 billion parsecs (6 billion light years) away, probably produced by a collision between two neutron stars1. A network of telescopes had scanned the area of sky in which an FRB had been picked up by the Parkes radio telescope in New South Wales, Australia, and had discovered a fading afterglow of radio waves in an elliptical galaxy. The odds of finding such a radio signal by chance were just one or two in a thousand, wrote the team led by Evan Keane of the Square Kilometre Array Organisation, which is headquartered at the Jodrell Bank Observatory outside Manchester, UK.

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The Australia Telescope Compact Array, in New South Wales, which helped to identify the location of a fast radio burst.

For the first time, astronomers have traced an enigmatic blast of radio waves to its source.

Mark Zastrow
24 February 2016 Corrected: 25 February 2016

Since 2007, astronomers have detected curious bright blasts of radio waves from the cosmos, each lasting no more than a few milliseconds. Now scientists have been able to pinpoint the source of one of these pulses: a galaxy 1.9 billion parsecs (6 billion light years) away. It probably came from two colliding neutron stars, says astronomer Evan Keane, a project scientist for the Square Kilometre Array (SKA). Keane, who works at the SKA Organization's headquarters at Jodrell Bank Observatory outside Manchester, UK, led the team that reports the detection in Nature1.

The discovery is the “measurement the field has been waiting for”, says astronomer Kiyoshi Masui of the University of British Columbia in Vancouver, Canada. By finding more such fast radio bursts (FRBs) and measuring the distance to their source, astronomers hope to use the signals as beacons to shed light on the evolution of the Universe.

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                     Jim West/Alamy
The Green Bank Telescope in West Virginia is the third facility to have detected a fast radio burst.

American telescope detects clue to source of fast radio bursts.

Elizabeth Gibney
02 December 2015

For the past eight years, astronomers have been mystified by sudden, very short blasts of radio waves that defy explanation.

Now the most detailed study so far1 has furnished a clue to the origin of at least one of these strange pulses, or 'fast radio bursts' (FRBs). It came from a dense, magnetized region of space, and was probably emitted by a young neutron star (a compact core left in the aftermath of a supernova), says study author Kiyoshi Masui at the University of British Columbia in Canada.

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Recent discoveries provided more decisive evidence for the magnetic structure of matter

Posted by The Watcher on January 24, 2016

Since the beginning of the space age, many observations sharply contradict the theories of a gravity-dominated Cosmos, yet recent observations have created even larger holes in those theories. Now it is impossible to cover these holes with any theoretical solution, such as the so-called red giants.

According to the consensus model, a star becomes a red giant in the later part of its life. In this stage, most of the fuel powering nuclear fusion in the core of the star is exhausted. As a result of this deficiency, "gravitational collapse" is induced. In other words, the star would collapse on itself due to a lack of light pressure which is pushing out against the force of gravity.

When this self-collapse takes place, it heats up a shell of hydrogen that surrounds the core. That heat would be sufficient to reignite fusion reaction, causing the star to become bigger as a result of increased light pressure and this process would make the star 1 000-10 000 times more luminous.

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Christian Krueger (right), IceCube/NSF

Week 1 at the Pole
By Jean DeMerit, 22 Jan 2016 10:30 AM

… now you don’t. These two photos show the spot of the geographical South Pole, just before and after the old marker was removed—as we mentioned last week, at the beginning of each year a new marker is situated at the current location, which shifts constantly due to the movement of the ice sheet. This year’s marker, which can be seen below, is about 10 meters away from the old spot (here's a close-up view).
Inside, they were busy last week packing data disks for shipment north—a lot of disks, in a lot of boxes. IceCube’s winterovers are standing next to their completed tower of boxes, which altogether contains every bit of data collected by IceCube for 2015. Off it goes.
Outside, there was some interesting work in the area of ice studies. Two deep holes were dug, separated by about half a meter (bottom images). One hole is open and receives full sunlight, the other has a plywood cover. The last image shows the view of the backlit wall of the open hole from inside the closed hole, with visible lines delineating snow and ice accumulation over time. The bright lines indicate summer seasons, when the new snow is compacted from the heat of the Sun.

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The artist’s impression above shows what it would look like from an exoplanet 10,000 light-years away in its home galaxy.

By Daniel Clery

Jan. 14, 2016

Kaboom! Astronomers have found the most violently explosive supernova so far detected in the history of the universe. Supernovae are already some of the brightest events out there but in recent decades astronomers have seen a rare new class of blasts, superluminous supernovae (SLSNe)—sometimes dubbed hypernovae. The new discovery was spotted last June by the All Sky Automated Survey for SuperNovae (ASAS-SN), a system of eight small 14-centimeter telescopes at two sites in Chile and Hawaii that can scan the entire sky every 2 to 3 days. At its peak, ASAS-SN-15lh, as the new supernova is known, was twice as luminous as any previously seen, thousands of times brighter than a normal supernova, and outshone our entire Milky Way galaxy by 50 times. 

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