New Herschel Maps Reveal Stellar Nurseries

ESA’s Herschel mission releases today a series of unprecedented maps of star-forming hubs in the plane of our Milky Way galaxy. This is accompanied by a set of catalogs of hundreds of thousands of compact sources that span all phases leading to the birth of stars in our Galaxy.

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These maps and catalogs will be very valuable resources for astronomers, to exploit scientifically and for planning follow-up studies of particularly interesting regions in the Galactic Plane.

During its four years of operations (2009-2013), the Herschel space observatory scanned the sky at far-infrared and sub-millimeter wavelengths. Observations in this portion of the electromagnetic spectrum are sensitive to some of the coldest objects in the Universe, including cosmic dust, a minor but crucial component of the interstellar material from which stars are born.

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The Herschel infrared Galactic Plane Survey (Hi-GAL) is the largest of all observing programs carried out with Herschel, in terms of both observing time – over 900 hours of total observations, equivalent to almost 40 days – and sky coverage – about 800 square degrees, or two percent of the entire sky. Its aim was to map the entire disc of the Milky Way, where most of its stars form and reside, in five of Herschel’s wavelength channels: 70, 160, 250, 350 and 500 μm.

Over the past two years, the Hi-GAL team has processed the data to obtain a series of calibrated maps of extraordinary quality and resolution. With a dynamical range of at least two orders of magnitude, these maps reveal the emission by diffuse material as well as huge filament structures and individual, point-like sources scattered across the images.

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The images provide an unprecedented view of the Galactic Plane, ranging from diffuse interstellar material to denser filament structures of gas and dust that fragment into clumps where star formation sets in. They include pre-stellar clumps, proto-stars in various evolutionary stages and compact cores on the verge of turning into stars, as well as fully-fledged stars and the bubbles carved by their highly energetic radiation.

Today, the team releases the first part of this data set, consisting of 70 maps, each measuring two times two degrees, and provided in the five surveyed wavelengths.

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“These maps are not only stunning from an aesthetic point of view, but they represent a rich data set for astronomers to investigate the different phases of star formation in our Galaxy,” explains Sergio Molinari from IAPS/INAF, Italy, Principal Investigator for the Hi-GAL Project.

Astronomers have been able to avail of data from Hi-GAL from the very beginning of the observing program since the team agreed to waive their right to a proprietary period. The observations have been made available through the ESA Herschel Science Archive, including raw data as well as data products generated by systematic pipeline processing. The data has regularly been reprocessed to gradually higher quality and fidelity products.

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The present release represents an extra step in the data processing. The newly released maps are accompanied by source catalogs in each of the five bands, which can be directly used by the community to study a variety of subjects, including the distribution of diffuse dust and of star-forming regions across the Galactic Plane.

The maps cover the inner part of the Milky Way, towards the Galactic Center as seen from the Sun, with Galactic longitudes between +68° and -70°. A second release, with the remaining part of the survey, is foreseen for the end of 2016.

“It is not straightforward to extract compact sources from far-infrared images, where pre-stellar clumps and other proto-stellar objects are embedded in the diffuse interstellar medium that also shines brightly at the same wavelengths,” explains Molinari.

“For this reason, we developed a special technique to extract individual sources from the maps, maximising the contrast in order to amplify the compact objects with respect to the background.”

The result is a set of five catalogs, one for each of the surveyed wavelengths, listing the source position, flux, size, signal-to-noise ratio and other parameters related to their emission. The largest catalogue is the one compiled from the 160-μm maps, with over 300 000 sources.

“The Hi-GAL maps and catalogs provide a complete census of stellar nurseries in the inner Galaxy,” says Göran Pilbratt, Herschel Project Scientist at ESA.

“These will be an extremely useful resource for studies of star formation across the Milky Way, helping astronomers to delve into the Galactic Plane and also to identify targets for follow-up observations with other facilities.”

Cosmic Beacons Reveal The Milky Way’s Ancient Core

An international team of astronomers led by Dr. Andrea Kunder of the Leibniz Institute for Astrophysics Potsdam (AIP) in Germany has discovered that the central 2000 light years within the Milky Way Galaxy hosts an ancient population of stars. These stars are more than 10 billion years old and their orbits in space preserve the early history of the formation of the Milky Way.

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For the first time the team kinematically disentangled this ancient component from the stellar population that currently dominates the mass of the central Galaxy. The astronomers used the AAOmega spectrograph on the Anglo Australian Telescope near Siding Spring, Australia, and focussed on a well-known and ancient class of stars, called RR Lyrae variables. These stars pulsate in brightness roughly once a day, which make them more challenging to study than their static counterparts, but they have the advantage of being “standard candles.” RR Lyrae stars allow exact distance estimations and are found only in stellar populations more than 10 billion years old, for example, in ancient halo globular clusters. The velocities of hundreds of stars were simultaneously recorded toward the constellation of Sagittarius over an area of the sky larger than the full moon. The team therefore was able to use the age stamp on the stars to explore the conditions in the central part of our Milky Way when it was formed.

Just as London and Paris are built on more ancient Roman or even older remains, our Milky Way galaxy also has multiple generations of stars that span the time from its formation to the present. Since heavy elements, referred to by astronomers as “metals,” are brewed in stars, subsequent stellar generations become more and more metal-rich. Therefore, the most ancient components of our Milky Way are expected to be metal-poor stars. Most of our Galaxy’s central regions are dominated by metal-rich stars, meaning that they have approximately the same metal content as our Sun, and are arrayed in a football-shaped structure called the “bar.” These stars in the bar were found to orbit in roughly the same direction around the Galactic Centre. Hydrogen gas in the Milky Way also follows this rotation. Hence it was widely believed that all stars in the centre would rotate in this way.

But to the astronomers’ astonishment, the RR Lyrae stars do not follow football-shaped orbits, but have large random motions more consistent with their having formed at a great distance from the centre of the Milky Way. “We expected to find that these stars rotate just like the rest of the bar” states lead investigator Kunder. Coauthor Juntai Shen of the Shanghai Astronomical Observatory adds, “They account for only one percent of the total mass of the bar, but this even more ancient population of stars appears to have a completely different origin than other stars there, consistent with having been one of the first parts of the Milky Way to form.”

The RR Lyrae stars are moving targets — their pulsations result in changes in their apparent velocity over the course of a day. The team accounted for this, and was able to show that the velocity dispersion or random motion of the RR Lyrae star population was very high relative to the other stars in the Milky Way’s center. The next steps will be to measure the exact metal content of the RR Lyrae population, which gives additional clues to the history of the stars, and enhance by three or four times the number of stars studied, that presently stands at almost 1000.

JUST IN: New High-Energy Sources of Gamma and Cosmic Rays Discovered

A new sky map using the High Altitude Water Cherenkov (HAWC) Gamma-Ray Observatory shows many new gamma ray sources within our own Milky Way galaxy. HAWC gives us a new way to see the high-energy sky. “This new data from HAWC shows the galaxy in unprecedented detail, revealing new high-energy sources and previously unseen details about existing sources.” said Jordan Goodman, professor of physics at the University of Maryland.

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Today, scientists operating HAWC released a new survey of the sky made from the highest energy gamma rays ever observed. The new sky map, which uses data collected since the observatory began running at full capacity last March, offers a deeper understanding of high-energy processes taking place in our galaxy and beyond.

In a region of the Milky Way where researchers previously identified a single gamma ray source named TeV J1930+188, HAWC identified several hot spots, indicating that the region is more complicated than previously thought.

new_equation 2012_m

New Equation:
Increase Charged Particles  and Decreasing Magnetic Field → Increase Outer Core Convection → Increase of Mantle Plumes → Increase in Earthquake and Volcanoes → Cools Mantle and Outer Core → Return of Outer Core Convection (Mitch Battros – July 2012)

“Studying these objects at the highest energies can reveal the mechanism by which they produce gamma rays and possibly help us unravel the hundred-year-old mystery of the origin of high-energy cosmic rays that bombard Earth from space,” said Goodman.

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HAWC-located 13,500 feet above sea level on the slopes of Mexico’s Volcán Sierra Negra-contains 300 detector tanks, each holding 50,000 gallons of ultrapure water with four light sensors anchored to the floor. When gamma rays or cosmic rays reach Earth’s atmosphere they set off a cascade of charged particles, and when these particles reach the water in HAWC’s detectors, they produce a cone-shaped flash of light known as Cherenkov radiation. The effect is much like a sonic boom produced by a supersonic jet, because the particles are traveling slightly faster than the speed of light in water when they enter the detectors.

HAWC Gamma-ray Observatory

Because HAWC observes 24 hours per day and year-round with a wide field-of-view and large area, the observatory boasts a higher energy reach for extended objects. In addition, HAWC can uniquely monitor for gamma ray flares by sources in our galaxy and other active galaxies, such as Markarian 421 and Markarian 501.

Interstellar Dust From Beyond Our Solar System Analyzed

Interstellar dust is one of the last bastions of the unknown in space, its individual particles being only about 200 nanometers in size and very hard to find,” explains Prof. Dr. Mario Trieloff, Earth scientist from Heidelberg University. The dust is part of the interstellar material consisting of gas and helium, as well as heavy metals, and which can arise from the condensation processes of stars and planets. These particles are the raw material that were the main building blocks for Earth and other terrestrial planets.

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When it comes to studying interstellar dust, science has so far depended on particles reaching our solar system. The Stardust space probe was already able to capture particles of the very weak flux crossing our solar system. “But these particles were unusually large, so the research findings are possibly not representative,” Prof. Trieloff says. By contrast, the Cassini probe could identify 36 particles of interstellar dust among millions of planetary dust particles. Furthermore the CDA is in a position to analyze them on the spot with the assistance of mass spectrometry. This has enabled much more precise results than before.

Dr. Frank Postberg, on a Heisenberg grant at the Institute for Earth Science, notes that mass spectrometric measurements can now be made for the first time on “a statistically significant quantity of such dust particles.” This process had only become possible through a complex series of tests conducted in Heidelberg to calibrate laboratory models of the CDA. To achieve this aim, silicate dust had to be accelerated in the laboratory to upwards of 40 km a second, which is roughly the speed of interstellar dust.

“The result of the measurements was truly amazing,” Dr. Postberg reports. “The 36 particles of interstellar origin, that are very similar in their composition, contain a mix of the most important rock-forming elements — magnesium, iron, silicon and calcium — in average cosmic abundance. Although a dust particle has a mass of less than a trillionth of a gram, the whole element mix of the cosmos is collected there, with the exception of very volatile gases. Such particles cannot be found in our solar system.” Most scientists had expected dust populations with different compositions, corresponding to the different processes of origin in atmospheres of dying stars. These differences are also found in the stellar dust of meteorites, which is highly individual in its isotope composition. “Our data tells a completely different story,” he underlines.

According to the scientists, the dust has lost its individuality because it was homogenized in the cosmic “witch’s cauldron” of the interstellar medium. It contains gigantic, million-degree hot bubbles of supernova explosions, whose edges arise from shock fronts expanding at hundreds of kilometers per second, explains Dr. Nicolas Altobelli, who is the first author and a scientist at the European Space Agency (ESA).

There had already been a theory, he says, that interstellar dust can survive this energy-rich environment for only a few hundred million years and that very few “lucky survivors” succeed in reaching newly forming planetary systems as intact stellar dust. The latest research results now confirm that most particles are destroyed and reformed in molecular clouds, i.e. cool, dense regions of outer space. Interstellar winds bring these particles as homogenized dust into our solar system.

Do Black Holes Really Suck In All Matter?

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For the last four years, physicists studying the mathematical underpinnings of black holes have been wrestling with a strange idea; that black holes contain a region known as a “firewall,” which would stop matter from entering. However, a new paper titled Naked Black Hole Firewalls.

For the last four years, physicists studying the mathematical underpinnings of black holes have been wrestling with a strange idea; that black holes contain a region known as a “firewall,” which would stop matter from entering. However, a new paper titled Naked Black Hole Firewalls.

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“The hypothetical black hole firewall is one of the hottest problems in physics today, and we hope that our paper makes a significant contribution to the field,” says of Alberta physics professor Don N. Page.

Page’s contributors include Pisin Chen of the National Taiwan University and Stanford University, Yen Chin Ong of the Nordic Institute for Theoretical Physics (Nordita), Misao Sasaki of Kyoto University and Dong-han Yeom of the National Taiwan University.

The classic picture of a black hole comes directly from Einstein’s theory of general relativity: a massive object that warps the fabric of space-time and becomes so steep that not even light has sufficient speed to escape.

In the 1970s, physicist Stephen Hawking proposed that some particles could in fact escape from a black hole through a process involving the creation of entangled particles, in a theory now known as Hawking radiation. Since then, the field of black hole physics has been a wellspring of interesting phenomena, requiring the mathematics of both quantum theory and general relativity for a complete description.

In quantum mechanics, the two principles of quantum determinism and reversibility suggest that information must always be preserved. But since material falling into a black hole – along with the information describing that material, it be lost sometime after they cross the event horizon.

“If a firewall exists, not only would an in-falling object be destroyed by it, but the destruction could be visible, even from the outside,” says Misao Sasaki, of Yukawa Institute for Theoretical Physics in Kyoto, Japan.

If a firewall actually exists, the authors argue that it would not simply be confined to a region within the black hole, but its destructive power could reach beyond the limits of the event horizon, into a region of space that could be observed. This makes the notion of firewalls less conservative than previously thought, and suggests putting more effort into finding a better solution to the firewall paradox.

BREAKING NEWS: New Discovery of Mysterious Alignment of Black Holes

Deep radio imaging by researchers in the University of Cape Town and University of the Western Cape, in South Africa, has revealed that supermassive black holes in a region of the distant universe are all spinning out radio jets in the same direction. The astronomers publish their results to the Royal Astronomical Society.

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The jets are produced by the supermassive black holes at the center 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 Monthly Notices study.

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Earlier observational studies had previously detected deviations from uniformity (so-called isotropy) in the orientations of galaxies. But these sensitive radio images offer a first opportunity to use jets to reveal alignments of galaxies on physical scales of up to 100 Mpc. And measurements from the total intensity radio emission of galaxy jets have the advantage of not being affected by effects such as scattering, extinction and Faraday Radiation, which may be an issue for other studies.

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So what could these large-scale environmental influences during galaxy formation or evolution have been? There are several options: cosmic magnetic fields; fields associated with exotic particles (axions); and cosmic strings are only some of the possible candidates that could create an alignment in galaxies even on scales larger than galaxy clusters. It’s a mystery, and it’s going to take a while for technology and theory alike to catch up.

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New Equation:
Increase Charged Particles  and Decreased Magnetic Field → Increase Outer Core Convection → Increase of Mantle Plumes → Increase in Earthquake and Volcanoes → Cools Mantle and Outer Core → Return of Outer Core Convection (Mitch Battros – July 2012)

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The finding wasn’t planned for: the initial investigation was to explore the faintest radio sources in the universe, using the best available telescopes – a first view into the kind of universe that will be revealed by the South African MeerKAT radio telescope and the Square Kilometer Array (SKA), the world’s most powerful radio telescope and one of the biggest scientific instruments ever devised.

ancient black hole

UWC Prof Romeel Dave, SARChI Chair in Cosmology with Multi-Wavelength Data, who leads a team developing plans for universe simulations that could explore the growth of large-scale structure from a theoretical perspective, agrees: “This is not obviously expected based on our current understanding of cosmology. It’s a bizarre finding.”
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New Theories on Stellar Winds – Pulsating Magnetically Driven Radiative Energy

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A new study of the mechanism that drives stellar winds from the upper atmosphere of a star has shed new light. Astronomers think there are three possibilities: radiative, in which the pressure of the light pushes out the grains, magnetically driven, in which the stellar magnetic field plays a role in powering the flow, and pulsation driven, in which a periodic build-up of radiative energy in the stellar interior is suddenly released.

A new study of the mechanism that drives stellar winds from the upper atmosphere of a star has shed new light. Astronomers think there are three possibilities: radiative, in which the pressure of the light pushes out the grains, magnetically driven, in which the stellar magnetic field plays a role in powering the flow, and pulsation driven, in which a periodic build-up of radiative energy in the stellar interior is suddenly released.

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The winds of stars more evolved than the Sun (like the so-called giant stars that are cooler and larger in diameter than the Sun) often contain dust particles which enrich the interstellar medium with heavy elements. These winds also contain small grains on whose surfaces chemical reactions produce complex molecules. The dust also absorbs radiation and obscures visible light. Understanding the mechanism(s) that produce these winds in evolved stars is important both for modeling the wind and the character of the stellar environment, and for predicting the future evolution of the star.

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Nearly all stars have winds. The Sun’s wind, which originates from its hot outer layer (corona), contains charged particles emitted at a rate equivalent to about one-millionth of the moon’s mass each year. Some of these particles bombard the Earth, producing radio static, auroral glows, and (in extreme cases) disrupted global communications.

NASA'S Chandra Finds Fastest Wind From Stellar-Mass Black Hole
NASA’S Chandra Finds Fastest Wind From Stellar-Mass Black Hole

Over the years scientific opinion has varied among these alternatives, depending on each particular stellar example. Harvard–Smithsonian Center for Astrophysics Chris Johnson, and his colleagues explored the problem of wind-driving mechanism in giant stars by measuring the motion of the outflowing CO (carbon monoxide) gas around one the nearest and brightest giant stars, EU Del, which is only about 380 light-years away and shines with 1600 solar-luminosities.

new_equation 2012_m

New Equation:
Increase Charged Particles and Decreased Magnetic Field → Increase Outer Core Convection → Increase of Mantle Plumes → Increase in Earthquake and Volcanoes → Cools Mantle and Outer Core → Return of Outer Core Convection (Mitch Battros – July 2012)

Its radius, if the star were placed at the position of the Sun, would extend past the orbit of Venus. EU Del is known to be a semi-regular variable star which pulses every sixty days or so (but with some secondary periods as well), and infrared observations suggest it has a circumstellar dust shell.

The astronomers used the submillimeter APEX (Atacama Pathfinder Experiment) telescope to look at warm CO gas in the wind, making EU Del one of the first stars of its class to be studied with this relatively new tool. The team reports finding the CO moving at about ten kilometers per second (twenty two thousand miles per hour) with a total mass-loss rate equal to about the mass of the Moon each year.