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TOPIC: Milky Way


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Independent Researchers Solve Galactic Mystery.

The Milky Way is revealed as tightly wound "grand design" two-armed spiral - not a four-armed spiral as has previously been supposed.
Independent mathematician Charles Francis of Hastings, U.K., and amateur astronomer Erik Anderson of Ashland, Oregon, had been working on a quite different problem when the discovery was made.

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Every Star in the Sky, in One Picture
Axel Mellinger says that by the age of 12, he was in love with night.
Two years ago he went on a mission. He set out to create a massive photographic panorama of all the stars in the night sky. He is now finished -- having created an image with something like 25 million stars in it.

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So-called tramp stars, flung from their galaxies in past gravitational interactions, could exist in great numbers outside the Milky Way Galaxy

Columbia University graduate student Maureen Teyssier, along with Shara and Columbia astronomy professor Kathryn Johnston, unpack in the December 10 issue of Astrophysical Journal Letters some of the mechanisms by which stars can be ejected from their home galaxies to become tramps - wandering or even escaped stars. Wanderers roam deep into space but remain loosely bound to a galaxy, whereas escapees are thrown clear to travel through space on their own.
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A never-before-seen view of the turbulent heart of our Milky Way galaxy is being unveiled by NASA on Nov. 10. This event will commemorate the 400 years since Galileo first turned his telescope to the heavens in 1609. In celebration of this International Year of Astronomy, NASA is releasing images of the galactic center region as seen by its Great Observatories to more than 150 planetariums, museums, nature centres, libraries, and schools across the country.
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360°x45° panorama with constellations

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Virtual Reality All-Sky Panorama
(requires Java)

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All-Sky Milky Way Panorama 2.0
Between October 2007 and August 2009, a new digital all-sky mosaic image was assembled from more than 3000 individual CCD frames. Using an SBIG STL-11000 camera, 70 fields (each covering 40° × 27°) were imaged from dark-sky locations in South Africa, Texas and Michigan.

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WMAP haze
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Monster supernovae may explain galaxy's mystery haze
What is causing a mysterious "haze" of radiation at the centre of the Milky Way? It may be a load of monster supernovae kicking out radiation which is then amplified by magnetic stellar winds and turbulence near the galaxy's core.
In 2003, the Wilkinson Microwave Anisotropy Probe found a patch of particularly energetic microwave radiation in the centre of our galaxy - dubbed the "WMAP haze". It was proposed that this could be caused by collisions of a new type of dark-matter particle.

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Herschel views deep-space pearls on a cosmic string
G299_SPIRE_PACS_Crop_L.jpg
Reservoir of cold gas in the constellation of the Southern Cross
Credit ESA

Herschel has delivered spectacular vistas of cold gas clouds lying near the plane of the Milky Way, revealing intense, unexpected activity. The dark, cool region is dotted with stellar factories, like pearls on a cosmic string.
On 3 September, The Herschel Space Observatory aimed its telescope at a reservoir of cold gas in the constellation of the Southern Cross near the Galactic Plane. As the telescope scanned the sky, the spacecraft's Spectral and Photometric Imaging REceiver, SPIRE, and Photoconductor Array Camera and Spectrometer, PACS instruments snapped the pictures. The region is located about 60° from the Galactic Centre, thousands of light-years from Earth.
The five original infrared wavelengths have been colour-coded to allow scientists to differentiate extremely cold material (red) from the surrounding, slightly warmer stuff (blue).

The images reveal structure in cold material in our Galaxy, as we have never seen it before, and even before a detailed analysis, scientists have gleaned information on the quantity of the material, its mass, temperature, composition and whether it is collapsing to form new stars. 

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Milky Way Galaxy
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Title: Tidal Imprints Of A Dark Sub-Halo On The Outskirts Of The Milky Way
Authors: Sukanya Chakrabarti, Leo Blitz
(Version v2)

We present a new analysis of the observed perturbations of the HI disk of the Milky Way to infer the existence of a dark sub-halo that tidally interacted with the Milky Way disk. We examine tidal interactions between perturbing dark sub-halos and the gas disk of the Milky Way using high resolution Smoothed Particle Hydrodynamics (SPH) simulations. We compare our results to the observed HI map of the Milky Way to find that the Fourier amplitudes of the planar disturbances are best-fit by a perturbing dark sub-halo with a mass that is one-hundredth of the Milky Way with a pericentric distance of 5 kpc. This best-fit to the Fourier modes occurs about a dynamical time after pericentric approach, when the perturber is 90 kpc from the galactic center. Our analysis here represents a new method to indirectly characterise dark sub-halos from the tidal gravitational imprints they leave on the gaseous disks of galaxies. We also elucidate a fundamental property of parabolic orbits. We show that under certain conditions, one can break the degeneracy between the mass of the perturber and the pericentric distance in the evaluation of the tidal force -- to directly determine the mass of the dark perturber that produced the observed disturbances.

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