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TOPIC: Milky Way


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Teasing Apart Galaxy Collisions

A few billion years from now, our Milky Way galaxy will collide with the Andromeda galaxy. This will mark a moment of both destruction and creation. The galaxies will lose their separate identities as they merge into one. At the same time, cosmic clouds of gas and dust will smash together, triggering the birth of new stars.
To better understand collisions like these, astronomers have assembled an atlas of several galactic "train wrecks."

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Milky Way in mid-life crisis

The Milky Way is suffering from a mid-life crisis with most of it star formation behind it, new research from Swinburne University of Technology has shown.
Galaxies typically fall into one of two categories energetic blue galaxies that form new stars at an impressive rate, or lethargic red galaxies which are slowly dying.
In a paper accepted for publication in the Astrophysical Journal, Mr Simon Mutch, Dr Darren Croton and Dr Gregory Poole, have shown that our own Milky Way galaxy is neither of these. Rather it is a rare green valley galaxy that is half way between a youthful blue galaxy and a geriatric red one.
This is the first time that astronomers have compared both the colour and the star formation rate of the Milky Way to that of other galaxies in the Universe.

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Astronomers Spot a Newfound Piece of the Milky Way Galaxy

A new study identifies a previously unseen spiral arm of the Milky Way.
The newfound structure, some 70,000 light-years away, may be the continuation of a major, previously known spiral arm, part of which is visible much closer to Earth. Thomas Dame and Patrick Thaddeus of the HarvardSmithsonian Centre for Astrophysics announce the finding in a study that is set to appear in The Astrophysical Journal Letters.

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It may be our home but just how special is the Milk Way?

That's the question a team including Oxford University scientists have been looking to answer using simulations of our galaxy and our neighbours, the Magellanic Clouds.
Their findings, reported in a paper in The Astrophysical Journal could help in the hunt for dark matter. I asked one of the paper's authors, Phil Marshall of Oxford University's Department of Physics, about Universal assumptions, starless galaxies, and telltale gamma rays...

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milkyway1b.jpg
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Title: The mid-life crisis of the Milky Way and M31
Authors: Simon J. Mutch, Darren J. Croton, Gregory B. Poole (Swinburne University of Technology)

Upcoming next generation galactic surveys, such as GAIA and HERMES, will deliver unprecedented detail about the structure and make-up of our Galaxy, the Milky Way, and promise to radically improve our understanding of it. However, to benefit our broader knowledge of galaxy formation and evolution we first need to quantify how typical the Galaxy is with respect to other galaxies of its type. Through modelling and comparison with a large sample of galaxies drawn from the Sloan Digital Sky Survey and Galaxy Zoo, we provide tentative yet tantalizing evidence to show that both the Milky Way and nearby M31 are undergoing a critical transformation of their global properties. Both appear to possess attributes that are consistent with galaxies midway between the distinct blue and red bimodal colour populations. In extragalactic surveys, such 'green valley' galaxies are transition objects whose star formation typically will have all but extinguished in less than ~5 Gyrs. This finding reveals the possible future of our own galactic home, and opens a new window of opportunity to study such galactic transformations up close.

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Just Four Percent of Galaxies Have Neighbours Like the Milky Way

How unique is the Milky Way?
To find out, a group of researchers led by Stanford University astrophysicist Risa Wechsler compared the Milky Way to similar galaxies and found that just four percent are like the galaxy Earth calls home.
The research team compared the Milky Way to similar galaxies in terms of luminosity--a measure of how much light is emitted--and distance to other bright galaxies. They found galaxies that have two satellites that are as bright and close by as the Milky Way's two closest satellites, the Large and Small Magellanic Clouds, are rare.
Published in the May 20 issue of the Astrophysical Journal, the findings are based on analyses of data collected from the Sloan Digital Sky Survey (SDSS). The work is the first of three papers that study the properties of the Milky Way's two most massive satellites.

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The whole milky way

AllSkySurvey_Risinger1500.jpg

Majestic nebulae and stars of our Milky Way Galaxy stretch across this panoramic image of the entire night sky. At full resolution, the 5 gigapixel mosaic was stitched together from over 37,000 images, the result of a season following, year long effort and 60,000 travel miles in search of still dark skies in the American west and the western Cape of South Africa.

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Title: Observational Properties of the Metal-Poor Thick Disk of the Milky Way Galaxy and Insights into Its Origins
Authors: Gregory R. Ruchti, Jon P. Fulbright, Rosemary F. G. Wyse, Gerard F. Gilmore, Olivier Bienayme, Joss Bland-Hawthorn, Brad K. Gibson, Eva K. Grebel, Amina Helmi, Ulisse Munari, Julio F. Navarro, Quentin A. Parker, Warren Reid, George M. Seabroke, Arnaud Siebert, Alessandro Siviero, Matthias Steinmetz, Fred G. Watson, Mary Williams, Tomaz Zwitter

We have undertaken the study of the elemental abundances and kinematic properties of a metal-poor sample of candidate thick-disk stars selected from the RAVE spectroscopic survey of bright stars to differentiate among the present scenarios of the formation of the thick disk. In this paper, we report on a sample of 214 red giant branch, 31 red clump/horizontal branch, and 74 main-sequence/sub-giant branch metal-poor stars, which serves to augment our previous sample of only giant stars. We find that the thick disk [alpha/Fe] ratios are enhanced, and have little variation (<0.1 dex), in agreement with our previous study. The augmented sample further allows, for the first time, investigation of the gradients in the metal-poor thick disk. For stars with [Fe/H] < -1.2, the thick disk shows very small gradients, <0.03 0.02 dex/kpc, in alpha-enhancement, while we find a +0.01 0.04 dex/kpc radial gradient and a -0.09 0.05 dex/kpc vertical gradient in iron abundance. In addition, we show that the peak of the distribution of orbital eccentricities for our sample agrees better with models in which the stars that comprise the thick disk were formed primarily in the Galaxy, with direct accretion of stars contributing little. Our results thus disfavour direct accretion of stars from dwarf galaxies into the thick disk as a major contributor to the thick disk population, but cannot discriminate between alternative models for the thick disk, such as those that invoke high-redshift (gas-rich) mergers, heating of a pre-existing thin stellar disk by a minor merger, or efficient radial migration of stars.

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The Milkyway

Credit the Open University



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