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RE: Local Interstellar Cloud
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Eleven Spacecraft Show Interstellar Wind Changed Direction Over 40 Years

Like the wind adjusting course in the middle of a storm, scientists have discovered that the particles streaming into the solar system from interstellar space have most likely changed direction over the last 40 years. Such information can help us map out our place within the galaxy surrounding us, and help us understand our place in space.
The results, based on data spanning four decades from 11 different spacecraft, were published in Science on Sept. 5, 2013.

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Local Interstellar Neutral Hydrogen
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Title: Local Interstellar Neutral Hydrogen sampled in-situ by IBEX
Authors: Lukas Saul, Peter Wurz, Diego Rodriguez, Jürgen Scheer, Eberhard Möbius, Nathan Schwadron, Harald Kucharek, Trevor Leonard, Maciej Bzowski, Stephen Fuselier, Geoff Crew, Dave McComas

Hydrogen gas is the dominant component of the local interstellar medium. However, due to ionisation and interaction with the heliosphere, direct sampling of neutral hydrogen in the inner heliosphere is more difficult than sampling the local interstellar neutral helium, which penetrates deep into the heliosphere. In this paper we report on the first detailed analysis of the direct sampling of neutral hydrogen from the local interstellar medium. We confirm that the arrival direction of hydrogen is offset from that of the local Helium component. We further report the discovery of a variation of the penetrating Hydrogen over the first two years of IBEX observations. Observations are consistent with hydrogen experiencing an effective ratio of outward solar radiation pressure to inward gravitational force greater than unity ({\mu}>1); the temporal change observed in the local interstellar hydrogen flux can be explained with solar variability.

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Interstellar Medium
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Imaging the Interstellar Medium

With an average density of less than 1 proton per cubic centimetre, the matter that exists between stars might seem unimportant. But in actual fact, our galaxy the Milky Way and the stars, planets and people it contains wouldn't be here without it.
Comprised mostly of gas (~99%) and dust (< 1%), the Interstellar Medium (ISM) is described by astronomers and astrophysicists as 'clumpy', meaning the material has a tendency to coalesce through gravitational forces and collisions.
Throughout the ISM, massive stars, planetary nebulae and supernova explosions drive strong winds and shock waves through the medium. These mechanisms deposit energy, sustain the highly inhomogeneous state of the ISM and enrich it with heavy elements from which the next generation of stars and planets will eventually form.

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New evidence for supernova-driven galactic fountains in the Milky Way

Observing the X-ray-bright gas in the halo of the Milky Way, ESA's XMM-Newton has gathered new data which favour a process involving fountains of hot gas in our Galaxy. Such a scenario, with the gas flowing from the galactic disc into the halo where it then condenses into cooler clouds and subsequently falls back to the disc, confirms the importance of supernova explosions in forging the evolution of the interstellar medium and of the entire Galaxy.
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Interstellar gas
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New 3D gas density maps of Na I and Ca II interstellar absorption within 300 pc

Astronomy & Astrophysics is publishing new 3D maps of the interstellar gas in the local area around our Sun. A French-American team of astronomers presents new absorption measurements towards more than 1800 stars. They were able to characterise the properties of the interstellar gas within each sight line.
This week, Astronomy & Astrophysics publishes new 3D maps of the interstellar gas situated in an area 300 parsecs around the Sun. A French-American team of astronomers presents new measurements of the absorption by the interstellar gas in the Sun's local area. Knowledge of the interstellar medium properties, including the spatial distribution, dynamics, and the chemical and physical characteristics, allow astronomers to better understand the interplay between the evolution of stars and their exchange of matter with the ambient interstellar medium. The local area around our Sun has been studied with many surveys at various wavelengths, but the whole picture is still far from being either complete or fully understood.

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Image3-6.jpg
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Credit B. Y. Welsh, R. Lallement, J.-L. Vergely, and S. Raimond.

Map of partially ionised interstellar gas within 300 parsecs around the Sun, as viewed in the Galactic plane. Triangles represent the sight-line positions of the stars used to produce the map.

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Local Interstellar Cloud
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The Local Interstellar Cloud, casually called the Local Fluff, is the interstellar cloud (roughly 30 light years across) through which the Solar System is currently moving. The Solar System entered the Local Interstellar Cloud at some time between 44,000 and 150,000 years ago and is expected to remain within it for another 10,000 to 20,000 years.
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Image1-4.jpg
An artist's concept of the Local Interstellar Cloud, also known as the "Local Fluff."
Credit: Linda Huff (American Scientist) and Priscilla Frisch (University of Chicago)


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