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galactic-centre: NGC 5477 - Dwarf Galaxy Distance: 20 million light years Credit: ESA/Hubble & NASA
viddyspace: (via APOD: 2010 June 5 - Thor’s Helmet)  Credit & Copyright: Star Shadows Remote Observatory and PROMPT/UNC (Steve Mazlin, Jack Harvey, Rick Gilbert, and Daniel Verschatse)
looking-at-the-universe: Omega Centauri Cluster
iliveinaspiralgalaxy: Horsehead Nebula by David Plesko and Warren Keller by Horsehead Heritage on Flickr.
electricspacekoolaid: Star-Forming Region Captured By Danish Telescope Image: The Danish 1.54-metre telescope located at ESO’s La Silla Observatory in Chile has captured a striking image of NGC 6559, an object that showcases the anarchy that reigns when stars form inside an interstellar cloud. This region of sky includes glowing red clouds of mostly hydrogen gas, blue regions where starlight is being reflected from tiny particles of dust and also dark regions where the dust is thick and opaque. Credit: ESO The Danish 1.54-metre telescope located at ESO’s La Silla Observatory in Chile has released a new image of the star-forming region NGC 6559. Located relatively nearby, a mere 5000 light-years from Earth, NGC 6559 is found in the constellation ofSagittarius (The Archer). The nebula is only a few light years across, a stark contrast to its more well-known neighbor, the Lagoon Nebula, which stretches more than 100-light years in diameter. NGC 6559 is dominated by hydrogen gas, the basic building block of stars. When regions of the nebula are disturbed, the gas can begin to clump together. Gravity then takes over and begins drawing in more and morehydrogen. Eventually the temperature at the center of the forming object will approach 10 million kelvin, sufficient to drive nuclear fusion in the core. Through this process hydrogen nuclei will begin fusing into helium, establishing hydrostatic equilibrium as the outward radiation pressure balances the inward gravitational force. At this point, a star is formed. As the stars inject energy into the surrounding nebula, the gas becomes ionized as the electrons are stripped from their atoms. The consequence is the release of energy, which appears as red light, giving NGC 6559 its signature glow. This type of system defines what we know as an emission nebula, since the gas itself is radiating energy into outer space. In contrast, a nearby region of the nebula, seen in the right hand portion of the above image, is dominated more by particles of dust, made of heavier elements, such as carbon, iron or silicon. Here, the light from the stars interacts with the dust particles through a process known as Rayleigh scattering, accordingtoan ESO release.
spaceplasma: Supernova Shock Wave Paints Cosmic Portrait Remnants from a star that exploded thousands of years ago created a celestial abstract portrait, as captured in this NASA Hubble Space Telescope image of the Pencil Nebula. Officially known as NGC 2736, the Pencil Nebula is part of the huge Vela supernova remnant, located in the southern constellation Vela. Discovered by Sir John Herschel in the 1840s, the nebula’s linear appearance triggered its popular name. The nebula’s shape suggests that it is part of the supernova shock wave that recently encountered a region of dense gas. It is this interaction that causes the nebula to glow, appearing like a rippled sheet. In this snapshot, astronomers are looking along the edge of the undulating sheet of gas. This view shows large, wispy filamentary structures, smaller bright knots of gas, and patches of diffuse gas. The Hubble Heritage Team used the Advanced Camera for Surveys in October 2002 to observe the nebula. The region of the Pencil Nebula captured in this image is about three fourths of a light-year across. The Vela supernova remnant is 114 light-years (35 parsecs) across. The remnant is about 815 light-years (250 parsecs) away from our solar system. The nebula’s luminous appearance comes from dense gas regions that have been struck by the supernova shock wave. As the shock wave travels through space [from right to left in the image], it rams into interstellar material. Initially the gas is heated to millions of degrees, but then subsequently cools down, emitting the optical light visible in the image. The colors of the various regions in the nebula yield clues about this cooling process. Some regions are still so hot that the emission is dominated by ionized oxygen atoms, which glow blue in the picture. Other regions have cooled more and are seen emitting red in the image (cooler hydrogen atoms). In this situation, color shows the temperature of the gas. The nebula is visible in this image because it is glowing. The supernova explosion left a spinning pulsar at the core of the Vela region. Based on the rate at which the pulsar is slowing down, astronomers estimate that the explosion may have occurred about 11,000 years ago. Although no historical records of the blast exist, the Vela supernova would have been 250 times brighter than Venus and would have been easily visible to southern observers in broad daylight. The age of the blast, if correct, would imply that the initial explosion pushed material from the star at nearly 22 million miles per hour. As the Vela supernova remnant expands, the speed of its moving filaments, such as the Pencil Nebula, decreases. The Pencil Nebula, for example, is moving at roughly 400,000 miles per hour. Credit: NASA and The Hubble Heritage Team (STScI/AURA)
n-a-s-a: An Extraordinary Celestial Spiral  Credit:ESA/NASA & R. Sahai 
n-a-s-a: Flocculent Spiral NGC 2841   Credit:NASA, ESA and the Hubble Heritage 
galactic-centre: “White dwarf in star cluster in the Large Magellanic cloud” Credit: Rebecca Elson and Richard Sword, Cambridge UK, and NASA/ESA (Original WFPC2image courtesy J. Westphal, Caltech)
gemmacorrell: Sky Cats (my monthly cartoon for Emirates Airlines Open Skies In-Flight magazine)