Cygnus Loop Supernova Blast Wave
This is an image of a small portion of the Cygnus Loop supernova remnant, which marks the edge of a bubble-like, expanding blast wave from a colossal stellar explosion, occurring about 15, 000 years ago. The HST image shows the structure behind the shock waves, allowing astronomers for the first time to directly compare the actual structure of the shock with theoretical model calculations. Besides supernova remnants, these shock models are important in understanding a wide range of astrophysical phenomena, from winds in newly-formed stars to cataclysmic stellar outbursts. The supernova blast is slamming into tenuous clouds of insterstellar gas. This collision heats and compresses the gas, causing it to glow. The shock thus acts as a searchlight revealing the structure of the interstellar medium. The detailed HST image shows the blast wave overrunning dense clumps of gas, which despite HST's high resolution, cannot be resolved. This means that the clumps of gas must be small enough to fit inside our solar system, making them relatively small structures by interstellar standards. A bluish ribbon of light stretching left to right across the picture might be a knot of gas ejected by the supernova; this interstellar "bullet" traveling over three million miles per hour (5 million kilometres) is just catching up with the shock front, which has slowed down by ploughing into interstellar material. The Cygnus Loop appears as a faint ring of glowing gases about three degrees across (six times the diameter of the full Moon), located in the northern constellation, Cygnus the Swan. The supernova remnant is within the plane of our Milky Way galaxy and is 2, 600 light-years away. The photo is a combination of separate images taken in three colors, oxygen atoms (blue) emit light at temperatures of 30, 000 to 60, 000 degrees Celsius (50, 000 to 100, 000 degrees Farenheit). Hydrogen atoms (green) arise throughout the region of shocked gas. Sulfur atoms (red) form when the gas cools to around 10, 000 degrees Celsius (18, 000 degrees Farenheit).
Artist concept of a galaxy inside of a glowing hydrogen blob
Artist concept of a galaxy inside of a glowing hydrogen blob. The artist's representation shows what one of the galaxies inside a blob might look like if viewed at a relatively close distance. A two-sided outflow powered by the supermassive black hole buried inside the middle of the galaxy is shown in bright yellow, above and below the spiral arms of the galaxy. This outflow illuminates and heats gas surrounding the galaxy. Radiation from regions close to the black hole will also play a significant role in lighting up and heating the blob. Stars are forming at a rapid rate in this galaxy, and young stars are being destroyed in supernova explosions. The three bright stars above the central bulge of the galaxy are examples of such supernovas.
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Giant galactic blobs
This artist's concept illustrates one possible answer to the puzzle of the giant galactic blobs. These blobs (red), first identified about five years ago, are mammoth clouds of intensely glowing material that surround distant galaxies (white). Astronomers using visible-light telescopes can see the glow of the blobs, but they didn't know what provides the energy to light them up. The Spitzer Space Telescope set its infrared eyes on one well-known blob located 11 billion light-years away, and discovered three tremendously bright galaxies, each shining with the light of more than one trillion Suns, headed toward each other.
Spitzer also observed three other blobs in the same galactic neighborhood and found equally bright galaxies within them. One of these blobs is also known to contain galaxies merging together. The findings suggest that galactic mergers might be the mysterious source of blobs.
If so, then one explanation for how mergers produce such large clouds of material is that they trigger intense bursts of star formation. This star formation would lead to exploding massive stars, or supernovae, which would then shoot gases outward in a phenomenon known as superwinds. Blobs produced in this fashion are illustrated in this artist's concept.
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