Sculpted by stellar winds and radiation, the star factory known as Messier 17 lies some 5,500 light-years away in the nebula-rich constellation Sagittarius. At that distance, this 1/3 degree wide field of view spans over 30 light-years. The sharp composite, color image, highlights faint details of the region’s gas and dust clouds against a backdrop of central Milky Way stars. Stellar winds and energetic light from hot, massive stars formed from M17 stock of cosmic gas and dust have slowly carved away at the remaining interstellar material producing the cavernous appearance and undulating shapes. M17 is also known as the Omega Nebula or the Swan Nebula.
The north pole of Saturn’s moon Enceladus is unexpectedly fascinating and complex. Previous to the latest flyby of the robotic Cassini spacecraft, the northern region was known mostly for its unusually high abundance of craters. Last week’s flyby, however, returned images of unprecedented detail, including the featured image showing the expected craters coupled with an unexpected and circuitous pattern of picturesque cracks and fractures. Broken terrain has been recorded at lower latitudes, with deep canyons dubbed Tiger Stripes near Enceladus’ South Pole. The fractures may further indicate global interplay between the surface and potential seas underneath, seas that future missions might target for signs of life.
Have you ever seen the Southern Cross? This famous constellation is best seen from Earth’s Southern Hemisphere. Captured from Rio de Janeiro, Brazil, the four bright stars that mark the Southern Cross are visible just above the horizon in the featured image. On the left of this constellation, also known as The Crux, is the orange star Gamma Crucis. The band of stars, dust, and gas rising through the middle of the image mosaic is part our Milky Way Galaxy. Just to the right of the Southern Cross is the dark Coal Sack Nebula, and the bright nebula at the top of the image is the Carina Nebula. The Southern Cross is such a famous constellation that it is depicted on the national flags of Australia and New Zealand.
Why is this cloud so bubbly? Normally, cloud bottoms are flat. The flatness is caused by moist warm air that rises and cools and so condenses into water droplets at a specific temperature, which usually corresponds to a very specific height. As water droplets grow, an opaque cloud forms. Under some conditions, however, cloud pockets can develop that contain large droplets of water or ice that fall into clear air as they evaporate. Such pockets may occur in turbulent air near a thunderstorm. Resulting mammatus clouds can appear especially dramatic if sunlit from the side. These mammatus clouds were photographed over Regina, Saskatchewan, Canada during the summer of 2012.
One of the brightest galaxies in planet Earth’s sky is similar in size to our Milky Way Galaxy: big, beautiful M81. The grand spiral galaxy can be found toward the northern constellation of the Great Bear (Ursa Major). This superbly detailed image reveals M81’s bright yellow nucleus, blue spiral arms, tell tale pinkish star forming regions, and sweeping cosmic dust lanes with a scale comparable to the Milky Way. Hinting at a disorderly past, a remarkable dust lane actually runs straight through the disk, to the left of the galactic center, contrary to M81’s other prominent spiral features. The errant dust lane may be the lingering result of a close encounter between between M81 and its smaller companion galaxy, M82. Scrutiny of variable stars in M81 has yielded one of the best determined distances for an external galaxy — 11.8 million light-years. M81’s dwarf companion galaxy Holmberg IX can be seen just above the large spiral.
Stars come out as evening twilight fades in this serene skyscape following the Persian proverb “Night hides the world, but reveals a universe.” The scene finds the Sun setting over northern Kenya and the night will soon hide the shores of Lake Turkana, home to many Nile crocodiles. The region is also known for its abundance of hominid fossils. On that past November night, a brilliant Venus, then the world’s evening star, dominates the starry skies above. But also revealed are faint stars, cosmic dust clouds, and glowing nebulae along the graceful arc of our own Milky Way galaxy.
A star cluster around 2 million years young surrounded by natal clouds of dust and glowing gas, M16 is also known as The Eagle Nebula. This beautifully detailed image of the region includes cosmic sculptures made famous in Hubble Space Telescope close-ups of the starforming complex. Described as elephant trunks or Pillars of Creation, dense, dusty columns rising near the center are light-years in length but are gravitationally contracting to form stars. Energetic radiation from the cluster stars erodes material near the tips, eventually exposing the embedded new stars. Extending from the ridge of bright emission left of center is another dusty starforming column known as the Fairy of Eagle Nebula. M16 and the Eagle Nebula lie about 7,000 light-years away, an easy target for binoculars or small telescopes in a nebula rich part of the sky toward the split constellation Serpens Cauda (the tail of the snake).