How do stars form? Images of the star forming region W5 like those in the infrared by NASA’s Wide Field Infrared Survey Explorer (WISE) satellite provide clear clues with indications that massive stars near the center of empty cavities are older than stars near the edges. A likely reason for this is that the older stars in the center are actually triggering the formation of the younger edge stars. The triggered star formation occurs when hot outflowing gas compresses cooler gas into knots dense enough to gravitationally contract into stars. In the featured scientifically-colored infrared image, spectacular pillars, left slowly evaporating from the hot outflowing gas, provide further visual clues. W5 is also known as IC 1848, and together with IC 1805 form a complex region of star formation popularly dubbed the Heart and Soul Nebulas. The above image highlights a part of W5 spanning about 2,000 light years that is rich in star forming pillars. W5 lies about 6,500 light years away toward the constellation of Cassiopeia.

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Why do some places on Earth have higher gravity than others? Sometimes the reason is unknown. To help better understand the Earth’s surface, sensitive measurements by the orbiting satellites GRACE and CHAMP were used to create a map of Earth’s gravitational field. Since a center for studying this data is in Potsdam, Germany, and since the result makes the Earth look somewhat like a potato, the resulting geoid has been referred to as the Potsdam Gravity Potato. High areas on this map, colored red, indicate areas where gravity is slightly stronger than usual, while in blue areas gravity is slightly weaker. Many bumps and valleys on the Potsdam Gravity Potato can be attributed to surface features, such as the North Mid-Atlantic Ridge and the Himalayan Mountains, but others cannot, and so might relate to unusually high or low sub-surface densities. Maps like this also help calibrate changes in the Earth’s surface including variable ocean currents and the melting of glaciers. The above map was made in 2005, but more recent and more sensitive gravity maps of Earth was produced in 2011.

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Where did all the stars go? What used to be considered a hole in the sky is now known to astronomers as a dark molecular cloud. Here, a high concentration of dust and molecular gas absorb practically all the visible light emitted from background stars. The eerily dark surroundings help make the interiors of molecular clouds some of the coldest and most isolated places in the universe. One of the most notable of these dark absorption nebulae is a cloud toward the constellation Ophiuchus known as Barnard 68, pictured above. That no stars are visible in the center indicates that Barnard 68 is relatively nearby, with measurements placing it about 500 light-years away and half a light-year across. It is not known exactly how molecular clouds like Barnard 68 form, but it is known that these clouds are themselves likely places for new stars to form. In fact, Barnard 68 itself has been found likely to collapse and form a new star system. It is possible to look right through the cloud in infrared light.

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This remarkable synthetic color composite image was assembled from archives of visible light and infrared astronomy image data. The field of view spans the Andromeda Galaxy (M31), a massive spiral a mere 2.5 million light-years away. In fact, with over twice the diameter of our own Milky Way, Andromeda is the largest nearby galaxy. Andromeda’s population of bright young blue stars lie along its sweeping spiral arms, with the telltale reddish glow of star forming regions traced in space- and ground-based visible light data. But infrared data from the Spitzer Space Telescope, also blended directly into the detailed composite’s red and green color channels, highlight the the lumpy dust lanes warmed by the young stars as they wind even closer to the galaxy’s core. Otherwise invisible at optical wavelengths, the warm dust takes on orange hues. Two smaller companion galaxies, M110 (below) and M32 (above) are also included in the frame.

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This extreme close-up, a mosaic from the Mars Hand Lens Imager (MAHLI) on the Curiosity rover, spans a breathtaking 5 centimeters. It captures what appear to be elongated crystal shapes formed by the precipitation of minerals dissolved in water, a likely result of the evaporation of ancient lake or river from the Martian surface. Brushed by a dust removal tool and illuminated by white LEDs, the target rock named Mojave was found on the Pink Cliffs outcrop of the Pahrump Hills at the base of Mount Sharp. The MAHLI images were acquired on Curiosity’s sol 809, known on planet Earth as November 15, 2014. Of course, the inset 1909 Lincoln Cent image is provided for a comparison scale. Covered with Mars dust itself, the penny is a MAHLI calibration target attached to the rover.

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In this night scene from the early hours of November 14, light from a last quarter Moon illuminates clouds above the mountaintop domes of Kitt Peak National Observatory near Tucson, Arizona. Bright Jupiter is just left of the overexposed lunar disk with a streak of camera lens flare immediately to the right, but that’s no fireball meteor exploding near the center of the picture. Instead, from the roadside perspective a stunningly bright moondog or paraselene stands directly over Kitt Peaks’s WIYN telescope. Analogous to a sundog or parhelion, a paraselene is produced by moonlight refracted through thin, hexagonal, plate-shaped ice crystals in high cirrus clouds. As determined by the crystal geometry, paraselenae (plural) are seen at an angle of 22 degrees or more from the Moon. Compared to the bright lunar disk they are more often faint and easier to spot when the Moon is low. About 10 minutes after the photograph even this bright moondog had faded from the night.

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Now known to be a globular star cluster at the tender age of 10 billion years, M71 is a mere 13,000 light-years away within the narrow boundaries of the faint constellation Sagitta. Close to the plane of the Milky Way galaxy in planet Earth’s sky, its 10,000 or so member stars are gathered into a region about 27 light-years across near the center of this color composite view. In fact, the line-of-sight to M71 passes along the galactic plane through much intervening diffuse interstellar dust. The dust dims starlight and scatters blue light more efficiently, masking the brightness of M71’s stars and shifting true star colors toward the red. How much are the star colors shifted? Slide your cursor over the image (or follow this link) to use an estimate of the dust reddening or galactic extinction to correct the star colors in M71. Corrections to the brightness and colors of M71 member stars are needed to measure the cluster’s distance and age using a Color-Magnitude diagram.

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What lights up the Flame Nebula? Fifteen hundred light years away towards the constellation of Orion lies a nebula which, from its glow and dark dust lanes, appears, on the left, like a billowing fire. But fire, the rapid acquisition of oxygen, is not what makes this Flame glow. Rather the bright star Alnitak, the easternmost star in the Belt of Orion visible just to the right of the nebula, shines energetic light into the Flame that knocks electrons away from the great clouds of hydrogen gas that reside there. Much of the glow results when the electrons and ionized hydrogen recombine. The above false-color picture of the Flame Nebula (NGC 2024) was taken is a composite of both visible and infrared light, the later energy band being where a young star cluster becomes visible. The Flame Nebula is part of the Orion Molecular Cloud Complex, a star-forming region that includes the famous Horsehead Nebula.

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Northern Lights, or aurora borealis, haunted skies over the island of Kvaløya, near Tromsø Norway on 2009 December 13. This 30 second long exposure records their shimmering glow gently lighting the wintery coastal scene. A study in contrasts, it also captures the sudden flash of a fireball meteor from the excellent Geminid meteor shower in 2009 December. Streaking past familiar stars in the handle of the Big Dipper, the trail points back toward the constellation Gemini, off the top of the view. Both aurora and meteors occur in Earth’s upper atmosphere at altitudes of 100 kilometers or so, but aurora caused by energetic charged particles from the magnetosphere, while meteors are trails of cosmic dust. Toward the end of this week the 2014 Geminids meteor shower will peak, although they will compete with the din of last quarter moonlight.

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Headed for two orbits of planet Earth and a splashdown in the Pacific, Orion blazed into the early morning sky on Friday at 7:05am ET. The spacecraft was launched atop a United Launch Aliance Delta IV Heavy rocket from Cape Canaveral Air Force Station in Florida. Its first voyage into space on an uncrewed flight test, the Orion traveled some 3,600 miles from Earth, about 15 times higher than the orbital altitude of the International Space Station. In fact, Orion traveled farther into space than any spacecraft designed for astronauts since the Apollo missions to the Moon. The Orion crew module reached speeds of 20,000 miles per hour and temperatures approaching 4,000 degrees Fahrenheit as it re-entered Earth’s atmosphere about 4.5 hours after launch.

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