Spiral Galaxy NGC 7742

Spiral Galaxy NGC 7742



Thismight resemble a fried egg you've ha for breakfast, but it'sactually much larger.In fact, ringed by blue-tinte star forming regions andfaintly visible spiral arms,the yolk-yellow center of this face-on spiral galaxy, NGC 7742, is about 3,000 light-years across.About 72 million light-years away in the constellation Pegasus,NGC 7742 is known to b a Seyfert galaxy - a type o active spiral galaxy with a center ornucleus which is very brigh atvisible wavelengths.Across the spectrum,the tremendous brightness of Seyferts can change over periods ofjust days to months and galaxies like NGC 7742 aresuspected of harborin massiveblack holes at their cores.This beautiful color picture is courtesy of the Hubble Space Telescope Heritage Project.

Dumbbell Nebula Halo

Dumbbell Nebula Halo



In 1764, French astronome CharlesMessier sighted this gorgeouscosmic cloud whic hedescribed as an oval nebula without stars Cataloged as M27,it is now popularly known as th DumbbellNebula, not for its substandard academic performance butfor the elongated shape, like a bar with weights on each end, whic firstcaught Messier's eye. This deep image of the bright planetarynebula does reveal the Dumbell's central star though, andan array of foreground and background starstoward the sly constellatio Vulpecula.The picture i a compositethat includes 8 hours ofexposure through a filter designed to record only the lightof hydrogen atoms, tracing the intricate details ofthe nebula's faint outer halowhich spans light-years.Thought to be an example of th fate awaiting our ownSun 5 billion years hence, the Dumbbell Nebula isabout 1,200 light-years away.

Mars at the Moon's Edge

Mars at the Moon's Edge



What was that bright "star" near the Moon last week Mars of course, asthe Red Planet wandered near thewaning gibbous Moon early last Thursday morning, passingbehind the lunar orb when viewedfrom some locationsin South and Central America, the Caribbean, and Florida.The Clay Center Observatory expedition to Bonita Springs, Floridaproduced this evocative picture o Mars grazing the Moon's dark edge bydigitally stacking and processing a series of telescopicimages of the event. With the cratered Moon in the foreground,the bright planet Mars seems alarminglyclose, its global scale featuresand white south polar cap easily visible.Already impressive, the apparent size of the martian diskwill continue to grow in the coming weeks,until, on August 27, Mars reaches itsclosest approach to planet Earth in over 50,000 years.

GRACE Maps the Gravity of Earth

GRACE Maps the Gravity of Earth



Why do some places on Earth have higher gravity than others? Sometimes the reason is unknown. To help better understand the Earth's surface, slight distance changes between a pair of identically orbiting satellites named GRACE have been used to create the best ever map of Earth' gravitational field. High points on thismap, also colored red, indicate areas where gravity is slightly stronger than usual, while in blue areas gravity isslightly weaker.Many bumps and valleys on the map can be attributed to surface features, such as the NorthMid-Atlantic Ridge and the Himalayan Mountains, but others cannot, and so might relate to unusually high or low sub-surface densities. Mapslike this also help calibrate changes in the Earth's surface including variable ocean currents and the melting of glaciers.

A Tornado on Planet Earth

A Tornado on Planet Earth



Large storms on Earth can spawn unusual, small, violent clouds known as tornadoes. Tornado clouds swirl as fast as hundreds of kilometers per hour and, when they touch down, can destroy nearly everything in their long, narrow path. Many tornadoes last only a few minutes, but the largest and most dangerous can endure for hours. The above image, although somewhat unfocussed, appears to show a dropping funnel cloud interacting with a light pole. If so, and this interpretation is controversial, this photograph would be one of the few indicating a clear distance to the funnel cloud. The pictured tornado occurred in 1981 in Dallas, Texas, USA. Tornadoes occur all over Earth but are most commonly found over parts of central North America during spring. Much about tornadoes remains under study, including predicting when they will occur.

IC 4603 Reflection Nebula in Ophiuchius

IC 4603 Reflection Nebula in Ophiuchius



Why does this starfield photograph resemble an impressionistic painting? The effect is created not by digital trickery but by large amounts of interstellar dust. Dust, minute globs rich in carbon and similar in size to cigarette smoke, frequently starts in the outer atmospheres of large, cool, young stars.The dust is dispersed as the star dies and grows as things stick to it in the interstellar medium. Dense dust clouds are opaque to visible light and can completely hide background stars. For less dense clouds, the capacity of dust to preferentially reflect blue starlight becomes important, effectively blooming the stars blue light out and marking the surrounding dust. Nebular gas emissions, typically brightest in red light, can combine to form areas seemingly created on an artist's canvas. Photographed above is roughly one square degree of the nebula IC 4603 near the bright star Antares toward the constellation of Ophiuchus.

An Ion Drive for Deep Space 1

An Ion Drive for Deep Space 1



Space travel entered the age of the ion drive in 1998 with the launch of Deep Space 1, a NASA mission designed primarily to test new technologies. Although the ion drive on Deep Space 1 provided acceleration much smaller than we feel toward Earth, it gradually gave the spacecraft the speed it needed to travel across our Solar System. The propulsion drive worked by ionizing xenon atoms with power provided by large panels that collect sunlight. As these ions were expelled by a strong electric field out the back, the spacecraft slowly gained speed. Pictured above, hot blue ions emerge from a prototype drive that was successfully tested at JPL in 1997. Deep Space 1 successfully zoomed past asteroid 9969 Braille in July 1999 and then Comet Borrelly in September 2001, then obtaining the most detailed photograph ever taken of a comet nucleus.The spacecraft was retired in December 2001