Mapex

Archive for the ‘Earth’ Category

The sands of time are running out for the central star of this the Hourglass Nebula. With its nuclear fuel exhausted, this brief, spectacular, closing phase of a sun-like star’s life occurs as its outer layers are ejected and its core becomes a cooling, fading white dwarf. In 1995, astronomers used the Hubble Space Telescope to make a series of images of planetary nebulae, including the one above. Here, delicate rings of colorful glowing gas (nitrogen-red, hydrogen-green, and oxygen-blue) outline the tenuous walls of the ‘hourglass.’ The unprecedented sharpness of Hubble’s images revealed surprising details of the nebula ejection process and may resolve the outstanding mystery of the variety of complex shapes and symmetries of planetary nebulae. Image Credit: NASA, WFPC2, HST, R. Sahai and J. Trauger (JPL)

The Expedition 24 crew on the International Space Station photographed this image of polar mesospheric clouds illuminated by an orbital sunrise. Polar mesospheric, or noctilucent (“night shining”), clouds usually are seen at twilight, following the setting of the sun below the horizon and darkening of Earth’s surface. Occasionally the station’s orbital track becomes nearly parallel to Earth’s day/night terminator for a time, allowing the clouds to be visible to the crew at times other than the usual twilight because of the station’s altitude. This photograph shows polar mesospheric clouds illuminated by the rising, rather than setting, sun at center right. Low clouds on the horizon appear yellow and orange, while higher clouds and aerosols are illuminated a brilliant white. Polar mesospheric clouds appear as light blue ribbons extending across the top of the image. The station was located over the Greek island of Kos in the Aegean Sea (near the southwestern coastline of Turkey) when the image was taken at approximately midnight local time. The orbital complex was tracking northeastward, nearly parallel to the terminator, making it possible to observe an apparent “sunrise” located almost due north. A similar unusual alignment of the ISS orbit track, terminator position and seasonal position of Earth’s orbit around the sun allowed for this striking imagery of over the Southern Hemisphere. Image Credit: NASA

Backdropped by red hills, the Development Motor-2, or DM-2, ignites during an Aug. 31, 2010, static test that was conducted by ATK Aerospace Systems in Promontory, Utah. DM-2, the largest and most powerful solid rocket motor designed for flight, is managed by the Ares Projects Office at NASA’s Marshall Space Flight Center in Huntsville, Ala. Image Credit: NASA

The current Geostationary Operational Environmental Satellite GOES-13 captured this image of Hurricane Danielle heading for the north Atlantic (top center), Hurricane Earl with a visible eye hitting the Leeward Islands (left bottom) and a developing tropical depression 8 (lower right) at 1:45 p.m. EDT on Aug. 30. Image Credit: NASA/NOAA GOES Project

Spiral galaxy NGC 4921 presently is estimated to be 320 million light years distant. This image, taken by the Hubble Space Telescope, is being used to identify key stellar distance markers known as Cepheid variable stars. The magnificent spiral NGC 4921 has been informally dubbed anemic because of its low rate of star formation and low surface brightness. Visible in the image are, from the center, a bright nucleus, a bright central bar, a prominent ring of dark dust, blue clusters of recently formed stars, several smaller companion galaxies, unrelated galaxies in the far distant universe, and unrelated stars in our Milky Way Galaxy. Image Credit: NASA, ESA, K. Cook (LLNL)

Is this one galaxy or two? Astronomer Art Hoag first asked this question when he chanced upon this unusual extragalactic object. On the outside is a ring dominated by bright blue stars, while near the center lies a ball of much redder stars that are likely much older. Between the two is a gap that appears almost completely dark. How Hoag’s Object formed remains unknown, although similar objects have been identified and collectively labeled as a form of ring galaxy. Genesis hypotheses include a galaxy collision billions of years ago and the gravitational effect of a central bar that has since vanished. This image, taken by the Hubble Space Telescope in July 2001, reveals unprecedented details of Hoag’s Object and may yield a better understanding. Hoag’s Object spans about 100,000 light years and lies about 600 million light years away toward the constellation of the Snake (Serpens). Coincidentally, visible in the gap (at about one o’clock) is yet another ring galaxy that likely lies far in the distance. Image Credit: NASA, R. Lucas (STScI/AURA)

The picturesque, but snow-capped volcanoes, composing the Islands of the Four Mountains in Alaska’s Aleutian Island chain look suspiciously like an alien world in this August 2010 image from the ASTER camera aboard NASA’s orbiting Terra satellite. The islands contain restless Mt. Cleveland, an active volcano currently being watched to see if it emits an ash cloud that could affect air travel over parts of North America. A close look at Mt. Cleveland, seen near the image center, shows red vegetation (false color), a white snow-covered peak, a light plume of gas and ash, and dark lanes where ash and debris fell or flowed. Millions of volcanoes have likely been active over the turbulent history of the Earth’s surface, while about 20 volcanoes are erupting even today, at any given time. Image Credit: NASA

Cloudless skies allowed a clear view of dust and hydrogen sulfide plumes along the coast of Namibia in early August 2010. The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA?s Terra satellite captured this natural-color image on Aug. 10, 2010. Multiple dust plumes blow off the coast toward the ocean, most or all of them probably arising from streambeds. Unlike the reddish-tan sands comprising the dunes directly south of the Kuiseb River, the stream-channel sediments are lighter in color. Wind frequently pushes dust plumes seaward along the Namibian Coast. Easterly trade winds blow from the Indian Ocean over the African continent, losing much of their moisture as they go. The winds are hot and dry as they pass over Namibia?s coastal plain, where they are prone to stir fine sediments. Even with dust plumes overhead, the marked change in land cover is obvious along the Kuiseb River. South of the river, sand dunes predominate, but the vegetation along the Kuiseb River prevents the dunes from advancing northward. North of the river, the land surface consists primarily of gravel plains punctuated by rocky hills. Hydrogen sulfide appears as a swath of irridescent green running parallel to the coast north of Walvis Bay. A 2009 study linked the emissions in this region to ocean currents, biological activity in the water column, and carbon-rich organic sediments under the water column. The meeting of hydrogen sulfide gas and oxygen-rich surface waters causes pure sulfur to precipitate into the water. The sulfur?s yellow color makes the water appear green to the satellite sensor. Image Credit: NASA

James Cameron, director of the award-winning film “Avatar,” is featured in a series of new NASA public service announcements that describe the many contributions of NASA’s Earth science program to environmental awareness and exploration of our home planet.

This image from the Lunar Reconnaissance Orbiter shows the floor of the moon’s Anaxagoras crater, including a portion of the crater’s anorthositic central uplift. The boulders perched on ridges are eroding out of densely fractured bedrock. This image was taken by the Lunar Reconnaissance Orbiter Camera, or LROC, which consists of a pair of narrow-angle cameras and a single wide-angle camera. The mission is expected to return over 70 terabytes of image data. Image Credit: NASA/GSFC/Arizona State University