1999 Leonid Fireball Credit & Copyright: Arne Danielsen - Explanation: Most Leonid meteoroids, the bits of comet debris which produce the annual Leonid meteor shower, range from a mere millimeter to a centimeter in diameter. Yet these cosmic grains of sand and gravel can put on quite a spectacular show. How can something so small generate so much light? The answer is their astronomical speed, as these particles enter Earth's atmosphere at around 71 kilometers per second. In the high-speed collisions with air molecules, electrons are stripped from atoms as meteroid material is blasted away. When the electrons recombine with the atoms, light is emitted. This dramatic example of a brilliant 1999 Leonid meteor was photographed while tracking the stars in partly foggy skies on November 18, from a location near Dagali, Norway. The two bright reddish-orange stars visible are the familiar giant stars Betelgeuse (left) and Aldebaran. Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (USRA) NASA Technical Rep.: Jay Norris. LHEA at NASA/ GSFC & Michigan Tech. U.
Henize 70: A SuperBubble In The LMC (Small Version)Credit: FORS Team, 8.2-meter VLT, ESO Explanation: Massive stars -- upwards of tens of times the mass of the Sun - profoundly affect their galactic environment. Churning and mixing the clouds of gas and dust between the stars, they leave their mark on the compositions and locations of future generations of stars and star systems. Dramatic evidence of this is illustrated in our neighboring galaxy, the Large Magellanic Cloud (LMC), by the above ring shaped nebula, Henize 70 (also known as N70 and DEM301). It is actually a luminous "superbubble" of interstellar gas about 300 light-years in diameter, blown by winds from hot, massive stars and supernova explosions, its interior filled with tenuous hot expanding gas. These superbubbles offer astronomers a chance to explore this crucial connection between the lifecycles of stars and the evolution of galaxies. Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (USRA) NASA Technical Rep.: Jay Norris. LHEA at NASA/ GSFC & Michigan Tech. U.
Arcs and Jets in Herbig-Haro 34 (Large versionWOW!) Credit: FORS Team, 8.2-meter VLT, ESO - Explanation: Some features of HH-34 are understood -- some are not. At the core of Herbig-Haro 34 lies a seemingly typical young star. This star, though, somehow ejects energetic "bullets" of high-energy particles, appearing as red streaks toward the lower right of the this image. Astronomers speculate that a burst of these particles might rebound when gas from a disk surrounding the star momentarily collapses onto the star. Visible near the end of each light-year long jet is a glowing cap. HH-34 lies about 1500 light-years away in the Orion Nebula star-forming region. The cause of the large arc of gas on the upper left known as the waterfall remains unexplained. Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (USRA) NASA Technical Rep.: Jay Norris. Specific rights apply. A service of: LHEA at NASA/ GSFC & Michigan Tech. U.
Beneath Venus' Clouds Credit: Magellan Spacecraft, Arecibo Radio Telescope, NASA - Explanation: If the thick clouds covering Venus were removed, how would the surface appear? Using an imaging radar technique, the Magellan spacecraft was able to lift the veil from the Face of Venus and produce this spectacular high resolution image of the planet's surface. Red, in this false-color map, represents mountains, while blue represents valleys. This 3-kilometer resolution map is a composite of Magellan images compiled between 1990 and 1994. Gaps were filled in by the Earth-based Arecibo Radio Telescope. The large yellow/red area in the north is Ishtar Terra featuring Maxwell Montes, the largest mountain on Venus. The large highland regions are analogous to continents on Earth. Scientists are particularly interested in exploring the geology of Venus because of its similarity to Earth. Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (USRA) NASA Technical Rep.: Jay Norris. Specific rights apply. A service of: LHEA at NASA/ GSFC & Michigan Tech. U.
Dawn of the Mineral World - Far away from the city, a world of red rock awakens from darkness. Sentinels of Stone - visions of Arches & Canyonlands, PhotoTripUSA.
Elliptical Galaxy NGC 4881 in Coma Credit: W. A. Baum (U. Washington), WFPC2, HST, NASA - Explanation: Elliptical galaxies are unlike spiral galaxies and hence unlike our own Milky Way Galaxy. The giant elliptical galaxy named NGC 4881 on the upper left lies at the edge of the giant Coma Cluster of Galaxies. Elliptical galaxies are ellipsoidal in shape, contain no spiral arms, contain little interstellar gas or dust, and are found mostly in rich clusters of galaxies. Elliptical galaxies appear typically yellow-red, as opposed to spirals which have spiral arms that appear quite blue. Much speculation continues on how each type of galaxy can form, on whether ellipticals can evolve from colliding spirals, or spirals can be created from colliding ellipticals, or both. Besides the spiral galaxy on the right, all other images in this picture are of galaxies that lie well behind the Coma Cluster. Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (USRA) NASA Technical Rep.: Jay Norris. Specific rights apply. A service of: LHEA at NASA/ GSFC & Michigan Tech. U.
Lower Proxy Falls, Cascade Mountains - One of many spectacular waterfalls in Oregon, these are just a short hike into the Three Sisters Wilderness in the Willamette National Forest. - Greg Vaughn, PhotoTripUSA
Mercury And The Sun Credit: Brian Handy (Montana State Univ.), TRACE Project - Explanation: Just days before the peak of the Leonid meteor shower, skywatchers were offered another astronomical treat as planet Mercury crossed the face of the Sun on November 15. Viewed from planet Earth, a transit of Mercury is not all that rare. The last occurred in 1993 and the next will happen in 2003. Enjoying a mercurial transit does require an appropriately filtered telescope, still the event can be dramatic as the diminutive well-done world drifts past the dominating solar disk. This slow loading gif animation is based on images recorded by the earth-orbiting TRACE satellite. The false-color TRACE images were made in ultraviolet light and tend to show the hot gas just above the Sun's visible surface. Mercury's disk is silhouetted against the seething plasma as it follows a trajectory near the edge of the Sun. Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (USRA) NASA Technical Rep.: Jay Norris. Specific rights apply. A service of: LHEA at NASA/ GSFC & Michigan Tech. U.
A Sirius Leonid Meteor Credit & Copyright: Wally Pacholka - Explanation: In the sky or on the web, have you seen this year's Leonid meteor shower? If you have, a bright meteor flashing through the night sky should be a familiar sight. Recorded last year during the 1998 apparition of the Leonids, this time-exposure of the sky around the constellation Canis Major (big dog) shows the trail of a spectacular fireball meteor. The meteor, by chance, seems to leap from the constellation's brightest star Sirius, near the top right. In the foreground is the beautiful desert scenery of Joshua Tree National Park. Reports of bright meteors from this year's Leonids are already wide-spread, with the 1999 shower predicted to peak around 0200 UTC on November 18. Awe inspiring as they are, the Leonids pose no danger to earthbound skywatchers. Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (USRA) NASA Technical Rep.: Jay Norris. Specific rights apply. A service of: LHEA at NASA/ GSFC & Michigan Tech. U.
A RADARSAT Map of Antarctica Credit: AMM, SVC, NASA, CSA Explanation: It's not easy to make a map of Antarctica. Earth's southern most continent is so cold and inhospitable that much of it remains unexplored. From space, though, it is possible to map this entire region by radar: by systematically noting how long it takes for radio waves to reflect off the terrain. The Canadian satellite RADARSAT has been orbiting the Earth for the past five years making radar maps, and has recently released the most detailed map of Antarctica ever created. Above is a computer-generated map of Antarctica at relatively low resolution. From the RADARSAT map, scientists have been able to better study this mysterious continent, including information about how ancient ice-shelves are crumbling. Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (USRA) NASA Technical Rep.: Jay Norris. LHEA at NASA/ GSFC & Michigan Tech. U.