This Wonderful Universe ~ {ERG} - Page 16

LoneRanger · #**226** 08-15-2008, 03:17 PM

Facing NGC 6946

Quote:

Credit & Copyright: Volker Wendel (Spiegelteam)

Explanation: From our vantage point in the Milky Way Galaxy, we see NGC 6946 face-on. The big, beautiful spiral galaxy is located just 10 million light-years away, behind a veil of foreground dust and stars in the high and far-off constellation of Cepheus. From the core outward, the galaxy's colors change from the yellowish light of old stars in the center to young blue star clusters and reddish star forming regions along the loose, fragmented spiral arms. NGC 6946 is also bright in infrared light and rich in gas and dust, exhibiting a high star birth and death rate. In fact, since the early 20th century at least nine supernovae, the death explosions of massive stars, were discovered in NGC 6946. In this deep color composite image, a small barred structure is just visible at the galaxy's core. Nearly 40,000 light-years across, NGC 6946 is also known as the Fireworks Galaxy.

The Perseus Cluster of Galaxies

Quote:

Credit and Copyright: Digitized Sky Survey

Explanation: Here is one of the largest objects that anyone will ever see on the sky. Each of the fuzzy blobs in the above picture is a galaxy, together making up the Perseus Cluster, one of the closest clusters of galaxies. We view the cluster through the foreground of faint stars in our own Milky Way Galaxy. It takes light roughly 300 million years to get here from this region of the Universe, so we see this cluster as it existed before the age of the dinosaurs. Also known as Abell 426, the center of the Perseus Cluster is a prodigious source of X-ray radiation, and so helps astronomers explore how clusters formed and how gas and dark matter interact. The Perseus Cluster of Galaxies is part of the Pisces-Perseus supercluster of galaxies, which spans over 15 degrees and contains over 1000 galaxies.

LoneRanger · #**227** 08-16-2008, 03:54 PM

Perseid over Vancouver

Quote:

Credit & Copyright: Yuichi Takasaka (Blue Moon Promotions (Yuichi Takasaka) presents Canadian Aurora / TWAN)

Explanation: Colorful and bright, the city lights of Vancouver, Canada are reflected in the water in this portrait of the world at night. Recorded on August 12 during the Perseid Meteor Shower, the wide-angle view takes in a large swath along the photographer's eastern horizon. The picture is a composite of many consecutive 2 second exposures that, when added together, cover a total time of an hour and 33 minutes. During that time, stars trailed through the night sky above Vancouver, their steady motion along concentric arcs a reflection of planet Earth's rotation. The dotted trails of aircraft also cut across the scene. Of course, two of the frames captured the brief, brilliant flash of a Perseid fireball as it tracked across the top of the field of view. The large gap in the single meteor trail corresponds to the time gap between the consecutive frames.

Doomed Star Eta Carinae

Quote:

Credit: J. Morse (U. Colorado), K. Davidson (U. Minnesota) et al., WFPC2, HST, NASA

Explanation: Eta Carinae may be about to explode. But no one knows when - it may be next year, it may be one million years from now. Eta Carinae's mass - about 100 times greater than our Sun - makes it an excellent candidate for a full blown supernova. Historical records do show that about 150 years ago Eta Carinae underwent an unusual outburst that made it one of the brightest stars in the southern sky. Eta Carinae, in the Keyhole Nebula, is the only star currently thought to emit natural LASER light. This image, taken in 1996, resulted from sophisticated image-processing procedures designed to bring out new details in the unusual nebula that surrounds this rogue star. Now clearly visible are two distinct lobes, a hot central region, and strange radial streaks. The lobes are filled with lanes of gas and dust which absorb the blue and ultraviolet light emitted near the center. The streaks remain unexplained. Will these clues tell us how the nebula was formed? Will they better indicate when Eta Carinae will explode?

LoneRanger · #**228** 08-17-2008, 03:47 PM

Io's Surface: Under Construction

Quote:

Credit: Galileo Project, JPL, NASA

Explanation: Like the downtown area of your favorite city, the roads you drive to work on, and any self-respecting web site ... Io's surface is constantly under construction. This moon of Jupiter holds the distinction of being the Solar System's most volcanically active body -- its bizarre looking surface continuously formed and reformed by lava flows. Generated using 1996 data from NASA's Galileo spacecraft, this high resolution composite image is centered on the side of Io that always faces away from Jupiter. It has been enhanced to emphasize Io's surface brightness and color variations, revealing features as small as 1.5 miles across. The notable absence of impact craters suggests that the entire surface is covered with new volcanic deposits much more rapidly than craters are created. What drives this volcanic powerhouse? A likely energy source is the changing gravitational tides caused by Jupiter and the other Galilean moons as Io orbits the massive gas giant planet. Heating Io's interior, the pumping tides would generate the sulfurous volcanic activity.

Comet Hyakutake and the Milky Way

Quote:

Credit & Copyright: T. Polakis

Explanation: Two years ago, the Great Comet of 1996, Comet Hyakutake, inched across our northern sky during its long orbit around the Sun. Visible above as the bright spot with the faint tail near the picture's center, Comet Hyakutake shares the stage with part of the central band of the Milky Way Galaxy, prominent in the picture's upper right. Also visible are Antares, the bright orange star in the upper right, Arcturus, the bright star on the lower left, and the Pipe Nebula, which is perhaps harder to find. Comet Hyakutake's unusually close approach to the Earth allowed astronomers to learn many things, including that comets can emit much X-ray light.

LoneRanger · #**229** 08-18-2008, 02:59 PM

Baily's Beads near Solar Eclipse Totality

Quote:

Credit & Copyright: Leonid Durman

Explanation: Just before the Sun blacks out, something strange occurs. As the Moon moves to completely cover the Sun in a total solar eclipse, beads of bright sunlight stream around the edge of the Moon. This effect, known as Baily's beads, is named after Francis Baily who called attention to the phenomenon in 1836. Although, the number and brightness of Baily's beads used to be unpredictable, today the Moon is so well mapped that general features regarding Baily's beads are expected. When a single bead dominates, it is called the diamond ring effect, and is typically seen just before totality. Pictured above, a series of images recorded Baily's beads at times surrounding the recent total solar eclipse visible from Novosibirsk, Russia. The complete series can be seen by scrolling right. At the end of totality, as the Sun again emerges from behind the moon, Baily's beads may again be visible -- but now on the other side of the Moon.

APM 08279+5255: The Brightest Object Yet Known

Quote:

Credit: M.J. Irwin (RGO), R.A. Ibata (ESO), G.F. Lewis (U. Washington, U. Victoria), and E.J. Totten (Keele U.), Isaac Newton 2.5-m Telescope

Explanation: It shines with the brightness of 100 billion Suns. Is it a mirage? The recently discovered quasar labeled APM 08279+5255 has set a new record as being the brightest continuously emitting object yet known. APM 08279+5255's great distance, though, makes it only appear as bright as magnitude 15.2, an object which can be seen with a moderate sized telescope. It is the quasar's extreme redshift of 3.87 that places it far across our universe, and implies a truly impressive energy output. One possible explanation of APM 08279+5255's record luminosity is that it is partly a mirage: its light is highly magnified by an intervening galaxy that acts as a gravitational lens. Alternatively, APM 08279+5255 might be the most active known center of an intriguing class of colliding galaxies rich in gas and dust.

LoneRanger · #**230** 08-19-2008, 11:41 AM

NGC 6960: The Witch's Broom Nebula

Quote:

Credit & Copyright: Adam Block, Mount Lemmon SkyCenter, Univ. Arizona

Explanation: Ten thousand years ago, before the dawn of recorded human history, a new light must suddenly have appeared in the night sky and faded after a few weeks. Today we know this light was an exploding star and record the colorful expanding cloud as the Veil Nebula. Pictured above is the west end of the Veil Nebula known technically as NGC 6960 but less formally as the Witch's Broom Nebula. The expanding debris cloud gains its colors by sweeping up and exciting existing nearby gas. The supernova remnant lies about 1400 light-years away towards the constellation of Cygnus. This Witch's Broom actually spans over three times the angular size of the full Moon. The bright star 52 Cygnus is visible with the unaided eye from a dark location but unrelated to the ancient supernova.

M13: The Great Globular Cluster in Hercules

Quote:

Credit & Copyright: Michael Richmann

Explanation: M13 is one of the most prominent and best known globular clusters. Visible with binoculars in the constellation of Hercules, M13 is frequently one of the first steps beyond the ordinary visible to the casual sky gazer. M13 is a colossal home to over 100,000 stars, spans over 150 light years across, lies over 20,000 light years distant, and is over 12 billion years old. At the 1974 dedication of Arecibo Observatory, a radio message about Earth was sent in the direction of M13. The reason for the low abundance of unusual blue straggler stars in M13 is currently unknown.

ะộ§ộะ мя žǒǒŁ ะộ§ộะ · #**231** 08-19-2008, 12:00 PM

rajnilprasad · #**232** 08-20-2008, 04:36 AM

thanx

LoneRanger · #**233** 08-20-2008, 04:38 PM

Earth's Shadow

Quote:

Credit & Copyright: Anthony Ayiomamitis (TWAN)

Explanation: The dark, inner shadow of planet Earth is called the umbra. Shaped like a cone extending into space, the umbra has a circular cross section that can be most easily seen during a lunar eclipse. For example, last Saturday the Full Moon slid across the northern edge of the umbra. Entertaining moon watchers throughout Earth's eastern hemisphere, the lunar passage created a deep but partial lunar eclipse. This composite image uses successive pictures recorded during the eclipse from Athens, Greece to trace out a large part of the umbra's curved edge. The result nicely illustrates the relative size of the umbra's cross section at the distance of the Moon, as well as the Moon's path through the Earth's shadow.

SOHO Composite: Coronal Mass Ejection

Quote:

Credit: SOHO - LASCO - EIT Consortium, ESA, NASA

Explanation: This complex composite image of an ominous and spectacular event - an expanding storm of energetic particles from the Sun - was constructed using data recorded by the SOHO spacecraft on November 6, 1997. Four images from two SOHO (Solar Orbiting Heliospheric Observatory) instruments have been nested to show the ultraviolet Sun at center and a large eruption of material from the right-hand solar limb. Known as a Coronal Mass Ejection or CME, the expanding cloud has become relatively cool and dark in the middle with bright edges still connected to the solar surface. High energy protons have peppered the SOHO detectors causing the crazed streaks and blemishes. The picture covers a region extending about 13.5 million miles from the Sun (32 Solar Radii).

On June 25, after successfully completing its planned mission, contact with SOHO was lost -- but has recently been re-established! Hopefully SOHO will soon be able to continue operating in an extended mission phase.

LoneRanger · #**234** 08-26-2008, 09:59 PM

47 Tuc: A Great Globular Cluster of Stars

Quote:

Credit & Copyright: Thomas V. Davis (tvdavisastropix.com)

Explanation: Stars come in bunches. Of the over 200 globular star clusters that orbit the center of our Milky Way Galaxy, 47 Tucanae is the second brightest globular cluster (behind Omega Centauri). Light takes about 13,000 years to reach us from 47 Tuc which can be seen on the sky near the Small Magellanic Cloud in the southern constellation of Tucana. Also known as NGC 104, the dense cluster is made up of several million stars in a volume only about 120 light-years across. Its population of red giant stars are particularly easy to see in this picture. The globular cluster is also home to exotic x-ray binary star systems.

The Magellanic Stream

Quote:

Illustration Credit: Dallas Parr (CSIRO)

Explanation: Spanning the sky behind the majestic Clouds of Magellan is an unusual stream of gas: the Magellanic Stream. The origin of this gas might hold a clue to origin and fate of our Milky Way's most famous satellite galaxies: the LMC and the SMC. Two leading genesis hypotheses have surfaced: that the stream was created by gas stripped off these galaxies as they passed through the halo of our Milky Way, or that the stream was created by the differential gravitational tug of the Milky Way. Measurements of slight angular motions by the Hipparcos satellite have indicated that the Clouds are leading the Stream. Now, recent radio measurements have located fresh gas emerging from the Clouds, bolstering the later, tidal explanation. Most probably, in a few hundred million years, the Magellanic Clouds themselves will fall victim to this same tidal force.

LoneRanger · #**235** 08-27-2008, 09:43 PM

IC 5146: The Cocoon Nebula

Quote:

Credit & Copyright: Ken Crawford (Rancho Del Sol Observatory)

Explanation: Inside the Cocoon Nebula is a newly developing cluster of stars. Cataloged as IC 5146, the beautiful nebula is nearly 15 light-years wide, located some 4,000 light years away toward the northern constellation Cygnus. Like other star forming regions, it stands out in red, glowing, hydrogen gas excited by young, hot stars and blue, dust-reflected starlight at the edge of an otherwise invisible molecular cloud. In fact, the bright star near the center of this nebula is likely only a few hundred thousand years old, powering the nebular glow as it clears out a cavity in the molecular cloud's star forming dust and gas. This color view of the Cocoon Nebula traces remarkably subtle features within and surrounding the dusty stellar nursery.

Hercules Galaxies

Quote:

Credit: Dr. Victor Andersen ( University of Alabama, KPNO)
Courtesy W. Keel

Explanation: These are galaxies of the Hercules Cluster, an archipelago of "island universes" a mere 650 million light-years distant. This cluster is loaded with gas and dust rich, star forming, spiral galaxies but has relatively few elliptical galaxies, which lack gas and dust and the associated newborn stars. Colors in the composite image show the star forming galaxies with a blue tint and ellipticals with a slightly yellowish cast. In this cosmic vista many galaxies seem to be colliding or merging while others seem distorted - clear evidence that cluster galaxies commonly interact. Over time, the galaxy interactions are likely to affect the the content of the cluster itself. Researchers believe that the Hercules Cluster is significantly similar to young galaxy clusters in the distant, early Universe and that exploring galaxy types and their interactions in nearby Hercules will help unravel the threads of galaxy and cluster evolution.

LoneRanger · #**236** 08-28-2008, 09:36 PM

Fermi's First Light

Quote:

Credit: NASA, DOE, International LAT Team

Explanation: Launched on June 11 to explore the universe at extreme energies, the Gamma-ray Large Area Space Telescope has been officially renamed the Fermi Gamma-ray Space Telescope, in honor of Nobel Laureate Enrico Fermi (1901-1954), pioneer in high-energy physics. After testing, Fermi's two instruments, the Gamma-ray Burst Monitor (GBM) and the Large Area Telescope (LAT), are now regularly returning data. Fermi's first map of the gamma-ray sky from the LAT is shown in this false-color image, an all-sky view that looks toward the center of our Milky Way Galaxy with the galactic plane projected across the middle. What shines in the gamma-ray sky? Along the galactic plane, energetic cosmic rays collide with gas and dust to produce the diffuse gamma-ray glow. Strong emission from spinning neutron stars or pulsars, and distant active galaxies known as blazars, can be identified by placing your cursor over the map. A prelude to future discoveries, the remarkable result combines only 4 days of observations, equivalent to a year of observations with the Compton Gamma-ray Observatory mission of the 1990s. In addition to the ability to monitor gamma-ray bursts, the greatly improved sensitivity will allow Fermi to look deeper into the high-energy Universe.

Hydrogen Trifid

Quote:

Credit and Copyright: David McDavid ( Limber Observatory)

Explanation: Clouds of glowing hydrogen gas mingle with dark dust lanes in the Trifid Nebula, a star forming region in the constellation Sagittarius. In this and other similar emission nebulae, energetic ultraviolet light from an embedded hot young star strips electrons from the surrounding hydrogen atoms. As the electrons and atoms recombine they emit longer wavelength, lower energy light in a well known characteristic pattern of bright spectral lines. At visible wavelengths, the strongest emission line in this pattern is in the red part of the spectrum and is known as "Hydrogen-alpha" or just H-alpha. This image of the nebula was taken using a filter to select only light near the H-alpha wavelength. It shows those regions with substantial emission from atomic hydrogen. The relative strength of this emission can trace the densities of atoms within the gas cloud.

LoneRanger · #**237** 08-29-2008, 09:10 PM

Generations of Stars in W5

Quote:

Credit Lori Allen, Xavier Koenig (Harvard-Smithsonian CfA) et al., JPL-Caltech, NASA

Explanation: Giant star forming region W5 is over 200 light-years across and about 6,500 light-years away in the constellation Cassiopeia. W5's sculpted clouds of cold gas and dust seem to form fantastic shapes in this impressive mosaic of infrared images from the Spitzer Space Telescope. In fact, the area on the right includes the structures previously dubbed the Mountains of Creation. New evidence indicates that successive generations of stars formed in the W5 region in an expanding pattern of triggered star formation. The older, earlier generations of stars seem to cluster near the middle of the enormous cavities, with younger stars seen near the rims. Winds and radiation from the older, central stars likely carve out and compress surrounding interstellar material, triggering the collapse that gave rise to younger, later generations of stars farther out. In the false-color image, heated dust still within the cavities appears red, while the youngest stars are forming in the whitish areas. W5 is also known as IC 1848, and together with IC 1805 it is part of a complex region popularly dubbed the Heart and Soul Nebulae.

Orion Star Colours

Quote:

Credit and Copyright: David Malin

Explanation: What determines a star's colour? Its temperature. Red stars are cool, around 3,000 kelvins (K), while blue stars are hotter and can have temperatures over 30,000 K. Our own lovely yellow Sun's temperature is a comforting 6,000 K. Differences in star colours are dramatically illustrated in the above photo of the constellation Orion, made using a "star trail step-focus" technique. In this technique, a time exposure is used to create star trails, but during the exposure, the focus is changed in steps. For the brighter stars, the blurred image produces more saturated colours in photographs. At the upper left, the cool red supergiant Betelgeuse stands out from the other, hotter, bluish stars composing the body of the constellation. Bright Rigel, a blue supergiant, is at the lower right.