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The Andromeda Galaxy from GALEX
.jpg) Credit: GALEX team, Caltech, NASA
Why does the Andromeda Galaxy have a giant ring? Viewed in ultraviolet light, the closest major galaxy to our Milky Way Galaxy looks more like a ring galaxy than a spiral. The ring is highlighted beautifully in this newly released image mosaic of Andromeda (M31) taken by the GALaxy Evolution Explorer (GALEX), a satellite launched into Earth orbit. In the image, ultraviolet colors have been digitally shifted to the visual. Young blue stars dominate the image, indicating the star forming ring as well as other star forming regions even further from the galactic center. The origin of the huge 150,000-light year ring is unknown but likely related to gravitational interactions with small satellite galaxies that orbit near the galactic giant. M31 lies about three million light-years distant and is bright enough to be seen without binoculars toward the constellation of Andromeda.
The Antennae Galaxies in Collision
.jpg) Credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA)-ESA/Hubble Collaboration; Acknowledgment: B. Whitmore (Space Telescope Science Institute) et al.
Two galaxies are squaring off in Corvus. When two galaxies collide, however, the stars that compose them usually do not. This is because galaxies are mostly empty space and, however bright, stars take up only a small amount of that space. During the slow, hundred million year collision, however, one galaxy can rip the other apart gravitationally, and dust and gas common to both galaxies does collide. In the above clash of the titans, dark dust pillars mark massive molecular clouds that are being compressed during the galactic encounter, causing the rapid birth of millions of stars, some of which are gravitationally bound together in massive star clusters.
Barred Spiral Milky Way
 Illustration Credit: R. Hurt (SSC), JPL-Caltech, NASA
Survey Credit: GLIMPSE Team
A survey of stars conducted with the Spitzer Space Telescope is convincing astronomers that our Milky Way Galaxy is not just your ordinary spiral galaxy anymore. Looking out from within the Galaxy's disk, the true structure of the Milky Way is difficult to discern. However, the penetrating infrared census of about 30 million stars indicates that our Galaxy is distinguished by a very large central bar, some 27,000 light-years long. In fact, from a vantage point that viewed our galaxy face-on, astronomers in distant galaxies would likely see a striking barred spiral galaxy suggested in this artist's illustration. While previous investigations have identified a small central barred structure, the new results indicate that the Milky Way's large bar would make about a 45 degree angle with a line joining the Sun and the Galaxy's center. But DON'T PANIC... astronomers still place the Sun beyond the central bar region, about a third of the way in from the Milky Way's outer edge.
Carina Nebula Panorama from Hubble
 Credit: NASA, ESA, N. Smith (U. California, Berkeley) et al., and The Hubble Heritage Team (STScI/AURA)
In one of the brightest parts of Milky Way lies a nebula where some of the oddest things occur. NGC 3372, known as the Great Nebula in Carina, is home to massive stars and changing nebula. Eta Carinae, the most energetic star in the nebula, was one of the brightest stars in the sky in the 1830s, but then faded dramatically. The Keyhole Nebula, visible left of center, houses several of the most massive stars known and has also changed its appearance. The entire Carina Nebula spans over 300 light years and lies about 7,500 light-years away in the constellation of Carina. Pictured above is the most detailed image of the Carina Nebula ever taken. The controlled color image is a composite of 48 high-resolution frames taken by the Hubble Space Telescope. Wide-field annotated and zoomable image versions are also available.
Cone Nebula Close-Up
 Credit: ACS Science & Engineering Team, NASA
Cones, pillars, and majestic flowing shapes abound in stellar nurseries where natal clouds of gas and dust are buffeted by energetic winds from newborn stars. A well-known example, the Cone Nebula within the bright galactic star-forming region NGC 2264, was captured in this close-up view from the Hubble Space Telescope's Advanced Camera for Surveys. While the Cone Nebula, about 2,500 light-years away in Monoceros, is around 7 light-years long, the region pictured here surrounding the cone's blunted head is a mere 2.5 light-years across. In our neck of the galaxy that distance is just over half way from the Sun to its nearest stellar neighbor, Alpha Centauri. The massive star NGC 2264 IRS, seen by Hubble's infrared camera in 1997, is the likely source of the wind sculpting the Cone Nebula and lies off the top of the image. The Cone Nebula's reddish veil is produced by glowing hydrogen gas.
Composite Crab
 Credit: NASA - X-ray: CXC, J.Hester (ASU) et al.;
Optical: ESA, J.Hester and A.Loll (ASU); Infrared: JPL-Caltech, R.Gehrz (U. Minn)
The Crab Nebula is cataloged as M1, the first object on Charles Messier's famous list of things which are not comets. In fact, the Crab is now known to be a supernova remnant, the expanding debris from the death explosion of a massive star. This intriguing false-color image combines data from the space-based observatories: Chandra, Hubble, and Spitzer. The composite picture helps to explore the debris cloud through a combination of x-rays (blue-purple), optical (green), and infrared (red) light. One of the most exotic objects known to modern astronomers, the Crab Pulsar, a neutron star spinning 30 times a second, is the bright spot near picture center. Like a cosmic dynamo, this collapsed remnant of the stellar core powers the Crab's emission across the electromagnetic spectrum. Spanning about 12 light-years, the Crab Nebula is 6,500 light-years away in the constellation Taurus.
Crab Pulsar Wind Nebula
 Credit: NASA / CXC / SAO / F. D. Seward, W. H. Tucker, R. A. Fesen
The Crab Pulsar, a city-sized, magnetized neutron star spinning 30 times a second, lies at the center of this remarkable image from the orbiting Chandra Observatory. With more mass than the Sun and the density of an atomic nucleus, the spinning pulsar itself is the collapsed core of a massive star. The stellar core collapse resulted in a supernova explosion that was witnessed in the year 1054. The deep x-ray image gives the first clear view of the convoluted boundaries of the Crab's pulsar wind nebula. Like a cosmic dynamo the pulsar powers the x-ray emission. The pulsar's energy accelerates charged particles, producing eerie, glowing x-ray jets directed away from the poles and an intense wind in the equatorial direction. Intriguing edges are created as the charged particles stream away, eventually losing energy as they interact with the pulsar's strong magnetic field. This Chandra image spans just under 9 light-years at the Crab's estimated distance of 6,000 light-years.
The Double Ring Galaxies of Arp 147 From Hubble
 Credit: M Livio et al. (STScI), ESA, NASA
How could a galaxy become shaped like a ring? Even more strange: how could two? The rim of the blue galaxy pictured on the right shows an immense ring-like structure 30,000 light years in diameter composed of newly formed, extremely bright, massive stars. This blue galaxy is part of the interacting galaxy system known as Arp 147, and shows a ring because it has recently collided with the other galaxy in the frame, the red galaxy on the left. Unusually, even this red galaxy shows a ring like band, although it is seen nearly edge-on. When galaxies collide, they pass through each other -- their individual stars rarely come into contact. Clouds of interstellar gas and dust become condensed, causing a wave of star formation to move out from the impact point like a ripple across the surface of a pond. The above image was taken by NASA's Hubble Space Telescope to demonstrate the ability of its Wide Field Planetary Camera 2 after some technical difficulties.
Dust and the Helix Nebula
 Credit: NASA, JPL-Caltech, Kate Su (Steward Obs, U. Arizona) et al.
Dust makes this cosmic eye look red. The eerie Spitzer Space Telescope image shows infrared radiation from the well-studied Helix Nebula, a mere 700 light-years away in the constellation Aquarius. The two light-year diameter shroud of dust and gas around a central white dwarf has long been considered an excellent example of a planetary nebula, representing the final stages in the evolution of a sun-like star. But the Spitzer data show the nebula's central star itself is immersed in a surprisingly bright infrared glow. Models suggest the glow is produced by a dust debris disk. Even though the nebular material was ejected from the star many thousands of years ago, the close-in dust could be generated by collisions in a reservoir of objects analogous to our own solar system's Kuiper Belt or cometary Oort cloud. Formed in the distant planetary system, the comet-like bodies have otherwise survived even the dramatic late stages of the star's evolution.
Dusty Spiral M66
 Credit: M. Neeser (Univ.-Sternwarte Munchen), P. Barthel (Kapteyn Astron. Institute), H. Heyer, H. Boffin (ESO), ESO
When morning twilight came to the Paranal Observatory in Chile, astronomers Mark Neeser and Peter Barthel interrupted their search for faint quasars, billions of light-years away. And just for a moment, they used Very Large Telescopes at the European Southern Observatory to appreciate the beauty of the nearby universe. One result was this stunning view of beautiful spiral galaxy M66, a mere 35 million light-years away. About 100 thousand light-years across with striking dust lanes and bright star clusters along sweeping spiral arms, M66 is well known to astronomers as a member of the Leo Triplet of galaxies. Gravitational interactions with its neighborhood galaxies have likely influenced the shape of dusty spiral M66.
THE ESKIMO NEBULA FROM HUBBLE
 Credit: Andrew Fruchter (STScI) et al., WFPC2, HST, NASA
In 1787, astronomer William Herschel discovered the Eskimo Nebula. From the ground, this nebula resembles a person's head surrounded by a parka hood. In 2000, the Hubble Space Telescope photographed this image. From space, this nebula displays gas clouds so complex that they are not fully understood. The Eskimo Nebula is clearly a planetary nebula, and gas composed the outer layers of a Sun-like star only 10,000 years ago. The inner filaments are being ejected by strong wind of particles from the central star. The outer disk contains unusual light-year long orange filaments. The Eskimo Nebula spans about 1/3 of a light year and lies in our Milky Way Galaxy, about 3,000 light years distant, toward the constellation of the Twins (Gemini).
Star EGGs in the Eagle Nebula
 Credit: J. Hester & P. Scowen (Arizona State U.), HST, NASA
Where do stars form? One place, star forming regions known as "EGGs", are uncovered at the end of this giant pillar of gas and dust in the Eagle Nebula. EGGs, short for evaporating gaseous globules, are dense regions of mostly molecular hydrogen gas that fragment and gravitationally collapse to form stars. Light from the hottest and brightest of these new stars heats the end of the pillar and causes further evaporation of gas – revealing yet more EGGs and more young stars. This picture was taken by the Wide Field and Planetary Camera on board the Hubble Space Telescope.
The Fairy of Eagle Nebula
 Credit: The Hubble Heritage Team, (STScI/AURA), ESA, NASA
The dust sculptures of the Eagle Nebula are evaporating. As powerful starlight whittles away these cool cosmic mountains, the statuesque pillars that remain might be imagined as mythical beasts. Pictured here is one of several striking dust pillars of the Eagle Nebula that might be described as a gigantic alien fairy. This fairy, however, is ten light years tall and spews radiation much hotter than common fire. The greater Eagle Nebula is actually a giant evaporating shell of gas and dust inside of which is a growing cavity filled with a spectacular stellar nursery currently forming an open cluster of stars. The above image in scientifically re-assigned colors was released as part of the fifteenth anniversary celebration of the launch of the Hubble Space Telescope.
Pillars of Creation
Credit: J. Hester, P. Scowen (ASU), HST, NASA 
This has become one of the most famous images of modern times. This image, taken with the Hubble Space Telescope in 1995, shows evaporating gaseous globules (EGGs) emerging from pillars of molecular hydrogen gas and dust. The giant pillars are light years in length and are so dense that interior gas contracts gravitationally to form stars. At each pillars' end, the intense radiation of bright young stars causes low density material to boil away, leaving stellar nurseries of dense EGGs exposed. The Eagle Nebula, associated with the open star cluster M16, lies about 7000 light years away. The pillars of creation were imaged recently by the orbiting Chandra X-ray Observatory, and it was found that most EGGS are not strong emitters of X-rays.
Recycling Cassiopeia A
 Credit: Hubble Heritage Team (STScI / AURA), R. Fesen (Dartmouth) and J. Morse (CASA, U. Colorado), NASA
For billions of years, massive stars in our Milky Way Galaxy have lived spectacular lives. Collapsing from vast cosmic clouds, their nuclear furnaces ignite and create heavy elements in their cores. After a few million years, the enriched material is blasted back into interstellar space where star formation begins anew. The expanding debris cloud known as Cassiopeia A is an example of this final phase of the stellar life cycle. Light from the explosion which created this supernova remnant was probably first seen in planet Earth's sky just over 300 years ago, although it took that light more than 10,000 years to reach us. In this gorgeous Hubble Space Telescope image of cooling filaments and knots in the Cas A remnant, light from specific elements has been color coded to help astronomers understand the recycling of our galaxy's star stuff. For instance, red regions are dominated by emission from sulfur atoms while blue shades correspond to oxygen. The area shown is about 10 light-years across.
Thor's Helmet
 Credit: Christine and David Smith, Steve Mandel, Adam Block (KPNO Visitor Program), NOAO, AURA, NSF
Thor's Helmet is a striking emission nebula. It has also been suggested that its winged appearance might justify its being called the "duck nebula", but if you were a nebula, which name would you choose? By any name this is a bubble-like nebula some 30 light-years across, blown by energetic winds from an extremely hot star seen near the center and classified as a Wolf-Rayet star. Wolf-Rayet stars are rare, massive blue giants which develop stellar winds with speeds of millions of kilometers per hour. Interactions with a nearby large molecular cloud are thought to have contributed to this nebula's more complex shape and curved bow-shock structures. Thor's Helmet is about 15,000 light-years distant toward the constellation Canis Major.
Welcome to Planet Earth
 Credit: Apollo 17 Crew, NASA
Welcome to Planet Earth, the third planet from a star named the Sun. The Earth is shaped like a sphere and composed mostly of rock. Over 70 percent of the Earth's surface is water. The planet has a relatively thin atmosphere composed mostly of nitrogen and oxygen. Earth has a single large Moon that is about 1/4 of its diameter and, from the planet's surface, is seen to have almost exactly the same angular size as the Sun. With its abundance of liquid water, Earth supports a large variety of life forms, including potentially intelligent species such as dolphins, whales and humans. Please enjoy your stay on Planet Earth.
Wings of a Butterfly Nebula
 Credit: B. Balick (U. Washington) et al., WFPC2, HST, NASA
Are stars better appreciated for their art after they die? Actually, stars usually create their most artistic displays as they expire. In the case of low-mass stars like our Sun and the Butterfly Nebula pictured here, the stars transform themselves from normal stars to white dwarfs by casting off their outer gaseous envelopes. The expended gas frequently forms an impressive display called a planetary nebula that fades gradually over thousand of years. This butterfly planetary nebula, 2100 light-years away, is shown in representative colors and has wings that tell a strange but incomplete tale. In the center, two stars orbit inside a gaseous disk 10 times the orbit of Pluto. The expelled envelope of the dying star breaks out from the disk creating the bipolar appearance. Much remains unknown about the physical processes that cause planetary nebulae.
X-Rays from the Cat's Eye Nebula
 Credit: X-ray: NASA/CXC/SAO; Optical: NASA/STScI
Haunting patterns within the planetary Cat's Eye Nebula readily suggest its popular moniker. Starting in 1995, stunning false-color optical images from the Hubble Space Telescope detailed the swirls of this glowing nebula, known to be the gaseous shroud expelled from a dying sun-like star about 3,000 light-years from Earth. This composite picture combines the latest Hubble optical image of the Cat's Eye with new x-ray data from the orbiting Chandra Observatory and reveals surprisingly intense x-ray emission indicating the presence of extremely hot gas. X-ray emission is shown as blue-purple hues superimposed on the nebula's center. The nebula's central star itself is clearly immersed in the multimillion degree, x-ray emitting gas. Other pockets of x-ray hot gas seem to be bordered by cooler gas emitting strongly at optical wavelengths, a clear indication that expanding hot gas is sculpting the visible Cat's Eye filaments and structures. Gazing into the Cat's Eye, astronomers see the fate of our sun, destined to enter its own planetary nebula phase of evolution... in about 5 billion years.
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