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Echoes from the Edge
Variable star V838 Monocerotis lies near the edge of the Milky Way Galaxy, about 20,000 light-years from our sun. Still, ever since a sudden outburst was detected in January 2002, this enigmatic star has taken the center of an astronomical stage. As astronomers watch, light from the outburst echoes across pre-existing dust shells around V838 Mon, progressively illuminating ever more distant regions.
This stunning image of swirls of dust surrounding the star was recorded by the Hubble Space Telescope in September 2006. The picture spans about 14 light-years. Astronomers expect the expanding echoes to continue to light up the dusty environs of V838 Mon for at least the rest of the current decade. Researchers now have found that V838 Mon is likely a young binary star, but the cause of its extraordinary outburst remains a mystery.
Image credit: NASA, ESA, and H. Bond (STScI)
Eskimo Nebula
In 1787, astronomer William Herschel discovered the Eskimo Nebula, which from the ground resembles a person's head surrounded by a parka hood. In 2000, the Hubble Space Telescope imaged the nebula that displays gas clouds so complex they are not fully understood. The Eskimo Nebula is clearly a planetary nebula, and the gas seen above composed the outer layers of a sun-like star only 10,000 years ago. The inner filaments visible above are being ejected by strong wind of particles from the central star. The outer disk contains unusual light-year long orange filaments.
Image credit: NASA/Andrew Fruchter (STScI)
NGC 602 and Beyond
Near the outskirts of the Small Magellanic Cloud, a satellite galaxy some 200 thousand light-years distant, lies the young star cluster NGC 602. Surrounded by natal gas and dust, NGC 602 is featured in this Hubble image of the region. Fantastic ridges and undulating shapes strongly suggest that energetic radiation and shock waves from NGC 602's massive young stars have eroded the dusty material and triggered a progression of star formation moving away from the cluster's center. At the estimated distance of the Small Magellanic Cloud, the picture spans about 200 light-years, but a tantalizing assortment of background galaxies are also visible in the sharp Hubble view. The background galaxies are hundreds of millions of light-years or more beyond NGC 602.
Image credit: NASA, ESA and the Hubble Heritage Team (STScI / AURA)
Windblown
A fast and powerful wind from a hot young star created this stunning bubble-shaped nebula, poised on the end of a bright filament of hydrogen gas. Cataloged as N44F, the cosmic windblown bubble is seen at the left of this Hubble Space Telescope image. N44F lies along the northern outskirts of the N44 complex of emission nebulae in the Large Magellanic Cloud, a mere 160,000 light-years away.
The bright, blue, hot star itself is just below the center of the bubble. Peering into the bubble's interior, the Hubble image reveals dramatic structures, including pillars of dust, aligned toward N44F's hot central star. Reminiscent of dust pillars in stellar nurseries within our Milky Way galaxy, they likely contain young stars at their tips. Expanding into the surrounding gas and dust at about 12 kilometers, or 7.5 miles, per second, N44F is around 35 light-years across.
Image credit: NASA/GSFC/MITI/ERSDAC/JAROS, and U.S./Japan ASTER Science Team
Reflection Nebula
Just weeks after NASA astronauts repaired the Hubble Space Telescope in December 1999, the Hubble Heritage Project snapped this picture of NGC 1999, a reflection nebula in the constellation Orion.
Like fog around a street lamp, a reflection nebula shines only because the light from an embedded source illuminates its dust; the nebula does not emit any visible light of its own. The nebula is famous in astronomical history because the first Herbig-Haro object was discovered immediately adjacent to it (it lies just outside the new Hubble image). Herbig-Haro objects are now known to be jets of gas ejected from very young stars.
The nebula is illuminated by a bright, recently formed star, visible just to the left of center. This star is cataloged as V380 Orionis, and its white color is due to its high surface temperature of about 10,000 degrees Celsius, nearly twice that of our own sun. Its mass is estimated to be 3.5 times that of the sun. The star is so young that it is still surrounded by a cloud of material left over from its formation, here seen as the NGC 1999 reflection nebula.
NGC 1999 shows a remarkable jet-black cloud near its center, located just to the right and lower right of the bright star. This dark cloud is an example of a "Bok globule," named after the late University of Arizona astronomer Bart Bok. The globule is a cold cloud of gas, molecules and cosmic dust, which is so dense it blocks all of the light behind it. The globule is seen silhouetted against the reflection nebula illuminated by V380 Orionis. Astronomers believe that new stars may be forming inside Bok globules, through the contraction of the dust and molecular gas under their own gravity.
Stellar Nursery
NASA's Spitzer Space Telescope captured a glowing stellar nursery within a dark globule that reveals the birth of new protostars, or embryonic stars, and young stars never before seen.
The Elephant's Trunk Nebula is an elongated dark globule within the emission nebula IC 1396 in the constellation of Cepheus. Within the globule, a half dozen newly discovered protostars are easily discernible as the bright red-tinted objects, mostly along the southern rim of the globule. These were previously undetected at visible wavelengths due to obscuration by the thick cloud ('globule body') and by dust surrounding the newly forming stars. The newborn stars form in the dense gas because of compression by the wind and radiation from a nearby massive star (located outside the field of view to the left). The winds from this unseen star are also responsible for producing the spectacular filamentary appearance of the globule itself, which resembles that of a flying dragon.
Image credit: NASA/JPL-Caltech/W. Reach (SSC/Caltech)
Omega Nebula; Close-Up of a Stellar Nursery
Sculpted by stellar winds and radiation, these fantastic, undulating shapes lie within the stellar nursery known as M17, the Omega Nebula, some 5,500 light-years away in the nebula-rich constellation Sagittarius. The lumpy features in the dense cold gas and dust are illuminated by stars off the upper left of the image and may themselves represent sites of future star formation. Colors in the fog of surrounding hotter material indicate M17's chemical make up. The predominately green glow corresponds to abundant hydrogen, with trace sulfur and oxygen atoms contributing red and blue hues. The picture spans about 3 light-years.
Image credit: NASA, ESA, J. Hester (ASU)
Ring Holds a Delicate Flower
NASA's Spitzer Space Telescope finds a delicate flower in the Ring Nebula, as shown in this image. The outer shell of this planetary nebula looks surprisingly similar to the delicate petals of a camellia blossom. (A planetary nebula is a shell of material ejected from a dying star.) Located about 2,000 light years from Earth in the constellation Lyra, the Ring Nebula is also known as Messier Object 57 and NGC 6720. It is one of the best examples of a planetary nebula and a favorite target of amateur astronomers.
The "ring" is a thick cylinder of glowing gas and dust around the doomed star. As the star begins to run out of fuel, its core becomes smaller and hotter, boiling off its outer layers. Spitzer's infrared array camera detected this material expelled from the withering star. Previous images of the Ring Nebula taken by visible-light telescopes usually showed just the inner glowing loop of gas around the star. The outer regions are especially prominent in this new image because Spitzer sees the infrared light from hydrogen molecules. The molecules emit the infrared light that they have absorbed ultraviolet radiation from the star or have been heated by the wind from the star.
Image credit: NASA/JPL-Caltech/Harvard-Smithsonian CfA
Natal Microcosm
In the quest to better understand the birth of stars and the formation of new worlds, astronomers have used NASA's Spitzer Space Telescope to examine the massive stars contained in a cloudy region called Sharpless 140. This cloud is a star-forming microcosm that exhibits, within a relatively small area, all of the classic manifestations of stellar birth.
Sharpless 140 lies almost 3,000 light-years from Earth in the constellation Cepheus. At its heart is a cluster of three deeply embedded young stars, which are each several thousand times brighter than the sun. Though they are strikingly visible in this image from Spitzer's infrared array camera, they are completely obscured in visible light, buried within the core of the surrounding dust cloud.
The extreme youth of at least one of these stars is indicated by the presence of a stream of gas moving at high velocities. Such outflows are signatures of the processes surrounding a star that is still gobbling up material as part of its formation.
The bright red bowl, or arc, seen in this image traces the outer surface of the dense dust cloud encasing the young stars. This arc is made up primarily of organic compounds called polycyclic aromatic hydrocarbons, which glow on the surface of the cloud. Ultraviolet light from a nearby bright star outside of the image is "eating away" at these molecules. Eventually, this light will destroy the dust envelope and the masked young stars will emerge.
This false-color image was taken on Oct. 11, 2003.
Image credit: NASA/JPL-Caltech
Bow Tie Nebula
Planetary nebula NGC 2440 has an intriguing bow-tie shape in this stunning view from space. The nebula is composed of material cast off by a dying sun-like star as it enters its white dwarf phase of evolution. Details of remarkably complex structures are revealed within NGC 2440, including dense ridges of material swept back from the nebula's central star.
The star itself is one of the hottest known, with a surface temperature of about 200,000 kelvins. About 4,000 light-years from planet Earth toward the nautical constellation Puppis, the nebula spans more than a light-year and is energized by ultraviolet light from the central star. The false-color image was recorded using the Hubble's Wide-Field Planetary Camera 2 (WFPC2), demonstrating still impressive imaging capabilities following the failure of the Advanced Camera for Surveys.
Image credit: NASA, ESA, K. Noll (STScI)
Cone Nebula
Resembling a nightmarish beast rearing its head from a crimson sea, this monstrous object is actually a pillar of gas and dust. Called the Cone Nebula because of its conical shape in ground-based images, this giant pillar resides in a turbulent star-forming region. Taken by the Hubble Space Telescope in April 002, this image shows the upper 2.5 light-years of the nebula, a height that equals 23 million round trips to the moon. The entire nebula is 7 light years in length. The Cone Nebula resides 2,500 light-years away in the constellation Monoceros.
Radiation from hot, young stars has slowly eroded the nebula over millions of years. Ultraviolet light heats the edges of the dark cloud, releasing gas into the relatively empty region of surrounding space. There, additional ultraviolet radiation causes the hydrogen gas to glow, which produces the red halo of light seen around the pillar. A similar process occurs on a much smaller scale to gas surrounding a single star, forming the bow-shaped arc seen near the upper left side of the Cone. This arc is 65 times larger than the diameter of our solar system. The blue-white light from surrounding stars is reflected by dust. Background stars can be seen peeking through the evaporating tendrils of gas, while the turbulent base is pockmarked with stars reddened by dust. Over time, only the densest regions of the Cone will be left. Inside these regions, stars and planets may form.
The Cone Nebula is a cousin of the M16 pillars, which the Hubble imaged in 1995. Monstrous pillars of cold gas like the Cone and M16 are common in large regions of star birth. Astronomers believe the pillars are incubators for developing stars.
Image credit: NASA, H. Ford (JHU), G. Illingworth (UCSC/LO), M. Clampin (STScI), G. Hartig (STScI), the ACS Science Team and ESA
Cosmic Epic Unfolds in Infrared
This majestic view, taken by NASA's Spitzer Space Telescope, tells an untold story of life and death in the Eagle Nebula, an industrious star-making factory located 7,000 light-years away in the Serpens Constellation. The image shows the region's entire network of turbulent clouds and newborn stars in infrared light.
But it is the color red that speaks of the drama taking place in this region. Red represents hotter dust thought to have been warmed by the explosion of a massive star about 8,000 to 9,000 years ago. Since light from the Eagle Nebula takes 7,000 years to reach us, this supernova explosion would have appeared as an oddly bright star in our skies about 1,000 to 2,000 years ago.
According to astronomers' estimations, the explosion's blast wave would have spread outward and toppled the three pillars about 6,000 years ago (which means we wouldn't witness the destruction for another 1,000 years or so). The blast wave would have crumbled the mighty towers, exposing newborn stars that were buried inside, and triggering the birth of new ones.
Image credit: NASA/JPL-Caltech/ Institut d'Astrophysique Spatia
Cygnus Loop Supernova Remnant
This 1991 image from NASA's Hubble Space Telescope captures a small section of the Cygnus Loop supernova remnant. The Cygnus Loop marks the edge of a bubble-like, expanding blast wave from a colossal stellar explosion which occurred about 15,000 years ago. Supernova remnants play an import!!ant role in stellar evolution by enriching space with heavy elements, and triggering new star formation by compressing interstellar gas.
The image shows the structure behind the shock waves in the Cygnus Loop with unprecedented clarity, allowing astronomers to compare directly the actual structure of the shock with theoretical model calculations for the first time. Besides supernova remnants, these shock models are import!!ant in understanding a wide range of astrophysical phenomena, ranging from winds in newly-formed stars to cataclysmic stellar outbursts.
As the supernova blast wave slams into tenuous clouds of interstellar gas, the resulting collision heats and compresses the gas, causing it to glow. The shock acts as a searchlight by revealing the structure of the interstellar medium.
A bluish ribbon of light stretching left to right across the picture might be a knot of gas ejected by the supernova. This interstellar "bullet," traveling over three million miles per hour (5 million km), is just catching up with the shock front, which has been slowed by plowing into interstellar material.
The Cygnus Loop appears as a faint ring of glowing gases about three degrees across (six times the diameter of the full moon), located in the northern constellation Cygnus the Swan. The supernova remnant is within the plane of our Milky Way Galaxy and is 2,600 light-years away.
Image credit: NASA and J.J. Hester (Arizona State University)
Cat's Eye Nebula
Three thousand light-years away, the Cat's Eye Nebula, a dying star throws off shells of glowing gas. This image from the Hubble Space Telescope reveals the nebula to be one of the most complex planetary nebulae known. In fact, the features seen in the Cat's Eye are so complex that astronomers suspect the bright central object may actually be a binary star system. The term planetary nebula is misleading; although these objects may appear round and planet-like in small telescopes, high resolution images reveal them to be stars surrounded by cocoons of gas blown off in the late stages of stellar evolution.
Image credit: NASA, J. P. Harrington (U. Maryland) and K. J. Borkowski (NCSU)
Sun Storm!
The sun-orbiting SOHO spacecraft has imaged many erupting filaments lifting off the active solar surface and blasting enormous bubbles of magnetic plasma into space. This image shows the sun in ultraviolet light, while the field of view extends over 2 million kilometers, or 1.243 million miles, from the solar surface.
While hints of these explosive sun storms, called coronal mass ejections or CMEs, were discovered by spacecraft in the early 1970s, this dramatic image is part of a detailed record of this CME's development from the presently operating SOHO spacecraft. At a minimum, solar activity cycle CMEs occur about once a week, with maximum rates of two or more per day. Strong CMEs may profoundly influence space weather and those directed toward our planet can have serious effects.
Image credit: NASA/JPL
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