As the dome of twilight sinks below the horizon, a mechanical corps de ballet starts a slow-motion pirouette with each dancer keeping the unblinking eye of a telescope locked on a single spot in the heavens. Shutters open and ancient photons, ending a journey that may have started before the earth was born, collide with sensors that store an electron to mark that photon’s arrival. With the dance in motion the directors sit back to watch the show; another imaging session has begun . . . .
There is something rewarding in catching photons, having traveled for millennia, just before they hit my grass and are lost forever. Turn off the lights and click the images to enlarge.
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M42, the Orion Nebula is an emission/reflection nebula and the nearest star-forming region at a distance of 1,344 light years and is approximately 24 light years across. It contains about 700 stars in various stages of formation, dominated by an open star cluster call the Trapezium which contains Theta1 C Orionis, 40 times the Sun’s mass with a surface temperature of 72,000 degrees Fahrenheit which produces tremendous amounts of ultraviolet radiation, causing nearby gas clouds to fluoresce. Theta1 is 210,000 times brighter than the Sun, and produces a stellar wind that blows at 5.7 million mph, blowing planet-forming dust particles away from the surrounding stars, making it impossible for planets to form.
M81, Bode's Galaxy, is a grand design spiral galaxy about 12 m.l.y. away, with a diameter of 90,000 light years, in the constellation Ursa Major. Its active galactic nucleus harbors a 70 million solar mass supermassive black hole. It was first discovered by Johann Elert Bode on 31 December 1774 and is home to over 250 billion stars. Messier 81 has two well resolved spiral arms that contain large quantities of interstellar dust associated with numerous starburst regions. The hot, young, blue stars in the star forming regions of M81 heat the dust, increasing the emissions from these regions.
Barnard 33, the Horsehead Nebula, is part of the much larger Orion Molecular Cloud Complex. It is 1,375 light-years away. The deep-red color originates from ionized hydrogen gas behind the nebula. Magnetic fields channel the gases, leaving the nebula into streams, shown as foreground streaks against the background glow. A glowing strip of hydrogen gas marks the edge of the enormous cloud, and the densities of nearby stars are noticeably different on either side. The darkness of the Horsehead is caused by thick dust blocking the light of stars behind it. The visible dark nebula emerging from the gaseous complex is an active site of the formation of "low-mass" stars.
NGC 2024, the Flame nebula, is an emission nebula in the constellation Orion and is about 900 to 1,500 light-years away. The bright star Alnitak, the easternmost star in the Belt of Orion, shines energetic ultraviolet light into the Flame and this knocks electrons away from the great clouds of hydrogen gas. Much of the glow results when the electrons and ionized hydrogen recombine. Additional dark gas and dust lies in front of the bright part of the nebula and this is what causes the dark network that appears in the center of the glowing gas. At the center of the Flame Nebula is a cluster of newly formed stars showing several hundred young stars, out of an estimated population of 800 stars.
M45, the Pleiades, is an open star cluster containing middle-aged stars and lies 444 light years away. The cluster is dominated by hot blue and luminous stars that have formed within the last 100 million years. Reflection nebulae around the brightest stars are likely an unrelated dust cloud in the interstellar medium through which the stars are currently passing. The constellation is known in Japan as Subaru and was chosen as the brand name of Subaru automobiles and is depicted in the firm's star logo. The cluster contains many brown dwarfs, which are objects with less than about 8% of the Sun's mass, not heavy enough for nuclear fusion reactions to start in their cores and become proper stars.
Hickson Compact Group 44 is four galaxies in a tight group, all about 80 m.l.y. away. NGC 3190 is the largest, in the center of the frame. It is a tightly would spiral galaxy about 80 thousand l.y. across (about half the size of the Milky Way which contains about 400 billion stars). Above it is NGC 3187, a dim but striking barred galaxy. In the upper right is NGC 3185, a barred spiral galaxy with an outer ring. The fuzzy snowball below left of NGC 3190 is the featureless elliptical galaxy NGC3193. These four are in a gravitational tug of war that will eventually result in galaxy mergers. There are at least 24 more distant galaxies in this field of view.
Spiral galaxy M33, the Triangulum, is about half the size of our Milky Way. Blue-colored regions scattered throughout the image reveal numerous sites of rapid star formation. It may be a gravitationally bound companion of the Andromeda Galaxy and home to 40 billion stars compared to 400 billion for the Milky Way and 1 trillion for Andromeda. 2.73 million light years away and 60,000 light years wide, it is the most distant object visible to naked eye although viewing requires averted vision and the absence of all light pollution. It may be orbiting Andromeda and both are heading our way for a collision in about 2.5 billion years.
M13, the Great Globular Cluster in Hercules, is a globular cluster about 145 light years in diameter and 25,000 light years from Earth, composed of several hundred thousand stars, the brightest of which is a red giant, the variable star V11. They are so densely packed together that they sometimes collide and produce new stars called "blue stragglers". Globular clusters orbit the Milky Way galaxy outside the galactic disk at tens of thousands of light-years away.
M27, the Dumbbell Nebula, at a distance of about 1227 light-years, was the first planetary nebula to be discovered, by Charles Messier in 1764. Despite its class, the Dumbbell Nebula has nothing to do with planets. It consists of very rarified gas that has been ejected from the hot central star (well visible on this photo), now in one of the last evolutionary stages. The gas atoms in the nebula are excited (heated) by the intense ultraviolet radiation from this star and emit strongly at specific wavelengths. Expansion velocity is 31 km/s or 70,000 mph.
M57, the Ring Nebula, is a planetary nebula in the northern constellation of Lyra. It is formed by a shell of ionized gas expelled into the surrounding interstellar medium by a central star in the last stages of evolution before becoming a white dwarf. Photographs taken over a period of 50 years show the rate of nebula expansion is roughly 44,000 mph. All the interior parts of this nebula have a blue-green tinge that is caused by the doubly ionized oxygen emission. The observed nebulosity is estimated to have been expanding for approximately 1,610 years.
Saturn is s gas giant with a solid core about twice the size of Earth. 29.4 year orbit, 10.5 hour rotation. Surface temp of -139 C and winds over 1,000 mph. 82 moons. Tytan, the largest, is bigger than Mercury and is the only moon in our solar system with an atmosphere. Saturn is approximately 4.5 billion years old and named after the Roman god of harvest and time. Saturn's rings are 230,000 miles in diameter and would nearly fit between the Earth and Moon. The rings are only 60 feet thick and disappear every 15 years as Saturn's axis passes perpendicular to us and the rings are edge-on. The rings are composed of ice, dust, lost luggage, and mismatched socks.
Named for the Roman god of war, Mars is the only planet ruled by robots (since 1971). It has a thin atmosphere and polar ice caps. It's red color is due to its iron oxide surface geology. Mars has 2 moons which may be captured asteroids. 1.88 year orbit, 24 hour 49 minute rotation. Because of axis tilt similar to Earth's, Mars has seasons and temps vary between -143C to 35C. Storms are common and dust can cover the entire planet as it did in 2018, obscuring all surface features.
Jupiter is more than twice as massive as all the other planets combined and its stripes and swirls are cold, windy clouds of ammonia and water, floating in an atmosphere of hydrogen and helium. Jupiter’s iconic Great Red Spot is a giant storm bigger than Earth that has raged for hundreds of years. Jupiter rotates once about every 10 hours, but takes about 12 years to complete one orbit of the Sun. Jupiter is a gas giant and so lacks an Earth-like surface. If it has a solid inner core at all, it’s likely only about the size of Earth. Jupiter has more than 75 moons.
M65 and M66 are two galaxies in the Leo Triplet group that are interacting with each other as well as NGC3268 just out of the field of view. The group is 35 m.l.y. away and M66 is 95 l.y. across.
Asteroid 8-Flora looks like a faint star (asteroid means "star-like") but it's only 91 miles across. Named for the Latin goddess of flowers, Flora appears to be a chunk of a larger asteroid that was disrupted by an impact and is the largest member of the Flora family, a group of more than 13,000 asteroids that share similar orbits. Its surface composition is a mixture of silicate rock and nickel-iron metal. Flora is a good candidate for being the parent body of the L chondrite meteorites which comprise about 38% of all meteorites impacting the Earth. In the 1968 science-fiction film "The Green Slime", an orbital perturbation propels the asteroid Flora into a collision course with Earth. In the sky, Flora looks like just another dim star but its orbit in the main asteroid belt imparts a different apparent motion that can be recorded. In this 2-hour image, the telescope is tracking the apparent motion of the stars and the different motion of 8-Flora appears as a streak in the upper right corner. For a time lapse video, CLICK HERE
The Christmas Tree Cluster is part of a larger area 2,700 ly away designated as NGC 2264 that includes the Cone Nebula, Snowflake Cluster, and the Fox Fur Nebula. The Cone Nebula's shape comes from a dark absorption nebula consisting of cold molecular hydrogen and dust in front of a faint emission nebula containing hydrogen ionized by S Monocerotis, the brightest star of NGC 2264. The faint nebula is approximately seven light-years long. 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. The blue-white light from surrounding stars is reflected by dust. Over time, only the densest regions of the Cone will be left and these regions form stars and planets.
In 5,500 B.C., a star in the constellation Taurus died a violent, fiery death creating an expanding wave of gas and dust as the pressure within the star became stronger than the gravity holding it together. Centuries later, on July 4, AD 054, the first light of the explosion reached Earth and was observed by astronomers worldwide. The “guest” star was bright enough to be seen in the daytime for 23 days, originally shining six times brighter than Venus, and remained visible in the night sky, to the naked eye, for nearly 2 years. This supernova is now known as Messier 1, the Crab Nebula. It is much dimmer now that the gas and debris has spread out 6 light years. The ejected material is moving at more than 3 million mph. The ultra dense core of the exploded star is now a neutron star embedded in the center of the nebula. Electrons orbiting at nearly the speed of light in its magnetic field lines produce blue light in the interior of the nebula. This pulsar is only a few miles in diameter but 100,000 times as energetic as our sun and emits twin beams of radiation that make it appear to pulse 30 times per second as it spins.
M31, The Andromeda galaxy, is only 2.5 million light years away, contains approximately a trillion stars compared to the 250 billion in the Milky Way, and is 61,000 light years wide. There are about 40 black holes with two supermassive ones closely orbiting each other. The snowball to the left is satellite galaxy M110, a dwarf elliptical galaxy that is interacting with Andromeda. Andromeda is traveling towards us on a collision course at 70 miles per second with the crash expected in about 4 billion years. Not to worry, long before that the Sun will have swollen into a red giant and swallowed all the planets.
Andromeda to the naked eye on a clear night at a dark site. Same scale as the image to the left.
M101, the Pinwheel Galaxy is a face-on spiral galaxy 21 m.l.y. away from Earth with a diameter of 170,000 light-years, nearly twice the Milky Way. It has around a trillion stars, twice the number in the Milky Way, a disk mass on the order of 100 billion solar masses, along with a small central bulge of about 3 billion solar masses. M101 is asymmetrical due to the tidal forces from interactions with its six prominent companion galaxies. These gravitational interactions compress interstellar hydrogen gas, which then triggers strong star formation activity in M101's spiral arms that can be detected in ultraviolet images.
M 104, the Sombrero Galaxy, is a spiral galaxy in the constellation borders of Virgo and Corvus, being about 31 m.l.y. from Earth. It has a diameter of approximately 49,000 light-years making it about one-third the size of the Milky Way. It has a bright nucleus, an unusually large central bulge, and a prominent dust lane in its outer disk, which is viewed almost edge-on. Its large bulge surrounds a supermassive black hole. The extended halo is composed of unusually metal-rich stars.
Messier 106 is an intermediate spiral galaxy about 24 m.l.y. away from Earth and 126,000 l.y. in diameter. M106 contains an active nucleus, a central supermassive black hole, and is a possible companion galaxy of Messier 106. Spectral observations detect warm and dense water vapor. To its left is NGC 4248, 106's irregular dwarf galaxy companion. In the upper right corner is NGC 4232, a barred spiral galaxy Just above that is NCG 4231, a lenticular galaxy an estimated 333 m.l.y. from the Milky Way and about 120,000 light years in diameter. Together with NGC 4232, it forms the gravitationally bound galaxy pair.
Messier 82, the Cigar Galaxy, is a starburst galaxy approximately 12 m.l.y. years away. A member of the M81 Group, it is about five times more luminous than the Milky Way and has a center one hundred times more luminous. The starburst activity is thought to have been triggered by interaction with neighboring galaxy M81. As the closest starburst galaxy to Earth, M82 is the prototypical example of this galaxy type. A supernova, was discovered in the galaxy in 2014 and it also contain the brightest pulsar yet known, designated M82 X-2. Around the galaxy’s center, young stars are being born 10 times faster than they are inside our entire Milky Way. Radiation and energetic particles from these newborn stars carve into the surrounding gas and the resulting galactic wind compresses enough gas to make millions of more stars.
Our Milky Way is a barred spiral galaxy with an estimated diameter of 150-200,000 l.y. A dark matter disk may extend almost 2 million light-years. The Milky Way has several satellite galaxies and is part of the Local Group which forms part of the Virgo Supercluster, which is itself part of the Laniakea Supercluster. The Milky Way contains 100-400 billion stars and at least that number of planets. Our Solar System is 27,000 l.y. from the Galactic Center. The galactic center is a supermassive black hole of 4.1 million solar masses. Stars and gases orbit at 492,000 mph and we make a round trip every 240 million years. Up to 90% its mass is dark matter, invisible to telescopes, neither emitting nor absorbing electromagnetic radiation. The whole Milky Way is moving through space at about 1.3 million mph.
The bright object on the right is Jupiter.
In 1989, the ESA launched Hipparcos. It’s job was to map our arm of our galaxy in 3D. It plotted star locations, age, size, velocity, and direction. When it died in 1993, it had sent back data on 120,000 stars which changed the face of modern astronomy. In 2013, the ESA launched Gaia. Same mission but better technology. It also analyzes luminosity, temperature, gravity, and elemental composition. In 2016, it dumped its first telemetry data set: 1.1 billion stars. In 2018, the second data dump covered 1.3 billion stars. The third data dump happned in December of 2020 and Gaia is expected to operate a little past 2025 before it runs out of fuel.
We now have a 3D map of part of our arm of our galaxy and we can apply correct motion and velocity and use data visualization to plot star movement over time. Here is what’s happening: CLICK HERE
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The Sun in Hydrogen-Alpha. The entire spectrum is blocked except the Hydrogen-Alpha emission line at 656 nm. The granular nature of the surface convective sells is seen as light areas of hot, rising plasma and dark areas of cooler, descending plasma. The small prominences on the limb are about the size of the Earth. Solar activity is on an 11-year cycle and we are currently coming out of the most inactive part of the current cycle.
NGC 4565, the Needle Galaxy, is an edge-on spiral galaxy about 42 m.l.y. away in the constellation Coma Berenices. It has a population of roughly 240 globular clusters, more than the Milky Way. The disk is slightly warped and extended due to ongoing interactions with neighboring satellite galaxies or other galaxies in the Coma I group. It is the same age as the Milky Way; about billion years. The smaller galaxy is the barred spiral NGC 4562. Above the core of the Needle, and just a little to the right, irregular galaxy IC 3571 appears as a faint fuzzy spot.
IC 443, the Jellyfish Nebula is a supernova remnant 5,000 light years from Earth. Having an apparent angular diameter nearly twice the diameter of the full moon, it corresponds to a physical size of roughly 70 light years. When a massive star runs out of fuel, it implodes, forming a dense stellar core called a neutron star. The outer layers of the star collapse toward the neutron star then bounce outward in a supernova explosion. The explosion is thought to have happened 30,000 years ago although some date it as recent as 3,000 years ago. The explosion that created the Jellyfish Nebula may have also formed a rapidly spinning neutron star, or pulsar on the southern edge of the remnant. The radiation sweeps by like a beacon of light from a lighthouse and can be detected as pulses of radio waves and other types of radiation.
Backyard galaxies that can be seen with C11 telescope. What we can see depends upon brightness and our ability to resolve objects. Brightness is measured on a scale of stellar magnitude where the higher the magnitude the dimmer the object. Each step in magnitude is 2.5x the previous step so 5 steps = 100x dimmer. The human eye has a limiting magnitude of about 6.5 so you can only see one galaxy and it is just a dot. The C11 limiting magnitude is 14.7. All galaxies tagged in this photo are brighter than 13. Seeing is of little use if we can’t resolve individual parts of an object. A young human eye can split two basketballs held 12" apart at a distance of over 1,000'. C11 can do it from Austin to San Antonio. Hubble can do it from Austin to Toronto. Estimates of the number of galaxies in the current observable universe range up to 2 trillion.
M51, the Whirlpool Galaxy, is a grand design spiral galaxy 31 m.l.y. away and less than half the size of our Milky Way with a diameter of 76,000 l.y. The pronounced spiral structure is the result of the close interaction between it and its companion galaxy NGC 5195, which may have passed through the main disk of M51 about 500 to 600 million years ago. In this proposed scenario, NGC 5195 came from behind M51 through the disk towards the observer and made another disk crossing as recently as 50 to 100 million years ago until it is where we observe it to be now, slightly behind M51. The central region of M51 appears to be undergoing a period of enhanced star formation and the current high rate of star formation can last no more than another 100 million years or so. Below NGC 5195 is IC4278, an edge-on spiral galaxy about 230 m.l.y. away. To the lower left of NGC 5195 is another edge-on spiral also about 230 m.l.y distant, IC 4277.
The Eagle Nebula, M16, is a young open cluster of stars and diffuse emission nebula containing several active star-forming gas and dust regions, including the Pillars of Creation (the 3 central pillars). This region of active current star formation is about 7,000 l.y. away. The cluster associated with the nebula has approximately 8100 stars and is about 1–2 m.y. old. The pillars are composed of interstellar hydrogen gas and dust which act as incubators for new stars and are part of an active star-forming region within the nebula which hides newborn stars in their wispy columns. The pillars are bathed in the scorching ultraviolet light from a cluster of young stars and the winds from these stars are slowly eroding the towers. The Spitzer Telescope (infrared) uncovered a cloud of hot dust in the vicinity of the Pillars thought to be a shock wave produced by a supernova that would have destroyed the Pillars of Creation 6,000 years ago. Given the distance of roughly 7,000 light-years to the Pillars of Creation, this would mean that they have actually already been destroyed and this destruction should be visible from Earth in about 1,000 years.
NGC 7635, the Bubble Nebula, is a massive star trapped inside a bubble. About 7,100 light-years away, The star forming this nebula is 45 times more massive than our sun. Gas on the star gets so hot that it escapes away into space as a "stellar wind" moving at over 4 million miles per hour. This outflow sweeps up the cold, interstellar gas in front of it, forming the outer edge of the bubble much like a snowplow piles up snow in front of it as it moves forward. As the surface of the bubble's shell expands outward, it slams into dense regions of cold gas on one side of the bubble. This asymmetry makes the star appear dramatically off-center from the bubble, with its location in the 2 o'clock position. Dense pillars of cool hydrogen gas laced with dust appear at the upper right of the picture, and more "fingers" can be seen nearly face-on, behind the translucent bubble. Based on the rate the star is expending energy, in 10 to 20 million years it will explode as a supernova. And the bubble will succumb to a common fate: It’ll pop. The Bubble is 8 ly in diameter.
Comet C/2021 A1 Leonard passed Earth at 21 million miles away (88 times the distance to the moon), passed Venus at 2.6 million, and passes the sun at 56 million. If still intact, it then follows its elliptical orbit until it is 550 billion miles away before turning back to us. It's an ultrafast, long period comet traveling 160,000 mph but because its large orbit, it won't be back for 80,000 years. Its nucleus is a little more than a half mile in diameter.
The Rosette Nebula is an H II region located in the giant molecular cloud in the Monoceros region of the Milky Way. The open cluster NGC 2244 is closely associated with the nebulosity, the stars of the cluster having been formed from the nebula's matter. The cluster and nebula lie at a distance of 5,000 l.y. from Earth and measure roughly 130 l.y. in diameter. The radiation from the young stars excites the atoms in the nebula, causing them to emit radiation themselves producing the emission nebula we see. There are numerous new-born stars inside the Rosette Nebula and studded within a dense molecular cloud. approximately 2,500 young stars lie in this star-forming complex, including massive O-type stars which are primarily responsible for blowing the ionized bubble. Most of the ongoing star-formation activity is occurring in the dense molecular cloud to the south east of the bubble.
The Cat's Eye Nebula, NGC 6543, is a planetary nebula; a type of emission nebula consisting of an expanding, glowing shell of ionized gas ejected from a red giant star late in its life. The term "planetary nebula" is a misnomer because they are unrelated to planets. The term originates from the planet-like round shape of these nebulae observed by early astronomers. The star is ejecting its mass in a series of pulses at 1,500-year intervals. These convulsions created dust shells, making a layered, onion-skin structure around the dying star. The bright nebulosity has temperatures of 7,000 to 9,000 K, the outer halo has the higher temperature around 15,000 K, and the surface temperature for the central star is about 80,000 K, being 10,000 times as luminous as the sun. Velocity of the stellar wind is over 4 million mph and the star is mass loss is twenty trillion tons per second.
While many of the nebulae are emission nebulae - clouds of dust and gas that are hot enough to emit their own radiation and light the Iris Nebula, NGC 7023, is a reflection nebula. Its color comes from the scattered light of its central star, 1,400 l.y. away. The Iris Nebula’s glowing gaseous petals stretch roughly 6 l.y. across. This nebula is of particular interest because of its colors. Reflection nebulae glow because they are made up of extremely tiny particles of solid matter, up to 10 or even 100 times smaller than dust particles on Earth. These particles diffuse the light around them, giving the nebula a second-hand glow that’s typically bluish (like our sky). While the Iris Nebula appears predominantly blue, it includes large filaments of deep red, indicating the presence of an unknown chemical compound likely based on hydrocarbons.
NGC 7662, nicknamed the Blue Snowball Nebula, is a planetary nebula located about 2,500 l.y. from Earth. Nebulae like these represent a stage in evolution that stars like our Sun undergo when they run out of fuel. Stars are nuclear furnaces that spend most of their lives fusing hydrogen into helium. Massive stars have fiery fates, exploding as supernovae, but medium-mass stars like the Sun swell to become red giants as they exhaust their fuel. The process begins when, after billions of years of nuclear fusion, the star starts to shut down. Gravity (no longer balanced by the outward pressure created by nuclear fusion) compresses the stellar core. The star’s outer layers of gas puff away into space, creating a planetary nebula (so named because these objects aft en appear roundish). At the center lie the remains of the original star’s compressed core, a small white dwarf. The Blue Snowball's diameter is approximately 0.2 l.y.
I love you to 3C273 and back! That’s 5 Billion l.y. and it’s the farthest object I have seen. It’s a quasar (QUASi-stellAR radio source): a super luminous active galactic nucleus with a luminosity 4 trillion times that of our sun. It’s powered by a super-massive black hole at the center of the host galaxy and its accretion disk, composed of interstellar gas, dust, and even whole stars, is heated to very high energies and radiate from the radio to the X-ray. In 1962, Radio astronomy was sensitive but its eyesight was somewhat fuzzy and an exact location for 3C273 was impossible to determine. Without an exact location, optical telescopes could not find out if it were a star, a galaxy, or some more exotic object. Astronomer Cyril Hazard realized the moon would pass over the likely position of 3C273 and he could record the moment the moon obstructed the radio signal and determine the precise location of the quasar. Brilliant but he took the wrong train and missed the occultation. His team was able to make the observation and found an optical object at 3C273’s position.
IC 405 (also known as the Flaming Star Nebula) is an emission and reflection nebula that lies about 1,500 light-years away and is about 5 light-years across. Rippling dust and gas lanes give the Flaming Star Nebula its name. The intensely bright star AE Aurigae is so hot that it is blue, and emits energetic light that knocks electrons away from the surrounding gas. The hydrogen emission gas makes up the “flame” of IC 405, while the blue reflection nebula resembles smoke.
NGC 2359, or Thor’s Helmet, is an emission nebula located in the constellation Canis Major, the Great Dog. With its round shape and wing-like filamentary structures, this visually stunning nebula bears a striking resemblance to the helmet worn into battle by Thor, the well-known Norse god of thunder. Thor’s Helmet spans 30 l.y across making it more than 10 times larger than our entire solar system. It lies approximately 11,960 l.y. away and contains several hundred solar masses, At its core is WR7, an extremely hot Wolf-Rayet star thought to be over 280,000 times brighter than our Sun and 16 times more massive. The helmet is like an interstellar bubble, blown as a fast wind from the bright, massive WR7 near the bubble's center inflates a region within the surrounding molecular cloud.
The Elephant's Trunk Nebula is a concentration of interstellar gas and dust within the much larger ionized gas region IC 1396 about 2,400 l.y. away. The piece of the nebula shown here is the dark, dense globule IC 1396A. The bright rim is the surface of the dense cloud that is being illuminated and ionized by a very bright, massive star (HD 206267) that is just to the east of IC 1396A. The entire IC 1396 region is ionized by the massive star, except for dense globules that can protect themselves from the star's harsh ultraviolet rays. The Elephant's Trunk Nebula is a site of star formation, containing several very young (less than 100,000 yr) stars that were discovered in infrared images in 2003. Two older stars are present in a small, circular cavity in the head of the globule. Winds from these young stars may have emptied the cavity. The combined action of the light from the massive star ionizing and compressing the rim of the cloud, and the wind from the young stars shifting gas from the center outward lead to very high compression and this pressure has triggered the current generation of protostars.
The Owl Nebula, Messier 97, is a planetary nebula 2,030 l.y. from Earth. The Nebula was formed when a central star ran out of hydrogen fuel and expelled its outer gaseous layers about 6,000 BC. As the outer layers were gradually blown off over thousands of years, what was left of the original star contracted to form a hot white dwarf. The central star has 55 to 60 percent of the Sun’s mass, only 4 percent of the Sun’s radius, and an estimated surface temperature of 123,000 K. The star can be seen between the Owl’s eyes and its radiation is responsible for the nebula’s glow. Most stars that expel material to form planetary nebulae expel a large amount of it in two opposing directions. The jets blown off by the progenitor star of the Owl Nebula are almost aligned with our line of sight. The dust within the jets blocks enough light from the expanding nebula to create the appearance of owl-like eyes. One of the nebula’s eyes appears darker than the other. This is the jet that is emitted in our direction, while the fainter eye marks the jet expelled in the opposite direction, away from us. The nebula will continue to disperse over the next several thousand years, while the central white dwarf will cool and fade away. The Owl Nebula’s outermost gaseous halo was not observed until 1991.
IC 410 is a faint and dusty emission nebula of more than 100 light-years across, located near the Flaming Star Nebula (IC 405) in a large star forming (HII) region about 12,000 l.y. away in the constellation of Auriga. The cloud of glowing gas is sculpted by stellar winds and radiation from the embedded open star cluster catalogued as NGC 1893, which is just about 4 million years old. The massive, hot stars of this cluster are all very young, having only been recently formed from IC 410. The bright stars of this cluster are seen just above the prominent dark dust cloud near picture center. Notable are two streamers of material, known as the “Tadpoles of IC 410”. These tadpoles, which consist of denser, cooler gas and dust, are approximately 10 light-years long and potentially sites of ongoing star formation. Form given by the winds and radiation of the cluster’s stars, the tadpoles are pointing their tails outwards, away from the nebula’s central regions. Because of these tadpoles, IC 410 is sometimes nicknamed the Tadpoles Nebula.