- 2811 - NEBULAE - Boomerang, Butterfly, and Jewel Bug? - This Review is about “nebulae”. A nebula is a tenuous cloud of gas and dust that occur in outer space. About 1% of the interstellar medium is in the form of dust, small solid particles that are efficient in absorbing and scattering radiation.
------------------------------------- Orion Nebula
--------------- 2811 - NEBULAE - Boomerang, Butterfly, and Jewel Bug?
- Hubble telescope was recently been studying “NGC 6302“, known as the "Butterfly Nebula," to observe it across a more complete spectrum of light, from near-ultraviolet to near-infrared. This wide spectrum will help researchers better understand the mechanics at work in the technicolor "wings" of gas nebulae.
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- These new observations highlight a new pattern of near-infrared emission from singly ionized iron, which traces an S-shape from lower left to upper right. This iron emission likely traces the central star system's most recent ejections of gas, which are moving at much faster speeds than the previously expelled mass.
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- The star, or stars, at its center are responsible for the nebula's appearance. In their death throes, they have cast off layers of gas periodically over the past couple thousand years.
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- The "wings" of the Butterfly Nebula are regions of gas heated to more than 36,000 degrees Fahrenheit that are tearing across space at more than 600,000 miles an hour. The nebula lies between 2,500 and 3,800 light-years away in the constellation Scorpius.
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- As nuclear fusion engines, most stars live placid lives for hundreds of millions to billions of years. But near the end of their lives they can turn into crazy nebulae, puffing off shells and jets of hot gas.
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- Astronomers have employed Hubble's full range of imaging capabilities to dissect such crazy fireworks happening in two nearby young planetary nebulas. The Butterfly Nebula got its name because of its wing-like appearance. In addition, NGC 7027 resembles a jewel bug, an insect with a brilliantly colorful metallic shell.
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- The researchers have found unprecedented levels of complexity and rapid changes in jets and gas bubbles blasting off of the stars at the centers of both nebulas. Hubble is allowing the researchers to converge on an understanding of the mechanisms underlying the chaos.
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- This team is examining this pair of nebulas with Hubble's full capabilities, making observations in near-ultraviolet to near-infrared light. In particular, the new Hubble images reveal in vivid detail how both nebulas are splitting themselves apart on extremely short timescales allowing astronomers to see changes over the past couple decades. Some of this rapid change may be indirect evidence of one star merging with its companion star.
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- The nebula NGC 7027 shows emission at an incredibly large number of different wavelengths, each of which highlights not only a specific chemical element in the nebula, but also the significant, ongoing changes in its structure.
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- The research team also observed the Butterfly Nebula, which is a counterpart to the "jewel bug" nebula. Both are among the dustiest planetary nebulas known and both also contain unusually large masses of gas because they are so newly formed. This makes them a very interesting pair to study in parallel.
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- Hubble's broad multi-wavelength views of each nebula are helping the researchers to trace the nebulas' histories of shock waves. Such shocks typically are generated when fresh, fast stellar winds slam into and sweep up more slowly expanding gas and dust ejected by the star in its recent past, generating bubble-like cavities with well-defined walls.
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- Researchers suspect that at the hearts of both nebulas are two stars circling around each other, like a pair of figure skaters. Evidence for such a central "dynamic duo" comes from the bizarre shapes of these nebulas. Each has a pinched, dusty waist and polar lobes or outflows, as well as other, more complex symmetrical patterns.
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- A leading theory for the generation of such structures in planetary nebulas is that the mass-losing star is one of two stars in a binary system. The two stars orbit one another closely enough that they eventually interact, producing a gas disk around one or both stars. The disk is the source of outflowing material directed in opposite directions from the central star.
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- Similarly, the smaller star of the pair may merge with its bloated, more rapidly evolving stellar companion. This also can create outflowing jets of material that may wobble over time. This creates a symmetric pattern, like the one that gives NGC 6302 its "butterfly" nickname. Such outflows are commonly seen in planetary nebulas.
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- The suspected companion stars in NGC 6302 and NGC 7027 haven't been directly detected because they are next to, or perhaps have already been swallowed by, larger red giant stars, a type of star that is hundreds to thousands of times brighter than the Sun.
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- Imagine a lawn sprinkler spinning wildly, tossing out two S-shaped streams. At first it appears chaotic, but if you stare for a while, you can trace its patterns. The same S-shape is present in the “Butterfly Nebula“, except in this case it is not water in the air, but gas blown out at high speed by a star. And the "S" only appears when captured by the Hubble camera filter that records near-infrared emission from singly ionized iron atoms.
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- The S-shape directly traces the most recent ejections from the central region, since the collisions within the nebula are particularly violent in these specific regions of NGC 6302. This iron emission is a sensitive tracer of energetic collisions between slower winds and fast winds from the stars.
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- The fact that the iron emission is only showing up along these opposing, off-center directions implies that the source of the fast flows is wobbling over time, like a spinning top that's about to fall.
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- The 'Jewel Bug' planetary nebula NGC 7027 had been slowly puffing away its mass in quiet, spherically symmetric or perhaps spiral patterns for centuries. Something recently went haywire at the very center, producing a new cloverleaf pattern, with bullets of material shooting out in specific directions.
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- Since the 1960s, we've known that a 5° temperature (Fahrenheit) bathes the universe, the leftover heat from the Big Bang, usually expressed as 2.73 K. This means some morsel of warmth remains absolutely everywhere. To achieve absolute cold, you would have to not merely isolate yourself from this all-pervasive cosmic microwave background (CMB) radiation, but also find a way to suck out every bit of remaining atomic motion.
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- Earthly laboratories using clever processes have actually attained this sort of perfect cold to within a billionth of a degree. The coldest artificial place in the known universe is at the lab at MIT.
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- Some 5,000 light-years distant, the Boomerang Nebula’s central dying star spews gas and dust that carries heat away, significantly lowering the temperature around it.
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- As for the coldest natural place in the universe, scientists have found that, too. It’s a location that, amazingly enough, manages to be chillier than space; a thermometer would read less than the 2.73 K temperature of the CMB in the “Boomerang Nebula“.
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- When observing the Boomerang, we actually view the first stages of a planetary nebula. Ironically, such objects are usually extremely hot because their central star is typically fiercely blue, the hottest type of star. The surface temperature of this sun is 10 times that of our Sun and sends sizzling ultraviolet radiation spewing outward to excite the surrounding gases.
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- But the Boomerang Nebula is so young that it expels gas at a furious pace. This outrush not only blocks the cosmic microwaves that might otherwise warm it, but it also carries heat away. Even in normal terrestrial life, we see examples of how expanding gas has a chilling effect, discharging a can of whipped cream or tire-inflation gas makes that container feel colder in your hand.
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- In the constellation Centaurus, an impressive 5,000 light-years away, the newly minted planetary nebula expands so rapidly that the Boomerang has a temperature of only –458° F (–272° C), a mere 1° above absolute zero. This is the only known object whose temperature is naturally lower than the background radiation of the universe.
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- Astronomers using the 15-meter scope at the European Southern Observatory in Chile made this discovery in 1995. They would have liked to give it a better name, as “Boomerang” didn’t seem relevant either to the concept of cold or to the object’s appearance.
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- In any case, the faint arcs and filaments streaking through and around the gas give the Boomerang an appearance different from other planetary nebulae, which often resemble doughnuts or giant bubbles, although they occasionally boast complex structures.
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- The best guess is that the Boomerang eventually will evolve and develop those same bubble-like structures. Presently, this ancient sun spews out at least 10 times more material yearly than normal for the early stages of a nascent planetary nebula.
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- This “wind” blows at more than 300,000 mph, carrying the super cold gas away from the dying star in the middle. In time, this star should grow much hotter before it finally peaks, collapses, and settles into the ultimate white dwarf state that is the destiny of all planetary nebula progenitors. Then, the current extreme cold will be replaced by its exact opposite.
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- The Boomerang Nebula’s central star has lost an entire Sun’s worth of material just since A.D. 500. That unsustainable mass-loss will not endure much longer. For today’s observers, the resulting super fast nebula expansion is creating the ultimate Big Chill in the universe.
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------------------------------------- Other reviews about nebulae:
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- 1694 - Nebulae are like Snowflakes, no two are alike. The physics part of the story is even more interesting. Scroll the internet for some beautiful pictures and then try to imagine what is really going on with atoms and elements being created.
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- 1491 - Globular Nebulae are dark silhouettes surrounded by star light. The Globules are dark clouds in space that are often silhouetted by light emissions in the background. The dark clouds are called Bok Globules after the Dutch-American astronomer Bart Bok.
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- 1333 - The Red Rectangle Nebula Explained? The Red Rectangle Nebula can also be described as a giant “X” with interconnecting ladder-like steps. The color is unusual too. Astronomers expect the red glow of energetic hydrogen. But, this rectangle’s color is orange- red created by fluorescing dust. The source has only recently been discovered to be organic carbon-rich molecules bathed in ultraviolet light.
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- September 1, 2020 2811
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