Posts Tagged ‘planetary nebula’

Eye of Stars


Set against a starry backdrop, ESO 456-67 glows like a cat’s eye or in the shape of Mas Amedda from Star Wars in this image from the NASA/ESA Hubble Space Telescope.

Explore the planetary nebula ESO 456-67. What shapes do you see? Leave a note in the comments below.

Although called a planetary nebula, these starry objects have nothing to do with planets. In early telescopes of the 18th century, while astronomers were searching for new planets, these small and round nebulae looked like planets. The nebulae are much farther away and much larger than any planet in our solar system. Planetary nebulae are the last stage in the life of a star similar to our Sun in size. As these stars approach the end of their long lives, they run out of hydrogen fuel. They bloat and throw off shells of gas and dust. Sometimes, the bubbles they produce are smooth and round. But other times, they are complex with material shooting away in different directions.

As you explore ESO 456-67, look for the remaining star in the center of the blue area. Astronomers call these stars white dwarfs. They are hot and small. Over billions of years, this star will cool to become a warm cinder. The blue area surrounding the white dwarf is a hot bubble of gas. White dwarfs give off intense ultraviolet radiation that causes the gas of the planetary nebula to glow. Other regions of the nebula contain different elements that glow different colors.

ESO 456-67 is found about 10,000 light-years from Earth toward the rich starfields in the constellation Sagittarius, the Archer. Light from the planetary nebula began traveling toward our eyes on Earth just about the time when humans developed agriculture techniques in Mesopotamia.

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Ethereal Purple Petals


Purple petals, an eerie purplish eye or tire glow in this image from the European Southern Observatory.

IC 5148, or the Spare Tire Nebula, is a planetary nebula with a diameter of just a couple of light-years. It is one of fastest expanding planetary nebula known to astronomers, growing at more than 50 kilometers per second. Planetary nebulae have nothing to do with planets. In the 19th century, astronomers searching for planets observed objects that looked similar to the outer gas giants Uranus and Neptune. Stars about the same size or slightly larger than our Sun will become planetary nebula at the end of their lives. As these stars burn the last of their hydrogen fuel, they begin to puff up and throw off their outer layers. Blistering ultraviolet radiation from the exposed hot white dwarf excites atoms in the expanding ring of material causing it to glow. While beautiful, planetary nebulae are a short-lived stage in a star’s life. Eventually the glowing shell will fade away.

IC 5148 is found about 3,000 light-years from Earth toward the southern constellation Grus, the Crane.

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Butterflies Beyond the Tail of a Swan


A butterfly-shaped nebula, the blasted remains of a star similar to our Sun, lies just beyond the tip of the tail of Cygnus, the Swan, in this image from the NASA/ESA Hubble Space Telescope.

Explore the glowing gas and dust of this butterfly-shaped nebula known as NGC 7026. What shapes or stories can you tell? Leave a note in the comments below.

NGC 7026 is a planetary nebula. While astronomers using early telescopes thought these objects resembled planets, they are far beyond our solar system. As a star like our Sun ends its long life, it runs out of hydrogen atoms, the nuclear fuel that runs it. The star puffs off its outer layers creating bubbles of expanding gas and dust surrounding the white-hot core. Astronomers call this core a white dwarf. It is a dead star but is still incredibly hot. Eventually, after tens of billions of years, it will cool enough so you could touch it. But as a white dwarf, the star gives off strong solar winds that push material away from the star while blistering ultraviolet radiation causes the gas to glow. Different atoms in the expanding bubble give off different colors like a fluorescent sign on Earth. Red in this image is glowing nitrogen (the gas that makes up most of Earth’s atmosphere); blue is oxygen. Although in reality oxygen glows with a greenish color, astronomers have shifted the light in this image so they can see more detail.

NGC 7026 is found just 6,000 light-years from Earth toward the constellation Cygnus the Swan. That means that the light we see coming from this object has been traveling since before the beginning of recorded history.

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Starlike Butterfly

Credit: ESA/NASA Hubble


A starlike butterfly flits in the dark in this image from the NASA/ESA Hubble Space Telescope.

Explore the body and wings of planetary nebula NGC 6881. What shapes and patterns do you see? Leave a note below.

The inner part of NGC 6881 is about one-fifth of a light-year across. Light, traveling at about 6 trillion miles per year, would take about one year to zip between the symmetrical tips of this cosmic butterfly. The wings of NGC 6881 formed at about the same rate in the same way. Symmetrical means that one side is almost a mirror image of the other side. Some planetary nebulae have jumbled interiors while others form in cylinders that from our vantage on Earth look like donuts.

Planetary nebula are the final stage of life for stars like our own Sun. After billions of years, the star runs out of hydrogen fuel. In an attempt to keep burning the star balloons in size to become a red giant. The star puffs out its outer layers creating an expanding bubble. Eventually, all that remains is the bright and hot core called a white dwarf. Strong solar winds shape the new nebula, pushing gas and dust away from the star. Blistering ultraviolet radiation from the white dwarf warm and excite molecules in the gas cloud causing it to glow. A planetary nebula is born.

Planetary nebulae have nothing to do with planets however. When astronomers first sought out planets in their telescopes, they ran across objects that looked much like the giant planets of Uranus and Neptune. It wasn’t until the 20th century that the true nature and distance of planetary nebula was discovered.

NGC 6881 is found about 13,000 light-years from Earth toward the constellation of Cygnus, the Swan.

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A Shrouded Petal

Credit: ESA/NASA Hubble

A shrouded star opens its irregular petals in this image from the NASA/ESA Hubble Space Telescope.

Explore the planetary nebula known as Henize 3-1333. What shapes and stories do you see? Leave a note below.

The expanding layers and irregular globes of glowing gas surrounding Hen 3-1333 is all that is left of a star that was much like our Sun. Those globes of gas make the petals of our star flower. During the death throes of Sun-like, medium sized stars, they puff off their outer layers. Sometimes the layers come off in circular patterns like the Ring Nebula or Helix Nebula. Other times the layers become more complicated because of possible companion stars or uneven spinning. At the heart of the planetary nebula is the exposed, hot core of the star called a white dwarf. Strong solar winds and blistering ultraviolet radiation from the core shapes the expanding clouds and cause them to glow.

Hen 3-1333 interests astronomers because our Sun is destined to become a planetary nebula. The light from the star also changes dramatically from time to time. Astronomers call this type of star a Wolf-Rayet type star. Astronomers believe that the light fluctuates because a thick disk of dust occasionally blocks light from the star. This change in brightness mimics a Wolf-Rayet star.

Wolf-Rayet stars change their brightness quickly because of unstable conditions within the star. Their cores no longer burn hydrogen as they had during the billions of years of its life. It takes more energy to burn helium and other heavier elements. So the star becomes smaller and contracts. Surface temperatures soar to 25,000 to 50,000 degrees Celsius. This is far hotter than the Sun’s 5,500 degree surface.

Hen 3-1333 is found in the H-shaped southern constellation of Ara, the Altar. In Greek mythology, Centaurus the centaur sacrificed Lupus the wolf from this altar. According to myths, the altar was constructed by the Cyclopes as a place to sacrifice to the Olympian gods. If you turn the altar over, the Milky Way creates a “smoke” rising from this constellation.

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The ancient peoples saw pictures in the sky. From those patterns in the heavens, ancient storytellers created legends about heroes, maidens, dragons, bears, centaurs, dogs and mythical creatures...
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