Category: Eyes in the Sky

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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Sparks in the Dark


Violent things can come in small faint packages as shown in this NASA/ESA Hubble Space Telescope image of the starburst galaxy NGC 3738.

Explore the glowing red reservoirs of hydrogen gas, filaments of dust, and diffuse glow of thousands of stars in this faint irregular galaxy. What shapes and stories do you see? Leave a note in the comments below.

NGC 3738 is a dwarf galaxy in the middle of extreme star formation. The glowing red areas are full of hydrogen, the stuff that helps make new stars. Gravity pulls together gas and dust in pockets within the cloud. As the pocket becomes more massive, it begins to heat up until eventually it can become hot enough to fuse hydrogen atoms in a sustainable nuclear reaction. These new stars give off strong stellar winds and ultraviolet radiation that excites hydrogen atoms in the rest of the cloud causing it to glow a characteristic red.

This galaxy is relatively close to Earth; just 12 million light-years from the Sun; meaning light, traveling nearly 6 trillion miles per year, took 12 million years to cross the intergalactic distance. NGC 3738 is a compact bluish dwarf galaxy, the faintest of starburst galaxies. Blue compact dwarfs are generally blue because of large clusters of hot, blue and young stars. These stars tend to be massive, meaning they burn through their supply of hydrogen fuel within just a million years. If they are massive enough, they will end their lives in cataclysmic stellar explosions called supernovae. For a time, a single star can outshine an entire galaxy, releasing more energy in a few moments than our Sun produces in its entire expected lifespan of 8 billion years.

As you explore NGC 3738, you may notice it seems jumbled and disorganized. These galaxies don’t have spiral arms nor bright center bulges. Some astronomers believe these galaxies resemble some of the earliest galaxies that formed in the early Universe and may provide clues into how stars and galaxies formed during that time. As you pan across the image, look for dozens of faint and faraway galaxies scattered throughout this deep image of the cosmos.

NGC 3738, first observed by British astronomer William Herschel in 1789, is found in the constellation Ursa Major, The Great Bear or Big Dipper. It belongs to the Messier 81 group of galaxies, a nearby galactic cluster.

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Arching Eyebrow Frames Galactic Eye


An arching lane of dark dust resembles an eyebrow above a blue eye in this image of Arp 116 from the NASA/ESA Hubble Space Telescope.

Explore this unusual galactic pair. What stories or pictures do you see? Leave a note in the comments below.

These two galaxies couldn’t be more different. The giant elliptical galaxy in the center is known as Messier 60. The smaller spiral galaxy is NGC 4647. M60 is a classic example of elliptical galaxies. The massive galaxies are usually featureless, egg shaped galaxies that are very bright. Nearly a trillion stars can make up their bright cores and diffuse halos. Most notable in this pair is the color. Elliptical galaxies tend to have less gas and dust used in star making. So the stars in these galaxies are older yellow and red stars.

NGC 4647, on the other hand, is full of new blue stars. Dark lanes of dust and faint blotches of nebulae line the galactic arms offering fuel for future star formation. The galaxy is about the size of our own Milky Way Galaxy but is a lightweight compared to the M60 galaxy. The smaller spiral galaxy is only about two-thirds the size of its massive companion.

As you explore, look for dozens of faraway galaxies of various shapes through the bright haze of M60.

While the two galaxies overlap as seen from Earth, astronomers are not sure whether the two are close enough to interact. Waves of star formation at the edges of the galaxies usually offer the clearest signs that interactions are occurring. Recent studies from the Hubble Space Telescope do suggest that early interactions, a slight pushing and pulling of galaxies spiral arms, between the two are occurring.

M60 lies about 50 million light-years from Earth toward the constellation Virgo, the Virgin. NGC 4647 is a little more distant, roughly 63 million light-years away.

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Colossal Fireworks

X-ray: NASA/CXC/Rutgers/G.Cassam-Chenaï, J.Hughes et al.; Radio: NRAO/AUI/NSF/GBT/VLA/Dyer, Maddalena & Cornwell; Optical: Middlebury College/F.Winkler, NOAO/AURA/NSF/CTIO Schmidt & DSS

An expanding translucent bubble is all that remains of a star in this combinded image from NASA’s Chandra X-ray Observatory and other observatories.

Explore the bumps, ribbons and sheets throughout this image of SN 1006. What stories or images do you see? Leave a note in the comments below.

In the spring of 1006, night-time observers in China, Japan, Europe, the Arab world and the Americas documented a new light in the sky. To this day the supernova of 1006 is the brightest stellar event in recorded history. Reports from China and Arab astronomers report the star was more than twice as big as Venus and objects cast shadows. While this new “guest star” glowed for months, ancient observers had no way of knowing that a star had exploded. This was a different type of supernova. Instead of a massive star collapsing and exploding, a white dwarf star captured mass from a companion star. When enough material lands on the surface of a white dwarf it becomes unstable and explodes. White dwarf stars are the burned out cores of stars that were once like our Sun. After billions of years fusing hydrogen atoms in the core, the star runs out of fuel. When this occurs, the star puffs off its outer layers and all that remains is the white-hot core. In this case, the white dwarf probably orbited a much larger red giant star.

SN 1006 is found about 7,000 light-years from Earth toward the constellation Lupus, the Wolf. The remnant of the supernova of 1006 was not found until 1965 when astronomers using found that a previously known radio source was surrounded by a large shell. We now know that the shell extends for about 65 light-years. The shell is so large that the Hubble Space Telescope can image only parts of the supernova remnant.

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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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