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Stand outside on a clear night and look up. You’ll see that the stars are thicker along the Milky Way (shown above).
Our galaxy looks like a fuzzy gray ribbon of light across the sky. A low-power telescope shows that the Milky Way is actually made up of countless stars. They are too far away to be seen separately by the naked eye.
Astronomers have looked along the Milky Way with high-power telescopes for the last 200 years. They have found nebulae in many different colors and shapes. Spiral-shaped nebulae were later discovered to be whole distant cities of stars, called galaxies. Nebulae can tell us things about the evolution of stars. That’s because they are part of the birth and death of stars.
▲ Emission Nebula
An emission nebula is a group of gases that glow. The Cat’s Paw Nebula (above) looks like a huge paw print on the sky. The bright blobs are where clusters of young stars are blowing bubbles into the cloud. That makes the gases around them light up. They glow in shades of red, the color emitted by hot hydrogen gas.
Use your mouse or finger to scrub through the animation below.
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▲ An artist’s illustration of a nebula
Use your mouse or finger to scrub through the animation below.
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▲ An artist’s illustration of a nebula
◀ Reflection Nebula
A reflection nebula is made of dust that we can see only because light from nearby stars bounces off it. The Witch Head Nebula (left) glows mainly from light reflected by the bright star Rigel. Rigel is in the Orion constellation. The nebula is blue partly because Rigel is blue. It’s also because the dust reflects blue light better than it reflects red light.
▲ Planetary Nebula
A planetary nebula is usually round. It looks like the disk of a planet when seen through a low-power telescope. It is actually an expanding blanket of gas around a dying star. To some, the Eskimo Nebula (above) looks like a person’s head surrounded by a parka. Planetary nebulae are the expanding remains of a star that is burning out.
▲ Supernova Remnant
When a massive star runs out of fuel, it explodes. It leaves behind a collection of newly formed elements. This leftover material is known as a supernova remnant. The blast itself is called a supernova. All elements heavier than iron are made in supernova explosions. The Crab Nebula (above) was discovered in 1731. It lies where a mysterious bright object briefly appeared in 1054. Astronomers later concluded that the Crab Nebula is the expanding debris from a star explosion in 1054.
▲ Combo Nebula
In deep-space photographs, it looks like rose petals. The Trifid Nebula (above) gets its name from the dark lanes of dust that divide it into three (tri) pieces. The pink area is an emission nebula. The blue area is a reflection nebula. A bright cluster of stars lies in the center, lighting up the nebula.
Use your mouse or finger to scrub through the animation below.
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▲ An artist’s illustration of a nebula
