Planetary Nebulae - What Are They?

The word “nebula” comes from the Latin word for cloud, and nebulae come in many different shapes and sizes. Some nebulae occur in regions of space where new stars are being formed, and others occur as the remnants of stars that have exhausted their fuel source and are now dying or dead.

When a star runs out of fuel to burn, it blows off its outer layers. These layers of gas expand into space and form a nebula in the shape of a ring or bubble. The central core of the dying planet can be seen in many planetary nebulae.

Planetary Nebula

Image courtesyof Ask an Astronomer for Kids (http://coolcosmos.ipac.caltech.edu/cosmic_kids/AskKids/planetaryneb.shtml)

The first planetary nebula recorded was discovered by astronomer, Charles Messier, in 1764. It is called the Dumbell Nebula M27.

M27

Image courtesy of Students for the Exploration and Development of Space (http://www.seds.org/messier/m/m027.html)

In 1792 William Herschel discovered the Saturn Nebula NGC 7009, so called because of its resemblance to the planet Saturn, with its rings.

NGC 7009

Image courtesy of Students for the Exploration and Development of Space (http://www.seds.org/messier/xtra/ngc/n7009.html)

Herschel soon realized that many of the nebulae he encountered resembled planets, such as the one he had discovered, Uranus. Because of this, he invented the name “planetary nebula” for objects in this classification.

Planetary nebulae were originally thought to be unresolved clusters of gas and dust; however, in 1790 Herschel discovered the nebula NGC 1514 and noticed its brightly burning central core. This led him to the belief that the planetary nebulae were associated with a central core, and not unresolved clusters of nebulous material.

NGC 1514

Image courtesy of Students for the Exploration and Development of Space (http://www.seds.org/~spider/spider/Misc/n1514.html)

In the 20th Century, advances in technology have significantly helped in the study of planetary nebulae. Space telescopes, such as Hubble, have provided high resolution imagery of nebulae, and advancements in UV and IR technology have allowed scientists to determine the physical characteristics of nebulae with much more accuracy. The study of planetary nebulae continues to provide us with more information about the formation of our universe.

Ask an Astronomer for Kids. (http://coolcosmos.ipac.caltech.edu/cosmic_kids/AskKids/planetaryneb.shtml).

"planetary nebula." Students for the Exploration and Development of Space. (http://www.seds.org/messier/planetar.html).

"planetary nebula." Wikipedia (http://en.wikipedia.org/wiki/Planetary_nebula).