Related topics: stars · white dwarfs · hubble space telescope

Image: Hubble views star nearing its end

This image from the NASA/ESA Hubble Space Telescope shows NGC 5307, a planetary nebula that lies about 10,000 light-years from Earth. It can be seen in the constellation Centaurus (the Centaur), which can be seen primarily ...

Image: Hubble captures dynamic dying star

This atmospheric image taken with the NASA/ESA Hubble Space Telescope shows a dark, gloomy scene in the constellation of Gemini (the Twins). The subject of this image confused astronomers when it was first studied—rather ...

Image: Hubble's portrait of star's gaseous glow

Although it looks more like an entity seen through a microscope than a telescope, this rounded object, named NGC 2022, is certainly not algae or tiny, blobby jellyfish. Instead, it is a vast orb of gas in space, cast off ...

Image: the Egg Nebula

The Egg Nebula is a preplanetary nebula, created by a dying star in the process of becoming a planetary nebula. Planetary nebulas have nothing to do with planets – the name arose when 18th century astronomers spotted them ...

A fleeting moment in time

The faint, ephemeral glow emanating from the planetary nebula ESO 577-24 persists for only a short time—around 10,000 years, a blink of an eye in astronomical terms. ESO's Very Large Telescope captured this shell of glowing ...

The Saturn Nebula reveals its complexity

A planetary nebula is the corpse that remains when a star dies. When planetary nebulae were observed for the first time with a telescope, they presented a roughly circular shape, resembling that of the gas giant planets. ...

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Planetary nebula

A planetary nebula is an emission nebula consisting of a glowing shell of gas and plasma formed by certain types of stars when they die. The name originated in the 18th century because of their similarity in appearance to giant planets when viewed through small optical telescopes, and is unrelated to the planets of the solar system. They are a relatively short-lived phenomenon, lasting a few tens of thousands of years, compared to a typical stellar lifetime of several billion years.

At the end of the star's life, during the red giant phase, the outer layers of the star are expelled via pulsations and strong stellar winds. Without these opaque layers, the remaining core of the star shines brightly and is very hot. The ultraviolet radiation emitted by this core ionises the ejected outer layers of the star which radiate as a planetary nebula.

Planetary nebulae are important objects in astronomy because they play a crucial role in the chemical evolution of the galaxy, returning material to the interstellar medium which has been enriched in heavy elements and other products of nucleosynthesis (such as carbon, nitrogen, oxygen and calcium). In other galaxies, planetary nebulae may be the only objects observable enough to yield useful information about chemical abundances.

In recent years, Hubble Space Telescope images have revealed many planetary nebulae to have extremely complex and varied morphologies. About a fifth are roughly spherical, but the majority are not spherically symmetric. The mechanisms which produce such a wide variety of shapes and features are not yet well understood, but binary central stars, stellar winds and magnetic fields may all play a role.

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