Related topics: stars · white dwarfs · hubble space telescope

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. ...

Ultra-close stars discovered inside a planetary nebula

An international team of astronomers have discovered two stars in a binary pair that complete an orbit around each other in a little over three hours, residing in the planetary nebula M3-1. Remarkably, the stars could drive ...

Tellurium is detected in one of its places of origin

An international team led by a Ph.D. student from the Instituto de Astrofísica de Canarias (IAC) and the University of La Laguna (ULL) has identified the emission of tellurium in the infrared spectra of two planetary nebulae ...

Planetary nebula lasers

Astronomical masers (the radio wavelength analogs of lasers) were first identified in space over fifty years ago and have since been seen in many locations; astronomical lasers have since been seen as well. Some of the most ...

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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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