Nebulae: Nebula, Interstellar Cloud, Supernova Remnant, Planetary Nebula, Molecular Cloud, Emission Nebula, H II Region, Herbig Source Wikipedia

ISBN: 9781156545423

Published: August 15th 2011

Paperback

40 pages


Description

Nebulae: Nebula, Interstellar Cloud, Supernova Remnant, Planetary Nebula, Molecular Cloud, Emission Nebula, H II Region, Herbig  by  Source Wikipedia

Nebulae: Nebula, Interstellar Cloud, Supernova Remnant, Planetary Nebula, Molecular Cloud, Emission Nebula, H II Region, Herbig by Source Wikipedia
August 15th 2011 | Paperback | PDF, EPUB, FB2, DjVu, AUDIO, mp3, RTF | 40 pages | ISBN: 9781156545423 | 10.15 Mb

Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. Pages: 38. Chapters: Nebula, Interstellar cloud, Supernova remnant, Planetary nebula, Molecular cloud, Emission nebula, HMorePlease note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. Pages: 38. Chapters: Nebula, Interstellar cloud, Supernova remnant, Planetary nebula, Molecular cloud, Emission nebula, H II region, Herbig-Haro object, Visibly dark X-ray source, First X-ray source in Cancer, Nebulae in fiction, Centaurus XR-2, Cygnus X-ray ring, Centaurus X-1, X-ray halo, Cygnus X-4, Protoplanetary nebula, Bipolar nebula, Centaurus X-2, Bok globule, Nebulium, Norma XR-2, Circumstellar disk, Pulsar wind nebula, Scorpius XR-5, Reflection nebula, Zanstra method, Dark nebula, H I region, Lynds Catalogue of Bright Nebulae, Elephant trunks, Variable nebula, Nebular contraction, Butterfly Nebula.

Excerpt: A planetary nebula is an emission nebula consisting of an expanding glowing shell of ionized gas ejected during the asymptotic giant branch phase of certain types of stars late in their life. This name originated with their first discovery in the 18th century because of their similarity in appearance to giant planets when viewed through small optical telescopes, and is otherwise 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 stars 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 hot, luminous core emits ultraviolet radiation that ionizes the ejected outer layers of the star. This energized shell radiates as a planetary nebula. Planetary nebulae play a crucial role in the chemical evolution of the galaxy, returning material to the interstellar medium that has been enriched in heavy elements and other products of nucleosynthesis (such as carbon, nitrogen, oxygen and calcium).

In more distant galaxies, planetary nebulae may be the only objects that can be res...



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