What are nebulas?
M2-9: Wings of a Butterfly Nebula
Credit: B. Balick (U. Washington) et al., WFPC2, HST, NASA
Explanation: Are stars better appreciated for their art after they die? Actually, stars usually create their most artistic displays as they die. In the case of low-mass stars like our Sun and M2-9 pictured above, the stars transform themselves from normal stars to white dwarfs by casting off their outer gaseous envelopes. The expended gas frequently forms an impressive display called a planetary nebula that fades gradually over thousand of years. M2-9, a butterfly planetary nebula 2100 light-years away shown in representative colors, has wings that tell a strange but incomplete tale. In the center, two stars orbit inside a gaseous disk 10 times the orbit of Pluto. The expelled envelope of the dying star breaks out from the disk creating the bipolar appearance. Much remains unknown about the physical processes that cause planetary nebulae.
Many nebulae or stars form from the gravitational collapse of gas in the interstellar medium or ISM. As the material collapses under its own weight, massive stars may form in the center, and their ultraviolet radiation ionises the surrounding gas, making it visible at optical wavelengths. Examples of these types of nebulae are the Rosette Nebula and the Pelican Nebula. The size of these nebulae, known as HII regions, varies depending on the size of the original cloud of gas. These are sites where star formation occurs. The formed stars are sometimes known as a young, loose cluster.
Some nebulae are formed as the result of supernova explosions, the death throes of massive, short-lived stars. The materials thrown off from the supernova explosion are ionized by the energy and the compact object that it can produce. One of the best examples of this is the Crab Nebula, in Taurus. The supernova event was recorded in the year 1054 and is labelled SN 1054. The compact object that was created after the explosion lies in the center of the Crab Nebula and is a neutron star.
Other nebulae may form as planetary nebulae. This is the final stage of a low-mass star’s life, like Earth’s Sun. Stars with a mass up to 8-10 solar masses evolve into red giants and slowly lose their outer layers during pulsations in their atmospheres. When a star has lost enough material, its temperature increases and the ultraviolet radiation it emits can ionize the surrounding nebula that it has thrown off. The nebula is 97% Hydrogen and 3% Helium with trace materials.
- Created. Ge 1:16;Ps 8:3; 148:5
Set, in the firmament of heaven. Ge 1:17
Appointed to give light by night. Ge 1:16,14;Ps 136:9;Jer 31:35
Numbers and names. Ps 147:4
Established, for ever. Ps 148:3,6;Jer 31:36
Obscures. Job 9:7
- Morning star. Re 2:28
Arcturus. Job 9:9; 38:32
Pleiades. Job 9:9; 38:31;Am 5:8
Orion. Job 9:9; 38:31;Am 5:8
Mazzaroth. Job 38:32
One of extraordinary brightness appeared at Christ’s birth Mt 2:2,9
Idolaters worshipped Jer 8:2; 19:13
The Israelites forbidden to worship De 4:19; 17:2-4
Punishment for worshipping De 17:5-7
False gods frequently worshipped under the representation of Am 5:26;Ac 7:43
Astrology and star-gazing practised by the Babylonians Isa 47:13
Use of, in navigation, alluded to Ac 27:20
Illustrative Of Christ. Nu 24:17
Of angels. Job 38:7
Of ministers. Re 1:16,20; 2:1
Of princes and subordinate governors. Da 8:10;Re 8:12
(Bright and morning star,) of Christ. Re 22:16
(Morning star,) of glory to be given to faithful saints. Re 2:28
(Shining of,) of the reward of faithful ministers. Da 12:3
(Withdrawing their light,) of severe judgments. Isa 13:10;Eze 32:7; Joe 2:10; 3:15
(Setting the nest amongst,) of pride and carnal security. Ob 1:4
(Wandering,) of false teachers. Jude 1:13