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Nebulae:  1 | 2

Definition

A nebula is a diffuse mass of instellar dust or gas, or both, visible as luminous patches, or areas of darkness, depending on the way the mass absorbs, or reflects, incident radiation. There are five types of nebulae: 1) Dark (2) Emission (3) Planetary (4) Reflection (5) Supernova remnant.

Dark Nebulae

Dark nebulae are non-luminous clouds of interstellar gas and dust that absorb and thus obscure the light from stars behind them; appearing as dark patches in front of a bright nebula, or in an otherwise bright area of space. For example, the Horsehead Nebula, photo no. 5.

Emission Nebulae

Emission nebulae absorb ultraviolet radiation from nearby stars and re-emit it as visible light, as a result of the ionization of their gas atoms. For example, the Orion Nebula, photo no. 13.

Planetary Nebulae

Planetary nebulae are created when stars blow off their outer layers after they have run out of fuel to burn. These outer layers of gas expand into space, forming a nebula, which is often the shape of a ring or bubble. About 200 years ago, William Herschel called these spherical clouds planetary nebulae because they were round like the planets. At the center of a planetary nebula, the glowing, leftover central part of the star from which it came, can usually still be seen. For example, NGC 2440, photo no. 3.

Reflection Nebulae

Reflection nebulae reflect the light of a nearby star or stars. For example, NGC 1977, the Running Man Nebula located in Orion, photo no. 16.

Supernovae Remnants

Supernova remnants consist of expanding shells of gas that have been ejected by supernova explosions. For example, the Crab Nebula (photo no. 1) and Cassiopeia A (photo no. 20).

Photos 1, 2, 3, 4, 6, 7, 8, 10, 12, 13 & 21 were taken by the Hubble Telescope

Crab Nebula M1

1

Monocerotis V838

2

Planetary Nebula NGC 2440

3

Omega Nebula M17

4

Horsehead Nebula B33

5

Stingray Nebula Hen 1357

6

Helix Nebula NGC 7293

7

Saturn Nebula NGC 7009

8

Tarantula Nebula NGC 2070

9

Butterfly Nebula NGC 6302

10

Bear Claw Nebula NGC 6334

11

War & Peace Nebula NGC 6357

12

Orion Nebula

13

Thor's Helmet Nebula NGC 2359

14

Seagull Nebula IC 2177

15

Running Man Nebula NGC 1977

16

Reflection Nebula Messier 78

17

(Western) Veil Nebula NGC 6960

18

The Wizard Nebula NGC 7380

19

Cassiopeia A

20

Eagle Nebula-Star Queen Nebula

21


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