Diffuse Nebulae

Bright nebulae are usually vast concentrations of gas and dust in which stars have been or are being formed. There are three main types of bright diffuse nebulae:

Emission Nebulae
Interstellar clouds of hydrogen which glow because of the intense radiation of hot stars inside the nebula. Emission nebulae are typically red.
Reflection Nebulae
Clouds of gas and dust which emit no light of their own, but shine because they reflect light from nearby stars. Reflection nebulae are typically blue.
Supernova remnants
A supermassive star at the end of its life will explode ejecting the outer layers of the star into interstellar space. The most famous example is the Crab nebula which is the supernova remnant of a star that exploded in 1054.
Digitized Sky Survey images
Three famous nebulae. On the left is the Cocoon nebula (IC 5146) - a dense emission nebula in Cygnus. In the middle is M78 - a reflection nebula near the Orion nebula. On the right is the Crab Nebula - the remnant of an exploded star.

Below is a list of the brighter diffuse nebulae.

  1                      2                   3      4       5     6     7       8         9        10   11
 NGC                  Common               Equatorial      Galactic  Nebula   Size     Distance   Size  Con
 Number                Name                Coordinates    Coordinates Type  (arcmins)    (ly)     (ly)
                                          RA (2000) Dec     l    b
7822                                     00 03.6  +68 37  118.6  +6.2   E    65'x20'   2800400     50  Cep
 281                                     00 52.8  +56 36  123.1  -6.3   E    30'x25'   80002000    70  Cas
IC59,IC63        Gamma Cas Nebula        00 56.7  +61 04  123.6  -1.8   RE   40'x10'    600100      7  Cas
 602                                     01 29.6  -73 33  299.2 -43.3   E     2'x1'  21000010000  120  Hyi
IC1795,IC1805    Heart Nebula            02 33.4  +61 26  134.8  +0.9   E   100'x80'   6000500    170  Cas
IC1848           Soul Nebula             02 51.3  +60 25  137.2  +0.9   E   105'x60'   6500500    200  Cas
1333                                     03 29.3  +31 25  158.3 -20.4   R     9'x7'    1100?        3  Per
1432,1435        Pleiades Nebula         03 47.0  +24 67  165.9 -22.8   R   180'x180'   40025      20  Tau
1499             California Nebula       04 00.7  +36 37  160.1 -12.3   E   150'x40'   1500500     70  Per
1491                                     04 02.9  +51 17  150.6  -1.0   E     3'x3'   100002000     9  Per
1554-55          Hind's Nebula (T Tau)   04 21.8  +19 32  176.2 -20.9   R     1'x1'     500200    0.2  Tau
1579                                     04 30.7  +35 15  165.5  -8.9   R     8'x12'   2600?        9  Per
1624                                     04 40.0  +50 27  155.3  +2.5   E     3'x3'   200005000    17  Per
IC2118           Witch Head Nebula       05 06.9  -07 13  207.3 -26.5   R   180'x60'   1000500     50  Eri
IC405            Flaming Star Nebula     05 16.2  +34 16  172.1  -2.3   RE   30'x20'   1700500     15  Aur
IC410                                    05 22.2  +33 23  173.6  -1.8   E    20'x20'  110002000    60  Aur
1931                                     05 31.4  +34 14  173.9  +0.3   RE    8'x8'    59001000    14  Aur
1952             Crab Nebula (M1)        05 34.5  +22 01  184.6  -5.8   S     6'x4'    70002000    12  Tau
 --              Lambda Orionis (S264)   05 35.2  +09 56  195.0 -12.0   E    60'x60'   1400300     25  Ori
1973,1975,1977                           05 35.4  -04 50  208.5 -19.1   RE   40'x25'   1300200     16  Ori
1976,1982        Orion Nebula (M42,M43)  05 35.4  -05 27  209.1 -19.4   E    60'x60'   1300200     25  Ori
1999                                     05 36.3  -06 43  210.4 -19.7   R     2'x2'    1300300      1  Ori
2070             Tarantula Nebula        05 38.7  -69 06  279.5 -31.7   E    40'x25' 17000010000 2000  Dor
IC434            Horsehead Nebula        05 41.0  -02 24  206.9 -16.7   E    60'x10'   1300300     25  Ori
2023-24          Flame Nebula            05 42.0  -01 50  206.5 -16.3   RE   30'x30'   1300300     12  Ori
2068,2071        (M78)                   05 46.7  +00 03  205.4 -14.3   R    30'x20'   1300300     12  Ori
 --              Barnard's Loop (S276)   05 55.0  -01 30  207.8 -13.2   E   840'x60'   1300300    350  Ori
2149                                     06 03.5  -09 44  216.3 -15.0   E     3'x2'        ?         -  Mon
2174                                     06 09.8  +20 19  190.2  +0.4   E    40'x30'   60001000    70  Ori
IC443                                    06 17.0  +22 29  189.1  +2.9   S    50'x40'   50001000    70  Gem
2237-38-39,2246  Rosette Nebula          06 32.3  +05 03  206.3  -1.9   E    80'x60'   47001000   110  Mon
2261             Hubble's Nebula (R Mon) 06 39.2  +08 44  203.8  +1.3   RE    2'x2'    30001500     2  Mon
2264             Cone Nebula (S Mon)     06 40.9  +09 54  202.9  +2.2   E    25'x15'   2200500     16  Mon
2327,IC2177      Seagull Nebula          07 04.0  -11 18  224.4  -2.4   E   150'x50'   3800500    170  CMa
2359             Thor's Helmet           07 17.6  -13 12  227.6  -0.3   E    10'x5'   200008000    60  CMa
2467                                     07 52.5  -26 24  243.2  +0.4   E     8'x7'   150003000    35  Pup
2736             Gum Nebula (part of)    09 00.4  -45 54  266.9  +0.2   S    10'x20'   1500500      9  Vel
3199                                     10 17.1  -57 55  283.6  -1.0   E    22'x20'  150003000    90  Car
3372             Eta Carina Nebula       10 43.8  -59 52  287.5  -0.9   E    85'x80'   90001000   220  Car
3576,3581-82                             11 12.1  -61 18  291.3  -0.7   E    30'x20'   60002000    50  Car
3603                                     11 15.1  -61 16  291.6  -0.5   E    20'x20'  200005000   120  Car
5367,IC4347                              13 57.7  -39 59  316.5 +21.1   E     2'x1'    2100500      1  Cen
IC4604                                   16 25.6  -23 26  353.7 +17.7   RE   60'x25'    600200     10  Oph
6188                                     16 41.4  -48 05  337.2  -1.1   E    20'x12'   44001000    25  Ara
6334             Cat's Paw Nebula        17 20.3  -36 04  351.1  +0.6   E    40'x30'   55001000    60  Sco
6357                                     17 24.4  -34 09  353.2  +1.0   E    90'x60'   3300800     90  Sco
6514             Trifid Nebula (M20)     18 02.6  -23 02    7.0  -0.3   RE   29'x27'   40001500    35  Sag
6523             Lagoon Nebula (M8)      18 03.8  -24 23    6.0  -1.2   E    80'x40'   45001000   100  Sag
6611,IC4703      Eagle Nebula (M16)      18 18.8  -13 47   17.0  +0.8   E    35'x30'   57001000    60  Ser
6618             Omega Nebula (M17)      18 20.8  -16 11   15.1  -0.8   E    40'x30'   45001000    50  Sag
IC1287                                   18 31.3  -10 50   21.0  -0.5   R     5'x4'    1000?         2  Scu
6726-27,6729     R CrA Nebula            19 01.5  -36 54    0.0 -17.8   RE   10'x10'    42050       1  CrA
6820                                     19 42.5  +23 05   59.1  -0.1   E    20'x20'   65001000    40  Vul
6888             Crescent Nebula         20 12.0  +38 21   75.5  +2.4   E    20'x10'   40001000    25  Cyg
IC1318           Gamma Cyg Nebula        20 22.2  +40 15   78.1  +1.9   E    50'x50'   40001000    60  Cyg
6960             Veil Nebula West        20 45.6  +30 42   73.3  -7.6   S    70'x6'    2000700     40  Cyg
IC5067-68,IC5070 Pelican Nebula          20 50.8  +44 21   84.6  +0.1   E    80'x70'   1900500     40  Cyg
6992,6995        Veil Nebula East        20 56.4  +31 43   75.6  -8.8   S    80'x8'    2000700     50  Cyg
7000             North America Nebula    20 58.8  +44 20   85.5  -1.0   E   120'x100'  1900500     70  Cep
7023                                     21 01.8  +68 12  104.1 +14.2   R    18'x18'   1500500      8  Cep
IC1396                                   21 39.0  +57 29   99.3  +3.7   E   170'x140'  2700400    130  Cep
IC5146           Cocoon Nebula           21 53.5  +47 16   94.4  -5.5   RE   10'x10'   3200500      9  Cyg
 --              Cave Nebula (S155)      22 56.8  +62 37  110.2  +2.6   E    50'x30'   2400500     35  Cep
7538                                     23 13.2  +61 29  111.5  +0.8   E    10'x7'    90003000    25  Cep
7635             Bubble Nebula           23 20.7  +61 12  112.2  +0.2   E    15'x8'   120003000    50  Cas

Column 1: NGC (or IC) catalog number of the nebula.
Column 2: Common name of the nebula.
Column 3: Right Ascension in hours and minutes for epoch 2000.
Column 4: Declination in degrees and minutes for epoch 2000.
Column 5: Galactic longitude of the nebula.
Column 6: Galactic latitude of the nebula.
Column 7: Nebula type, either Emission (E), Reflection (R) or Supernova remnant (S).
Column 8: Angular size of the nebula in arcminutes.
Column 9: Distance in light years to the nebula with the error.
Column 10: Diameter of the nebula in light years calculated using the distance and the angular size.
Column 11: Constellation in which the majority of the nebula lies.

References:
Clark R., (1990), Visual Astronomy of the Deep Sky, Cambridge University Press.
Blitz L., Fich M., Stark A., (1982), Catalog of CO Radial Velocities
           toward Galactic H II Regions.  Astrophys J Supp, 49, 183.
Caswell J.L., Haynes R.F., (1987) Southern HII Regions: an extensive study of radio
           recombination line emission, Astron. Astrophys. 171, 261.
Cruz-Gonzalez C., Recillas-Cruz E., Costero R., Peimbert M., Torres-Peimbert S., (1974)
           Catalogue of Galactic O Stars,  Rev. Mex. Astron. Astrof. 1, 211.
Codella C., Felli M., Natale V., Palagi F., Palla F., (1994) The occurrence of H2O masers
           in HII regions, Astron. Astrophys. 291, 261.
Guarinos J., (1992) Interstellar matter in the Galactic Disk, Catalogue of Extinctions
           and Distances Derived from UBV data.
Digitized Sky Survey image
NGC 7635 is a bright nebula that lies 12 000 light years away. This nebula is also called the Bubble Nebula, for obvious reasons.
The Orion arm Back to the Orion Arm page