|
|
|
Sharpless 279 (The Running Man), NGC 1977, 1973, 1975 and
1981 |
|
Description of
object:
Just north of the
Orion Nebula, which is visible with its extensions at the lower edge of the
picture there is a blue reflection nebula area, embedded in an H-II star
formation area. The whole region, including the Orion Nebula, belongs to the
large Orion molecular cloud Orionis A. This region is located at a distance of
about 1500 light years from the solar system. NGC 1977 is the name of the large
open star cluster and the brightest parts of the blue reflection nebulae,
Sharpless 279 is the catalogue reference for the reddish H-II region. NGC 1973
and NGC 1975 are the catalogue numbers of the fainter blue reflection nebulae.
The interstellar dust here reflects most of the light of the embedded
luminous young blue stars. Inside the reflection nebulae, the radiation of the
stars is strong enough to ionize hydrogen gas and produce a fainter, reddish
emission nebula (Sharpless 279), which resembles the shape of a running man,
see also this picture detail. |
|
The
hydrogen gas of the H-II region is mainly stimulated by the hot young star 42
Orionis (HD 37018). Other massive stars are the yellow giant 45 Orionis and the
variable KX Orioni, which contribute to the ionization of the nebular
region.
NGC 1977 was discovered on January 18, 1786 by Friedrich Wilhelm
Herschel and noted as "42 Ori and nebula" in his logbook.
NGC 1981 is an open star cluster which is a little
closer to the Solar System than NGC 1977 with a distance of about 1300 light
years. It consists of only a few, widely spaced but quite bright stars, which
are estimated to be only a few million years old. It is classified as type III
2 p (n) according to R. Trumpler. The star cluster was discovered by John
Herschel on January 4, 1872.
« The annotated image shows the size comparison with the
moon. |
|
|
|