M 42 / 43 - Orion Nebula

M42, the Great Orion Nebula, can be easily seen with the naked eye. Nevertheless, astronomers did not become aware of this object until the first telescopes were constructed. Therefore, it is believed that the nebula was fainter in past centuries than it is today. M42 was discovered in 1611 by Nicholas-Claude Fabri de Peiresc and independently by Johann Baptist Cysatus. M43 is just a part of the nebula.

The Orion Nebula is a showcase of a galactic nebula just 1,300 light-years away. M42 is the visible end of the almost dark molecular cloud OMC-1, which spans 10° in the sky. M78 and the Horsehead Nebula are also part of this structure. A star cluster is born in the inner part of M42. Most of the stars are still hidden in dense dust clouds. Only the four bright stars of the Trapezium have blown away this dust with their intense radiation. The brightest star, Theta1 Orionis C, delivers most of the energy to ionize the entire nebula. M42 is a mixture of emission and reflection nebulae and dark dust clouds. In the inner parts of the nebula, very young stars become visible, surrounded by protoplanetary disks. Most of these disks will be destroyed by the intense radiation of the bright stars in the near future. These protoplanetary disks, or proplyds, were discovered by the Hubble Space Telescope at the beginning of this century. The brightest of these proplyds can be imaged even with amateur telescopes.