December 20, 2012
The Southern Cliff, a portion of the Lagoon Nebula
Image Credit: Julia I. Arias and Rodolfo H. Barbá (Dept. Fisica, Univ. de La Serena), ICATE-CONICET, Gemini Observatory/AURA
The Southern Cliff is an emission nebula and H II region of about 20 light-years across in the Lagoon Nebula (Messier 8), a star-forming region located some 5,000 light-years away in the southern Milky Way, in the constellation of Sagittarius.
This stellar nursery of intermediate- and low-mass stars is surrounded by undulating bright ridges and clouds of dust and gas. Beyond the “cliff,” light from a spattering of young background stars in the upper left of the image shines through the cloudscape.
Most of the newborn stars are imbedded in the tips of the bright-rimmed, thick dusty clouds and what are called Herbig-Haro objects.
Herbig–Haro (HH) objects – after astronomers George Herbig and Guillermo Haro – are narrow jets of gas and matter ejected by young stars at speeds of 100 to 1000 kilometers per second that collide with the surrounding nebula, producing bright shock fronts that glow as the gas is heated by friction while the surrounding gas is excited by the high-energy radiation of nearby hot stars.
There are a dozen of these HH objects in the image, spanning sizes that range from a few thousand astronomical units (about a trillion kilometers) to 4.6 light-years. Astronomers explore the evolutionary relationship between the newborn stars and the HH objects.
This highly detailed image, taken with the Gemini Multi-Object Spectrograph on the 8-meter Gemini South Telescope, is a false-color composite of individual images obtained with two narrow-band optical filters sensitive to hydrogen (red) and ionized sulfur (green) emission, and another that transmits far red light (blue).