This dramatic picture reveals newborn stars emerging in the Eagle Nebula (also known as M16) in the constellation Serpens, a region of star formation 7,000 light years away. The newly forming stars are in oval-shaped clumps of interstellar gas appropriately named `EGGs' - for `evaporating gaseous globules'. Many of the EGGs are at the tips of finger-like features on great columns of cold gas and dust called `elephant trunks', which protrude from the edges of a vast cloud of hydrogen molecules. Three `elephant trunks' feature on this image. The tallest one, on the left, is about one light year long. Illuminated from behind by starlight, several EGGs can be seen at the top of this pillar of gas, looking as if they are just coming free.
Subject to a flood of ultraviolet light from young hot stars nearby (off the top edge of the picture), the surface of the molecular cloud is gradually being eroded in a process called `photoevaporation'. The pillars seen here have survived longer than their surroundings because they are denser concentrations of gas. As the pillars themselves are eroded away, the small globules of even more dense gas growing inside them, the EGGs, are left behind. Eventually the EGGs break off. After separating, they cannot grow any more because they are isolated from the molecular cloud that was supplying them with new material. In time, even the EGGs succumb to photoevaporation and the newly forming stars inside them emerge.
EGGs at various different stages of development can be seen in the HST image. Some appear only as tiny bumps on the surfaces of the gas pillars. Others have been uncovered more and are joined to the pillar by a bridge of gas which has been protected from photoevaporation by the shadow of the EGG. Then there are some EGGs that have pinched off the pillar completely. In a few cases, the stars forming in the EGGs are directly visible.
Camera: WFPC2
Technical Information: Color image constructed from three separate images taken in the light of emission from singly ionized sulfur (red), hydrogen (green) and doubly ionized oxygen (blue). This image has been artistically enhanced.
Credit: J. Hester and P. Scowen (Arizona State University), and NASA
