The Hubble pictures show photoevaporating gas as ghostly streamers flowing away from the columns. But not all of the gas boils off at the same rate. The EGGs, which are denser than their surroundings, are left behind after the gas around them is gone. As the wind blows away the lighter sand, heavier rocks buried in the sand are uncovered. But in M16, instead of rocks, the ultraviolet light is uncovering the denser egg-like globules of gas that surround stars that were forming inside the gigantic gas columns.
Some EGGs appear as nothing but tiny bumps on the surface of the columns.
Some EGGs have pinched off completely from the larger column from which they emerged, and now look like teardrops in space. By stringing together these pictures of EGGs caught at different stages of being uncovered, Hester and his colleagues from the Wide Field and Planetary Camera Investigation Definition Team are getting an unprecedented look at how stars and their surroundings appear before they are truly stars. In some ways it seems more like archaeology than astronomy. As soon as the star in an EGG is exposed, the object looks something like an ice cream cone, with a newly uncovered star playing the role of the cherry on top. This process is markedly different from the process that governs the sizes of stars forming in isolation.