In time for the autumn foliage season, the Hubble Space Telescope, a joint project by NASA and ESA, offers a captivating glimpse of a crimson scene. The photograph unveils a segment of the Westerhout 5 nebula, positioned some 7,000 light-years away from Earth. In this radiant image, we encounter a fascinating element: a solitary Evaporating Gaseous Globule with a tadpole-like appearance, affectionately referred to as a frEGG.
The frEGG, prominently featured in the upper center-left portion, goes by two distinct names – [KAG2008] globule 13 and J025838.6+604259. These frEGGs are a specific category of Evaporating Gaseous Globules (EGGs). Both frEGGs and EGGs represent denser pockets of gas that are less susceptible to photoevaporation compared to the surrounding, less dense gas. Photoevaporation occurs when intense sources of radiation, typically young and hot stars emitting copious amounts of ultraviolet (UV) light, ionize and disperse gas.
EGGs were only recently identified, notably at the tips of the iconic Pillars of Creation, as captured by Hubble in 1995. FrEGGs, on the other hand, were classified even more recently and are set apart by their detached, ‘head-tail’ shape. These intriguing frEGGs and EGGs draw significant interest because of their density, which shields the gas within from ionization and photoevaporation caused by intense UV radiation present in regions rich with young stars. Astronomers believe this protection is crucial for the formation of protostars, and many FrEGGs and EGGs may serve as nurseries for new stars.
The frEGG within this image emerges as a dark contrast within a sea of red light. The crimson hue arises from a specific type of light emission known as H-alpha emission. H-alpha occurs when a highly energetic electron within a hydrogen atom sheds a precise amount of its energy, resulting in the emission of this distinct red light as it transitions to a lower energy state.