Protostars in the Elephant Trunk Nebula

The optically-dark globule IC 1396A is revealed using Spitzer images at 3.6,4.5, 5.8, 8, and 24 microns to be infrared-bright and to contain a set ofpreviously unknown protostars. The mid-infrared colors of the 24 micronsdetected sources indicate several very young (Class I or 0) protostars and adozen Class II stars. Three of the new sources (IC 1396A: gamma, delta, andepsilon) emit over 90% of their bolometric luminosities at wavelengths greaterthan 3 microns, and they are located within ~0.02 pc of the ionization front atthe edge of the globule. Many of the sources have spectra that are still risingat 24 microns. The two previously-known young stars LkHa 349 a and c are bothdetected, with component c harboring a massive disk and component a being bare.Of order 5% of the mass of material in the globule is presently in the form ofprotostars in the 10^5 to 10^6 yr age range. This high star formation rate waslikely triggered by radiation from a nearby O star.Comment: Spitzer first ApJS special issue (in press