Stars are formed by gravitational collapse of dense gas condensations in the interstellar space. Figure 1 is an image
of the Elephant's Trunk Nebula (a globule in IC 1396) where protostars are visible as bright redish dots mostly along the southern rim
of the globule.
A protostar collects its mass via accretion. Due to angular momentum constrains the infalling material cannot reach
directly the stellar surface but flows through a flattened circumstellar structure. Such a disk is seen edge-on in the HH30 system (Figure 2)
where the circumstellar material surrounds and hides the central source. The characteristic sizes of typical disks is several 100 AU.
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Figure 2: Left panel: the young star in the HH30 system is hidden by a flattened edge-on circumstellar disk visible as a dark horizontal lane (from the Hubble Space Telescope). The green structures are powerful gaseous jets emitted by the source. Right panel: artist's impression of a HH30-like system. |
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Figure 1: Newborn stars in the Elephant's Trunk Nebula visible as bright redish dots mostly along the southern rim of the globule (from Spitzer Space Telescope).
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