In 1983, the IRAS satellite provided evidence for the existence of these objects when it showed that about one-Âfth of mainsequence A stars near the Sun exhibited excess emission in the infrared. The evolutionary dynamics of these objects wereworked out by Safronov, who proposed that structures developed within these objects by agglomerating "signiÂcantly smallerbodies that were not fragmented during... collisions," a theory worked out in further detail by Lissauer. The Perri-Cameronmodel is a theory of structure formation in these objects that builds on an earlier theory of Cameron which proposes thatstructure formation proceeds via breakup of these objects into axisymmetric rings due to gravitational instability, contrary tothe aforementioned core accretion hypothesis. These objects have a lifespan of about 10 million years, aftfter which their masshas either coalesced into structures or been destroyed by photoevaporation driven by the stars they surround. For 10 points,identify these objects, a cloud of dust gravitationally bound
In 1983, the IRAS satellite provided evidence for the existence of these objects when it showed that about one-Âfth of mainsequence A stars near the Sun exhibited excess emission in the infrared. The evolutionary dynamics of these objects wereworked out by Safronov, who proposed that structures developed within these objects by agglomerating "signiÂcantly smallerbodies that were not fragmented during... collisions," a theory worked out in further detail by Lissauer. The Perri-Cameronmodel is a theory of structure formation in these objects that builds on an earlier theory of Cameron which proposes thatstructure formation proceeds via breakup of these objects into axisymmetric rings due to gravitational instability, contrary tothe aforementioned core accretion hypothesis. These objects have a lifespan of about 10 million years, aftfter which their masshas either coalesced into structures or been destroyed by photoevaporation driven by the stars they surround. For 10 points,identify these objects, a cloud of dust gravitationally bound to a star which serves as the location for the formation of objectslike Earth and Jupiter.
In 1983, the IRAS satellite provided evidence for the existence of these objects when it showed that about one-Âfth of mainsequence
protoplanetary disk [accept circumsolar disk before "star"; do not accept or prompt on "protoplanetary nebula" or "planetary nebula"]