Definition of protostar in English:
 protostar
noun ˈprəʊtəʊstɑːˈproʊdəˌstɑr
Astronomy A contracting mass of gas which represents an early stage in the formation of a star, before nucleosynthesis has begun.
 Example sentencesExamples
-  Elongated chains of dust grains like these appear in the early stages of planet formation around a young protostar, according to a microgravity experiment inside a rocket.
 -  In this, a passing protostar, loosely held together, passes close to our Sun whose gravity pulls off a filament of the star's material, which breaks up into segments that become six planets (not the current nine).
 -  By peering in wavelengths not visible to the naked eye, through the nebula's gas and dust, astronomers can identify very young stars and even protostars - those that are about to light up, once the gases reach a critical density.
 -  We already knew that planets form in the disks of gas and dust that surround young protostars.
 -  Rotation forces some of the matter to accumulate in a disk rotating around the protostar (s).
 
  Definition of protostar in US English:
 protostar
nounˈproʊdəˌstɑrˈprōdəˌstär
Astronomy A contracting mass of gas which represents an early stage in the formation of a star, before nucleosynthesis has begun.
 Example sentencesExamples
-  Elongated chains of dust grains like these appear in the early stages of planet formation around a young protostar, according to a microgravity experiment inside a rocket.
 -  By peering in wavelengths not visible to the naked eye, through the nebula's gas and dust, astronomers can identify very young stars and even protostars - those that are about to light up, once the gases reach a critical density.
 -  In this, a passing protostar, loosely held together, passes close to our Sun whose gravity pulls off a filament of the star's material, which breaks up into segments that become six planets (not the current nine).
 -  Rotation forces some of the matter to accumulate in a disk rotating around the protostar (s).
 -  We already knew that planets form in the disks of gas and dust that surround young protostars.