Final answer:
Observations indicate that young protostars typically have disks ranging from 10 to 1000 AU in size, containing 1-10% of the Sun's mass, suggesting the potential for planetary system formation. These dusty disks evolve over time, transitioning from full disks in protostars younger than 3 million years to donut-shaped configurations in older protostars due to dust clearance in the inner regions.
Step-by-step explanation:
Observations show that nearly all very young protostars are accompanied by disks, which play a crucial role in star and planetary system formation. The sizes of these disks around protostars range from 10 to 1000 AU (astronomical units). To provide context, this range is considerably larger than our own solar system, with the orbit of Pluto averaging at 80 AU and the outer extent of the Kuiper Belt being approximately 100 AU. The mass found within these disks can be quite substantial, typically accounting for 1-10% of the mass of our Sun, which is indicative of more than enough mass to form a planetary system.
These observations further reveal that in protostars less than 1 to 3 million years old, the disk stretches from near the star's surface out to hundreds of AUs. As the protostar ages, the inner regions of these disks lose most of their dust, taking on a donut-like appearance with a central protostar 'hole'. Eventually, protostars that reach around 10 million years old have generally lost the inner dense parts of their disks.