Protostellar and Protoplanetary Disks

It is barely a decade since the first molecular line images of disks around embedded and pre-main sequence stars were published (Beckwith et al., 1986; Mundy et al., 1986; Sargent & Beckwith 1987). In the intervening years there has been steady progress in detecting and analyzing these disks, which are an expected by-product of the star formation process cf. Shu et al., 1987; Shu et al., 1993), and there is now a veritable flood of new and intriguing results as millimeter-wave instrumentation improves (cf. Sargent & Welch 1993).