Star Formation: From OB Associations to Protostars

Abstract

The study of star formation is a relatively young discipline of the field of astronomy. Up until the mid point of the twentieth century only a most rudimentary understanding of the subject was possible. This is because prior to that time there did not exist any substantive body of empirical data which could be used to critically test even the most basic hypotheses concerning stellar origins. However, as a result of impressive advances in observational technology and in our understanding of stellar evolution during the last forty years, the subject of star formation has developed into one of the most important branches of modern astrophysical research. A large body of observational data and a considerable literature pertaining to this subject now exist and a significant fraction of the international astronomical community devotes their efforts towards trying to comprehend the origins of stars and planets. Yet, despite these efforts we have yet to observationally identify, with any certainty, a single object in the process of stellar birth! Moreover, we have not yet produced a viable theory of star formation, one capable of being tested and refined by critical experiment. In many ways, stellar birth is as much a mystery today as it was forty years ago. However, there can be little doubt that during the last two decades truly revolutionary progress has been made in the quest to understand the star formation process in our galaxy. This apparent paradox in the state of our knowledge concerning stellar origins is resolved with the realization that the history of the study of star formation has been a history of the study of progressively earlier and earlier stages of stellar evolution. Indeed, it is in precisely this area of endeavor that we have learned so much.

Submillimeter and Far-Infrared Polarimetric Observations of Magnetic Fields in Star-Forming Regions

“…Prestellar cores are the gravitationally bound subset of starless cores (Ward-Thompson et al, 1994). Protostellar cores are defined as envelope-dominated sources containing one to a few hydrostatic objects (i.e., Class 0 and I sources; Lada, 1987;Andre et al, 1993).…”

The ionizing effect of low-energy cosmic rays from a class II object on its protoplanetary disc

“…Low-mass star formation is an area of great interest as it allows us to study the physical conditions under which the solar system may have formed. Young stellar objects (YSOs) were initially separated into three main categories (Adams et al 1987;Lada 1987). Class I objects represent one of the earliest stages of low-mass star formation where the protostar is occluded by an envelope of infalling gas and dust.…”

A Brief Overview of Planet Formation

“…The kinematics of protoplanetary disks, their thermal and chemical structures, and their evolutionary histories are all key to planet formation. Most attention focuses on Class II Young Stellar Objects (YSOs) (Lada 1987), when the star has attained close to its final mass and the disk is low mass (M disk M * ) and relatively longlived (several Myr). (It remains possible, however, that significant particle growth occurs during prior embedded phases.)…”