Webb and Our Galaxy
Webb will improve our understanding of all stages of star formation — from birth to death and back again to the rise of the next stellar generation. Astronomers know that stars form out of collapsing clouds of gas and dust, but they don't yet know the exact sequence of how stars are born. What triggers a cloud to collapse and a star to begin forming? How much of that mother cloud does a star use up when it forms? How and when do planets begin to form around a newborn star?
At the end of their lives, stars die in a variety of exciting and interesting ways — from gentle exhales of material to violent explosions expelling stellar shrapnel into the galaxy. Many dying stars and stellar corpses are embedded in their ejected material, which shrouds our view in visible light but can be penetrated with Webb's infrared vision. Webb will help us probe and understand both this residual material and the stars that died. It will help astronomers test their theories for how stars end their lives and how the heavier elements forged within these dying stars are recycled into the galactic environment to help create the next generation of stars.
Webb will help us understand just how many stars there are and how those stars are distributed throughout the galaxy. The most common stars in the Milky Way are "dwarf" stars that are often too dim for Hubble to observe in visible light, but that glow brighter in infrared light. Webb will help astronomers get a firmer grip on just how many of these stars exist, and perhaps help us learn more about them. Knowing how many stars there are of different types also tells us how quickly or efficiently stars formed at various stages in the galaxy's history.
Webb will also study giant stellar swarms called globular clusters, which reside at the outskirts of the Milky Way and contain the oldest stars in the galaxy. Webb will analyze the composition of these ancient stars, and perhaps reveal whether globular clusters formed along with our galaxy or originated somewhere else, and were later absorbed into the galaxy.
Looking Inward and Outward
Webb's sharp and powerful infrared vision will allow it to peer farther into the Milky Way with greater clarity than infrared telescopes before it — uncovering parts of the galaxy that were once too dim, too distant, or too concealed to study. These investigations will not only help us understand our own Milky Way, but myriad galaxies throughout the universe.