Opening a Window of Discovery on the Dynamic Universe

Milky Way Structure & Formation

Moai under the Milky Way, Ahu Tongariki, Easter Island.

Astronomers who study the growth and evolution of galaxies would seem to have an advantage over colleagues who study such topics as black holes or the Big Bang. After all, our sun, considered a fairly typical star, is a member of the Milky Way—a fairly typical spiral galaxy. And as a fairly typical galaxy, the Milky Way should serve as an example for the general study of the growth and development of galaxies throughout the universe.

However, observing a galaxy from the inside out is not an easy task. Even a comprehensive census of stars in the Milky Way has been beyond our reach, with much of the stellar population consisting of small, faint, hard-to-see red dwarf stars, while many stars are hidden by vast clouds of dust. Creating a three-dimensional map of the Milky Way has also proven difficult, and any details such a map could give us about galactic structures or stellar associations remains beyond our reach. Even the question of whether the Milky Way has four spiral arms or two has only been settled in the last few years. (It has four.)

The LSST is poised to change our view of our home galaxy by enabling us to answer two basic questions:

  • What is the structure and evolutionary history of the Milky Way?
  • What are the fundamental properties of all the stars in the neighborhood of our Sun?

The basis for our answers: the LSST's gargantuan and exquisitely accurate collection of data. The LSST will survey at least half of the sky and will make hundreds of observations of each surveyed area of sky. A single visit of the entire survey area will map more than 10 times the volume of past surveys. When stitched together in time, this set of observations will yield the motions of millions of Milky Way stars; when stacked in depth, a map over 1000 times the volume of past surveys, cataloging the colors and brightnesses of billions of new stars.

Our modest galaxy and the surrounding cosmic neighborhood are laboratories for testing how stars form over a range of timescales, within a variety of masses of dark matter halos, in different environments in the early Universe, and with different interaction histories.

With the LSST, we could find answers to some of the Universe's big questions right here in our own backyard.

Image Credit: 
Anne Dirkse

Financial support for LSST comes from the National Science Foundation (NSF) through Cooperative Agreement No. 1258333, the Department of Energy (DOE) Office of Science under Contract No. DE-AC02-76SF00515, and private funding raised by the LSST Corporation. The NSF-funded LSST Project Office for construction was established as an operating center under management of the Association of Universities for Research in Astronomy (AURA).  The DOE-funded effort to build the LSST camera is managed by the SLAC National Accelerator Laboratory (SLAC). 

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