What are the objectives of astronomy?
First, to elucidate the nature of the myriad objects that inhabit the cosmos, including stars, planets, galaxies, and the universe as a whole. We aim to understand the structure of these objects as well as how they form and develop over time. We’re continually discovering new types of objects to explore. Some of the big questions currently under investigation include: Will the universe expand forever? (Recent observations show that the expansion is currently accelerating.) Normal matter, of which stars, planets, and people are made, accounts for only about 4% of the material content of the universe. What is the mysterious “dark matter” and “dark energy” that makes up the rest? How did structure in the universe, i.e. galaxies and clusters of galaxies, form? How do stars and planets form? What fraction of stars have planets that are hospitable to life? Is there life beyond Earth? Second, we attempt to make use of cosmic objects to shed light on fundamental physics questions. A famous, early instance of this occurred in the 1680s, when Newton developed a theory of gravitation that could account for both Galileo’s ground-based experiments with falling objects and Kepler’s laws of planetary motion, derived from Brahe’s detailed observations of planetary positions. More recently, radio observations of binary pulsars (two neutron stars orbiting one another) have indirectly confirmed the existence of gravitational radiation, predicted by Einstein’s general theory of relativity. Observations of neutrinos (a type of elementary particle) produced in the core of the Sun, together with a detailed understanding of the Sun’s structure developed over many decades, led astronomers to conclude that the neutrino has non-zero mass. Years later, particle physicists confirmed this in the lab.