An astronomer is a scientist who studies celestial bodies such as planets, stars and galaxies. Historically, astronomy was more concerned with the classification and description of phenomena in the sky, while astrophysics attempted to explain these phenomena and the differences between them using physical laws. Today, that distinction has mostly disappeared and the terms "astronomer" and "astrophysicist" are interchangeable. Professional astronomers are highly educated individuals who typically have a PhD in physics or astronomy and are employed by research institutions or universities.[1] They spend the majority of their time working on research, although they quite often have other duties such as teaching, building instruments, or aiding in the operation of an observatory. The number of professional astronomers in the United States is actually quite small. The American Astronomical Society, which is the major organization of professional astronomers in North America, has approximately 7,700 members. This number includes scientists from other fields such as physics, geology, and engineering, whose research interests are closely related to astronomy.[2] The International Astronomical Union comprises almost 10,145 members from 70 different countri

s who are involved in astronomical research at the PhD level and beyond.[3] Modern astronomers Galileo is often referred to as the Father of Modern Astronomy. Contrary to the classical image of an old astronomer peering through a telescope through the dark hours of the night, it is very rare for a modern professional astronomer to use an eyepiece on a larger telescope. It is far more common to use a charge-coupled device camera to record a long, deep exposure, allowing a more sensitive image to be created because the light is added over time. Before CCDs, photographic plates were a common method of observation. Modern astronomers spend relatively little time at telescopes - most spend a few weeks per year observing, and the rest of their time reducing the data (changing it from raw data to processed images) and analyzing it. Many astronomers work entirely from astronomical survey or space observatory data. Others work with radio telescopes like the Very Large Array, which is entirely automated, although it is maintained by telescope operators. Some astronomers do not work with data at all, but instead use computational simulations or analytical models to provide analysis of observed phenomena or make predictions for observational astronomers.