= Astronomer
{wiki}
An <astronomer> investigates <stars>, <planets>, <galaxies> and other astronomical systems through <observation> and <mathematical models>. <Telescopes> collect signals, <spectroscopy> separates their <wavelength> components, and repeated measurements reveal changes over <time>.
The distinctive difficulty is that the object under study is usually inaccessible to a controlled laboratory intervention. An astronomer instead compares independent observables: <stellar parallax> constrains <Euclidean distance>, a <radiation spectrum> constrains physical conditions, and orbital <motion> constrains <mass>. Agreement among these measurements can test a model more strongly than fitting a single observable.
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