STARS · LIGHT · MEASUREMENT
A point of light gives us a position, a brightness and a spectrum. Change how you observe it, and each tells a different part of the story.
Begin with geometry, then count the light reaching a detector, then spread that light into colours. Each route connects a visual experiment with a longer explanation and a calculation you can repeat.
01
Are neighbouring stars really neighbours?
As Earth travels around the Sun, a nearby star traces a small path against the distant sky. Follow that motion to measure distance, then see how uncertainty changes the answer.
Track a star across a year02
Did the star fade, or did the background change?
A telescope spreads each star over several pixels. A small aperture loses light; a large one admits neighbours. Move the aperture and measure brightness from the saved pixels.
Measure a star in a crowded field03
Why does one dark line deepen, widen and shift?
A stellar atmosphere absorbs particular colours. Moving atoms shift and broaden those dark lines. Follow one line to separate the effects of temperature, gas column and velocity.
Change an atmosphere and compare its lines