How do astronomers measure the distance, speed, and composition of stars?
More distance stars and galaxies are calculated by a few methods. A candle viewed from 10 feet is a lot brighter than when viewed from 50 feet, 100 feet or 1000 feet, if it is visible at all. Knowing how bright a candle is at source, how much light it gives out, and then measuring its apparent brightness from an unknown distance allows its distance to be calculated. Unfortunately different candles, and similarly different stars, burn hotter and/or brighter and there is no standard from which to make the calculation. However collecting the light from a star and analysing its chemical composition and makeup using a spectrometer gives much of the information required. This is easily demonstrated just looking at different flames found on Earth, such as candle flames, bunsen burners and acetylene torches. Yellow flames are relatively cool, blue flames much hotter and white very hot. Other calculations can give its mass and hence size. Another parameter used is its “Red shift”. Light, just l
