Wave length determined the colour of a light source. Amplitude (height) determines the intensity of a light source. Describe, in terms of amplitude and wavelength, how a wave from a bright blue light source is different from a wave from a faint red light source.At the same time, the waves are travelling away from the light source. According to the wave theory of light, what are all light waves composed of? In the wave theory, it’s said that light travels as a wave of oscillating electric and magnetic energy fields.Alpha Centauri is the nearest star beyond the sun, it has a distance of 270,000 AU or 4.4 light years. What is our nearest star beyond the Sun, and how far away is it (approximately) in light years? In 1838, Henderson was able to track the the third parallax detection of Alpha Centauri.In depth, 1 light year is equivalent to 63,239 AU or 9.5 billion km or 1/3 parsec (pc). For example, a star 5 light years away is seen as it appeared 5 years ago. Which unit is bigger, and by approximately how many times? A light year is the distance that light travels in 1 year. What is the definition of a light year? What is the definition of a parsec? (NOTE: the specific values in km aren't necessary).The two attributes of a star that indicate that it’s relatively nearby is their brightness and large motion (preferably, widely-space binaries). In the early 1800s, the star catalogues were looked at again and it revealed an increasing number of moving stars. This proved that stars moved, but very slowly.

What did Halley discovery about stars in the early 1700s? How did this discovery aid the detection of stellar parallax (ie, what 2 attributes of a star indicate that it is relatively nearby)? In Halley discovery, he compared ancient star catalogues with current star positions and discovered that there were 3 moving stars.

(Diameter of our orbit, 2AU, is the largest baseline length we can achieve, 1 arc second) All attempts to detect stellar parallax failed until the 1830s because astronomers mistakenly targeted the bright stars as nearby stars.

Since parallax decreases with distance and since our baseline is limited, parallax distances can only be measured for nearby stars. Why did all attempts to detect stellar parallax fail until the 1830s? Stars are extremely far away so they appear very small.NATS1745 SU20 History of Astronomy Lesson 8 Study Guide: Discoveries about the Stars 1.

Parsec unit breakdown