Earth Sciences 1086F/G Lecture 2: earth sci chapter 2
11 Oct 2017
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If you are studying a star that is 1 million light years away, you are looking at light that started its journey towards you 1 million years ago. You cant know what"s happened to that star until its reached earth: so really when looking at a distant object in telescope, you are looking back in time. This phenomenon, called trigonometric parallax, relies on an object appearing to be at a different place relative to the background, depending on your viewpoint: when we view a nearby star against a background of much more distant stars. As earth rotates around the sun, the nearby star appears to "wobble" relative to the distant stars. Once we have measured that angle, and knowing the distance that earth has travelled in six months (2 astronomical units, or 300 million km), we can calculate the distance to the star. 2: 500 to 500 million light years distant, main-sequence fitting (ie. brightness) chart called a hertzprung-russell.
