The diagram shows an astronomer measuring the apparent motion of a star from two positions of Earth in its orbit, six months apart. Nearby star N appears in...
Question 1 Report
The diagram shows an astronomer measuring the apparent motion of a star from two positions of Earth in its orbit, six months apart. Nearby star N appears in different directions against very distant background stars. The angle between these directions is 0.80 degrees. This effect is called parallax. The astronomer uses a telescope that detects visible light from the star.
(a) Describe what is meant by apparent motion in this observation. [1]
(b) Explain why the background stars can be treated as fixed. [2]
(c) Give the type of electromagnetic wave detected by the telescope. [1]
(d) What is the parallax angle given in the description? [1]
Fig. 1 shows an orbital debris monitor tracking a loose bolt near the International Space Station. The bolt and station are in nearly the same circular orbit. The monitor displays a velocity arrow for each object. The station is protected by a shield, but the bolt could damage a window because it has a high speed relative to the station.
(a) Give the name of the energy store that increases when the bolt's speed increases. [1]
(b) Explain why the bolt can stay in orbit rather than falling straight down to Earth. [2]
(c) What safety feature reduces the force on the station during a collision? [1]
(d) Describe one reason why the bolt is difficult to see from Earth. [1]
Answer Details
Parallax
(a) Apparent motion is the observed change in position or direction of N against the background stars, caused here by observing from different positions of Earth. [1]
(b) Background stars are much farther away than N. Their apparent shift is therefore too small to detect, so they can be treated as fixed. [2]
(c) The telescope detects visible light. [1]
(d) The parallax angle is 0.80 degrees. [1]
Orbital debris
(a) Increasing speed increases the kinetic energy store. [1]
(b) Gravity pulls the bolt towards Earth, while its sideways velocity means it continually falls around Earth along a curved path rather than falling straight down. [2]
(c) A protective shield reduces the force on the station during a collision. [1]
(d) The bolt is difficult to see because it is very small, very far away, or reflects little light. [1]
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