Category

Observing Venus Phases

Introduction

Observe Venus and think about the structure of Solar System

　How does the Venus look, whose orbit around the Sun lies inside the earth's orbit?. How is its appearance different from the stars?
Let's observe the Venus by telescope. If there is no telescope around you, try using an Internet Telescope before making the actual observation, try to predict how it will look from the observation log.
　Think about the relationship between the appearance of Venus and the position of Venus and Earth.

Morning Star・Evening Star

　The "Morning Star" you see early in the morning and the "Evening Star" you see just after sunset are both Venus.
　Why does Venus have two nicknames? Think about that through the exercise.

Experimental Method

Things to prepare

　PC connected to Internet, Writing materials, Record paper, Telescope, ( If you use Internet telescope, you need Windows Media Player)

Look at the photos of Venus

　Look at the page of Observation Log in this site and find out how Venus looks. Does it look the same all the time?

Check the position of Venus

　Go to Simulation of Venus Position and check the position of Venus against the earth in the month you are planning to observe.

1. Which part of Venus reflects light from the sun?
2. In that position, how does it look?

Observe Venus

　Observe Venus by telescope or Internet telescope. Sketch the shape of it.
　Make observations at regular interval if you can. How does it change?

Experimental Result(1)

Photos of Venus

Photos below are from the page: Observation Log in Venus Live

　Venus has phases like the moon, but at the same time its size viewed from the earth changes.

Positions of the earth and Venus

　How does Venus change phases depending on the positions of the earth and Venus?

The right figure shows the sun, the earth and Venus at various positions. It is an overhead view. The yellow part is the part which reflects light from the sun. Which position shows the phase like a half moon?
You see Venus like a half moon when the direction of the sunlight shining on Venus and our line of sight from the earth form a right angle.
You see Venus smaller and fatter, when it is further away than the half-moon position.
Conversely, approaching to the earth, Venus gets larger and thinner.

　How does Venus appear from the earth? Which position shows the phase like a full moon or a new moon?

Experimental Result(2)

Observing Sketch of Venus

　The worksheet below contains sketches of Venus as observed. In the telescopic view, the object looks rotated by 180 degrees, so the rerotated shape is also drawn. Think about the position of Venus and the earth from each sketch.

Discussion

1. Why does the moon have phases?
   
2. Does the earth change its shape when it is viewed from Venus or from Mars?

Venus Live

http://venus.miyakyo-u.ac.jp/