Measuring Star Apparent Brightness – SCOPES-DF
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Lesson Details

Subjects*
Computer Programming, Science
Age Ranges*
8-11, 11-14
Fab Tools*
electronics, Arduino, computer, Scratch software
Standards
5-ESS1-1
Author
DFRobot Edu

Author

DFRobot Edu
DFRobot Edu
Informal educator

Summary

When you look up at the night sky, have you ever wondered why some stars are brighter than others? This lesson will teach you how to build a scaled model and visualize the data to understand the relation between brightness(magnitude), distance and luminosity.

Astronomers define star brightness in terms of apparent Magnitude, which depends on:

– Luminosity: how bright it is physically.

– Distance: how far away it is from the earth.

Video reference : https://youtu.be/d7A-_5GFEVo

For more class contents, please visit edu.dfrobot.

What You'll Need

1 Wide Cardboard Box

1 Cardboard Sheet

1 Straw 

1 Bottle Cap

2 Wires

1 Arduino Uno with Extension Shield 

1 Ultrasonic Sensor

1 Ambient Light Sensor

1 LED

220Ω Resisitor 

Lesson Materials

The Instructions

Build the Model

In this model, a LED represents an individual "Star", the brightness and position can be varied. On the "Earth" side, there is an ambient light sensor to get the light intensity, and an ultrasonic sensor to detect the distance. The model connects to a microcontroller then visualize the data in Mind+.

 

Make the Base:

 

Make the Slider and Fix the Sensors:

Connect Hardwares

Connect sensors and LED to the Arduino. Then connect the arduino to your computer.

Activity 1.1 : Brightness-Distance Relationship

When the star's luminosity is fixed, we can study how the brightness of a star changes with distance by gently moving the LED and seeing the data visualize simultaneously in Mind+.

Download and install Mind+, the programming tool we will use.

 

Download the sample program 1 and open it, switch to offline mode, and Upload the code to your microcontroller(Arduino Uno). In this program, the LED is set to maximum brightness(255), and the sensor data is constantly read and sent to the serial port.

 

 

Switch to Online mode, where we can visualize the received data on the stage.

First, connect the device to start receiving upload(offline) mode data.

 

 

Second, click the green flag to draw the data on the stage. Pull or push the straw to change the LED position, here we translate the star distance into cm, at a scale of 1cm = 10 lightyears.

*Please note the distance reading would be unstable within 2cm (ultrasonic measurement range: 2cm～500cm)

 

 

This program sets a default max-brightness to be 3000, but if you find the graph is too big or small due to different lighting conditions, you can change this value according to the actual highest reading from the ambient light sensor (when the LED gets to the closest position).

 

Result: