Assignment 7
HUNTING FOR PLANETS
COMP-202, Summer 2010
Due: Saturday, July 03rd, 2010
Introduction
This last assignment is for the physics crowd. Their search for planets around stars other than our own is a young and exciting field of astronomy. One of the primary tools is the Kepler probe currently in space. It detects planets around other stars by staring continuously at the exact same region of space. If a planet transits in front of a star (i.e. it passes between the telescope and the star), the star's brightness will ever so slightly decrease. If this dimming is detected at regular intervals, it is safe to assume that it is caused by a transiting planet.
Kepler tracks about 100.000 stars, and in the image above there are actually 4.5 million stars. The analysis of this much data can only be done by computers. In this assignment we will write a program that attempts to find a planet.
Specifications
You are given 24 files, each representing the average of an hour of observation. We want you to write a Java program that finds out which pixels change. You can write your tool however you want, but you must follow the usual Java conventions, and you should write sensible code. You may use as many classes and/or methods as you wish. It is important to come up with a decent structure to solve this problem. I solved the problem in one class, with 5 methods.
Your tool should write an image file that puts a little red rectangle around the stars that have planet candidates around them. It should also output in some fashion (either as file, or on the terminal), for every pixel that changes, the brightness for every frame. Make a plot of the brightness of every pixel that changes. This will allow us to see the transit of a planet in front of a star.
Submit the image produced by your tool, and the plots for the brightness. You should also submit your Java program and a description of how it works.
Hints
- There are more than 0 pixels that change (there is a planet!) and fewer than 5. The data is synthetic to make sure of this, and to ensure that there is no noise.
- To find out whether any pixel is different between images, you only need to compare all pixels of one image with all pixels of all the other images.
- You should not load all images at once, because you will run out of memory. You should use the above trick and always compare only 2 images at a time.
- It would probably make sense to have 2 passes through all images: One to find the pixels that change, and one to print out the values for those pixels.
- In the first pass, it would make sense to store the coordinates of
every pixel you find that is different in an
ArrayList(orHashSet). Make sure you don't store pixels multiple times. - We provided you with an example Java file showing you how you can read/manipulate/write images. You should use that and the Javadocs as a reference.
- Note: You can represent a pixel coordinate using
java.awt.Point - You can print out your list of pixel values, and copy them to Excel (or some other spreadsheet program) to make a plot.
- Computation is going to take a while. It is advisable to print out information along the way, so that you can see the progress of your program.
- The given images are black and white. The image is still readable as an image with separate red,green,blue components, but they are going to have the same value.