# Comet Linear

## Button controls

Help button: This button will open a window with help information.
Reset: reload the applet and reset the parameters.
Rewind: press and hold to advance the applet in reverse.
Pause: temporarily stop the action in the applet.
Play: begin or resume the action in the applet.
Fast Forward: press and hold to advance the applet.
End: advance the applet to its end.
Speed: click to select the number and input a higher number to increase the speed of the rewind and fast forward buttons.
Slider bar: shows the progression through the animation.
Drag controller: click and drag over this symbol to reposition the controller buttons within the applet frame.
Collapse button: click this button to collapse controller button.
Drag markers: click and drag these markers onto the Sun and over top of one of the sunspots

## Using the applet

This applet has been designed to demonstrate how astronomical images can be used to extract information about the object in the image. Using the drag markers, images of the comet, and the time stamp, students will learn of the size and speed of the comet Linear. Students should begin by running the applet animation through twice, observing the motion of the comet across the frame.

After viewing the animation, students should click the "Reset" button followed by the "Calculate comet's speed" button. This last action will open a new window. Students should then position drag marker #1 over the comet's initial location, after which the animation can be run either by pressing the "Play" or "fastforward" button. After the animation has advanced several frames, the animation can be stopped and students can position drag marker #2 over the comet's new location. Students will also enter the stop time in the spaces provided. The calculate button will then display the comet's speed in both km/hr and in km/second.

Students should take time to reflect on the speed of the comet.

After calculating the speed of the comet, students can use the applet to determine the size of the comet. Students should click on the "Calculate comet's size" button to open the appropriate calculation window. Students can then position the drop markers to calculate the size of the comet's tail. Once the markers are positioned, students can click the "Calculate" button to display the comet's total size. To determine the size of the comet's coma, students will use the "Zoom in" button along with dragging and dropping the image itself to isolate the comet's coma. Once the comet is clearly visible, students will click the "Show/hide grid" button and will position the comet image alongside the red grid. Students will report a size for the comet in fractions of a cm (the spacing of the large grid lines). Students will then input the results into the space provided, and can click the "Calculate" button to display the results.

Students should take time to reflect on the size of the comet (both coma size and entire comet size) compared to Earth.