Name ______________________________ Date ___________________________

X-Ray Binary

Directions for Model


  1. Trace the larger end of the cup onto the center of four plates. Puncture the middle of the plate with the scissors and cut out the circles just to the inside of the line, creating a doughnut shape. The first plate may be used as a template for the other plates.

  2. Puncture the bottom of the cup from the inside with a screw eye creating a small hole. The hole should be large enough for the yarn to pull through.

  3. Place the four plates on top of each other and tape them together to keep from sliding. Secure the cup into the middle of the plates. The cup should be flush with the surface of the top plate.

  4. Place the screw eyes in the plates in a spiral fashion starting just outside the cup and working towards the outer rim of the plates. (see template) If the screw eyes puncture through the plates, cover the tips with masking tape.

  5. Wrap the end piece of the yarn with 1 inch of masking tape to create a point. Thus, making it easier to thread through the screw eyes.

  6. Thread the yarn through the screw eyes starting with the outside rim and working towards the cup. Continue to thread through the hole in the bottom of the cup until the string is hanging a few inches below the bottom of the cup.

  7. The ball of yarn will represent the COMPANION STAR. One person will hold the companion star. **Measure the circumference and the mass of the companion star and record in the chart.

  8. The cup will represent the BLACK HOLE and the string surrounding the hole will represent the ACCRETION DISK. The bottom of the cup represents the EVENT HORIZON. The second person will hold the black hole about 10-12 inches away from the companion star.

  9. The third person will slowly pull the yarn from bottom of the cup. Thus, showing how material is pulled from the companion star into the black hole.

  10. Once the material is pulled into the black hole it becomes a part of the total mass of the black hole. The material may no longer return to the companion star. Over time the companion star will continually decrease in size.

  11. Pull the yarn slowly for 5 seconds and record the circumference of the companion star and mass of both the companion star and the material added to the black hole. Repeat three times. Complete the activity sheet.