Black Hole LessonOverviewBlack Holes are objects which are extremely massive and extremely dense. The gravitational pull of these objects (like any mass) increases as you get closer. With a Black Hole, you can get so close that no force you apply will be strong enough to pull you away. Not even light generated from within this distance, called the event horizon, can escape. But, if we cannot see the light from a black hole, how do we know it is there? This lesson will have the students learn how scientists detect black holes by modeling the rotation of galaxies with larger and larger masses in the center.Preparation and MaterialsThe teacher should be familiar with the GalaxSee application (for those unfamiliar with this software, there is an online tutorial), have it loaded on a PC, and have some means of displaying the monitor to the class.This lesson also requires making calculations with GalaxSee data, and showing plots. A spreadsheet should also be installed on any student or display machines. ObjectivesStudents will
StandardsThis lesson fulfills portions of the following standards and curriculum guidelines:
Activities
Mac Users -
For more information about detecting and controlling error, see the section about the info window in the GalaxSee tutorial. Discussion of the SimulationAsk the students how the rotational speed within a galaxy with no central mass changes as you get closer to the center. Does the same thing happen with the angular velocity. If so, does this make sense? If not, how can this be explained?Ask the students why having a greater mass in the center would increase the rotational speed. Consider having the students (carefully) swing an object connected to a string in a circle. Do they have to provide a greater pull to get the object to rotate faster? Discussion of ObservationAsk the students how the curves for galaxies with larger and larger central objects were different. Remind the students that we can measure the difference in how one side of a galaxy is rotating from another side using redshift. How would the students propose measuring the mass of a black hole in the center of a galaxy?Assign them to write a report of what they modeled. Have them include in it a proposal for how they might use such a model to measure the mass of a black hole. Emphasize that it is important that they know what software was used, and what parameters were set. Be sure to go through the setup procedure again so that they can record this information. CollaborationAfter they have polished their reports, instruct them to prepare and post a note to WebCaMILE for another group of students to see. If possible, have the other group of students attempt to repeat the experiment as described in the note, verify the findings of the first group, and provide feedback about their methods and conclusions.Encourage both groups to ask questions of each other's procedure and observations. If another group of students is not available, you could split one class into two large groups and require them to communicate only through writing. ExtensionsFurther ExperimentationShow the students the Black Hole Companion galaxy. Open it with the Earth-Sun scale set. The black hole companion galaxy has two equal mass objects going on opposite directions, in orbit around each other. Before showing it to the students, hide one of the stars. Have the students try to build a galaxy which reproduces the motion that you show them.Thinking HarderAsk the students how else we might detect black holes. Remind them that we generally learn about massive black holes by the x-ray radiation given off as matter falls into the black hole. Have students look up different galaxies on the SkyView Non-Astronomer page, in visible and in x-ray. Do the galaxies they look at have an x-ray component?Be sure to point out to the students that the images are different scales. The web page will show how many degrees in the sky each image covers. Go to GalaxSee Curriculum Resources Please direct questions and comments about this page to WebMaster@shodor.org © Copyright 1996 The Shodor Education Foundation, Inc. |