Astro 11 Laboratory Exercise - Pulsars - Radio Astronomy of...

A Manual to Accompany Software for
the Inductory Astronomy Lab Exercise
Document SMG 8: Version 1
Department of Physics
Gettysburg College
Gettysburg, PA 17325
Telephone: [phone]
email: [email protected]
Contemporary Laboratory
Experiences in Astronomy
Radio Astronomy of Pulsars
Student Manual

Contents
Goals .....................................................................................................................................................
3
Objectives .............................................................................................................................................
3
Operating the Computer .......................................................................................................................
6
Starting the program .............................................................................................................................
7
Procedure ..............................................................................................................................................
7
Part 1: The Radio Telescope ........................................................................................................................................ 7
Part 2: Observation of a Pulsar with a Single-Channel Radio Receiver ....................................................................... 8
Part 3: The Periods of Different Pulsars ...................................................................................................................... 11
Part 4: Measurement of the Distance of Pulsars Using Dispersion ............................................................................ 12
A. Method ........................................................................................................................................................... 12
B. An Example from the Everyday World .......................................................................................................... 12
C. The Dispersion Formula for the Interstellar Medium ..................................................................................... 14
D. Measuring The Distances Of Pulsars ............................................................................................................. 15
Part 5: Determine the distance of Pulsar 2154+40 applying the techniques you have just learned . ........................... 17
Additional Exercises You Can Do With This Telescope .....................................................................
18
1. The Distance To Short-Period Pulsars .................................................................................................................... 18
2. Measuring the Telescope Beamwidth ..................................................................................................................... 18
3. Measuring the Pulsar Spin-Down Rate ................................................................................................................... 19
4. Searching for Pulsars .............................................................................................................................................. 19

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Goals
You should be understand the fundamental operation of a radio telescope and recognize how it is
similar to, and different from, an optical telescope. You should understand how astronomers, using
radio telescopes, recognize the distinctive properties of pulsars. You should understand what is
meant by interstellar dispersion, and how it enables us to measure the distances to pulsars.
Objectives
If you learn to .......
Use a simulated radio telescope equipped with a multi-channel receiver.
Operate the controls of the receiver to obtain the best display of pulsar signals.
Record data from these receivers.
Analyze the data to determine properties of the pulsars such as periods, signal strengths at
different frequencies, pulse arrival times, relative strengths of the signals.
Understand how the differences in arrival times of radio pulses at different frequencies tell
us the distance the pulses have travel.
You should be able to .....
Understand the basic operation and characteristics of a radio telescope.
Compare the periods of different pulsars, and understand the range of periods we find for
pulsars.
Understand how a pulsar’s signal strength depends on frequency.
Determine the distance of several pulsars.
Useful Terms You Should Review Using Your Textbook
Crab Nebula interstellar medium pulsar frequency
Declination Julian Date radio telescope parsecs
dispersion magnetic field radio waves period
electromagnetic spectrum neutron star resolution speed of light
electromagnetic radiation Universal Time (UT) Right Ascension

Student Manual
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Background: Neutron Stars and Pulsars
Many of the most massive stars, astronomers believe, end their lives as neutron stars. These are bizarre objects
so compressed that they consist entirely of neutrons, with so little space between them that a star containing the mass of
our sun occupies a sphere no larger than about 10 km. in diameter, roughly the size of Manhattan Island. Such objects,