What Are Pulsars?
a tutorial in stellar astronomy (This tutorial contains Java animations). Glossary: Electromagnetic Spectrum, Main Sequence, Neutron Star, Pulsar, Supernova Pulsars (PULSating stARS) are among the most exotic objects found in the galaxy. They are the peculiar relics of massive stars that have ended their lives in a tremendously powerful explosion called a supernova. A pulsar appears to flash on and off many times a second. The diagram at left simulates an “on” pulse. That’s a curious thing – how can a star turn itself on and off? During their lifetimes, all stars continuously perform an energy balancing act. The heat and energy generated in a star’s core want to make it expand, while the star’s gravity wants to make it contract. The perfect balance between the two can keep a star shining stably for billions of years. A star in this phase of life is said to be “on the main sequence.” Eventually, however, a star runs out of fuel in its center. When this happens, there is no longer a gene
Pulsars were discovered in 1967 by Jocelyn Bell and Anthony Hewish at the radio astronomy observatory (now the Nuffield Radio Astronomy Observatory) at Cambridge. Pulsar radio emission is very distinctive, a uniform series of pulses, spaced with great precision at periods of between a few milliseconds and several seconds. Over 700 radio pulsars are known. Some pulsars have also been detected by optical, X-ray and gamma-ray telescopes. The regularity of the pulses is phenomenal: observers can now predict the arrival times of pulses a year ahead with an accuracy better than a millisecond. How can a star behave as such an accurate clock? The only possibility for so rapid and so precise a repetition is for the star to be very small, rotating rapidly and emitting a beam of radiation which sweeps round the sky like a lighthouse, pointing towards the observer once per rotation. The only kind of star which can rotate fast enough without bursting from its own centrifugal force is a neutron star
A 106 Pulsars are remote stellar objects which emit more light in one direction than elsewhere, and which are spinning. From Earth they flash brightly every time they point at us. You can see this by hanging a torch so that it points sideways (not straight down) from a long string, twist the string a lot, retire to a distance and watch the flashing light. The speed at which a quasar flashes is very constant because angular momentum is conserved, so quasars act like stellar clocks. 12 May 96 – Lawrence Tuppen – rbd90@dial.pipex.com Candidate Questions and Answers Do YOU have candidate answers or questions for Science Matters? Posting Questions and/or Answers to Science Matters Thanks for visiting! http://www.treasure-net.com Copyright 1997 Treasure Net, Inc. All rights reserved.
