Astronomy Project 2007
ECoS Faculty: Mercedes Richards
ECoS Undergraduate Mentor: none
Astronomical Clocks in the Sky
Astronomical clocks have existed since the dawn of time. Ancient peoples measured
time using the positions of the Sun (to define the day and the year) and the Moon (to define the
month). However, many other objects in the sky behave like clocks. Some stars pulsate (expand
and contract) regularly with cycles that are only minutes long; others take years to complete one
cycle. In addition, all stars rotate like the Earth, with periods that range from milliseconds to
months. Some of these stars are rapidly rotating neutron stars called pulsars. Binary star
systems contain two stars that mutually orbit with regular cyclical periods of days to thousands
of years. So, a variety of clocks are found throughout the sky. In this project, we will use a well-
known pulsar called Cen X-3 to learn (1) how to discover if the light from a star varies with a
regular period, (2) how to determine the value of that period accurately, and (3) how to get
information about the size of the objects involved and the scale of the system.
Powerpoint Presentation