skip to content
 
Goddard Space Flight Center   What's New
  Site Map
HOME Science Special Exhibit Satellites and Data Teachers' Corner
Imagine the Universe!
Ask a High Energy Astronomer Dictionary Resources

Finding the Velocity and Period of Cygnus X-1

The following image is a plot of the velocity of Cygnus X-1's optical companion as a function of time. This plot was generated using optical spectral data of the star. The velocity changes over time as the star orbits around Cygnus X-1 - when the velocity is positive it is moving towards us and when it is negative it is moving away from us (XX check this convention). From this plot it is possible to determine the tangential velocity and the period of the optical companion, parameters which can then be used to solve for the mass of Cygnus X-1!

velocity plot of Cygnus X-1's optical companion

Quiz Click here for more information and a quiz on spectra and how this data is collected from spectra.
Return Click here return to solve for the mass of Cygnus X-1.

Home Imagine Science Special Exhibit Satellites and Data
Dictionary Resources Teachers' Corner Ask a High Energy Astronomer

Imagine the Universe is a service of the High Energy Astrophysics Science Archive Research Center (HEASARC), Dr. Nicholas White (Director), within the Laboratory for High Energy Astrophysics at NASA's Goddard Space Flight Center.

The Imagine Team
Project Leader: Dr. Jim Lochner
All material on this site has been created and updated between 1997-2004.

Useful plugins

NASA's privacy statement

Do you have a comment or question about this CD-ROM? Please send e-mail to itu@athena.gsfc.nasa.gov.

External links contain material that we found to be relevant. However they're not maintained by us and the content may have changed. If you find any external links that contain inappropriate material, please let us know by sending an e-mail to itu@athena.gsfc.nasa.gov.

CD Table of Contents