View Full Version : [Astronomical] Definitions

2013-Jun-14, 02:36 PM
Often it only matters if you want presice numbers instead of ball park. Solar systems might be defined as having a minimum of one main sequence star. If we call it a system instead of a solar system then it is possibly a compact "star" with something orbiting it, including an accretion disk. That would likely include all compact stars and brown dwarf that are (or are not) part of a system with one or more main sequence star. Some would prefer not to count anything as a system until we have compelling evidence that something is orbiting it even though it very probable that sub atomic particles orbit almost everything in space.
Is a star fusing helium or neon on main sequence?
Where objects are wide spaced, they are possibly temporarily orbiting each other, but over a google years, all orbits are likely temporary. I'm just giving some starting examples so take this thread to a discussion of definitions. Would any one care to write a book or assemble a "data" base with a million and one definitions related to astronomy? Neil

2013-Jun-14, 05:05 PM

2013-Jun-15, 06:33 PM
Is a star fusing helium or neon on main sequence?

Nope. That would be a Giant (Horizontal Branch, or Asymptotic Giant Branch). It would have STARTED on the Main Sequence because all stars have a relatively long hydrogen-burning phase.

2013-Jun-16, 12:01 AM
I would suggest "stellar planetary system" as a general term for systems similar to ours.