Some Terms You Should Know: the Crab Nebula

These are some terms you will come across in your lab class dealing with the Crab Nebula.
A large region of dust and gas in space.  The plural is nebulae.
A star that suddenly flares up in brightness.  This is possibly due to the nuclear reactions resulting from new material being deposited on the surface of a white dwarf.  The plural is novae.
A distance equal to 3.26 light years. An object one parsec away will have a parallax angle of 1 second of arc when viewed from a baseline of 1 AU.
Plate Scale
A conversion factor, for a specific photograph, of linear distance to angular distance (e.g., from mm to seconds of arc).
Proper Motion
Motion that is 90 degrees from a line between the observer and the object.  Motion to the left or right, e.g., would be proper motion, while motion towards you would be radial motion.
A neutron star that spins very rapidly and emits a radio "pulse" at regular times (usually on the order of seconds).

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This page was last updated on 13 April 1998
and is © 1998 by Jim McDonald.