User`s guide

42 Starry Night User’s Guide
In Starry Night Pro and Pro Plus, clicking
the words “Limit by Distance” in the
Options pane opens a dialog box that lets
you set numeric values for limiting by
distance or magnitude.
Mark Binaries/Mark Variables: You can set
special markers for variable stars (stars
whose brightness varies), binary stars
(double stars that orbit around a common
center of mass), Variable stars are marked
with one of four symbols, according to
how much they vary in brightness.
Proper Motion Vectors:
Every star is
moving rapidly through space, in a unique
direction. However, because the stars are
so far away, they appear to remain in the
same place in the sky. Only over thousands
of years can we see the stars shift position
with respect to each other. This slow
movement of the stars is called
proper
motion
. Starry Night lets you display
proper motion vectors, lines that represent
the speed and direction of each star’s
motion. The length of a star’s proper
motion vector indicates its relative speed.
The Proper Motion Options dialog box has
a “vector scaling” option that allows you
to change the length of all proper motion
vectors, and a “vector colour” option that
allows you to change the colour of these
vectors.
Mark Stars With Extrasolar Planets: These
options let you display special markers for
stars that are known to harbour planets.
Tip: If you turn on markers for extrasolar
planets, the star’s Info pane will include
information about the extrasolar planet,
such as the planet’s mass and distance
from its central star. See
“Extrasolar planet information fields
” on
page 95
for more details.