- The Sun is a hot ball of self-luminous gas. It has neither
a solid surface nor a solid interior and yet it
appears to have an edge.
Why?
- The Sun is a G2 V (Main Sequence) star.
The Sun
is a little above average
in mass for a star in our Galaxy (the average stellar
mass is 30 % of the mass of the Sun), but overall, it is a fairly
typical star.
- It resides in the large grouping of
stars referred to as the Milky Way
(optical,
DIRBE).
The Milky Way is a spiral galaxy
(e.g., see these views of a top down view of a spiral galaxy,
M51, the Whirlpool galaxy, and an edge-on view (a
side view) of a spiral galaxy
M104,
the Sombrero galaxy)
composed of
~ 200 billion stars. The Sun lives in one of its spiral arms
of the Milky Way, roughly 2/3 of
the way out from the center of the galaxy,
whizzing around the center of the
galaxy at a speed of around 200 kilometers per second.
For the next few lectures, we will consider the Sun in detail. We will
look at the following two topics:
