The imaginary circle around the
celestial sphere that separates
that sphere into a northern and
southern half. It is analogous, of
course, to the equator of Earth,
but out there on the sky.
celestial equator
The celestial meridian is an arch
across the sky which begins on the
horizon at the north point, passes
through the zenith, then proceeds
down to the horizon at the south
point. This vertical circle separates
the sky into an eastern half and a
western half. All celestial bodies
must cross the meridian once each
day. When the Sun crosses, we call
that ‘noon’
celestial meridian
The distinctive red layer of the Sun
which is a transition between the
bright photosphere that we see and
the faint, extended corona.
Fountains of gas called spicules
are found in the chromosphere.
chromosphere
(B-V) The numerical difference
between an object’s brightness in
the blue part of the spectrum, B,
and its brightness in yellow, V (for
visual). The color index of stars is
often used on the horizontal axis
of H-R diagrams.
color index
A relatively small, cold, icy, dirty
object orbiting the Sun. Comets
spend the vast majority of their
time far from the Sun in a region
known as the Oort Cloud. It’s
when they get gravitationally
bumped into a different orbit that
takes them very close to the Sun
when the fun begins!
comet
An alignment of two astronomical
bodies so that they are seen to be
in the same general direction in our
sky. Planets are occasionally in
conjunction with each other or the
Sun.
conjunction
A
grouping
a
stars
forming
some
mythological
figure
or
other
object
of
our
imagination.
There
are
eighty-eight
officially
recognized
constellations
in
the
sky.
Hey,
that’s
the
same
as
the
number of keys on a piano!
constellation
A concave indentation on the
surface of a planet or moon
usually caused by the impact of a
meteoroid.
crater