Universe
The sum total of all existing things.
For more about the Universe, please see the big bang cosmology primer.
Uranus
The seventh planet from the Sun, Uranus is a
gas giant planet with at least seventeen
moons. It is also well known because of its peculiar axis of rotation, which is almost
parallel to the ecliptic. Check out SEDS'
Nine Planets, for more
about Uranus. Or see StarDate's
Solar System Guide.
Uranus
Venus
Venus has an orbit of 108 million km. It is the
second planet from the Sun. Venus is very similar to Earth in many ways: both have
roughly the same diameter and mass, both are
terrestrial Planets and both have the same chemical make-up. Check out SEDS'
Nine Planets, for more
about Venus. Or see StarDate's
Solar System Guide.
Venus
Vernal Equinox
The place in the sky where the
Sun crosses the celestial equator moving
northwards. The vernal equinox falls on, or near, March 21, the first day of spring. See
celestial sphere for a helpful diagram.
VMOs
An acronym for Very Massive Object,
VMOs are dark matter candidates
which are thought to be 100 times more massive than our Sun. They are likely to be found in the form
of black holes.
WIMP
An exotic class of non-baryonic
particle, WIMPs (Weakly Interacting Massive Particles) are a prime dark matter
candidate. For more about dark matter and WIMPs, check out these
pages:
Winter Solstice
The point on the
ecliptic where the Sun is farthest south. The
winter solstice, which is the shortest day of the year, occurs on, or near, December 21,
and marks the first day of winter. See celestial
sphere for a helpful diagram.
X-Ray
A class of high energy photon, X-rays have
wavelengths of 0.012 to 12 nanometers. Not only are X-rays used for medical imaging (when
you break your arm an X-ray machine is used to take a picture of the broken bone), but
since black holes,
quasars, and other stellar objects emit X-rays,
X-Ray Astronomy is actively researched.
X-Ray Astronomy
A branch of astronomy which
deals primarily with X-Rays.
Year
The period required for an object to orbit a star
once. Note that the length of a year depends upon where you are: an Earth year is 365
days, but a Pluto year is almost 250 Earth years.
Zenith
The point on the
celestial sphere which is directly above
the observer.