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sun |sən| |sən| |sʌn|
noun
1 (also Sun) the star around which the earth orbits.
• any similar star in the universe, with or without planets.
The sun is the central body of the solar system. It provides the light and energy that sustains life
on earth, and its position relative to the earth's axis determines the terrestrial seasons. The sun is
a star of a type known as a G2 dwarf, a sphere of hydrogen and helium 870,000 miles (1.4
million km) in diameter that obtains its energy from nuclear fusion reactions in its interior,
where the temperature is about 15 million °C. The surface is a little under 6,000°C.
Comet
noun
a celestial object consisting of a nucleus of ice and dust and, when near the sun, a “tail” of gas
and dust particles pointing away from the sun.
Originating in the remotest regions of the solar system, most comets follow regular eccentric
orbits and appear in the inner solar system as periodic comets, some of which break up and can
be the origin of annual meteor showers. They were formerly considered to be supernatural
omens.
asteroid
noun
a small rocky body orbiting the sun. Large numbers of these, ranging in size from nearly 600
miles (1,000 km) across (Ceres) to dust particles, are found (as the asteroid belt) esp. between
the orbits of Mars and Jupiter, though some have more eccentric orbits, and a few pass close to
the earth or enter the atmosphere as meteors.
meteoroid
noun Astronomy
a small body moving in the solar system that would become a meteor if it entered the earth's
atmosphere.
dwarf
dwarf star) Astronomy a star of relatively small size and low luminosity, including the
majority of main sequence stars.
star |stär| |stɑr| |stɑː|
noun
1 a fixed luminous point in the night sky that is a large, remote incandescent body like the sun.
True stars were formerly known as the fixed stars, to distinguish them from the planets or
wandering stars. They are gaseous spheres consisting primarily of hydrogen and helium, there
being an equilibrium between the compressional force of gravity and the outward pressure of
radiation resulting from internal thermonuclear fusion reactions. Some six thousand stars are
visible to the naked eye, but there are actually more than a hundred billion in our own Galaxy,
while billions of other galaxies are known.
PHRASES
my stars! informal dated an expression of astonishment.
reach for the stars have high or ambitious aims.
see stars see flashes of light, esp. as a result of being hit on the head.
someone's star is rising see rise .
stars in one's eyes used to describe someone who is idealistically hopeful or enthusiastic about
their future : a singer selected from hundreds of applicants with stars in their eyes.
constellation
noun
a group of stars forming a recognizable pattern that is traditionally named after its apparent
form or identified with a mythological figure. Modern astronomers divide the sky into eightyeight constellations with defined boundaries.
Cassiopeia
1 Greek Mythology the wife of Cepheus, king of Ethiopia, and mother of Andromeda.
2 Astronomy a constellation near the north celestial pole, recognizable by the conspicuous “W”
pattern of its brightest stars.
Ursa Minor
Astronomy
a northern constellation (the Little Bear) that contains the north celestial pole and the polar star
Polaris. The brightest stars form a shape that is also known as the Little Dipper.
Ursa Major |ˈərsə ˈmājər| |ˌˈərsə ˌmeɪdʒər| |ˈəːsə ˌmeɪdʒə| Astronomy
one of the largest and most prominent northern constellations (the Great Bear). The seven
brightest stars form a familiar asterism known by various names (esp. the Big Dipper and the
Plow) and include the Pointers.
Corona Borealis |bôrēˈaləs| |kəˌroʊnə ˈbɔriˌeɪl1s| |kəˌroʊnə bɔriˌøləs| |ˈbɔːrɪˌeɪlɪs|
Astronomy
a northern constellation (the Northern Crown), in which the main stars form a small but
prominent arc.
Polaris |pəˈlarəs| |pəˌlɛrəs| |pəˌlɑːrɪs|
1 Astronomy a fairly bright star located within one degree of the north celestial pole, in the
constellation Ursa Minor. It is a double star, the bright component of which is a cepheid
variable. Also called North Star , polestar .