Rhea

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Rhea, in astronomy

Rhea,

in astronomy, one of the named moons, or natural satellites, of SaturnSaturn,
in astronomy, 6th planet from the sun. Astronomical and Physical Characteristics of Saturn

Saturn's orbit lies between those of Jupiter and Uranus; its mean distance from the sun is c.886 million mi (1.
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. Also known as Saturn V (or S5), Rhea is 950 mi (1530 km) in diameter, orbits Saturn at a mean distance of 327,487 mi (527,040 km), and has equal orbital and rotational periods of 4.517 earth days. The second largest of Saturn's moons, Rhea was discovered by the Italian-French astronomer Gian Domenico CassiniCassini
, name of a family of Italian-French astronomers, four generations of whom were directors of the Paris Observatory.

Gian Domenico Cassini, 1625–1712, was born in Italy and distinguished himself while at Bologna by his studies of the sun and planets,
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 in 1672. Rhea's density of 1.3 means that it is composed primarily of water ice, rocky material making up about a third of its mass. Its leading hemisphere is highly reflective and heavily cratered, strongly resembling the cratered highlands of the moon, although Rhea's craters do not have high walls or a towering central peak; the trailing hemisphere is darker with bright wispy streaks and few impact craters. In 2010 the space probe Cassini discovered that Rhea has an extremely thin atmosphere of oxygen and carbon dioxide.

Rhea, in Greek religion and mythology

Rhea,

in Greek religion and mythology, a Titan. She was the wife and sister of KronosKronos
or Cronus
, in Greek religion and mythology, the youngest Titan, son of Uranus and Gaea. With the help of his mother, he led the Titans in the revolt against Uranus and ruled the world.
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, by whom she bore Zeus, Poseidon, Pluto, Hestia, Hera, and Demeter. She eventually helped Zeus overthrow Kronos. Her worship, which was orgiastic and associated with fertility rites, was particularly prominent in Crete. The Greeks often identified her with Gaea and Cybele. In Rome, Rhea was worshiped as Magna Mater and identified with Ops. See Great Mother GoddessGreat Mother Goddess,
in ancient Middle Eastern religions, mother goddess, the great symbol of the earth's fertility. She was worshiped under many names and attributes. Similar figures have been known in every part of the world.
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.

rhea, in zoology

rhea

(rē`ə), common name for a South American bird of the family Rheidae, which is related to the ostrichostrich,
common name for a large flightless bird (Struthio camelus) of Africa and parts of SW Asia, allied to the rhea, the emu and the extinct moa. It is the largest of living birds; some males reach a height of 8 ft (244 cm) and weigh from 200 to 300 lb (90–135
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. Weighing from 44 to 55 lb (20–25 kg) and standing up to 60 in. (152 cm) tall, the rhea is slightly smaller than the ostrich and lacks that bird's extravagant plumelike tail feathers. The rhea also differs from the unrelated ostrich in structure of the palate, pelvis, and foot. It is yellow and gray above, with a black head and dirty-white underside. The greater, or common, rhea (Rhea americana) is found from northeastern Brazil to Argentina. The somewhat smaller lesser, or Darwin's, rhea (Pterocnemia pennata) occurs from Patagonia to the high Andes. The rhea is typically a creature of the pampas and savannas and may often be found feeding in mixed herds along with cattle or guanaco, occupying an ecological niche similar to that of the ostrich and the zebra of Africa. Rheas feed on several kinds of plants, insects, and small vertebrates. While the old males tend to stay solitary, the young male is aggressive and highly polygamous, gathering about itself from three to seven hens. The nest is built in a dry and protected area, preferably near water. The male excavates a shallow hole with his bill, lines it with dry vegetable matter, and assumes all the incubation duties. He may incubate as many as 50 eggs, produced by a number of females over a period of weeks. Incubation takes from 35 to 40 days. The eggs, lemon yellow when laid, or greenish in the case of Darwin's rhea, weigh up to 2 lb (almost 1 kg) each. When hatched, the chicks are gray with darker stripes. The rhea is one of the flat-breastboned, or ratite, flightless birds. Rheas are classified in the phylum ChordataChordata
, phylum of animals having a notochord, or dorsal stiffening rod, as the chief internal skeletal support at some stage of their development. Most chordates are vertebrates (animals with backbones), but the phylum also includes some small marine invertebrate animals.
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, subphylum Vertebrata, class Aves, order Struthioniformes, family Rheidae.

Rhea

(ree -ă) The second largest of the Saturn system of satellites, discovered in 1672 by Giovanni Domenico Cassini. It has a diameter of 1530 km and a density of 1.33 g cm–3. The low density indicates that Rhea is composed of a rocky core making up about a third of the satellite's mass surrounded by water ice. The northern hemisphere is particularly heavily cratered and resembles the rolling cratered highlands of the Moon. The crater density on the surface is irregular and suggests a varied geological history. The craters vary in size up to 75 km, the most prominent of which is Izanagi. The leading edge of Rhea as it moves in its orbit is brighter than the trailing edge, which contains bright wispy markings. The Cassini/Huygens spacecraft flew by Rhea in November 2005 at a distance of 500 km and was scheduled to make a second, much more distant, flyby in August 2007. See also Table 2, backmatter.

Rhea

 

in ancient Greek mythology, a Titan. Rhea was the daughter of Uranus and Gaea, the wife of Cronus, and the mother of Zeus, Demeter, and other Olympian gods.

rhea

[′rē·ə]
(botany)
(vertebrate zoology)
The common name for members of the avian order Rheiformes.

Rhea

[′rē·ə]
(astronomy)
A satellite of Saturn, with estimated diameter of 450 miles (1530 kilometers).

Rhea

worshiped orgy and fertility; mother of Zeus, Poseidon, Hera, Hades, Demeter, and Hestia. [Gk. Myth.: NCE, 1796]

Rhea

often titled Great Mother of the Gods. [Gk. Myth.: NCE, 1796]

rhea

either of two large fast-running flightless birds, Rhea americana or Pterocnemia pennata, inhabiting the open plains of S South America: order Rheiformes (see ratite). They are similar to but smaller than the ostrich, having three-toed feet and a completely feathered body