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Pasiphaë (moon)
Encyclopedia
Pasiphaë is a retrograde
irregular satellite
of Jupiter
. It was discovered in 1908 by Philibert Jacques Melotte
and later named after the mythological Pasiphaë
, wife of Minos
and mother of the Minotaur
from Greek legend
.
It was first spotted on a plate taken at the Royal Greenwich Observatory on the night of February 28, 1908. Inspection of previous plates found it as far back as January 27. It received the provisional designation , as it was not clear whether it was an asteroid or a moon of Jupiter. The recognition of the latter case came by April 10.
Pasiphaë did not receive its present name until 1975; before then, it was simply known as . It was sometimes called "Poseidon" between 1955 and 1975.
Pasiphaë orbits Jupiter on a high eccentricity and high inclination retrograde orbit. It gives its name to the Pasiphaë group
, irregular retrograde moons orbiting Jupiter at distances ranging between 22.8 and 24.1 million km, and with inclination
s ranging between 144.5° and 158.3°. The orbital elements are as of January 2000. They are continuously changing due to solar
and planetary perturbations. The diagram illustrates its orbit in relation to other retrograde irregular satellites of Jupiter. The eccentricity of selected orbits is represented by the yellow segments (extending from the pericentre
to the apocentre
). The outermost regular satellite Callisto
is located for reference.
Pasiphae is also known to be in a secular resonance with Jupiter (tying the longitude of its perijove with the longitude of perihelion of Jupiter).
and Elara
.
Spectroscopical measurements in infrared
indicate that Pasiphaë is a spectrally
featureless object, consistent with the suspected asteroid
al origin of the object. Pasiphaë is believed to be a fragment from a captured asteroid
along with other Pasiphaë group satellites.
In the visual spectrum the satellite appears grey (colour indices
B-V=0.74, R-V=0.38) similar to C-type asteroid
s.
Retrograde motion
Retrograde motion is motion in the direction opposite to the movement of something else, and is the contrary of direct or prograde motion. This motion can be the orbit of one body about another body or about some other point, or the rotation of a single body about its axis, or other phenomena such...
irregular satellite
Irregular satellite
In astronomy, an irregular moon is a natural satellite following a distant, inclined, and often eccentric and retrograde orbit. They are believed to have been captured by their parent planet, unlike regular satellites, which form in situ....
of Jupiter
Jupiter
Jupiter is the fifth planet from the Sun and the largest planet within the Solar System. It is a gas giant with mass one-thousandth that of the Sun but is two and a half times the mass of all the other planets in our Solar System combined. Jupiter is classified as a gas giant along with Saturn,...
. It was discovered in 1908 by Philibert Jacques Melotte
Philibert Jacques Melotte
Philibert Jacques Melotte was a British astronomer whose parents immigrated from Belgium.In 1908 he discovered a moon of Jupiter, today known as Pasiphaë. It was simply designated "Jupiter VIII" and was not given its present name until 1975.The asteroid 676 Melitta, the only one he discovered, is...
and later named after the mythological Pasiphaë
Pasiphaë
In Greek mythology, Pasiphaë , "wide-shining" was the daughter of Helios, the Sun, by the eldest of the Oceanids, Perse; Like her doublet Europa, her origins were in the East, in her case at Colchis, the palace of the Sun; she was given in marriage to King Minos of Crete. With Minos, she was the...
, wife of Minos
Minos
In Greek mythology, Minos was a king of Crete, son of Zeus and Europa. Every year he made King Aegeus pick seven men and seven women to go to Daedalus' creation, the labyrinth, to be eaten by The Minotaur. After his death, Minos became a judge of the dead in Hades. The Minoan civilization of Crete...
and mother of the Minotaur
Minotaur
In Greek mythology, the Minotaur , as the Greeks imagined him, was a creature with the head of a bull on the body of a man or, as described by Roman poet Ovid, "part man and part bull"...
from Greek legend
Greek mythology
Greek mythology is the body of myths and legends belonging to the ancient Greeks, concerning their gods and heroes, the nature of the world, and the origins and significance of their own cult and ritual practices. They were a part of religion in ancient Greece...
.
It was first spotted on a plate taken at the Royal Greenwich Observatory on the night of February 28, 1908. Inspection of previous plates found it as far back as January 27. It received the provisional designation , as it was not clear whether it was an asteroid or a moon of Jupiter. The recognition of the latter case came by April 10.
Pasiphaë did not receive its present name until 1975; before then, it was simply known as . It was sometimes called "Poseidon" between 1955 and 1975.
Orbit
Pasiphaë group
The Pasiphaë group is a group of retrograde irregular satellites of Jupiter that follow similar orbits to Pasiphaë and are thought to have a common origin....
, irregular retrograde moons orbiting Jupiter at distances ranging between 22.8 and 24.1 million km, and with inclination
Inclination
Inclination in general is the angle between a reference plane and another plane or axis of direction.-Orbits:The inclination is one of the six orbital parameters describing the shape and orientation of a celestial orbit...
s ranging between 144.5° and 158.3°. The orbital elements are as of January 2000. They are continuously changing due to solar
Sun
The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...
and planetary perturbations. The diagram illustrates its orbit in relation to other retrograde irregular satellites of Jupiter. The eccentricity of selected orbits is represented by the yellow segments (extending from the pericentre
Apsis
An apsis , plural apsides , is the point of greatest or least distance of a body from one of the foci of its elliptical orbit. In modern celestial mechanics this focus is also the center of attraction, which is usually the center of mass of the system...
to the apocentre
Apsis
An apsis , plural apsides , is the point of greatest or least distance of a body from one of the foci of its elliptical orbit. In modern celestial mechanics this focus is also the center of attraction, which is usually the center of mass of the system...
). The outermost regular satellite Callisto
Callisto (moon)
Callisto named after the Greek mythological figure of Callisto) is a moon of the planet Jupiter. It was discovered in 1610 by Galileo Galilei. It is the third-largest moon in the Solar System and the second largest in the Jovian system, after Ganymede. Callisto has about 99% the diameter of the...
is located for reference.
Pasiphae is also known to be in a secular resonance with Jupiter (tying the longitude of its perijove with the longitude of perihelion of Jupiter).
Physical characteristics
With diameter estimated at 58 km Pasiphaë is the largest retrograde and third largest irregular satellite after HimaliaHimalia (moon)
Himalia is the largest irregular satellite of Jupiter, the sixth largest overall in size, and the fifth largest in mass. It was discovered by Charles Dillon Perrine at the Lick Observatory on 3 December 1904 and is named after the nymph Himalia, who bore three sons of Zeus .- Discovery...
and Elara
Elara (moon)
Elara is a prograde irregular satellite of Jupiter. It was discovered by Charles Dillon Perrine at Lick Observatory in 1905. It is the eighth largest moon of Jupiter and is named after the mother by Zeus of the giant Tityus....
.
Spectroscopical measurements in infrared
Infrared
Infrared light is electromagnetic radiation with a wavelength longer than that of visible light, measured from the nominal edge of visible red light at 0.74 micrometres , and extending conventionally to 300 µm...
indicate that Pasiphaë is a spectrally
Electromagnetic spectrum
The electromagnetic spectrum is the range of all possible frequencies of electromagnetic radiation. The "electromagnetic spectrum" of an object is the characteristic distribution of electromagnetic radiation emitted or absorbed by that particular object....
featureless object, consistent with the suspected asteroid
Asteroid
Asteroids are a class of small Solar System bodies in orbit around the Sun. They have also been called planetoids, especially the larger ones...
al origin of the object. Pasiphaë is believed to be a fragment from a captured asteroid
Asteroid
Asteroids are a class of small Solar System bodies in orbit around the Sun. They have also been called planetoids, especially the larger ones...
along with other Pasiphaë group satellites.
In the visual spectrum the satellite appears grey (colour indices
Color index
In astronomy, the color index is a simple numerical expression that determines the color of an object, which in the case of a star gives its temperature...
B-V=0.74, R-V=0.38) similar to C-type asteroid
C-type asteroid
C-type asteroids are carbonaceous asteroids. They are the most common variety, forming around 75% of known asteroids, and an even higher percentage in the outer part of the asteroid belt beyond 2.7 AU, which is dominated by this asteroid type...
s.