The moon of Jupiter –
Megaclite (XIX) – was previously temporarily designated as S/2000
J8. It was discovered in late November 2000
by the following team of astronomers: S.S. Sheppard
,
D.C. Jewitt,
Y. Fernandez and G. Magnier. This discovery was achieved by
2.2-m telescope atop Mauna Kea (Hawaii).
Megaclite is one of eleven new satellites discovered since the →Voyager-2
Jupiter system fly-by which occured 21 years ago (1979). With this moon, the
team discovered also: Themisto, Kalyke,
Iocaste, Erinome, Harpalyke,
Isonoe, Praxidike,
Taygete, Chaldene and S/2000
J11.
The name of that moon is of mythological origin. Megaclite was daughter of Macareus, who with Zeus gave birth to Thebe and Locrus.
The moon by this name is in elliptical retrograde orbit (→eccentricity
e = 0.4198) with a →semimajor axis a = 23,493,000 km. At pericenter (closest to the planet) Megaclite is separated from the Jupiter a distance of q = 13,630,639 km. At apocenter (furthest from the planet) this moon is separated from the Jupiter a distance of Q = 33,355,361 km.
In future these parameters may vary due to a large orbital distance from Jupiter and the orbital motion being disturbed by the Sun and other factors. Perhaps it is a captured asteroid (with a microscopic mass: ~2.0981×1014 kg – it equals
35 times less than a mountain like Giewont
!),
and in future will possibly return to heliocentric orbit.
The orbital period is almost 2.1 earthly year, which means that the average speed of its celestial motion is
only 0°28'41'' per day. When this motion was detected and compared to the changes in Jupiter's position, this body was classified as a true planetary satellite (and not a distant celestial body with its position projected near the planet).
Other obstacle in detecting this moon earlier was its brightness of only 21.7m
(almost 2 million times fainter than the faintest stars visible to naked eye). For comparison: Jupiter's brightness is about –2.7m,
so Megaclite is shining fainter by about 24.4m.
The corresponding difference in brightness is over 5.75 billion times!
I have given some crucial data of Megaclite below. Table one
contains the basic information. Whereas table two gives more detailed parametrs
of its orbit (calculated using the following formulae).
Translated by Karol Pankowski
|
Megaclite
|
|---|
| Mean distance from the planet [×103 km] |
23,493.0
|
| Mean distance from the planet [planetary R] |
328.6
|
| Orbital period [days] |
752.86
|
| Orbital eccentricity [e] |
0.4198
|
| Orbit inclination [degrees] |
152.8
|
| Mean diameter [km] |
5.4
|
| Main discoverer and year of the discovery |
S.S. Sheppard 2000
|
| Visual magnitude [mag] |
21.7
|
| Mass [kg] |
~2.0981 × 1014
|
Orbital Parameters |
Pericenter
[q] |
Apocenter
[Q] |
| Distance from the planet [×103 km] |
13,630.6
|
33,355.4
|
| Distance from the planet [planetary R] |
190.7
|
466.6
|
| Angular size of the moon's orbit observed from the Earth* [degrees] |
1°14'31.88''
|
3°02'27.37''
|
|
| Angular diameter of the planet's disc as observed from the moon [degrees] |
0°36'03.71''
|
0°14'44.19''
|
| Brightness of the planet as observed from the moon** [mag] |
–11.0
|
–9.1
|
| Diameter of the moon's disc as observed from the planet's "surface" [degrees] |
0°00'00.08''
|
0°00'00.03''
|
| Brightness of the moon as observed from the planet's "surface"** [mag] |
13.4
|
15.3
|
|
Orbital velocity [km/sec] |
3.63
|
1.48
|
* This value is calculated for Jupiter at opposition (distance 628.8 million km = 4.2 AU)
** The given value of magnitude is not corrected for some decreasing factors (e.g. the changing phase of illumination)
|
See other related links:
Monde
des Monats
– PASIPHAEGRUPPE
Jupiter's New Satellites
The Astronomy Workshop – Satellite Viewer
Planetary Satellite Mean Orbital Parameters
Natural Satellite Physical Parameters
