The moon of Jupiter –
Erinome (XXV) – was previously temporarily designated as S/2000
J4. 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).
Erinome 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, Harpalyke, Isonoe,
Praxidike, Megaclite,
Taygete, Chaldene and S/2000
J11.
The name of that moon is of mythological origin. Erinome was daughter of Celes, compelled by Venus to fall in love with Jupiter...
The moon by this name is in elliptical retrograde orbit (→eccentricity
e = 0.2664) with a →semimajor axis a = 23,196,000 km. At pericenter (closest to the planet) Erinome is separated from the Jupiter a distance of q = 17,016,586 km. At apocenter (furthest from the planet) this moon is separated from the Jupiter a distance of Q = 29,375,414 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: ~4.4960×1013 kg – it equals
163 times less than a mountain like Giewont
!),
and in future will possibly return to heliocentric orbit.
The orbital period is a somewhat less than 2
earthly years, which means that the average speed of its celestial motion is
only 0°29'39'' 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 22.8m
(almost 5.25 million times fainter than the faintest stars visible to naked eye). For comparison: Jupiter's brightness is about –2.7m,
so Erinome is shining fainter by about 25.5m.
The corresponding difference in brightness is almost 16 billion times!
I have given some crucial data of Erinome 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
|
Erinome
|
|---|
| Mean distance from the planet [×103 km] |
23,196.0
|
| Mean distance from the planet [planetary R] |
324.5
|
| Orbital period [days] |
728.46
|
| Orbital eccentricity [e] |
0.2664
|
| Orbit inclination [degrees] |
164.9
|
| Mean diameter [km] |
3.2
|
| Main discoverer and year of the discovery |
S.S. Sheppard 2000
|
| Visual magnitude [mag] |
22.8
|
| Mass [kg] |
~4.4960 × 1013
|
Orbital Parameters |
Pericenter
[q] |
Apocenter
[Q] |
| Distance from the planet [×103 km] |
17,016.6
|
29,375.4
|
| Distance from the planet [planetary R] |
238.0
|
410.9
|
| Angular size of the moon's orbit observed from the Earth* [degrees] |
1°33'02.97''
|
2°40'40.12''
|
|
| Angular diameter of the planet's disc as observed from the moon [degrees] |
0°28'53.17''
|
0°16'43.99''
|
| Brightness of the planet as observed from the moon** [mag] |
–10.5
|
–9.4
|
| Diameter of the moon's disc as observed from the planet's "surface" [degrees] |
0°00'00.04''
|
0°00'00.02''
|
| Brightness of the moon as observed from the planet's "surface"** [mag] |
15.0
|
16.1
|
|
Orbital velocity [km/sec] |
3.07
|
1.78
|
* 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
– CARMEGRUPPE
Jupiter's New Satellites
The Astronomy Workshop – Satellite Viewer
Planetary Satellite Mean Orbital Parameters
Natural Satellite Physical Parameters
