The moon of Jupiter –
Callirrhoe (XVII) – was previously temporarily designated as S/1999
J1. It was discovered in Octomber 1999 by the following team of astronomers: J.V. Scotti, T.B. Spahr, R.S. McMillan,
J.A. Larsen, J. Montani, A.E. Gleason and T. Gehrels.
You can read additional details in The International Astronomical Union Circular
(→IAU).
Callirrhoe
is a new satellite discovered since the →Voyager-2
Jupiter system fly-by which occured 24 years ago (1979).
As the seventeenth moon of Jupiter it did not ''endanger'' the position of Saturn which was then still leading by one moon... Nobody could foresee that an era of mass discoveries of planetary moons was soon to come which will make Jupiter the real king among the planets with an impressive entourage of over moons!
The name of that moon is of mythological origin. Callirhoe was the daughter of Achelous and married Alcmaeon who unsuccessfully tried to conquer Thebe.
The moon by this name is in elliptical retrograde orbit (→eccentricity
e = 0.2829) with a →semimajor axis a = 24,103,000 km. At pericenter (closest to the planet) Callirrhoe is separated from the Jupiter a distance of q = 17,284,261 km. At apocenter (furthest from the planet) this moon is separated from the Jupiter a distance of Q = 30,921,739 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: ~8.6923×1014 kg – it equals
about 8 times less than a mountain like Giewont
!),
and in future will possibly return to heliocentric orbit.
The orbital period is almost 2.1 earthly years, which means that the average speed of its celestial motion is
only 0°28'28'' 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 20.7m
(almost 760 thousand times fainter than the faintest stars visible to naked eye). For comparison: Jupiter's brightness is about –2.7m,
so Callirrhoe is shining fainter by about 23.4m.
The corresponding difference in brightness is almost 2.3 billion times!
I have given some crucial data of Callirrhoe 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
|
Callirrhoe
|
|---|
| Mean distance from the planet [×103 km] |
24,103.0
|
| Mean distance from the planet [planetary R] |
337.1
|
| Orbital period [days] |
758.77
|
| Orbital eccentricity [e] |
0.2829
|
| Orbit inclination [degrees] |
147.2
|
| Mean diameter [km] |
8.6
|
| Main discoverer and year of the discovery |
J.V. Scotti 1999
|
| Visual magnitude [mag] |
20.7
|
| Mass [kg] |
~8.6923 × 1014
|
Orbital Parameters |
Pericenter
[q] |
Apocenter
[Q] |
| Distance from the planet [×103 km] |
17,284.3
|
30,921.7
|
| Distance from the planet [planetary R] |
241.8
|
432.5
|
| Angular size of the moon's orbit observed from the Earth* [degrees] |
1°34'30.82''
|
2°49'07.97''
|
|
| Angular diameter of the planet's disc as observed from the moon [degrees] |
0°28'26.33''
|
0°15'53.78''
|
| Brightness of the planet as observed from the moon** [mag] |
–10.5
|
–9.2
|
| Diameter of the moon's disc as observed from the planet's "surface" [degrees] |
0°00'00.10''
|
0°00'00.06''
|
| Brightness of the moon as observed from the planet's "surface"** [mag] |
12.9
|
14.2
|
|
Orbital velocity [km/sec] |
3.07
|
1.71
|
* 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
The Astronomy Workshop – Satellite Viewer
Planetary Satellite Mean Orbital Parameters
Natural Satellite Physical Parameters
