The moon of Jupiter –
Metis (XVI) – was previously designated as S/1979 J3. It was discovered in
photos sent from the →Voyager-2,
spacecraft which flew through the Jovian system on July 9, 1979. The one to draw
the right conclusions from these photos was S.P. Synnott and he is
currently known as the discoverer of that moon along with Thebe.
The name of that moon is of mythological origin. Giving the name Metis to the first moon of Jupiter (Zeus) is very suitable since it was the name of his first wife (followed by Themis, Dione, Mnemosyne, Eurynome, Demeter, Leto and Hera). Metis was the personification of wisdom, daughter of Oceanus and Tethys. When Zeus discovered that she was pregnant he swallowed her fearing she might give birth to a son and a daughter mightier than he. Subsequently, the goddess Athena sprang fully armed from his head and his son remained retained in side his own body where he could do him no
harm.
The moon by this name is in almost circular prograde orbit (→eccentricity
e = 0.0012) with a →semimajor axis a = 128,000 km. At pericenter (closest to the planet) Metis is separated from the Jupiter a distance of q = 127,846 km. At apocenter (furthest from the planet) this moon is separated from the Jupiter a distance of Q = 128,154 km.
The mass of this moon is diminutive ~1.1989×1017 kg
– comparable to less than about 16
a mountains like Giewont
!
An in teresting feature of that moon is that it revolves in side of the so called →Roche limit.
It is very small and must have a very rigid structure since the tidal forces of Jupiter haven't torn it apart yet! It also revolves slightly faster than Jupiter spins around its axis!
It's orbital period is only 0.3 day, which means that its mean celestial angular velocity in the sky is 1,220° (over 3.33
revolutions).
The main obstacle in discovery of that moon was its small angular distance from
Jupiter and also its low brightness of only 17.5m
(over 39.8 thousand times fainter than the faintest stars visible to the naked eye).
For comparison: Jupiter is about –2.7m, so
Metis is shining fainter by about 20.2m. It corresponds to a difference in brightness of
over 120.2 million times!
I have given some crucial data of Metis 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
|
Metis
|
|---|
| Mean distance from the planet [×103 km] |
128.0
|
| Mean distance from the planet [planetary R] |
1.8
|
| Orbital period [days] |
0.30
|
| Orbital eccentricity [e] |
0.0012
|
| Orbit inclination [degrees] |
0.0
|
| Mean diameter [km] |
43.0
|
| Main discoverer and year of the discovery |
S.P. Synnott 1980
|
| Visual magnitude [mag] |
17.5
|
| Mass [kg] |
~1.1989 × 1017
|
Orbital Parameters |
Pericenter
[q] |
Apocenter
[Q] |
| Distance from the planet [×103 km] |
127.8
|
128.2
|
| Distance from the planet [planetary R] |
1.8
|
1.8
|
| Angular size of the moon's orbit observed from the Earth* [degrees] |
0°00'41.94''
|
0°00'42.04''
|
|
| Angular diameter of the planet's disc as observed from the moon [degrees] |
68°00'51.48''
|
67°49'44.54''
|
| Brightness of the planet as observed from the moon** [mag] |
–21.2
|
–21.2
|
| Diameter of the moon's disc as observed from the planet's "surface" [degrees] |
0°02'37.39''
|
0°02'36.53''
|
| Brightness of the moon as observed from the planet's "surface"** [mag] |
–1.0
|
–1.0
|
|
Orbital velocity [km/sec] |
31.50
|
31.42
|
* 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:
Astronomy for every – Jupiter's moons
Monde
des Monats
– METIS
Views
of the Solar System – METIS
– Photo
Archives
Solar
System Exploration – METIS
The
Nine Planets – METIS
The Astronomy Workshop – Satellite Viewer
Planetary Satellite Mean Orbital Parameters
Natural Satellite Physical Parameters
 |
