- The moons of Pluto:
- Charon: Named for
the mythological Charon
the ferryman to the Greek underworld
which was the
land of the dead in Greek mythology
and which was ruled by Hades.
- Nix (AKA P2):
Named for the mythological Nyx,
the primordial goddess of night in
Greek mythology with another spelling.
- Hydra (AKA P1):
Named for the mythological Hydra,
a 9-headed chthonic serpent-thing in
Greek mythology.
- Kerberos (AKA P4):
The Greek form for Cerberus,
the hellhound who guards
the door of the Greek underworld.
- Styx (AKA P5):
Named for the River Styx that
that separates the land of living from the
Greek underworld.
The mythological Charon
ferries the dead across this river.
The
New Horizons spacecraft (2006--)
did a flyby of the
Pluto system with closest approach on
2015
Jul14.
It discovered NO new
Plutonian moons, and so it is likely
that the 5 currently known ones are all there are.
- The specifications of the Pluto system are given in the
table below.
_______________________________________________________________________________________
The Pluto System
_______________________________________________________________________________________
Astro-Body Discovery Year Radius Mass Orbital Radius Orbital Period
(km) (10**18 kg) (km) (days)
_______________________________________________________________________________________
Pluto 1930 1153 13050 2040 6.3872
70 % Moon 18 % Moon
Charon 1978 602 1520 17530 6.3872
35 % Moon 2 % Moon 15.20 Pluto radii
Nix 2005 44 1 48708 24.9
Hydra 2005 36 .391 64749 38
Kerberos 2011 20 approx ? 59000 32.1
Styx 2012 10--25 ? 42000±2000 20.2±0.1
_______________________________________________________________________________________
- Pluto and
Charon
are mutually tidally locked
as illustrated in the animation below.
Image Caption 2:
An animation
of the
Pluto-Charon
system from an outside of the orbital plane.
The animation is NOT
to-scale:
Pluto and
Charon
are shown at ∼ 10
Pluto
radii apart and really they are
∼ 8
Pluto
radii apart
(see Wikipedia: Moons of Pluto: List).
"Pluto and
Charon
are mutually tidally locked
to each other.
Charon
is massive enough that the
barycenter
of Pluto system
lies outside of Pluto,
thus Pluto and
Charon
are sometimes considered to be a
binary system."
(Slightly edited.)
- Because Pluto and
Charon
are mutually tidally locked,
their orbital periods and rotation periods are all exactly the same on average with the average
value being 6.3872 days.
- Tidal locking
means, among other things, on one side of
Pluto/Charon
you always see
Charon/Pluto
sitting in the sky at approximately the same orientation relative to the surface of
Pluto/Charon.
The same orientation relative to the ground means having the same
horizontal coordinates:
i.e., same altitude and
azimuth.
- On the other side of
Pluto/Charon,
you never see
Charon/Pluto.
- The rotation periods of the other
moons
are unknown, but
they may be tidally locked to
Pluto, and so have rotation periods equal to
their orbital periods---on the other hand, they might have some strange relation between
rotation period and the other periodicities of the system because of the
multiple sources of gravity.
-
Pluto videos
(i.e., Pluto
videos):
- New Horizons. Best View of Pluto.s Craters,
Mountains and Icy Plains | 0:50:
Fantastic close-ups from the
New Horizons spacecraft (2006--)
flyby of
Pluto on
2015
Jul14
(see Wikipedia:
New Horizons, Pluto system encounter (2015 Jul14)).
Short enough for the classroom.
- Pluto and Charon in binary orbit | 0:10:
This illustrates
orbits of
Pluto and Charon
around their mutual center of mass (CM)
which defines the local
free-fall frame: i.e.
inertial frame.
Schematically, the mutual tidal locking
Pluto and
Charon is shown.
Good and short enough for the classroom.
- Pluto/Charon Orbit Animations | 0:43:
OK and short enough for the classroom.
- Pluto's atmosphere and Charon over the horizon 0:18: Artist's conception of view from
Pluto
with Charon
perpetually in the same place in the sky relative to the ground.
Good and short enough for the classroom.
- Pluto and moons Charon, Nix, and Hydra in profile | 5:31:
This is all pre
pre-New Horizons spacecraft (2006--)
and yours truly CANNOT attest to its accuracy.
Too long for the classroom,
but one can show a bit.