The largest → planet in the → Solar System
and the fifth from the Sun, lying at a mean distance of about 5.2
→ astronomical units from the Sun.
Jupiter is a → gas giant,
mostly → hydrogen
and → helium, with a mass of 1.898 × 1027 kg, or
about 0.001 → solar masses, or 318 times
→ Earth masses. It is more than twice as massive as all the
other solar system planets combined. Jupiter’s diameter
measures 11 times that of Earth. Its → rotation period,
9.93 hours (Jupiter/Earth ratio = 0.41), is the shortest of all the solar system
planets. Its → orbital period is 11.857 Earth years.
Jupiter has an extensive
family of → satellites (79 known) and a faint
→ ring system; → Jupiter’s ring.
Jupiter probably has a core of rocky material amounting to something
like 10 to 15 Earth masses.
Above the core lies the main bulk of the planet in the form of liquid
→ metallic hydrogen.
This exotic form of the most common of elements is
possible only at pressures about 3 million bars, as is the case in
the interior of Jupiter (and Saturn).
Under the extreme pressure found deep inside Jupiter,
the electrons are released from the hydrogen molecules and are
free to move about the interior. This causes hydrogen to behave as a
metal; it becomes conducting for both heat and electricity.
See also → Jupiter’s atmosphere.
Etymology (EN): Jupiter “the king of ancient Roman gods, the ruler of Olympus,”
from L. Iupeter, from PIE *dyeu-peter- “god-father,”
from *deiw-os “god” (cf. Pers. div “devil, demon;” Mid.Pers. dêw;
O.Pers. daiva- “evil god, demon;” Av. daēva- “evil spirit,
false god;” Skt. deva-; Gk. Zeus “supreme god;”
from *dei- “to gleam, to shine”)
- *peter “father” (cf. Pers. pedar “father;” O.Pers. pitā-
“father;” Av. patar-, ptā-; Skt. pitár-; Gk. pater;
L. pater, O.H.G. fater).
Etymology (PE): Hormoz, from Mid.Pers. Ohrmazd “name of the highest god in Zoroastrianism,”
from O.Pers. aura-mazdā-, Av. ahura-mazdā- “Wise Lord,”
from ahura- “lord, god;” cf. Skt. ásura- “god, lord;”
Hittite hassu- “king;” M.H.G. Asen “name of a group of gods;”
O.N. āss “god;” PIE *ansu- “spirit, demon” + mazdā-
“wisdom,” mazdāθa- “what must be borne in mind,”
mazdāh- “memory;” cf.
Skt. medhā- “mental power, wisdom, intelligence;” Gk. mathein
“to learn, to know” (root of → mathematics).
