| Janus |
A moon of Saturn was discovered by Audouin Dollfus on December 15, 1966. Janus shares the same orbit as the Saturnian moon Epimetheus Janus also is designated as "Saturn X" and "S/1966 S2". Janus is named after the two-faced Roman god of doors, gates, beginnings & endings. |
| Jovian |
Having to do with the planet Jupiter. |
| Julian Calendar |
A revision of the Roman religious calendar ordered by Julius Caesar in 46 BC to clarify the rules for a civil calendar. Not to be confused with a "Julian Day." |
| Julian Date |
A Julian Date (JD) is a floating-point number rounded to the nearest Julian Day with the fraction of the day which has passed since 12 noon Greenwich Mean Time (UT or TT) of that day. This should not be confused with the "Julian Calendar" or the "Julian Date." Julian Dates are commonly used to simplify astronomical calculations. |
| Julian Day |
A Julian Day (also known as a Julian day Nukmber - JDN) is an integer number counting the days since Monday, January 1, 4713 BC in the Proleptic Julian Calendar (that is extending the Julian Calendar to dates before is offical use in 45 BC). This should not be confused with the "Julian calendar or the "Julian Date." the Julian Day was proposed by Joseph Scaliger in 1583, during the Gregorian calendar reform. The "Julian" in "Julian day" refers to Scaliger's father, Julius Scaliger. |
| Juliet |
A moon of Uranus was discovered by Stephen P. Synnott (Voyager 2) on January 13, 1986. Juliet is also designated as "Uranus XI" and "S/1986 U2". Juliet is the heroine of William Shakespeare's play Romeo and Juliet. |
| Jupiter |
Jupiter is the fifth planet from the Sun. Jupiter's diameter is 143,000 km and takes 11.86 years to orbit the Sun. Jupiter is named after the Roman king of gods. In Eastern Asian cultures Jupiter is also known as the 'Wood Star.' |
