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Epoch (astronomy) - Wikipedia, the free encyclopedia (934 words) |
 | The prefix "J" indicates that it is a Julian epoch. |
| The "B" in the prefix indicates that it is a Besselian epoch, as opposed to a Julian epoch. |
| The "J" in the prefix indicates that it is a Julian epoch, as opposed to a Besselian epoch. |
| Julian year (astronomy) - Wikipedia, the free encyclopedia (690 words) |
| Julian years are used primarily for convenience in ephemeris work where stating a number of days would be unwieldy (for instance, it is easier to express the orbital period of Pluto as 248 Julian years rather than 90,590 days). |
| A Julian day (or Julian date) is not a unit of time, but simply a running count of days with an arbitrarily chosen starting point in the distant past, with each day numbering one greater than the previous; it's a way to specify a date without reference to months or years. |
| The Julian epoch J2000.0 is synchronized to exactly 12:00 TT (close to but not exactly Greenwich mean noon) on January 1, 2000 in the Gregorian (not Julian!) calendar, and future epochs can be calculated and named according to the number of days since then, divided by 365.25. |
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