Besselian year
E579592
A Besselian year is a time interval used in astronomy, defined with respect to the Sun’s mean position relative to the stars and historically used as a reference for star catalogs and celestial coordinates.
Statements (38)
| Predicate | Object |
|---|---|
| instanceOf |
astronomical time interval
ⓘ
time scale ⓘ |
| appliesTo |
ecliptic coordinates
ⓘ
equatorial coordinates ⓘ |
| category |
astronomical time standards
ⓘ
units of time in astronomy ⓘ |
| closeTo | tropical year ⓘ |
| contrastedWith | Julian year of exactly 365.25 days ⓘ |
| coordinateSystemAssociation |
B1950.0 reference frame
ⓘ
FK4 star catalog system NERFINISHED ⓘ |
| definedSoThat | Besselian year begins when mean Sun’s ecliptic longitude is 280 degrees NERFINISHED ⓘ |
| definedWithRespectTo |
Sun’s mean position
ⓘ
ecliptic longitude of the mean Sun ⓘ mean Sun relative to the stars ⓘ |
| epochNotation | Besselian epoch NERFINISHED ⓘ |
| historicallyUsedAs |
reference epoch for celestial coordinates
ⓘ
reference epoch for star catalogs ⓘ |
| lengthApproximate |
365.242198781 days
ⓘ
365.2422 days ⓘ |
| namedAfter | Friedrich Bessel NERFINISHED ⓘ |
| referenceFrame | fixed stars ⓘ |
| relatedConcept |
Besselian epoch B1900.0
ⓘ
Besselian epoch B1950.0 ⓘ |
| replacedInPracticeBy | J2000.0 epoch ⓘ |
| status | largely obsolete in modern astrometry ⓘ |
| stillEncounteredIn |
legacy star catalogs
ⓘ
older astronomical literature ⓘ |
| supersededBy |
Julian epoch
ⓘ
Julian year ⓘ |
| timeScaleType | mean solar-based year ⓘ |
| typicalEpochExamples |
B1900.0
ⓘ
B1950.0 ⓘ |
| usedBefore | adoption of J2000.0 as standard epoch ⓘ |
| usedFor |
celestial coordinate systems
ⓘ
precession calculations ⓘ proper motion calculations ⓘ star catalogs ⓘ |
| usedIn | astronomy ⓘ |
Referenced by (1)
Full triples — surface form annotated when it differs from this entity's canonical label.