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P/2017 Y3 (Leonard)
ephemeris date magn radius delta ra dec elong phase PA
Nearest approach4 Feb 201818.81.273 AU1.498 AU 17h25m-02°09'57.3°40.7°288°
Perihelion6 Feb 201818.81.273 AU1.499 AU 17h33m-01°57'57.3°40.7°287°
Today21 Apr 202634.915.589 AU16.520 AU 02h03m-09°36'21.5°1.4°174°
P/2017 Y3 (Leonard)- 2026-04-21
astro.vanbuitenen.nl


 
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The interactive orbit chart above shows the comet's path through the solar system and its position at the given date. Green and blue lines are shown perpendicular to the ecliptic plane: Green if the path is above the ecliptic plane, blue if it is below. (Left-click and drag to rotate the view; Right-click and drag to move the view; Use scroll wheel to zoom in our out.)


Light curve

The light curve chart below shows the estimated development of the comet's magnitude. Blue and black dots are visual and photometric CCD observations from COBS. This lightcurve is being recalculated every 6 hours based on the available COBS/MPC observations (currently 16.9 + 5 log[∆] + 10.0 log[r]). An additional green curve is displayed when an increase in apparent brightness is expected due to forward scattering of sunlight, which occurs when a dust-rich comet is located between the Earth and the Sun. (See Marcus 2007)



Charts

The all-sky chart below shows the path of the comet over the same period as the light curve. The comet's current position is marked yellow.





The following chart shows the short-term path of the comet in a field of view that is optimized for (~10x50) binoculars and finderscopes.




Orbital elements

The orbital elements of P/2017 Y3 (Leonard) are: 

    e (Eccentricity)                : 0.8699960
    q (Perihelion distance)         : 1.2729730
    i (Inclination)                 : 27.64990
    Ω (Longitude of ascending node) : 154.07780
    ω (Argument of perihelion)      : 67.24240
    L (Longitude of perihelion)     : 218.73683
    B (Latitude of perihelion)      : 25.33689
    T (Time of perihelion passage)  : 2458156.12460
    P (Orbital period in years)     : 30.64

    Epoch                           : 2026 Mar 16
    Reference                       : MPEC 2026-E44

    Classification(s):              : Nearly isotropic; Returning (a < 10000 AU); Halley type (P < 200 years)

Ephemerides

Date       Time       RA (2000)    DEC (2000)    delta   radius  elong  phase   PA    magn
2026-04-20 00:00 UT   02 03 25.6   -09 38 26    16.518   15.586   21.2    1.3   171   34.9 
2026-04-21 00:00 UT   02 03 40.6   -09 37 12    16.519   15.589   21.4    1.3   173   34.9 
2026-04-21 08:47 UT   02 03 46.1   -09 36 45    16.520   15.589   21.5    1.4   174   34.9 
2026-04-22 00:00 UT   02 03 55.6   -09 35 59    16.520   15.591   21.7    1.4   176   34.9 
2026-04-23 00:00 UT   02 04 10.6   -09 34 48    16.521   15.593   21.9    1.4   178   34.9 
2026-04-24 00:00 UT   02 04 25.6   -09 33 38    16.521   15.595   22.2    1.4   180   34.9 
2026-04-25 00:00 UT   02 04 40.6   -09 32 29    16.521   15.597   22.6    1.4   183   34.9 
2026-04-26 00:00 UT   02 04 55.6   -09 31 22    16.521   15.600   22.9    1.4   185   34.9 
2026-04-27 00:00 UT   02 05 10.6   -09 30 16    16.521   15.602   23.3    1.5   187   34.9 
2026-04-28 00:00 UT   02 05 25.6   -09 29 11    16.520   15.604   23.7    1.5   189   34.9 
2026-04-29 00:00 UT   02 05 40.5   -09 28 08    16.519   15.606   24.2    1.5   191   34.9 
2026-04-30 00:00 UT   02 05 55.5   -09 27 06    16.518   15.608   24.6    1.5   193   34.9 
2026-05-01 00:00 UT   02 06 10.4   -09 26 06    16.516   15.610   25.1    1.6   195   34.9 




    Terminology:
            
    delta:  distance between comet and earth in AU
    radius: distance between comet and sun in AU
    magn:   magnitude (brightness) estimate    
    ra:     right ascension in hours (24h = 360deg)
    dec:    declination in degrees
    elong:  elongation in degrees (angle sun-earth-comet)    
    phase:  phase angle in degrees (angle sun-comet-earth)        
    AU:     Astronomical Unit (mean distance between earth and sun: 149597870.7 km

Orbital elements usually provided by the MPC (Minor Planet Center).
Observations contributed by observers worldwide, via COBS (Comet Observation Database) or the MPC (Minor Planet Center)
Calculations by a modified version of AAPlus, a C# implementation of the AA+ project by PJ Naughter from the algorithms presented in the book "Astronomical Algorithms" by Jean Meeus.
NGC2000 dso catalog and star labels from VizieR as provided by the Strasbourg astronomical Data Center.
Tycho2 catalog from the ESO archive.

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