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P/2017 Y3 (Leonard)
ephemeris date magn radius delta ra dec elong phase PA
Nearest approach4 Feb 201818.81.272 AU1.495 AU 17h25m-02°08'57.4°40.8°288°
Perihelion6 Feb 201818.81.272 AU1.495 AU 17h34m-01°56'57.4°40.8°287°
Today11 Sep 202634.815.895 AU15.166 AU 02h18m-11°07'135.1°2.6°275°
P/2017 Y3 (Leonard)- 2026-09-11
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)                : 0.8701090
    q (Perihelion distance)         : 1.2717230
    i (Inclination)                 : 27.65400
    Ω (Longitude of ascending node) : 154.09000
    ω (Argument of perihelion)      : 67.22290
    L (Longitude of perihelion)     : 218.72706
    B (Latitude of perihelion)      : 25.33672
    T (Time of perihelion passage)  : 2458156.33200
    P (Orbital period in years)     : 30.64

    Epoch                           : 2026 May 29
    Reference                       : MPC194154

    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
2026-09-10 00:00 UT   02 18 34.2   -11 03 30    15.181   15.891  133.5    2.6   273   34.8 
2026-09-11 00:00 UT   02 18 25.8   -11 05 27    15.173   15.893  134.3    2.6   274   34.8 
2026-09-11 20:34 UT   02 18 18.5   -11 07 07    15.166   15.895  135.1    2.6   275   34.8 
2026-09-12 00:00 UT   02 18 17.2   -11 07 23    15.165   15.895  135.2    2.6   275   34.8 
2026-09-13 00:00 UT   02 18 08.4   -11 09 20    15.157   15.897  136.0    2.5   276   34.8 
2026-09-14 00:00 UT   02 17 59.4   -11 11 16    15.150   15.899  136.8    2.5   277   34.8 
2026-09-15 00:00 UT   02 17 50.2   -11 13 13    15.143   15.901  137.7    2.4   278   34.8 
2026-09-16 00:00 UT   02 17 40.8   -11 15 09    15.136   15.903  138.5    2.4   279   34.8 
2026-09-17 00:00 UT   02 17 31.3   -11 17 04    15.130   15.905  139.3    2.4   279   34.8 
2026-09-18 00:00 UT   02 17 21.5   -11 18 59    15.123   15.907  140.1    2.3   280   34.8 
2026-09-19 00:00 UT   02 17 11.5   -11 20 54    15.117   15.909  140.9    2.3   281   34.8 
2026-09-20 00:00 UT   02 17 01.4   -11 22 49    15.111   15.911  141.7    2.2   283   34.8 
2026-09-21 00:00 UT   02 16 51.1   -11 24 43    15.106   15.913  142.4    2.2   284   34.8 




    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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