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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°
Today5 Jun 202634.915.688 AU16.319 AU 02h14m-09°07'50.1°2.8°230°
P/2017 Y3 (Leonard)- 2026-06-05
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
2026-06-04 00:00 UT   02 14 02.7   -09 07 30    16.333   15.684   48.8    2.8   229   34.9 
2026-06-05 00:00 UT   02 14 15.0   -09 07 26    16.324   15.687   49.6    2.8   230   34.9 
2026-06-05 13:54 UT   02 14 22.0   -09 07 25    16.319   15.688   50.1    2.8   230   34.9 
2026-06-06 00:00 UT   02 14 27.1   -09 07 25    16.315   15.689   50.4    2.9   230   34.9 
2026-06-07 00:00 UT   02 14 39.0   -09 07 25    16.306   15.691   51.3    2.9   231   34.9 
2026-06-08 00:00 UT   02 14 50.9   -09 07 26    16.296   15.693   52.1    2.9   232   34.9 
2026-06-09 00:00 UT   02 15 02.6   -09 07 30    16.287   15.695   52.9    3.0   232   34.9 
2026-06-10 00:00 UT   02 15 14.2   -09 07 35    16.277   15.697   53.7    3.0   233   34.9 
2026-06-11 00:00 UT   02 15 25.6   -09 07 42    16.267   15.699   54.5    3.0   233   34.9 
2026-06-12 00:00 UT   02 15 36.9   -09 07 51    16.257   15.702   55.3    3.0   234   34.9 
2026-06-13 00:00 UT   02 15 48.0   -09 08 02    16.246   15.704   56.2    3.1   234   34.9 
2026-06-14 00:00 UT   02 15 59.0   -09 08 14    16.236   15.706   57.0    3.1   234   34.9 
2026-06-15 00:00 UT   02 16 09.8   -09 08 29    16.225   15.708   57.8    3.1   235   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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