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C/2021 A1 (Leonard) - DISINTEGRATED
ephemeris date magn radius delta ra dec elong phase PA
Nearest approach13 Dec 20213.00.774 AU0.234 AU 17h15m-00°18'22.9°150.4°356°
Perihelion4 Jan 20225.90.614 AU0.926 AU 21h41m-35°14'37.3°76.4°98°
Disintegration1 Mar 202211.01.274 AU1.988 AU 21h25m-34°50'32.9°24.9°219°
Today21 May 2026-14.463 AU13.489 AU 16h09m-04°06'163.4°1.1°194°
C/2021 A1 (Leonard)- 2026-05-21
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 8.4 + 5 log[∆] + 10.9 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 C/2021 A1 (Leonard) are: 

    e (Eccentricity)                : 1.0002750
    q (Perihelion distance)         : 0.6136730
    i (Inclination)                 : 132.71440
    Ω (Longitude of ascending node) : 255.89110
    ω (Argument of perihelion)      : 225.09630
    L (Longitude of perihelion)     : 221.65078
    B (Latitude of perihelion)      : -31.36010
    T (Time of perihelion passage)  : 2459583.77850

    Epoch                           : 2026 May 21
    Reference                       : MPEC 2026-E44

    Classification(s):              : Nearly isotropic; New (a > 10000 AU)

Ephemerides

Date       Time       RA (2000)    DEC (2000)    delta   radius  elong  phase   PA    magn
2026-05-20 00:00 UT   16 10 02.6   -04 08 03    13.480   14.452  163.2    1.2   200   26.6 
2026-05-21 00:00 UT   16 09 44.8   -04 06 55    13.485   14.458  163.3    1.2   197   26.6 
2026-05-21 17:48 UT   16 09 31.6   -04 06 05    13.489   14.463  163.4    1.1   194   26.6 
2026-05-22 00:00 UT   16 09 27.0   -04 05 48    13.491   14.464  163.4    1.1   193   26.6 
2026-05-23 00:00 UT   16 09 09.2   -04 04 42    13.497   14.471  163.4    1.1   189   26.7 
2026-05-24 00:00 UT   16 08 51.4   -04 03 38    13.504   14.477  163.3    1.2   186   26.7 
2026-05-25 00:00 UT   16 08 33.7   -04 02 35    13.510   14.483  163.2    1.2   182   26.7 
2026-05-26 00:00 UT   16 08 15.9   -04 01 33    13.517   14.489  163.0    1.2   179   26.7 
2026-05-27 00:00 UT   16 07 58.2   -04 00 32    13.524   14.496  162.8    1.2   175   26.7 
2026-05-28 00:00 UT   16 07 40.5   -03 59 33    13.532   14.502  162.5    1.2   172   26.7 
2026-05-29 00:00 UT   16 07 22.8   -03 58 35    13.540   14.508  162.1    1.2   169   26.7 
2026-05-30 00:00 UT   16 07 05.1   -03 57 39    13.548   14.514  161.7    1.3   166   26.7 
2026-05-31 00:00 UT   16 06 47.5   -03 56 43    13.557   14.521  161.2    1.3   163   26.7 




    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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