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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 17h16m-00°10'23.0°150.2°357°
Perihelion4 Jan 20225.90.613 AU0.927 AU 21h41m-35°11'37.3°76.4°98°
Disintegration1 Mar 202211.01.273 AU1.987 AU 21h25m-34°50'32.8°25.0°219°
Today2 Aug 2026-14.918 AU14.606 AU 15h53m-03°47'106.0°3.7°107°
C/2021 A1 (Leonard)- 2026-08-02
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)                : 1.0002770
    q (Perihelion distance)         : 0.6132150
    i (Inclination)                 : 132.69880
    Ω (Longitude of ascending node) : 255.88280
    ω (Argument of perihelion)      : 225.08200
    L (Longitude of perihelion)     : 221.66364
    B (Latitude of perihelion)      : -31.36018
    T (Time of perihelion passage)  : 2459583.85830

    Epoch                           : 2026 Aug 02
    Reference                       : MPC194172

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

Ephemerides

Date       Time       RA (2000)    DEC (2000)    delta   radius  elong  phase   PA    magn
2026-08-01 00:00 UT   15 53 24.6   -03 46 56    14.564   14.906  107.8    3.7   108   26.9 
2026-08-02 00:00 UT   15 53 18.6   -03 47 29    14.586   14.912  106.9    3.7   108   27.0 
2026-08-02 22:23 UT   15 53 13.3   -03 47 60    14.606   14.918  106.0    3.7   107   27.0 
2026-08-03 00:00 UT   15 53 12.9   -03 48 02    14.608   14.919  105.9    3.8   107   27.0 
2026-08-04 00:00 UT   15 53 07.5   -03 48 37    14.629   14.925  105.0    3.8   107   27.0 
2026-08-05 00:00 UT   15 53 02.3   -03 49 13    14.651   14.931  104.1    3.8   107   27.0 
2026-08-06 00:00 UT   15 52 57.4   -03 49 50    14.674   14.937  103.1    3.8   106   27.0 
2026-08-07 00:00 UT   15 52 52.7   -03 50 27    14.696   14.943  102.2    3.8   106   27.0 
2026-08-08 00:00 UT   15 52 48.4   -03 51 06    14.718   14.950  101.3    3.8   106   27.0 
2026-08-09 00:00 UT   15 52 44.3   -03 51 46    14.740   14.956  100.3    3.8   106   27.0 
2026-08-10 00:00 UT   15 52 40.4   -03 52 27    14.762   14.962   99.4    3.8   105   27.0 
2026-08-11 00:00 UT   15 52 36.9   -03 53 08    14.785   14.968   98.5    3.8   105   27.0 
2026-08-12 00:00 UT   15 52 33.6   -03 53 51    14.807   14.974   97.5    3.8   105   27.0 




    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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