C/2021 A1 (Leonard) - DISINTEGRATED
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Nearest approach	13 Dec 2021	2.9	0.774 AU	0.233 AU	17h13m	-00°48'	22.4°	151.0°	356°
Perihelion	3 Jan 2022	5.9	0.615 AU	0.924 AU	21h40m	-35°23'	37.4°	76.5°	98°
Disintegration	1 Mar 2022	11.0	1.279 AU	1.992 AU	21h24m	-34°51'	32.9°	24.9°	220°
Today	29 Oct 2025	-	13.154 AU	14.026 AU	16h03m	-06°45'	27.6°	2.0°	74°

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[∆] + 11.0 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 C/2021 A1 (Leonard) are:

    e (Eccentricity)                : 1.0002670
    q (Perihelion distance)         : 0.6148670
    i (Inclination)                 : 132.74580
    Ω (Longitude of ascending node) : 255.90720
    ω (Argument of perihelion)      : 225.12640
    L (Longitude of perihelion)     : 221.62306
    B (Latitude of perihelion)      : -31.36069
    T (Time of perihelion passage)  : 2459583.48100

    Epoch                           : 2025 Oct 28
    Reference                       : MPEC 2025-A40

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

Ephemerides

Date       Time       RA (2000)    DEC (2000)    delta   radius  elong  phase   PA    magn
2025-10-28 00:00 UT   16 02 56.4   -06 44 20    14.006   13.144   28.8    2.1    75   26.4 
2025-10-29 00:00 UT   16 03 10.8   -06 45 12    14.019   13.151   28.0    2.0    74   26.4 
2025-10-29 12:02 UT   16 03 18.1   -06 45 38    14.026   13.154   27.6    2.0    74   26.4 
2025-10-30 00:00 UT   16 03 25.3   -06 46 04    14.033   13.157   27.2    2.0    73   26.4 
2025-10-31 00:00 UT   16 03 39.9   -06 46 54    14.046   13.164   26.4    1.9    72   26.4 
2025-11-01 00:00 UT   16 03 54.6   -06 47 44    14.058   13.170   25.6    1.9    71   26.4 
2025-11-02 00:00 UT   16 04 09.4   -06 48 33    14.071   13.177   24.8    1.8    70   26.4 
2025-11-03 00:00 UT   16 04 24.3   -06 49 21    14.083   13.183   24.0    1.8    68   26.4 
2025-11-04 00:00 UT   16 04 39.3   -06 50 09    14.095   13.190   23.3    1.7    67   26.4 
2025-11-05 00:00 UT   16 04 54.3   -06 50 56    14.106   13.197   22.5    1.6    65   26.4 
2025-11-06 00:00 UT   16 05 09.5   -06 51 42    14.118   13.203   21.8    1.6    64   26.4 
2025-11-07 00:00 UT   16 05 24.7   -06 52 27    14.129   13.210   21.1    1.5    62   26.5 
2025-11-08 00:00 UT   16 05 39.9   -06 53 11    14.140   13.216   20.4    1.5    60   26.5 

    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.