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°39'	22.5°	150.8°	356°
Perihelion	4 Jan 2022	5.9	0.614 AU	0.925 AU	21h40m	-35°20'	37.4°	76.5°	98°
Disintegration	1 Mar 2022	11.0	1.278 AU	1.990 AU	21h24m	-34°50'	32.9°	24.9°	219°
Today	7 Jan 2026	-	13.607 AU	14.298 AU	16h20m	-07°04'	43.9°	2.9°	295°

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)                : 1.0002760
    q (Perihelion distance)         : 0.6144940
    i (Inclination)                 : 132.73660
    Ω (Longitude of ascending node) : 255.90250
    ω (Argument of perihelion)      : 225.11680
    L (Longitude of perihelion)     : 221.63192
    B (Latitude of perihelion)      : -31.36005
    T (Time of perihelion passage)  : 2459583.57830

    Epoch                           : 2026 Jan 06
    Reference                       : MPC181179

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

Ephemerides

Date       Time       RA (2000)    DEC (2000)    delta   radius  elong  phase   PA    magn
2026-01-06 00:00 UT   16 20 18.1   -07 04 37    14.304   13.600   42.8    2.8   296   26.6 
2026-01-07 00:00 UT   16 20 30.0   -07 04 11    14.299   13.606   43.7    2.9   295   26.6 
2026-01-07 02:55 UT   16 20 31.5   -07 04 07    14.298   13.607   43.9    2.9   295   26.6 
2026-01-08 00:00 UT   16 20 41.8   -07 03 43    14.294   13.613   44.7    2.9   295   26.6 
2026-01-09 00:00 UT   16 20 53.5   -07 03 14    14.289   13.619   45.6    3.0   294   26.6 
2026-01-10 00:00 UT   16 21 04.9   -07 02 44    14.283   13.626   46.5    3.0   294   26.6 
2026-01-11 00:00 UT   16 21 16.1   -07 02 13    14.278   13.632   47.4    3.0   293   26.6 
2026-01-12 00:00 UT   16 21 27.2   -07 01 40    14.272   13.638   48.3    3.1   293   26.6 
2026-01-13 00:00 UT   16 21 38.1   -07 01 06    14.266   13.645   49.3    3.1   293   26.6 
2026-01-14 00:00 UT   16 21 48.7   -07 00 30    14.260   13.651   50.2    3.2   292   26.6 
2026-01-15 00:00 UT   16 21 59.2   -06 59 53    14.253   13.658   51.1    3.2   292   26.6 
2026-01-16 00:00 UT   16 22 09.4   -06 59 15    14.247   13.664   52.0    3.3   291   26.6 
2026-01-17 00:00 UT   16 22 19.5   -06 58 36    14.240   13.671   53.0    3.3   291   26.6 

    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.