C/2020 X4 (Leonard)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Perihelion	14 Nov 2020	19.7	5.218 AU	5.156 AU	20h39m	+22°58'	88.1°	10.9°	69°
Nearest approach	27 Aug 2021	19.8	5.585 AU	4.598 AU	22h37m	+02°55'	166.5°	2.4°	195°
Today	6 Oct 2026	26.1	13.833 AU	13.492 AU	03h29m	-59°36'	107.9°	3.9°	317°

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. The light curve is based on the absolute magnitude and slope parameter as calculated from an MPEC, or the latest values provided by the minor planet center. (9.0 + 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 C/2020 X4 (Leonard) are:

    e (Eccentricity)                : 0.8702780
    q (Perihelion distance)         : 5.2183850
    i (Inclination)                 : 80.66860
    Ω (Longitude of ascending node) : 161.97960
    ω (Argument of perihelion)      : 140.21050
    L (Longitude of perihelion)     : 154.28871
    B (Latitude of perihelion)      : 39.16089
    T (Time of perihelion passage)  : 2459168.29980
    P (Orbital period in years)     : 255.14

    Epoch                           : 2026 Oct 05
    Reference                       : MPC194172

    Classification(s):              : Nearly isotropic; Returning (a < 10000 AU); External (P > 200 years)

Ephemerides

Date       Time       RA (2000)    DEC (2000)    delta   radius  elong  phase   PA    magn
2026-10-05 00:00 UT   03 29 23.2   -59 32 58    13.487   13.828  108.0    3.9   316   26.1 
2026-10-06 00:00 UT   03 29 05.3   -59 36 10    13.492   13.833  107.9    3.9   317   26.1 
2026-10-06 00:31 UT   03 29 04.9   -59 36 14    13.492   13.833  107.9    3.9   317   26.1 
2026-10-07 00:00 UT   03 28 47.0   -59 39 19    13.498   13.837  107.9    3.9   318   26.1 
2026-10-08 00:00 UT   03 28 28.3   -59 42 25    13.504   13.842  107.8    3.9   319   26.1 
2026-10-09 00:00 UT   03 28 09.1   -59 45 27    13.509   13.846  107.7    3.9   320   26.1 
2026-10-10 00:00 UT   03 27 49.5   -59 48 25    13.515   13.851  107.6    3.9   321   26.1 
2026-10-11 00:00 UT   03 27 29.5   -59 51 20    13.521   13.855  107.5    3.9   322   26.1 
2026-10-12 00:00 UT   03 27 09.2   -59 54 10    13.527   13.860  107.5    3.9   323   26.1 
2026-10-13 00:00 UT   03 26 48.4   -59 56 57    13.534   13.864  107.4    3.9   325   26.1 
2026-10-14 00:00 UT   03 26 27.3   -59 59 40    13.540   13.869  107.2    3.9   326   26.1 
2026-10-15 00:00 UT   03 26 05.8   -60 02 19    13.546   13.873  107.1    3.9   327   26.1 
2026-10-16 00:00 UT   03 25 44.0   -60 04 54    13.553   13.878  107.0    3.9   328   26.1 

    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.