C/2021 L3 (Borisov)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Nearest approach	24 Nov 2021	19.9	8.476 AU	8.329 AU	18h33m	+70°47'	95.2°	6.7°	36°
Perihelion	14 Feb 2022	19.9	8.462 AU	8.428 AU	19h37m	+72°55'	88.6°	6.7°	327°
Today	20 Jan 2026	22.0	11.803 AU	11.131 AU	11h42m	+29°28'	131.3°	3.6°	272°

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. (6.0 + 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/2021 L3 (Borisov) are:

    e (Eccentricity)                : 1.0042670
    q (Perihelion distance)         : 8.4615640
    i (Inclination)                 : 78.52400
    Ω (Longitude of ascending node) : 345.02450
    ω (Argument of perihelion)      : 91.65940
    L (Longitude of perihelion)     : 263.30909
    B (Latitude of perihelion)      : 78.40624
    T (Time of perihelion passage)  : 2459625.45880

    Epoch                           : 2026 Jan 19
    Reference                       : MPEC 2024-H50

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

Ephemerides

Date       Time       RA (2000)    DEC (2000)    delta   radius  elong  phase   PA    magn
2026-01-19 00:00 UT   11 42 48.9   +29 25 57    11.143   11.797  129.7    3.7   273   22.0 
2026-01-20 00:00 UT   11 42 33.8   +29 27 17    11.136   11.800  130.6    3.6   272   22.0 
2026-01-20 16:58 UT   11 42 22.9   +29 28 14    11.131   11.803  131.3    3.6   272   22.0 
2026-01-21 00:00 UT   11 42 18.4   +29 28 38    11.128   11.804  131.5    3.6   271   22.0 
2026-01-22 00:00 UT   11 42 02.6   +29 29 59    11.121   11.808  132.4    3.5   271   22.0 
2026-01-23 00:00 UT   11 41 46.4   +29 31 20    11.115   11.812  133.3    3.5   270   22.0 
2026-01-24 00:00 UT   11 41 29.9   +29 32 41    11.108   11.816  134.2    3.4   269   22.0 
2026-01-25 00:00 UT   11 41 13.1   +29 34 01    11.102   11.819  135.1    3.4   268   22.0 
2026-01-26 00:00 UT   11 40 55.9   +29 35 22    11.095   11.823  135.9    3.3   267   22.0 
2026-01-27 00:00 UT   11 40 38.4   +29 36 42    11.090   11.827  136.8    3.3   266   22.0 
2026-01-28 00:00 UT   11 40 20.6   +29 38 02    11.084   11.831  137.7    3.2   265   22.0 
2026-01-29 00:00 UT   11 40 02.5   +29 39 21    11.078   11.835  138.5    3.2   264   22.0 
2026-01-30 00:00 UT   11 39 44.0   +29 40 40    11.073   11.838  139.4    3.1   263   22.0 

    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.