C/2021 L3 (Borisov)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Nearest approach	24 Nov 2021	19.9	8.477 AU	8.330 AU	18h33m	+70°47'	95.2°	6.7°	36°
Perihelion	14 Feb 2022	19.9	8.463 AU	8.428 AU	19h36m	+72°55'	88.6°	6.7°	327°
Today	21 Jun 2026	22.5	12.386 AU	12.729 AU	11h03m	+26°41'	68.0°	4.4°	106°

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)                : 1.0039100
    q (Perihelion distance)         : 8.4627760
    i (Inclination)                 : 78.51480
    Ω (Longitude of ascending node) : 345.02830
    ω (Argument of perihelion)      : 91.66450
    L (Longitude of perihelion)     : 263.33153
    B (Latitude of perihelion)      : 78.39642
    T (Time of perihelion passage)  : 2459625.29320

    Epoch                           : 2026 Jun 20
    Reference                       : MPC194175

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

Ephemerides

Date       Time       RA (2000)    DEC (2000)    delta   radius  elong  phase   PA    magn
2026-06-20 00:00 UT   11 03 04.1   +26 45 53    12.705   12.380   69.2    4.4   107   22.4 
2026-06-21 00:00 UT   11 03 07.8   +26 42 23    12.723   12.384   68.3    4.4   106   22.5 
2026-06-21 07:31 UT   11 03 09.0   +26 41 17    12.729   12.386   68.0    4.4   106   22.5 
2026-06-22 00:00 UT   11 03 11.8   +26 38 51    12.742   12.388   67.5    4.3   106   22.5 
2026-06-23 00:00 UT   11 03 16.1   +26 35 20    12.760   12.392   66.6    4.3   106   22.5 
2026-06-24 00:00 UT   11 03 20.6   +26 31 47    12.779   12.396   65.7    4.3   105   22.5 
2026-06-25 00:00 UT   11 03 25.5   +26 28 14    12.797   12.400   64.9    4.3   105   22.5 
2026-06-26 00:00 UT   11 03 30.6   +26 24 41    12.815   12.404   64.0    4.2   105   22.5 
2026-06-27 00:00 UT   11 03 36.0   +26 21 07    12.833   12.408   63.2    4.2   104   22.5 
2026-06-28 00:00 UT   11 03 41.7   +26 17 33    12.851   12.412   62.3    4.2   104   22.5 
2026-06-29 00:00 UT   11 03 47.6   +26 13 59    12.869   12.416   61.5    4.1   103   22.5 
2026-06-30 00:00 UT   11 03 53.9   +26 10 24    12.886   12.419   60.6    4.1   103   22.5 
2026-07-01 00:00 UT   11 04 00.3   +26 06 49    12.904   12.423   59.8    4.1   103   22.5 

    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.