2I/Borisov
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Perihelion	9 Dec 2019	15.6	1.998 AU	1.974 AU	11h27m	-18°35'	77.0°	28.7°	290°
Nearest approach	28 Dec 2019	15.7	2.042 AU	1.919 AU	11h58m	-33°16'	82.7°	28.5°	293°
Today	12 Oct 2026	51.7	519.510 AU	485.349 AU	18h19m	-52°09'	76.2°	0.1°	96°

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 11.2 + 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 2I/Borisov are:

    e (Eccentricity)                : 3.3459520
    q (Perihelion distance)         : 1.9977240
    i (Inclination)                 : 44.26240
    Ω (Longitude of ascending node) : 307.80240
    ω (Argument of perihelion)      : 209.29110
    L (Longitude of perihelion)     : 329.68965
    B (Latitude of perihelion)      : -19.96632
    T (Time of perihelion passage)  : 2458826.55720

    Epoch                           : 2025 Nov 21
    Reference                       : MPEC 2025-R69

    Classification(s):              : Interstellar

Ephemerides

Date       Time       RA (2000)    DEC (2000)    delta   radius  elong  phase   PA    magn
2026-10-11 00:00 UT   18 19 00.8   -52 10 20   466.892  498.420   77.8    0.1    95   51.5 
2026-10-12 00:00 UT   18 19 04.1   -52 10 01   476.973  509.924   76.9    0.1    95   51.6 
2026-10-12 19:36 UT   18 19 06.8   -52 09 47   485.349  519.510   76.2    0.1    96   51.7 
2026-10-13 00:00 UT   18 19 07.5   -52 09 44   487.248  521.685   76.1    0.1    96   51.8 
2026-10-14 00:00 UT   18 19 10.7   -52 09 27   497.720  533.711   75.2    0.1    96   51.9 
2026-10-15 00:00 UT   18 19 13.9   -52 09 10   508.392  546.005   74.4    0.1    97   52.1 
2026-10-16 00:00 UT   18 19 17.0   -52 08 54   519.267  558.575   73.5    0.1    97   52.2 
2026-10-17 00:00 UT   18 19 20.0   -52 08 38   530.347  571.425   72.7    0.1    98   52.3 
2026-10-18 00:00 UT   18 19 23.0   -52 08 23   541.637  584.563   71.8    0.1    98   52.5 
2026-10-19 00:00 UT   18 19 25.9   -52 08 08   553.138  597.995   71.0    0.1    99   52.6 
2026-10-20 00:00 UT   18 19 28.7   -52 07 53   564.853  611.727   70.1    0.1    99   52.8 
2026-10-21 00:00 UT   18 19 31.5   -52 07 39   576.786  625.766   69.3    0.1   100   52.9 
2026-10-22 00:00 UT   18 19 34.3   -52 07 25   588.939  640.118   68.4    0.1   100   53.1 

    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.