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	10 Oct 2025	35.5	41.894 AU	42.151 AU	17h52m	-53°54'	74.1°	1.3°	100°

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.)

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
        

The light curve chart below shows the estimated development of the comet's magnitude. Blue and black dots are visual and photometric CCD observations respectively from COBS or the MPC. The gray curve is based on the absolute magnitude and slope parameter as calculated from the original MPEC, or the latest values provided by the MPC (11.00 + 5 log[∆] + 10.00 log[r]), whereas the red curve is being recalculated every 6 hours based on the available COBS/MPC observations (currently 11.15 + 5 log[∆] + 10.00 log[r]).

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.
A more printer-friendly version of the same chart can be found further down this page as well.

The following chart shows the current location of the comet in a smaller, upside-down telescopic field of view.

A printable version of the short-term path of the comet in a field of view that is optimized for (~10x50) binoculars and finderscopes.

Ephemerides:

Date       Time       RA (2000)    DEC (2000)    delta   radius  elong  phase   PA    magn
2025-10-10 00:00 UT   17 52 44.9   -53 55 27    42.128   41.881   74.7    1.3   100   35.5 
2025-10-10 16:31 UT   17 52 47.7   -53 54 57    42.151   41.894   74.1    1.3   100   35.5 
2025-10-11 00:00 UT   17 52 48.9   -53 54 44    42.161   41.900   73.9    1.3   101   35.5 
2025-10-12 00:00 UT   17 52 53.1   -53 54 02    42.194   41.919   73.0    1.3   101   35.5 
2025-10-13 00:00 UT   17 52 57.4   -53 53 20    42.227   41.938   72.2    1.3   102   35.5 
2025-10-14 00:00 UT   17 53 01.9   -53 52 38    42.260   41.957   71.4    1.3   102   35.5 
2025-10-15 00:00 UT   17 53 06.5   -53 51 56    42.292   41.976   70.6    1.3   103   35.5 
2025-10-16 00:00 UT   17 53 11.2   -53 51 15    42.325   41.995   69.7    1.3   103   35.5 
2025-10-17 00:00 UT   17 53 16.1   -53 50 35    42.357   42.014   68.9    1.3   104   35.5 
2025-10-18 00:00 UT   17 53 21.1   -53 49 54    42.390   42.033   68.1    1.3   104   35.5 
2025-10-19 00:00 UT   17 53 26.2   -53 49 14    42.422   42.051   67.3    1.3   105   35.5 
2025-10-20 00:00 UT   17 53 31.5   -53 48 35    42.454   42.070   66.4    1.2   106   35.5 

    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.