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	19 Oct 2025	35.5	42.056 AU	42.430 AU	17h53m	-53°49'	67.1°	1.2°	105°

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
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 
2025-10-19 05:49 UT   17 53 27.5   -53 49 05    42.430   42.056   67.1    1.2   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 
2025-10-21 00:00 UT   17 53 37.0   -53 47 56    42.486   42.089   65.6    1.2   106   35.5 
2025-10-22 00:00 UT   17 53 42.5   -53 47 17    42.518   42.108   64.8    1.2   107   35.5 
2025-10-23 00:00 UT   17 53 48.2   -53 46 39    42.550   42.127   64.0    1.2   107   35.5 
2025-10-24 00:00 UT   17 53 54.0   -53 46 01    42.581   42.146   63.2    1.2   108   35.5 
2025-10-25 00:00 UT   17 53 60.0   -53 45 23    42.613   42.165   62.4    1.2   109   35.5 
2025-10-26 00:00 UT   17 54 06.0   -53 44 46    42.644   42.184   61.6    1.2   109   35.6 
2025-10-27 00:00 UT   17 54 12.2   -53 44 10    42.675   42.203   60.8    1.2   110   35.6 
2025-10-28 00:00 UT   17 54 18.5   -53 43 34    42.706   42.222   60.0    1.2   110   35.6 
2025-10-29 00:00 UT   17 54 25.0   -53 42 58    42.737   42.241   59.2    1.2   111   35.6 

    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.