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	30 Oct 2025	35.6	42.273 AU	42.788 AU	17h54m	-53°42'	57.8°	1.1°	112°

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
2025-10-29 00:00 UT   17 54 25.0   -53 42 58    42.737   42.241   59.2    1.2   111   35.6 
2025-10-30 00:00 UT   17 54 31.5   -53 42 23    42.768   42.260   58.4    1.1   112   35.6 
2025-10-30 15:45 UT   17 54 35.9   -53 42 00    42.788   42.273   57.8    1.1   112   35.6 
2025-10-31 00:00 UT   17 54 38.2   -53 41 48    42.799   42.279   57.6    1.1   112   35.6 
2025-11-01 00:00 UT   17 54 45.0   -53 41 14    42.829   42.298   56.8    1.1   113   35.6 
2025-11-02 00:00 UT   17 54 51.9   -53 40 40    42.859   42.317   56.0    1.1   114   35.6 
2025-11-03 00:00 UT   17 54 58.9   -53 40 07    42.890   42.336   55.2    1.1   114   35.6 
2025-11-04 00:00 UT   17 55 06.0   -53 39 35    42.920   42.355   54.4    1.1   115   35.6 
2025-11-05 00:00 UT   17 55 13.2   -53 39 02    42.949   42.374   53.7    1.1   116   35.6 
2025-11-06 00:00 UT   17 55 20.5   -53 38 31    42.979   42.393   52.9    1.1   117   35.6 
2025-11-07 00:00 UT   17 55 28.0   -53 37 60    43.008   42.412   52.1    1.1   117   35.6 
2025-11-08 00:00 UT   17 55 35.5   -53 37 29    43.038   42.431   51.4    1.0   118   35.6 
2025-11-09 00:00 UT   17 55 43.1   -53 36 59    43.067   42.450   50.6    1.0   119   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.