C/2023 T2 (Borisov)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Perihelion	22 Dec 2023	18.4	1.997 AU	1.487 AU	21h58m	+76°22'	106.1°	28.3°	55°
Nearest approach	6 Jan 2024	18.4	2.005 AU	1.474 AU	23h48m	+76°36'	107.6°	27.9°	66°
Today	21 Oct 2025	27.3	6.926 AU	7.638 AU	11h00m	-26°03'	41.6°	5.5°	256°

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. (14.5 + 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/2023 T2 (Borisov) are:

    e (Eccentricity)                : 0.9910580
    q (Perihelion distance)         : 1.9967980
    i (Inclination)                 : 48.58720
    Ω (Longitude of ascending node) : 317.52210
    ω (Argument of perihelion)      : 111.22790
    L (Longitude of perihelion)     : 257.94446
    B (Latitude of perihelion)      : 44.35296
    T (Time of perihelion passage)  : 2460301.20940
    P (Orbital period in years)     : 3336.95

    Epoch                           : 2025 Oct 20
    Reference                       : MPEC 2024-GJ3

    Classification(s):              : Nearly isotropic; Returning (a < 10000 AU); External (P > 200 years)

Ephemerides

Date       Time       RA (2000)    DEC (2000)    delta   radius  elong  phase   PA    magn
2025-10-20 00:00 UT   10 59 48.4   -25 51 55     7.638    6.912   40.6    5.4   255   27.3 
2025-10-21 00:00 UT   11 00 14.6   -25 58 41     7.638    6.920   41.2    5.4   256   27.3 
2025-10-21 18:31 UT   11 00 34.6   -26 03 54     7.638    6.926   41.6    5.5   256   27.3 
2025-10-22 00:00 UT   11 00 40.4   -26 05 27     7.638    6.928   41.8    5.5   257   27.3 
2025-10-23 00:00 UT   11 01 06.0   -26 12 15     7.638    6.936   42.4    5.5   258   27.3 
2025-10-24 00:00 UT   11 01 31.2   -26 19 03     7.638    6.943   43.0    5.6   258   27.3 
2025-10-25 00:00 UT   11 01 56.0   -26 25 52     7.637    6.951   43.6    5.7   259   27.3 
2025-10-26 00:00 UT   11 02 20.5   -26 32 42     7.636    6.959   44.2    5.7   260   27.3 
2025-10-27 00:00 UT   11 02 44.6   -26 39 33     7.635    6.966   44.9    5.8   261   27.3 
2025-10-28 00:00 UT   11 03 08.4   -26 46 24     7.634    6.974   45.5    5.8   262   27.3 
2025-10-29 00:00 UT   11 03 31.8   -26 53 17     7.633    6.982   46.1    5.9   263   27.4 
2025-10-30 00:00 UT   11 03 54.8   -27 00 09     7.632    6.989   46.8    5.9   263   27.4 
2025-10-31 00:00 UT   11 04 17.4   -27 07 03     7.630    6.997   47.4    6.0   264   27.4 

    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.