C/2017 E1 (Borisov)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Nearest approach	18 Mar 2017	11.5	0.995 AU	1.331 AU	20h42m	-08°22'	48.0°	48.1°	263°
Perihelion	10 Apr 2017	10.9	0.908 AU	1.417 AU	22h43m	-03°31'	39.6°	44.7°	253°
Today	9 Dec 2025	43.1	23.047 AU	22.118 AU	06h14m	+11°42'	160.0°	0.8°	306°

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 10.9 + 5 log[∆] + 18.7 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/2017 E1 (Borisov) are:

    e (Eccentricity)                : 1.0032610
    q (Perihelion distance)         : 0.9078320
    i (Inclination)                 : 14.57020
    Ω (Longitude of ascending node) : 142.57660
    ω (Argument of perihelion)      : 152.79570
    L (Longitude of perihelion)     : 116.12653
    B (Latitude of perihelion)      : 6.60403
    T (Time of perihelion passage)  : 2457853.85400

    Epoch                           : 2022 May 26
    Reference                       : MPC106346

    Classification(s):              : Nearly isotropic; New (a > 10000 AU)

Ephemerides

Date       Time       RA (2000)    DEC (2000)    delta   radius  elong  phase   PA    magn
2025-12-08 00:00 UT   06 14 50.1   +11 42 59    22.118   23.039  158.7    0.9   304   43.1 
2025-12-09 00:00 UT   06 14 40.1   +11 42 55    22.118   23.045  159.6    0.9   305   43.1 
2025-12-09 11:42 UT   06 14 35.2   +11 42 53    22.118   23.047  160.0    0.8   306   43.1 
2025-12-10 00:00 UT   06 14 30.0   +11 42 52    22.119   23.050  160.4    0.8   307   43.1 
2025-12-11 00:00 UT   06 14 19.9   +11 42 49    22.119   23.055  161.3    0.8   309   43.1 
2025-12-12 00:00 UT   06 14 09.7   +11 42 47    22.120   23.060  162.1    0.8   311   43.1 
2025-12-13 00:00 UT   06 13 59.5   +11 42 45    22.122   23.065  162.9    0.7   313   43.1 
2025-12-14 00:00 UT   06 13 49.2   +11 42 44    22.123   23.070  163.6    0.7   316   43.1 
2025-12-15 00:00 UT   06 13 38.9   +11 42 44    22.125   23.075  164.3    0.7   319   43.1 
2025-12-16 00:00 UT   06 13 28.6   +11 42 44    22.127   23.080  165.0    0.6   322   43.1 
2025-12-17 00:00 UT   06 13 18.2   +11 42 44    22.130   23.085  165.6    0.6   325   43.1 
2025-12-18 00:00 UT   06 13 07.8   +11 42 45    22.133   23.090  166.2    0.6   329   43.1 
2025-12-19 00:00 UT   06 12 57.4   +11 42 47    22.136   23.095  166.8    0.6   333   43.1 

    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.