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	25 Oct 2025	43.0	22.817 AU	22.362 AU	06h20m	+11°53'	116.1°	2.2°	278°

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
2025-10-24 00:00 UT   06 20 32.7   +11 54 20    22.375   22.811  114.8    2.3   277   43.0 
2025-10-25 00:00 UT   06 20 28.2   +11 53 56    22.365   22.816  115.8    2.2   278   43.0 
2025-10-25 06:43 UT   06 20 26.9   +11 53 49    22.362   22.817  116.1    2.2   278   43.0 
2025-10-26 00:00 UT   06 20 23.6   +11 53 32    22.355   22.821  116.8    2.2   278   43.0 
2025-10-27 00:00 UT   06 20 18.8   +11 53 09    22.345   22.826  117.8    2.2   278   43.0 
2025-10-28 00:00 UT   06 20 13.8   +11 52 46    22.335   22.831  118.8    2.2   278   43.0 
2025-10-29 00:00 UT   06 20 08.7   +11 52 23    22.326   22.836  119.8    2.2   279   43.0 
2025-10-30 00:00 UT   06 20 03.4   +11 52 00    22.317   22.841  120.8    2.1   279   43.0 
2025-10-31 00:00 UT   06 19 57.9   +11 51 38    22.308   22.846  121.8    2.1   279   43.0 
2025-11-01 00:00 UT   06 19 52.3   +11 51 16    22.299   22.851  122.7    2.1   280   43.0 
2025-11-02 00:00 UT   06 19 46.5   +11 50 55    22.290   22.857  123.7    2.1   280   43.0 
2025-11-03 00:00 UT   06 19 40.6   +11 50 34    22.281   22.862  124.7    2.0   280   43.0 
2025-11-04 00:00 UT   06 19 34.5   +11 50 13    22.273   22.867  125.7    2.0   280   43.0 

    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.