C/2017 E1 (Borisov)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Nearest approach	15 Mar 2017	11.6	0.994 AU	1.407 AU	20h41m	-09°14'	45.0°	45.0°	264°
Perihelion	5 Apr 2017	11.1	0.920 AU	1.479 AU	22h32m	-04°43'	37.7°	41.7°	254°
Today	14 Mar 2026	43.4	23.523 AU	23.383 AU	06h03m	+12°12'	96.8°	2.4°	89°

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)                : 1.0030010
    q (Perihelion distance)         : 0.9199110
    i (Inclination)                 : 14.48250
    Ω (Longitude of ascending node) : 143.03180
    ω (Argument of perihelion)      : 152.49160
    L (Longitude of perihelion)     : 116.27429
    B (Latitude of perihelion)      : 6.63296
    T (Time of perihelion passage)  : 2457848.84890

    Epoch                           : 2026 Mar 14
    Reference                       : MPEC 2026-E44

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

Ephemerides

Date       Time       RA (2000)    DEC (2000)    delta   radius  elong  phase   PA    magn
2026-03-13 00:00 UT   06 03 01.7   +12 11 24    23.345   23.514   98.5    2.4    89   43.4 
2026-03-14 00:00 UT   06 03 00.8   +12 11 55    23.367   23.519   97.6    2.4    89   43.4 
2026-03-14 18:18 UT   06 03 00.2   +12 12 18    23.383   23.523   96.8    2.4    89   43.4 
2026-03-15 00:00 UT   06 03 00.1   +12 12 26    23.389   23.524   96.6    2.4    89   43.4 
2026-03-16 00:00 UT   06 02 59.5   +12 12 56    23.410   23.529   95.6    2.4    89   43.4 
2026-03-17 00:00 UT   06 02 59.1   +12 13 27    23.432   23.534   94.6    2.4    89   43.4 
2026-03-18 00:00 UT   06 02 58.9   +12 13 58    23.454   23.539   93.6    2.4    90   43.4 
2026-03-19 00:00 UT   06 02 58.9   +12 14 29    23.476   23.544   92.7    2.4    90   43.4 
2026-03-20 00:00 UT   06 02 59.1   +12 14 60    23.498   23.549   91.7    2.4    90   43.4 
2026-03-21 00:00 UT   06 02 59.4   +12 15 30    23.520   23.554   90.7    2.4    90   43.4 
2026-03-22 00:00 UT   06 02 59.9   +12 16 01    23.542   23.559   89.7    2.4    90   43.4 
2026-03-23 00:00 UT   06 03 00.6   +12 16 32    23.564   23.564   88.8    2.4    91   43.4 
2026-03-24 00:00 UT   06 03 01.5   +12 17 02    23.586   23.569   87.8    2.4    91   43.4 

    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.