C/2017 A3 (Elenin)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Nearest approach	23 Jan 2017	18.0	3.864 AU	3.425 AU	06h19m	-45°26'	109.4°	13.9°	31°
Perihelion	27 Jan 2017	18.0	3.864 AU	3.426 AU	06h14m	-44°11'	109.2°	13.9°	36°
Today	8 May 2026	29.1	20.046 AU	20.316 AU	21h03m	+78°15'	73.1°	2.8°	267°

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. (9.5 + 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/2017 A3 (Elenin) are:

    e (Eccentricity)                : 0.9107720
    q (Perihelion distance)         : 3.8640750
    i (Inclination)                 : 98.43470
    Ω (Longitude of ascending node) : 97.67030
    ω (Argument of perihelion)      : 304.05950
    L (Longitude of perihelion)     : 109.91250
    B (Latitude of perihelion)      : -55.03433
    T (Time of perihelion passage)  : 2457780.87610
    P (Orbital period in years)     : 284.98

    Epoch                           : 2026 Mar 16
    Reference                       : MPEC 2026-E44

    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
2026-05-07 00:00 UT   21 03 52.2   +78 10 45    20.306   20.038   73.2    2.8   269   29.1 
2026-05-08 00:00 UT   21 03 44.9   +78 13 19    20.311   20.042   73.2    2.8   268   29.1 
2026-05-08 21:54 UT   21 03 37.3   +78 15 38    20.316   20.046   73.1    2.8   267   29.1 
2026-05-09 00:00 UT   21 03 36.6   +78 15 52    20.316   20.047   73.1    2.8   267   29.1 
2026-05-10 00:00 UT   21 03 27.3   +78 18 24    20.321   20.051   73.0    2.8   266   29.1 
2026-05-11 00:00 UT   21 03 17.0   +78 20 57    20.327   20.055   73.0    2.8   265   29.1 
2026-05-12 00:00 UT   21 03 05.8   +78 23 29    20.332   20.059   72.9    2.8   264   29.1 
2026-05-13 00:00 UT   21 02 53.5   +78 26 01    20.337   20.063   72.9    2.8   263   29.1 
2026-05-14 00:00 UT   21 02 40.3   +78 28 32    20.342   20.067   72.9    2.8   262   29.1 
2026-05-15 00:00 UT   21 02 25.9   +78 31 03    20.346   20.072   72.8    2.8   260   29.1 
2026-05-16 00:00 UT   21 02 10.6   +78 33 33    20.351   20.076   72.8    2.8   259   29.1 
2026-05-17 00:00 UT   21 01 54.2   +78 36 03    20.356   20.080   72.8    2.8   258   29.1 
2026-05-18 00:00 UT   21 01 36.8   +78 38 31    20.361   20.084   72.7    2.8   257   29.1 

    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.