C/2015 C2 (SWAN)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Nearest approach	12 Feb 2015	13.7	0.833 AU	1.256 AU	00h01m	-42°04'	41.5°	51.7°	122°
Perihelion	4 Mar 2015	13.3	0.721 AU	1.411 AU	00h55m	-07°57'	28.7°	41.3°	91°
Today	2 Apr 2026	35.4	27.029 AU	26.506 AU	16h16m	+24°46'	120.6°	1.8°	248°

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. (14.0 + 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/2015 C2 (SWAN) are:

    e (Eccentricity)                : 0.9981180
    q (Perihelion distance)         : 0.7206030
    i (Inclination)                 : 94.80390
    Ω (Longitude of ascending node) : 49.18690
    ω (Argument of perihelion)      : 334.17200
    L (Longitude of perihelion)     : 51.50810
    B (Latitude of perihelion)      : -25.73062
    T (Time of perihelion passage)  : 2457086.40640
    P (Orbital period in years)     : 7492.29

    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
2026-04-01 00:00 UT   16 16 57.6   +24 44 25    26.511   27.024  119.9    1.8   249   35.4 
2026-04-02 00:00 UT   16 16 51.9   +24 45 47    26.507   27.028  120.5    1.8   248   35.4 
2026-04-02 06:10 UT   16 16 50.4   +24 46 09    26.506   27.029  120.6    1.8   248   35.4 
2026-04-03 00:00 UT   16 16 46.1   +24 47 10    26.503   27.033  121.0    1.8   247   35.4 
2026-04-04 00:00 UT   16 16 40.1   +24 48 31    26.500   27.037  121.6    1.8   246   35.4 
2026-04-05 00:00 UT   16 16 34.0   +24 49 51    26.496   27.042  122.1    1.8   245   35.4 
2026-04-06 00:00 UT   16 16 27.7   +24 51 11    26.492   27.046  122.7    1.8   244   35.4 
2026-04-07 00:00 UT   16 16 21.3   +24 52 30    26.489   27.051  123.2    1.8   243   35.4 
2026-04-08 00:00 UT   16 16 14.8   +24 53 48    26.486   27.055  123.7    1.8   242   35.4 
2026-04-09 00:00 UT   16 16 08.2   +24 55 05    26.483   27.060  124.3    1.8   241   35.4 
2026-04-10 00:00 UT   16 16 01.4   +24 56 21    26.480   27.064  124.8    1.7   240   35.4 
2026-04-11 00:00 UT   16 15 54.5   +24 57 36    26.477   27.069  125.3    1.7   239   35.4 
2026-04-12 00:00 UT   16 15 47.5   +24 58 51    26.475   27.074  125.8    1.7   238   35.4 

    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.