C/2023 A2 (SWAN)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Nearest approach	25 Nov 2022	15.6	1.345 AU	1.462 AU	16h39m	+41°54'	63.2°	40.9°	10°
Perihelion	20 Jan 2023	14.5	0.944 AU	1.798 AU	19h17m	-03°29'	20.7°	21.6°	325°
Today	25 Oct 2025	28.6	10.180 AU	10.160 AU	07h08m	-51°19'	88.3°	5.6°	288°

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. (13.5 + 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/2023 A2 (SWAN) are:

    e (Eccentricity)                : 0.9976260
    q (Perihelion distance)         : 0.9441760
    i (Inclination)                 : 94.70550
    Ω (Longitude of ascending node) : 94.51130
    ω (Argument of perihelion)      : 142.47300
    L (Longitude of perihelion)     : 98.11665
    B (Latitude of perihelion)      : 37.37882
    T (Time of perihelion passage)  : 2459964.86810
    P (Orbital period in years)     : 7931.56

    Epoch                           : 2025 Oct 25
    Reference                       : MPEC 2023-J95

    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
2025-10-24 00:00 UT   07 09 00.6   -51 11 12    10.156   10.167   87.8    5.6   286   28.6 
2025-10-25 00:00 UT   07 08 48.0   -51 15 43    10.158   10.174   88.1    5.6   287   28.6 
2025-10-25 19:01 UT   07 08 37.6   -51 19 15    10.160   10.180   88.3    5.6   288   28.6 
2025-10-26 00:00 UT   07 08 34.8   -51 20 11    10.160   10.181   88.4    5.6   288   28.6 
2025-10-27 00:00 UT   07 08 20.9   -51 24 38    10.162   10.189   88.7    5.6   289   28.6 
2025-10-28 00:00 UT   07 08 06.3   -51 29 02    10.164   10.196   89.0    5.6   290   28.6 
2025-10-29 00:00 UT   07 07 51.1   -51 33 24    10.166   10.203   89.3    5.6   291   28.6 
2025-10-30 00:00 UT   07 07 35.2   -51 37 43    10.168   10.210   89.6    5.6   292   28.6 
2025-10-31 00:00 UT   07 07 18.7   -51 42 00    10.170   10.217   89.9    5.6   293   28.6 
2025-11-01 00:00 UT   07 07 01.5   -51 46 15    10.172   10.225   90.2    5.6   294   28.6 
2025-11-02 00:00 UT   07 06 43.7   -51 50 26    10.174   10.232   90.5    5.6   295   28.6 
2025-11-03 00:00 UT   07 06 25.3   -51 54 35    10.176   10.239   90.8    5.6   296   28.6 
2025-11-04 00:00 UT   07 06 06.2   -51 58 41    10.178   10.246   91.1    5.6   297   28.6 

    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.