501P/Rankin
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Today	14 Dec 2025	30.0	3.784 AU	3.557 AU	00h06m	-08°41'	95.7°	15.0°	65°
Perihelion	11 Aug 2027	20.7	0.672 AU	1.504 AU	10h50m	+11°14'	21.4°	33.4°	103°
Nearest approach	9 Sep 2027	21.3	0.827 AU	1.358 AU	13h33m	-03°36'	37.3°	47.6°	104°

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. (21.5 + 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 501P/Rankin are:

    e (Eccentricity)                : 0.6985710
    q (Perihelion distance)         : 0.6715400
    i (Inclination)                 : 10.04750
    Ω (Longitude of ascending node) : 139.78390
    ω (Argument of perihelion)      : 53.68500
    L (Longitude of perihelion)     : 193.04537
    B (Latitude of perihelion)      : 8.08134
    T (Time of perihelion passage)  : 2461629.42160
    P (Orbital period in years)     : 3.33

    Epoch                           : 2025 Dec 13
    Reference                       : MPEC 2025-W75

    Classification(s):              : Ecliptic; Encke type; Active asteroid
    Tisserand (Jupiter)             : 3.257

Ephemerides

Date       Time       RA (2000)    DEC (2000)    delta   radius  elong  phase   PA    magn
2025-12-13 00:00 UT   00 06 22.7   -08 44 56     3.536    3.784   97.0   15.0    65   30.0 
2025-12-14 00:00 UT   00 06 29.5   -08 42 11     3.552    3.784   96.1   15.0    65   30.0 
2025-12-14 08:38 UT   00 06 32.2   -08 41 10     3.557    3.784   95.7   15.0    65   30.0 
2025-12-15 00:00 UT   00 06 37.3   -08 39 19     3.567    3.784   95.1   15.0    66   30.0 
2025-12-16 00:00 UT   00 06 46.1   -08 36 22     3.583    3.784   94.1   15.0    66   30.1 
2025-12-17 00:00 UT   00 06 55.8   -08 33 19     3.599    3.784   93.2   15.1    66   30.1 
2025-12-18 00:00 UT   00 07 06.5   -08 30 11     3.615    3.784   92.3   15.1    66   30.1 
2025-12-19 00:00 UT   00 07 18.2   -08 26 57     3.631    3.784   91.3   15.1    66   30.1 
2025-12-20 00:00 UT   00 07 30.8   -08 23 38     3.647    3.784   90.4   15.1    66   30.1 
2025-12-21 00:00 UT   00 07 44.3   -08 20 14     3.663    3.784   89.4   15.1    66   30.1 
2025-12-22 00:00 UT   00 07 58.8   -08 16 45     3.679    3.784   88.5   15.1    67   30.1 
2025-12-23 00:00 UT   00 08 14.2   -08 13 12     3.695    3.783   87.6   15.1    67   30.1 
2025-12-24 00:00 UT   00 08 30.4   -08 09 33     3.711    3.783   86.7   15.0    67   30.1 

    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.