C/2011 L4 (PANSTARRS)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Nearest approach	4 Mar 2013	0.7	0.320 AU	1.089 AU	23h55m	-16°05'	16.9°	64.0°	123°
Perihelion	8 Mar 2013	0.4	0.296 AU	1.098 AU	00h14m	-05°54'	15.3°	61.8°	93°
Today	18 Dec 2025	27.8	30.386 AU	31.098 AU	16h28m	+15°18'	43.0°	1.3°	334°

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. (5.5 + 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/2011 L4 (PANSTARRS) are:

    e (Eccentricity)                : 0.9998370
    q (Perihelion distance)         : 0.2963480
    i (Inclination)                 : 84.04880
    Ω (Longitude of ascending node) : 65.86430
    ω (Argument of perihelion)      : 333.47960
    L (Longitude of perihelion)     : 62.90247
    B (Latitude of perihelion)      : -26.36641
    T (Time of perihelion passage)  : 2456359.52500
    P (Orbital period in years)     : 77521.40

    Epoch                           : 2020 Sep 26
    Reference                       : MPC115880

    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
2025-12-17 00:00 UT   16 28 29.0   +15 17 59    31.100   30.379   42.2    1.2   336   27.8 
2025-12-18 00:00 UT   16 28 36.6   +15 18 03    31.099   30.383   42.7    1.3   335   27.8 
2025-12-18 15:17 UT   16 28 41.4   +15 18 06    31.098   30.386   43.0    1.3   334   27.8 
2025-12-19 00:00 UT   16 28 44.1   +15 18 09    31.097   30.388   43.1    1.3   333   27.8 
2025-12-20 00:00 UT   16 28 51.6   +15 18 15    31.096   30.392   43.6    1.3   332   27.8 
2025-12-21 00:00 UT   16 28 59.0   +15 18 23    31.094   30.396   44.2    1.3   331   27.8 
2025-12-22 00:00 UT   16 29 06.3   +15 18 32    31.092   30.401   44.7    1.3   330   27.8 
2025-12-23 00:00 UT   16 29 13.7   +15 18 43    31.089   30.405   45.2    1.3   329   27.8 
2025-12-24 00:00 UT   16 29 20.9   +15 18 55    31.087   30.409   45.8    1.3   327   27.8 
2025-12-25 00:00 UT   16 29 28.2   +15 19 07    31.084   30.414   46.3    1.3   326   27.8 
2025-12-26 00:00 UT   16 29 35.3   +15 19 22    31.081   30.418   46.9    1.4   325   27.8 
2025-12-27 00:00 UT   16 29 42.4   +15 19 37    31.078   30.423   47.5    1.4   324   27.8 
2025-12-28 00:00 UT   16 29 49.5   +15 19 53    31.075   30.427   48.0    1.4   323   27.8 

    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.