C/2018 A4 (PANSTARRS)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Nearest approach	14 Nov 2017	20.4	3.013 AU	2.082 AU	01h51m	+07°10'	156.1°	7.6°	60°
Perihelion	22 May 2018	20.4	2.389 AU	3.289 AU	05h34m	+23°09'	22.9°	9.5°	88°
Today	21 Apr 2026	31.8	15.585 AU	14.788 AU	16h34m	-20°18'	141.3°	2.3°	276°

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/2018 A4 (PANSTARRS) are:

    e (Eccentricity)                : 0.8044720
    q (Perihelion distance)         : 2.3894300
    i (Inclination)                 : 3.15370
    Ω (Longitude of ascending node) : 97.53580
    ω (Argument of perihelion)      : 356.07010
    L (Longitude of perihelion)     : 93.61183
    B (Latitude of perihelion)      : -0.21603
    T (Time of perihelion passage)  : 2458261.08220
    P (Orbital period in years)     : 42.72

    Epoch                           : 2026 Mar 16
    Reference                       : MPEC 2026-E44

    Classification(s):              : Nearly isotropic; Returning (a < 10000 AU); Halley type (P < 200 years)

Ephemerides

Date       Time       RA (2000)    DEC (2000)    delta   radius  elong  phase   PA    magn
2026-04-20 00:00 UT   16 34 48.1   -20 19 28    14.802   15.580  139.5    2.4   276   31.8 
2026-04-21 00:00 UT   16 34 37.6   -20 19 03    14.794   15.583  140.5    2.4   276   31.8 
2026-04-21 19:36 UT   16 34 28.8   -20 18 43    14.788   15.585  141.3    2.3   276   31.8 
2026-04-22 00:00 UT   16 34 26.8   -20 18 38    14.786   15.586  141.5    2.3   276   31.8 
2026-04-23 00:00 UT   16 34 15.9   -20 18 13    14.779   15.589  142.5    2.2   276   31.8 
2026-04-24 00:00 UT   16 34 04.8   -20 17 47    14.771   15.591  143.5    2.2   276   31.8 
2026-04-25 00:00 UT   16 33 53.5   -20 17 21    14.764   15.594  144.6    2.1   276   31.8 
2026-04-26 00:00 UT   16 33 42.1   -20 16 55    14.757   15.597  145.6    2.1   276   31.8 
2026-04-27 00:00 UT   16 33 30.4   -20 16 28    14.750   15.600  146.6    2.0   276   31.8 
2026-04-28 00:00 UT   16 33 18.6   -20 16 02    14.744   15.603  147.6    2.0   276   31.8 
2026-04-29 00:00 UT   16 33 06.7   -20 15 34    14.737   15.606  148.6    1.9   276   31.8 
2026-04-30 00:00 UT   16 32 54.5   -20 15 07    14.731   15.609  149.6    1.9   276   31.8 
2026-05-01 00:00 UT   16 32 42.3   -20 14 39    14.726   15.612  150.7    1.8   276   31.8 

    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.