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	22 Mar 2026	31.8	15.497 AU	15.112 AU	16h38m	-20°28'	111.0°	3.4°	277°

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
2026-03-21 00:00 UT   16 38 16.9   -20 28 29    15.137   15.492  109.1    3.5   277   31.8 
2026-03-22 00:00 UT   16 38 13.7   -20 28 17    15.124   15.495  110.1    3.5   277   31.8 
2026-03-22 20:37 UT   16 38 10.7   -20 28 07    15.112   15.497  111.0    3.4   277   31.8 
2026-03-23 00:00 UT   16 38 10.1   -20 28 06    15.111   15.498  111.1    3.4   277   31.8 
2026-03-24 00:00 UT   16 38 06.4   -20 27 54    15.097   15.501  112.1    3.4   277   31.8 
2026-03-25 00:00 UT   16 38 02.3   -20 27 41    15.084   15.504  113.1    3.4   277   31.8 
2026-03-26 00:00 UT   16 37 58.0   -20 27 28    15.072   15.507  114.1    3.4   277   31.8 
2026-03-27 00:00 UT   16 37 53.4   -20 27 14    15.059   15.510  115.1    3.3   277   31.8 
2026-03-28 00:00 UT   16 37 48.5   -20 26 60    15.046   15.512  116.2    3.3   277   31.8 
2026-03-29 00:00 UT   16 37 43.4   -20 26 45    15.034   15.515  117.2    3.3   277   31.8 
2026-03-30 00:00 UT   16 37 38.0   -20 26 30    15.022   15.518  118.2    3.3   277   31.8 
2026-03-31 00:00 UT   16 37 32.3   -20 26 14    15.009   15.521  119.2    3.2   277   31.8 
2026-04-01 00:00 UT   16 37 26.4   -20 25 58    14.997   15.524  120.2    3.2   277   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.