C/2021 J2 (PANSTARRS)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Nearest approach	12 May 2021	21.7	4.810 AU	3.823 AU	15h07m	-04°23'	165.9°	2.9°	170°
Perihelion	20 Sep 2021	22.5	4.702 AU	5.567 AU	13h36m	-07°07'	27.8°	5.7°	106°
Today	20 Oct 2025	27.8	11.260 AU	11.188 AU	07h33m	-02°32'	91.6°	5.1°	281°

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. (12.0 + 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/2021 J2 (PANSTARRS) are:

    e (Eccentricity)                : 0.9576020
    q (Perihelion distance)         : 4.7016370
    i (Inclination)                 : 156.21170
    Ω (Longitude of ascending node) : 23.30200
    ω (Argument of perihelion)      : 171.86600
    L (Longitude of perihelion)     : 30.75307
    B (Latitude of perihelion)      : 3.27169
    T (Time of perihelion passage)  : 2459477.93440
    P (Orbital period in years)     : 1167.77

    Epoch                           : 2025 Oct 19
    Reference                       : MPEC 2023-XP6

    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
2025-10-19 00:00 UT   07 33 52.3   -02 29 03    11.209   11.249   89.7    5.1   280   27.8 
2025-10-20 00:00 UT   07 33 44.2   -02 30 54    11.198   11.254   90.7    5.1   280   27.8 
2025-10-20 22:58 UT   07 33 36.1   -02 32 40    11.188   11.260   91.6    5.1   281   27.8 
2025-10-21 00:00 UT   07 33 35.7   -02 32 44    11.187   11.260   91.6    5.1   281   27.8 
2025-10-22 00:00 UT   07 33 26.9   -02 34 34    11.176   11.265   92.6    5.1   281   27.8 
2025-10-23 00:00 UT   07 33 17.7   -02 36 22    11.166   11.270   93.5    5.1   281   27.8 
2025-10-24 00:00 UT   07 33 08.0   -02 38 09    11.155   11.276   94.4    5.0   282   27.8 
2025-10-25 00:00 UT   07 32 58.1   -02 39 56    11.144   11.281   95.4    5.0   282   27.8 
2025-10-26 00:00 UT   07 32 47.7   -02 41 42    11.133   11.286   96.3    5.0   283   27.8 
2025-10-27 00:00 UT   07 32 37.0   -02 43 26    11.122   11.292   97.3    5.0   283   27.8 
2025-10-28 00:00 UT   07 32 25.8   -02 45 10    11.112   11.297   98.2    5.0   284   27.8 
2025-10-29 00:00 UT   07 32 14.3   -02 46 52    11.101   11.302   99.2    5.0   284   27.8 
2025-10-30 00:00 UT   07 32 02.4   -02 48 33    11.091   11.308  100.1    5.0   284   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.