C/2021 R2 (PANSTARRS)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Nearest approach	20 Sep 2021	20.2	7.343 AU	6.395 AU	23h17m	+18°05'	159.3°	2.8°	155°
Perihelion	28 Dec 2021	20.5	7.316 AU	7.604 AU	22h29m	+13°54'	69.4°	7.2°	58°
Today	21 Dec 2025	23.5	11.451 AU	12.183 AU	17h41m	+16°41'	40.3°	3.2°	354°

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. (7.5 + 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/2021 R2 (PANSTARRS) are:

    e (Eccentricity)                : 0.9995830
    q (Perihelion distance)         : 7.3157490
    i (Inclination)                 : 134.47920
    Ω (Longitude of ascending node) : 16.35450
    ω (Argument of perihelion)      : 32.56140
    L (Longitude of perihelion)     : -7.75019
    B (Latitude of perihelion)      : 22.58233
    T (Time of perihelion passage)  : 2459577.09940

    Epoch                           : 2025 Dec 20
    Reference                       : MPEC 2022-X67

    Classification(s):              : Nearly isotropic; New (a > 10000 AU)

Ephemerides

Date       Time       RA (2000)    DEC (2000)    delta   radius  elong  phase   PA    magn
2025-12-20 00:00 UT   17 40 55.9   +16 41 31    12.179   11.445   40.2    3.2   356   23.5 
2025-12-21 00:00 UT   17 41 09.9   +16 41 16    12.182   11.449   40.3    3.2   355   23.5 
2025-12-21 12:11 UT   17 41 17.0   +16 41 09    12.183   11.451   40.3    3.2   354   23.5 
2025-12-22 00:00 UT   17 41 23.8   +16 41 03    12.185   11.453   40.4    3.2   353   23.5 
2025-12-23 00:00 UT   17 41 37.7   +16 40 55    12.188   11.458   40.5    3.2   352   23.5 
2025-12-24 00:00 UT   17 41 51.6   +16 40 49    12.190   11.462   40.6    3.2   350   23.5 
2025-12-25 00:00 UT   17 42 05.4   +16 40 47    12.193   11.466   40.8    3.2   349   23.5 
2025-12-26 00:00 UT   17 42 19.1   +16 40 48    12.195   11.471   41.0    3.2   348   23.5 
2025-12-27 00:00 UT   17 42 32.8   +16 40 52    12.197   11.475   41.2    3.2   346   23.5 
2025-12-28 00:00 UT   17 42 46.5   +16 40 59    12.198   11.479   41.4    3.2   345   23.5 
2025-12-29 00:00 UT   17 43 00.0   +16 41 10    12.200   11.484   41.6    3.3   343   23.5 
2025-12-30 00:00 UT   17 43 13.5   +16 41 24    12.201   11.488   41.9    3.3   342   23.5 
2025-12-31 00:00 UT   17 43 26.9   +16 41 41    12.202   11.492   42.1    3.3   340   23.5 

    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.