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°53'	69.4°	7.2°	58°
Today	7 Dec 2025	23.5	11.391 AU	12.118 AU	17h38m	+16°49'	40.8°	3.2°	15°

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)                : 0.9995760
    q (Perihelion distance)         : 7.3158510
    i (Inclination)                 : 134.47950
    Ω (Longitude of ascending node) : 16.35330
    ω (Argument of perihelion)      : 32.56140
    L (Longitude of perihelion)     : -7.75150
    B (Latitude of perihelion)      : 22.58220
    T (Time of perihelion passage)  : 2459577.10020

    Epoch                           : 2025 Dec 06
    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
2025-12-06 00:00 UT   17 37 40.7   +16 50 53    12.109   11.384   41.0    3.3    17   23.5 
2025-12-07 00:00 UT   17 37 54.5   +16 49 52    12.116   11.389   40.8    3.2    16   23.5 
2025-12-07 10:04 UT   17 38 00.3   +16 49 27    12.118   11.391   40.8    3.2    15   23.5 
2025-12-08 00:00 UT   17 38 08.3   +16 48 53    12.122   11.393   40.7    3.2    14   23.5 
2025-12-09 00:00 UT   17 38 22.2   +16 47 58    12.128   11.397   40.5    3.2    13   23.5 
2025-12-10 00:00 UT   17 38 36.1   +16 47 07    12.133   11.402   40.4    3.2    11   23.5 
2025-12-11 00:00 UT   17 38 50.0   +16 46 18    12.139   11.406   40.3    3.2    10   23.5 
2025-12-12 00:00 UT   17 39 04.0   +16 45 33    12.144   11.410   40.2    3.2     8   23.5 
2025-12-13 00:00 UT   17 39 17.9   +16 44 51    12.149   11.415   40.1    3.2     7   23.5 
2025-12-14 00:00 UT   17 39 31.9   +16 44 13    12.154   11.419   40.1    3.2     5   23.5 
2025-12-15 00:00 UT   17 39 46.0   +16 43 38    12.159   11.423   40.1    3.2     4   23.5 
2025-12-16 00:00 UT   17 39 60.0   +16 43 06    12.163   11.428   40.0    3.2     2   23.5 
2025-12-17 00:00 UT   17 40 14.0   +16 42 37    12.167   11.432   40.1    3.2     1   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.