C/2021 B2 (PANSTARRS)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Nearest approach	15 Dec 2020	20.5	2.929 AU	2.313 AU	03h32m	-29°28'	119.8°	17.0°	32°
Perihelion	4 May 2021	20.5	2.520 AU	3.178 AU	05h39m	+11°30'	42.0°	15.5°	101°
Today	29 May 2026	31.3	14.417 AU	13.652 AU	15h48m	+19°52'	137.5°	2.7°	167°

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/2021 B2 (PANSTARRS) are:

    e (Eccentricity)                : 0.9940840
    q (Perihelion distance)         : 2.5198320
    i (Inclination)                 : 38.09250
    Ω (Longitude of ascending node) : 120.40140
    ω (Argument of perihelion)      : 335.21880
    L (Longitude of perihelion)     : 100.43334
    B (Latitude of perihelion)      : -14.98641
    T (Time of perihelion passage)  : 2459339.30530
    P (Orbital period in years)     : 8790.53

    Epoch                           : 2026 May 29
    Reference                       : MPC194172

    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
2026-05-28 00:00 UT   15 48 31.6   +19 52 22    13.635   14.406  138.1    2.7   170   31.3 
2026-05-29 00:00 UT   15 48 16.6   +19 52 22    13.645   14.412  137.8    2.7   168   31.3 
2026-05-29 18:17 UT   15 48 05.2   +19 52 20    13.652   14.417  137.5    2.7   167   31.3 
2026-05-30 00:00 UT   15 48 01.6   +19 52 19    13.655   14.418  137.4    2.7   167   31.3 
2026-05-31 00:00 UT   15 47 46.7   +19 52 12    13.665   14.424  137.0    2.7   166   31.3 
2026-06-01 00:00 UT   15 47 31.9   +19 52 03    13.675   14.429  136.6    2.8   164   31.3 
2026-06-02 00:00 UT   15 47 17.2   +19 51 51    13.686   14.435  136.2    2.8   163   31.3 
2026-06-03 00:00 UT   15 47 02.5   +19 51 36    13.696   14.441  135.8    2.8   161   31.3 
2026-06-04 00:00 UT   15 46 47.9   +19 51 19    13.707   14.447  135.3    2.8   160   31.3 
2026-06-05 00:00 UT   15 46 33.5   +19 50 58    13.718   14.452  134.9    2.9   159   31.3 
2026-06-06 00:00 UT   15 46 19.1   +19 50 34    13.730   14.458  134.4    2.9   158   31.3 
2026-06-07 00:00 UT   15 46 04.9   +19 50 08    13.741   14.464  133.9    2.9   156   31.3 
2026-06-08 00:00 UT   15 45 50.7   +19 49 39    13.753   14.470  133.4    2.9   155   31.3 

    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.