C/2021 B3 (NEOWISE)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Nearest approach	12 Feb 2021	18.3	2.187 AU	1.875 AU	05h54m	-57°50'	94.5°	26.7°	55°
Perihelion	9 Mar 2021	18.4	2.169 AU	2.030 AU	05h02m	-36°08'	84.3°	27.1°	89°
Today	16 Sep 2025	30.0	12.789 AU	12.276 AU	22h37m	+57°30'	118.7°	4.0°	164°

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.)

The orbital elements of C/2021 B3 (NEOWISE) are:

            e (Eccentricity)                : 0.9366110
            q (Perihelion distance)         : 2.1694650
            i (Inclination)                 : 119.47930
            Ω (Longitude of ascending node) : 67.28740
            ω (Argument of perihelion)      : 293.61960
            L (Longitude of perihelion)     : 115.66255
            B (Latitude of perihelion)      : -52.90202
            T (Time of perihelion passage)  : 2459282.64870
            P (Orbital period in years)     : 200.22

            Epoch                           : 2025 Sep 15
            Reference                       : MPEC 2021-N06

            Classification(s):              : Nearly isotropic; Returning (a < 10000 AU); External (P > 200 years)
        

The light curve chart below shows the estimated development of the comet's magnitude. Blue and black dots are visual and photometric CCD observations respectively from COBS or the MPC. 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. (13.50 + 5 log[∆] + 10.00 log[r]).

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.
A more printer-friendly version of the same chart can be found further down this page as well.

The following chart shows the current location of the comet in a smaller, upside-down telescopic field of view.

A printable version of the short-term path of the comet in a field of view that is optimized for (~10x50) binoculars and finderscopes.

Ephemerides:

Date       Time       RA (2000)    DEC (2000)    delta   radius  elong  phase   PA    magn
2025-09-16 00:00 UT   22 37 43.6   +57 31 02    12.275   12.788  118.6    4.0   164   30.0 
2025-09-16 03:23 UT   22 37 38.4   +57 30 44    12.276   12.789  118.7    4.0   164   30.0 
2025-09-17 00:00 UT   22 37 06.5   +57 28 51    12.277   12.794  118.9    3.9   163   30.0 
2025-09-18 00:00 UT   22 36 29.6   +57 26 34    12.279   12.799  119.1    3.9   161   30.0 
2025-09-19 00:00 UT   22 35 53.0   +57 24 14    12.282   12.805  119.4    3.9   160   30.0 
2025-09-20 00:00 UT   22 35 16.6   +57 21 48    12.284   12.810  119.6    3.9   159   30.0 
2025-09-21 00:00 UT   22 34 40.5   +57 19 18    12.287   12.816  119.8    3.9   157   30.0 
2025-09-22 00:00 UT   22 34 04.8   +57 16 43    12.289   12.821  120.0    3.9   156   30.0 
2025-09-23 00:00 UT   22 33 29.3   +57 14 04    12.292   12.827  120.2    3.9   155   30.0 
2025-09-24 00:00 UT   22 32 54.2   +57 11 20    12.295   12.832  120.4    3.9   154   30.0 
2025-09-25 00:00 UT   22 32 19.4   +57 08 32    12.299   12.838  120.5    3.9   152   30.0 
2025-09-26 00:00 UT   22 31 45.0   +57 05 40    12.302   12.843  120.7    3.9   151   30.0 

    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.