C/2021 A2 (NEOWISE)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Perihelion	21 Jan 2021	11.5	1.420 AU	0.633 AU	09h08m	-37°31'	121.3°	36.3°	345°
Nearest approach	2 Feb 2021	11.1	1.431 AU	0.510 AU	07h29m	-10°25'	144.1°	23.8°	41°
Today	6 Sep 2026	62.2	16.335 AU	15.749 AU	20h31m	+37°51'	124.0°	2.9°	134°

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. This lightcurve is being recalculated every 6 hours based on the available COBS/MPC observations (currently 6.2 + 5 log[∆] + 41.2 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 A2 (NEOWISE) are:

    e (Eccentricity)                : 0.9939170
    q (Perihelion distance)         : 1.4203000
    i (Inclination)                 : 107.07360
    Ω (Longitude of ascending node) : 125.03120
    ω (Argument of perihelion)      : 338.85270
    L (Longitude of perihelion)     : 131.51048
    B (Latitude of perihelion)      : -20.17370
    T (Time of perihelion passage)  : 2459236.16990
    P (Orbital period in years)     : 3567.74

    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
2026-09-05 00:00 UT   20 31 58.1   +37 55 14    15.739   16.328  124.2    2.9   136   62.2 
2026-09-06 00:00 UT   20 31 43.7   +37 52 30    15.748   16.333  124.0    2.9   135   62.2 
2026-09-06 05:00 UT   20 31 40.8   +37 51 56    15.749   16.335  124.0    2.9   134   62.2 
2026-09-07 00:00 UT   20 31 29.6   +37 49 44    15.756   16.339  123.8    2.9   133   62.2 
2026-09-08 00:00 UT   20 31 15.8   +37 46 55    15.765   16.345  123.6    2.9   132   62.2 
2026-09-09 00:00 UT   20 31 02.1   +37 44 05    15.774   16.350  123.4    2.9   131   62.2 
2026-09-10 00:00 UT   20 30 48.7   +37 41 12    15.784   16.356  123.1    3.0   130   62.2 
2026-09-11 00:00 UT   20 30 35.6   +37 38 18    15.793   16.362  122.9    3.0   129   62.2 
2026-09-12 00:00 UT   20 30 22.7   +37 35 22    15.803   16.367  122.6    3.0   127   62.2 
2026-09-13 00:00 UT   20 30 10.0   +37 32 23    15.812   16.373  122.3    3.0   126   62.2 
2026-09-14 00:00 UT   20 29 57.6   +37 29 24    15.822   16.379  122.0    3.0   125   62.2 
2026-09-15 00:00 UT   20 29 45.4   +37 26 22    15.833   16.384  121.7    3.0   124   62.2 
2026-09-16 00:00 UT   20 29 33.5   +37 23 19    15.843   16.390  121.4    3.0   123   62.2 

    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.