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	4 Oct 2026	62.4	16.493 AU	16.060 AU	20h26m	+36°23'	114.0°	3.2°	103°

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
2026-10-03 00:00 UT   20 26 53.4   +36 28 11    16.043   16.485  114.6    3.2   104   62.4 
2026-10-04 00:00 UT   20 26 46.6   +36 24 49    16.056   16.491  114.1    3.2   103   62.4 
2026-10-04 06:51 UT   20 26 44.7   +36 23 51    16.060   16.493  114.0    3.2   103   62.4 
2026-10-05 00:00 UT   20 26 40.1   +36 21 26    16.070   16.497  113.6    3.2   102   62.4 
2026-10-06 00:00 UT   20 26 33.9   +36 18 02    16.083   16.502  113.1    3.2   101   62.4 
2026-10-07 00:00 UT   20 26 27.9   +36 14 38    16.097   16.508  112.6    3.2   100   62.4 
2026-10-08 00:00 UT   20 26 22.3   +36 11 14    16.110   16.514  112.1    3.2   100   62.4 
2026-10-09 00:00 UT   20 26 17.0   +36 07 50    16.124   16.519  111.6    3.2    99   62.4 
2026-10-10 00:00 UT   20 26 12.0   +36 04 25    16.138   16.525  111.1    3.2    98   62.4 
2026-10-11 00:00 UT   20 26 07.3   +36 01 00    16.152   16.530  110.6    3.2    97   62.4 
2026-10-12 00:00 UT   20 26 02.9   +35 57 35    16.166   16.536  110.1    3.3    96   62.5 
2026-10-13 00:00 UT   20 25 58.8   +35 54 11    16.181   16.542  109.5    3.3    95   62.5 
2026-10-14 00:00 UT   20 25 55.0   +35 50 46    16.195   16.547  109.0    3.3    94   62.5 

    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.