C/2021 A2 (NEOWISE)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Perihelion	21 Jan 2021	11.4	1.417 AU	0.631 AU	09h08m	-37°45'	121.1°	36.5°	346°
Nearest approach	2 Feb 2021	11.1	1.428 AU	0.508 AU	07h29m	-10°36'	143.8°	24.0°	41°
Today	19 Oct 2025	59.8	14.469 AU	14.173 AU	20h23m	+38°04'	105.4°	3.8°	89°

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)                : 0.9938500
    q (Perihelion distance)         : 1.4174810
    i (Inclination)                 : 107.06390
    Ω (Longitude of ascending node) : 125.04650
    ω (Argument of perihelion)      : 338.81380
    L (Longitude of perihelion)     : 131.53520
    B (Latitude of perihelion)      : -20.21174
    T (Time of perihelion passage)  : 2459236.29240
    P (Orbital period in years)     : 3499.16

    Epoch                           : 2025 Oct 18
    Reference                       : MPEC 2025-A40

    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
2025-10-18 00:00 UT   20 23 27.9   +38 10 58    14.150   14.460  106.2    3.8    91   59.8 
2025-10-19 00:00 UT   20 23 25.6   +38 06 55    14.165   14.466  105.6    3.8    90   59.8 
2025-10-19 13:04 UT   20 23 24.5   +38 04 42    14.173   14.469  105.4    3.8    89   59.8 
2025-10-20 00:00 UT   20 23 23.7   +38 02 52    14.180   14.472  105.1    3.8    89   59.8 
2025-10-21 00:00 UT   20 23 22.1   +37 58 49    14.195   14.478  104.6    3.8    88   59.8 
2025-10-22 00:00 UT   20 23 20.9   +37 54 47    14.210   14.484  104.0    3.8    87   59.8 
2025-10-23 00:00 UT   20 23 20.1   +37 50 46    14.225   14.490  103.5    3.8    86   59.8 
2025-10-24 00:00 UT   20 23 19.6   +37 46 46    14.240   14.496  103.0    3.8    85   59.8 
2025-10-25 00:00 UT   20 23 19.5   +37 42 46    14.255   14.502  102.4    3.8    84   59.8 
2025-10-26 00:00 UT   20 23 19.7   +37 38 48    14.271   14.508  101.8    3.8    83   59.8 
2025-10-27 00:00 UT   20 23 20.3   +37 34 50    14.286   14.514  101.3    3.9    83   59.8 
2025-10-28 00:00 UT   20 23 21.2   +37 30 54    14.301   14.520  100.7    3.9    82   59.9 
2025-10-29 00:00 UT   20 23 22.5   +37 26 58    14.317   14.526  100.2    3.9    81   59.9 

    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.