C/2021 A4 (NEOWISE)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Nearest approach	12 Feb 2021	12.2	1.278 AU	0.430 AU	06h44m	+59°24'	123.9°	39.9°	125°
Perihelion	19 Mar 2021	13.9	1.150 AU	1.142 AU	04h14m	-02°13'	64.7°	51.5°	91°
Today	9 May 2025	29.7	12.925 AU	12.810 AU	21h15m	-23°05'	94.2°	4.5°	253°

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 A4 (NEOWISE) are:

            e (Eccentricity)                : 0.9729410
            q (Perihelion distance)         : 1.1501740
            i (Inclination)                 : 111.63970
            Ω (Longitude of ascending node) : 307.09060
            ω (Argument of perihelion)      : 204.75040
            L (Longitude of perihelion)     : 297.44212
            B (Latitude of perihelion)      : -22.90218
            T (Time of perihelion passage)  : 2459293.05750
            P (Orbital period in years)     : 277.13

            Epoch                           : 2025 May 08
            Reference                       : MPEC 2022-ED3

            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 gray curve is based on the absolute magnitude and slope parameter as calculated from the original MPEC, or the latest values provided by the MPC (16.00 + 5 log[∆] + 10.00 log[r]), whereas the red curve is being recalculated every 6 hours based on the available COBS/MPC observations (currently 13.01 + 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
2025-05-09 00:00 UT   21 15 43.7   -23 05 54    12.814   12.923   93.9    4.5   253   29.7 
2025-05-09 07:02 UT   21 15 43.0   -23 05 58    12.810   12.925   94.2    4.5   253   29.7 
2025-05-10 00:00 UT   21 15 41.2   -23 06 08    12.803   12.929   94.9    4.5   253   29.7 
2025-05-11 00:00 UT   21 15 38.3   -23 06 24    12.792   12.935   95.9    4.5   253   29.7 
2025-05-12 00:00 UT   21 15 35.2   -23 06 40    12.781   12.941   96.9    4.4   253   29.7 
2025-05-13 00:00 UT   21 15 31.7   -23 06 58    12.770   12.946   97.8    4.4   253   29.7 
2025-05-14 00:00 UT   21 15 27.9   -23 07 18    12.759   12.952   98.8    4.4   254   29.7 
2025-05-15 00:00 UT   21 15 23.7   -23 07 39    12.748   12.958   99.8    4.4   254   29.7 
2025-05-16 00:00 UT   21 15 19.2   -23 08 01    12.737   12.964  100.8    4.4   254   29.7 
2025-05-17 00:00 UT   21 15 14.4   -23 08 24    12.726   12.970  101.7    4.4   254   29.7 
2025-05-18 00:00 UT   21 15 09.3   -23 08 49    12.715   12.976  102.7    4.4   254   29.7 
2025-05-19 00:00 UT   21 15 03.8   -23 09 15    12.705   12.982  103.7    4.3   254   29.7 

    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.