A/2021 E4
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Nearest approach	19 Feb 2022	19.7	4.710 AU	3.937 AU	11h41m	+49°48'	137.1°	8.2°	215°
Perihelion	24 Apr 2022	20.2	4.682 AU	4.528 AU	10h02m	+59°27'	92.5°	12.4°	121°
Today	19 Dec 2025	23.5	10.578 AU	10.464 AU	23h13m	+29°07'	94.0°	5.3°	65°

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. The displayed light curve is calculated under the assumption that the object remains inactive. (H=12.80; G=.15).

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 A/2021 E4 are:

    e (Eccentricity)                : 0.9907820
    q (Perihelion distance)         : 4.6816970
    i (Inclination)                 : 116.39370
    Ω (Longitude of ascending node) : 171.13090
    ω (Argument of perihelion)      : 48.30130
    L (Longitude of perihelion)     : 144.61355
    B (Latitude of perihelion)      : 41.97626
    T (Time of perihelion passage)  : 2459694.35630
    P (Orbital period in years)     : 11445.90

    Epoch                           : 2025 Dec 18
    Reference                       : MPEC 2024-N80

    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
2025-12-18 00:00 UT   23 13 12.5   +29 14 32    10.433   10.569   95.3    5.3    66   23.4 
2025-12-19 00:00 UT   23 13 17.0   +29 10 05    10.453   10.575   94.4    5.3    66   23.5 
2025-12-19 12:06 UT   23 13 19.5   +29 07 51    10.464   10.578   94.0    5.3    65   23.5 
2025-12-20 00:00 UT   23 13 22.0   +29 05 41    10.474   10.580   93.5    5.3    65   23.5 
2025-12-21 00:00 UT   23 13 27.4   +29 01 21    10.494   10.586   92.6    5.3    65   23.5 
2025-12-22 00:00 UT   23 13 33.1   +28 57 04    10.515   10.591   91.8    5.3    64   23.5 
2025-12-23 00:00 UT   23 13 39.3   +28 52 51    10.536   10.597   90.9    5.3    64   23.5 
2025-12-24 00:00 UT   23 13 45.8   +28 48 42    10.557   10.602   90.0    5.3    63   23.5 
2025-12-25 00:00 UT   23 13 52.7   +28 44 36    10.577   10.608   89.1    5.3    63   23.5 
2025-12-26 00:00 UT   23 13 59.9   +28 40 34    10.598   10.614   88.2    5.3    62   23.5 
2025-12-27 00:00 UT   23 14 07.5   +28 36 36    10.619   10.619   87.3    5.3    62   23.5 
2025-12-28 00:00 UT   23 14 15.5   +28 32 42    10.640   10.625   86.5    5.3    61   23.5 
2025-12-29 00:00 UT   23 14 23.8   +28 28 51    10.660   10.630   85.6    5.3    61   23.5 

    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.