A/2021 E4
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Nearest approach	19 Feb 2022	19.7	4.709 AU	3.937 AU	11h41m	+49°48'	137.1°	8.2°	215°
Perihelion	24 Apr 2022	20.2	4.681 AU	4.527 AU	10h03m	+59°27'	92.6°	12.4°	121°
Today	23 Nov 2025	23.3	10.434 AU	9.957 AU	23h13m	+31°18'	116.4°	4.9°	81°

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)                : 0.9907590
    q (Perihelion distance)         : 4.6813830
    i (Inclination)                 : 116.39190
    Ω (Longitude of ascending node) : 171.13230
    ω (Argument of perihelion)      : 48.29770
    L (Longitude of perihelion)     : 144.61929
    B (Latitude of perihelion)      : 41.97418
    T (Time of perihelion passage)  : 2459694.34310
    P (Orbital period in years)     : 11402.05

    Epoch                           : 2025 Nov 22
    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
2025-11-22 00:00 UT   23 13 43.0   +31 28 25     9.927   10.425  117.8    4.8    82   23.3 
2025-11-23 00:00 UT   23 13 36.1   +31 22 43     9.945   10.431  117.0    4.8    82   23.3 
2025-11-23 16:17 UT   23 13 31.8   +31 18 53     9.957   10.434  116.4    4.9    81   23.3 
2025-11-24 00:00 UT   23 13 29.8   +31 17 04     9.963   10.436  116.2    4.9    81   23.3 
2025-11-25 00:00 UT   23 13 23.9   +31 11 27     9.981   10.442  115.3    4.9    80   23.3 
2025-11-26 00:00 UT   23 13 18.5   +31 05 52     9.999   10.447  114.5    4.9    79   23.3 
2025-11-27 00:00 UT   23 13 13.5   +31 00 19    10.018   10.453  113.6    5.0    79   23.3 
2025-11-28 00:00 UT   23 13 09.0   +30 54 49    10.036   10.458  112.8    5.0    78   23.3 
2025-11-29 00:00 UT   23 13 05.0   +30 49 21    10.055   10.464  111.9    5.0    77   23.3 
2025-11-30 00:00 UT   23 13 01.5   +30 43 56    10.074   10.469  111.1    5.0    77   23.3 
2025-12-01 00:00 UT   23 12 58.4   +30 38 33    10.093   10.475  110.2    5.1    76   23.3 
2025-12-02 00:00 UT   23 12 55.7   +30 33 13    10.112   10.480  109.3    5.1    75   23.4 
2025-12-03 00:00 UT   23 12 53.5   +30 27 55    10.132   10.486  108.5    5.1    75   23.4 

    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.