A/2021 E4
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Nearest approach	18 Feb 2022	19.7	4.713 AU	3.941 AU	11h41m	+49°50'	137.1°	8.2°	215°
Perihelion	25 Apr 2022	20.2	4.685 AU	4.534 AU	10h02m	+59°28'	92.4°	12.4°	121°
Today	17 Sep 2026	23.7	12.073 AU	11.187 AU	23h33m	+27°09'	150.7°	2.3°	176°

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)                : 0.9910650
    q (Perihelion distance)         : 4.6850400
    i (Inclination)                 : 116.40960
    Ω (Longitude of ascending node) : 171.11990
    ω (Argument of perihelion)      : 48.34090
    L (Longitude of perihelion)     : 144.55787
    B (Latitude of perihelion)      : 42.00089
    T (Time of perihelion passage)  : 2459694.53070
    P (Orbital period in years)     : 12006.82

    Epoch                           : 2026 Sep 17
    Reference                       : MPC194173

    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
2026-09-16 00:00 UT   23 34 11.5   +27 16 03    11.182   12.063  149.9    2.4   180   23.7 
2026-09-17 00:00 UT   23 33 49.4   +27 12 47    11.184   12.068  150.3    2.4   178   23.7 
2026-09-17 22:27 UT   23 33 28.8   +27 09 42    11.187   12.073  150.7    2.3   176   23.7 
2026-09-18 00:00 UT   23 33 27.4   +27 09 29    11.187   12.074  150.7    2.3   176   23.7 
2026-09-19 00:00 UT   23 33 05.3   +27 06 08    11.190   12.079  151.1    2.3   174   23.7 
2026-09-20 00:00 UT   23 32 43.4   +27 02 44    11.193   12.085  151.4    2.3   172   23.7 
2026-09-21 00:00 UT   23 32 21.5   +26 59 17    11.196   12.090  151.7    2.3   170   23.7 
2026-09-22 00:00 UT   23 31 59.7   +26 55 48    11.200   12.095  152.0    2.2   168   23.7 
2026-09-23 00:00 UT   23 31 37.9   +26 52 16    11.204   12.101  152.2    2.2   165   23.7 
2026-09-24 00:00 UT   23 31 16.3   +26 48 42    11.208   12.106  152.4    2.2   163   23.7 
2026-09-25 00:00 UT   23 30 54.7   +26 45 05    11.212   12.112  152.6    2.2   161   23.7 
2026-09-26 00:00 UT   23 30 33.2   +26 41 26    11.217   12.117  152.7    2.2   158   23.7 
2026-09-27 00:00 UT   23 30 11.9   +26 37 45    11.222   12.123  152.8    2.2   156   23.7 

    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.