A/2021 E4
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Nearest approach	18 Feb 2022	19.7	4.714 AU	3.941 AU	11h41m	+49°50'	137.1°	8.2°	215°
Perihelion	25 Apr 2022	20.2	4.685 AU	4.535 AU	10h02m	+59°28'	92.4°	12.4°	121°
Today	17 Oct 2026	23.8	12.236 AU	11.396 AU	23h23m	+25°13'	146.1°	2.6°	112°

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)                : 0.9910880
    q (Perihelion distance)         : 4.6853760
    i (Inclination)                 : 116.41120
    Ω (Longitude of ascending node) : 171.11890
    ω (Argument of perihelion)      : 48.34460
    L (Longitude of perihelion)     : 144.55260
    B (Latitude of perihelion)      : 42.00314
    T (Time of perihelion passage)  : 2459694.54260
    P (Orbital period in years)     : 12054.63

    Epoch                           : 2026 Oct 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
2026-10-16 00:00 UT   23 23 56.7   +25 21 48    11.375   12.226  147.3    2.5   115   23.8 
2026-10-17 00:00 UT   23 23 39.1   +25 17 35    11.386   12.231  146.7    2.6   114   23.8 
2026-10-17 23:01 UT   23 23 22.4   +25 13 31    11.396   12.236  146.1    2.6   112   23.8 
2026-10-18 00:00 UT   23 23 21.7   +25 13 21    11.397   12.237  146.1    2.6   112   23.8 
2026-10-19 00:00 UT   23 23 04.6   +25 09 06    11.408   12.242  145.4    2.6   111   23.8 
2026-10-20 00:00 UT   23 22 47.8   +25 04 50    11.420   12.247  144.8    2.7   109   23.8 
2026-10-21 00:00 UT   23 22 31.2   +25 00 34    11.432   12.253  144.1    2.7   108   23.8 
2026-10-22 00:00 UT   23 22 14.9   +24 56 17    11.444   12.258  143.4    2.8   106   23.8 
2026-10-23 00:00 UT   23 21 58.9   +24 52 00    11.457   12.264  142.7    2.8   105   23.8 
2026-10-24 00:00 UT   23 21 43.1   +24 47 43    11.470   12.269  142.0    2.9   103   23.8 
2026-10-25 00:00 UT   23 21 27.7   +24 43 25    11.483   12.274  141.2    2.9   102   23.8 
2026-10-26 00:00 UT   23 21 12.5   +24 39 07    11.496   12.280  140.5    3.0   101   23.9 
2026-10-27 00:00 UT   23 20 57.7   +24 34 49    11.510   12.285  139.7    3.0   100   23.9 

    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.