A/2021 E4
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Nearest approach	19 Feb 2022	19.7	4.710 AU	3.938 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	2 Jan 2026	23.5	10.657 AU	10.762 AU	23h15m	+28°10'	81.3°	5.2°	58°

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)                : 0.9907930
    q (Perihelion distance)         : 4.6818590
    i (Inclination)                 : 116.39450
    Ω (Longitude of ascending node) : 171.13030
    ω (Argument of perihelion)      : 48.30310
    L (Longitude of perihelion)     : 144.61085
    B (Latitude of perihelion)      : 41.97734
    T (Time of perihelion passage)  : 2459694.36270
    P (Orbital period in years)     : 11467.01

    Epoch                           : 2026 Jan 01
    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
2026-01-01 00:00 UT   23 14 50.8   +28 17 42    10.723   10.647   82.9    5.3    59   23.5 
2026-01-02 00:00 UT   23 15 00.4   +28 14 06    10.743   10.652   82.0    5.2    59   23.5 
2026-01-02 21:22 UT   23 15 09.3   +28 10 57    10.762   10.657   81.3    5.2    58   23.5 
2026-01-03 00:00 UT   23 15 10.4   +28 10 34    10.764   10.658   81.2    5.2    58   23.5 
2026-01-04 00:00 UT   23 15 20.7   +28 07 06    10.785   10.663   80.3    5.2    58   23.5 
2026-01-05 00:00 UT   23 15 31.3   +28 03 42    10.805   10.669   79.4    5.2    57   23.5 
2026-01-06 00:00 UT   23 15 42.2   +28 00 22    10.826   10.674   78.5    5.2    57   23.5 
2026-01-07 00:00 UT   23 15 53.5   +27 57 05    10.846   10.680   77.7    5.2    56   23.5 
2026-01-08 00:00 UT   23 16 05.0   +27 53 53    10.867   10.685   76.8    5.1    56   23.6 
2026-01-09 00:00 UT   23 16 16.8   +27 50 44    10.887   10.691   75.9    5.1    55   23.6 
2026-01-10 00:00 UT   23 16 29.0   +27 47 39    10.907   10.697   75.1    5.1    55   23.6 
2026-01-11 00:00 UT   23 16 41.4   +27 44 38    10.928   10.702   74.2    5.1    54   23.6 
2026-01-12 00:00 UT   23 16 54.1   +27 41 40    10.948   10.708   73.3    5.0    54   23.6 

    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.