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	4.529 AU	10h02m	+59°27'	92.5°	12.4°	121°
Today	24 Jan 2026	23.6	10.776 AU	11.191 AU	23h19m	+27°10'	62.8°	4.7°	47°

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)                : 0.9908090
    q (Perihelion distance)         : 4.6821100
    i (Inclination)                 : 116.39590
    Ω (Longitude of ascending node) : 171.12920
    ω (Argument of perihelion)      : 48.30590
    L (Longitude of perihelion)     : 144.60638
    B (Latitude of perihelion)      : 41.97896
    T (Time of perihelion passage)  : 2459694.37110
    P (Orbital period in years)     : 11497.89

    Epoch                           : 2026 Jan 23
    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
2026-01-23 00:00 UT   23 19 30.8   +27 13 23    11.164   10.768   63.9    4.7    48   23.6 
2026-01-24 00:00 UT   23 19 46.4   +27 11 11    11.183   10.774   63.1    4.7    47   23.6 
2026-01-24 09:16 UT   23 19 52.5   +27 10 21    11.191   10.776   62.8    4.7    47   23.6 
2026-01-25 00:00 UT   23 20 02.3   +27 09 03    11.202   10.780   62.3    4.6    47   23.6 
2026-01-26 00:00 UT   23 20 18.4   +27 06 59    11.221   10.785   61.4    4.6    46   23.6 
2026-01-27 00:00 UT   23 20 34.7   +27 04 59    11.240   10.791   60.6    4.6    46   23.6 
2026-01-28 00:00 UT   23 20 51.2   +27 03 02    11.258   10.796   59.8    4.5    45   23.6 
2026-01-29 00:00 UT   23 21 07.8   +27 01 09    11.276   10.802   58.9    4.5    44   23.6 
2026-01-30 00:00 UT   23 21 24.7   +26 59 20    11.295   10.807   58.1    4.4    44   23.6 
2026-01-31 00:00 UT   23 21 41.7   +26 57 34    11.313   10.813   57.3    4.4    43   23.6 
2026-02-01 00:00 UT   23 21 58.9   +26 55 52    11.331   10.818   56.5    4.4    43   23.6 
2026-02-02 00:00 UT   23 22 16.3   +26 54 14    11.348   10.824   55.7    4.3    42   23.6 
2026-02-03 00:00 UT   23 22 33.8   +26 52 39    11.366   10.829   54.9    4.3    41   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.