A/2021 E4
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Nearest approach	19 Feb 2022	19.7	4.713 AU	3.941 AU	11h41m	+49°49'	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	18 Aug 2026	23.8	11.910 AU	11.229 AU	23h44m	+28°26'	130.4°	3.7°	217°

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)                : 0.9910340
    q (Perihelion distance)         : 4.6846590
    i (Inclination)                 : 116.40800
    Ω (Longitude of ascending node) : 171.12090
    ω (Argument of perihelion)      : 48.33640
    L (Longitude of perihelion)     : 144.56378
    B (Latitude of perihelion)      : 41.99800
    T (Time of perihelion passage)  : 2459694.51270
    P (Orbital period in years)     : 11943.15

    Epoch                           : 2026 Aug 13
    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
2026-08-17 00:00 UT   23 44 50.9   +28 29 14    11.239   11.900  128.8    3.8   219   23.8 
2026-08-18 00:00 UT   23 44 31.4   +28 27 37    11.233   11.905  129.6    3.8   218   23.8 
2026-08-18 22:21 UT   23 44 13.1   +28 26 03    11.229   11.910  130.4    3.7   217   23.8 
2026-08-19 00:00 UT   23 44 11.8   +28 25 56    11.228   11.911  130.5    3.7   217   23.8 
2026-08-20 00:00 UT   23 43 52.0   +28 24 12    11.223   11.916  131.3    3.7   216   23.8 
2026-08-21 00:00 UT   23 43 31.9   +28 22 24    11.219   11.921  132.1    3.6   215   23.8 
2026-08-22 00:00 UT   23 43 11.8   +28 20 33    11.214   11.927  133.0    3.6   215   23.8 
2026-08-23 00:00 UT   23 42 51.4   +28 18 39    11.210   11.932  133.8    3.5   214   23.8 
2026-08-24 00:00 UT   23 42 30.9   +28 16 41    11.206   11.938  134.6    3.5   213   23.8 
2026-08-25 00:00 UT   23 42 10.2   +28 14 39    11.202   11.943  135.4    3.4   212   23.8 
2026-08-26 00:00 UT   23 41 49.4   +28 12 34    11.199   11.949  136.2    3.4   211   23.8 
2026-08-27 00:00 UT   23 41 28.4   +28 10 26    11.195   11.954  136.9    3.3   210   23.8 
2026-08-28 00:00 UT   23 41 07.4   +28 08 14    11.192   11.960  137.7    3.3   209   23.8 

    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.