A/2021 E4
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Nearest approach	19 Feb 2022	19.7	4.708 AU	3.936 AU	11h41m	+49°47'	137.1°	8.2°	215°
Perihelion	24 Apr 2022	20.2	4.680 AU	4.525 AU	10h03m	+59°27'	92.6°	12.4°	121°
Today	5 Jul 2025	23.1	9.651 AU	9.669 AU	00h04m	+38°59'	86.0°	6.0°	244°

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.)

The orbital elements of A/2021 E4 are:

            e (Eccentricity)                : 0.9907190
            q (Perihelion distance)         : 4.6798920
            i (Inclination)                 : 116.38190
            Ω (Longitude of ascending node) : 171.14090
            ω (Argument of perihelion)      : 48.28310
            L (Longitude of perihelion)     : 144.64768
            B (Latitude of perihelion)      : 41.96694
            T (Time of perihelion passage)  : 2459694.32850
            P (Orbital period in years)     : 11323.00

            Epoch                           : 2025 Jul 05
            Reference                       : MPEC 2024-N80

            Classification(s):              : Nearly isotropic; Returning (a < 10000 AU); External (P > 200 years)
        

The light curve chart below shows the estimated development of the comet's magnitude. Blue and black dots are visual and photometric CCD observations respectively from COBS or the MPC. The gray curve indicates the expected brightness if this object is a comet (13.50 + 5 log[∆] + 5.00 log[r]), whereas the red curve indicates the expected lightcurve for an asteroid (H=12.80; G=.15).

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.
A more printer-friendly version of the same chart can be found further down this page as well.

The following chart shows the current location of the comet in a smaller, upside-down telescopic field of view.

A printable version of the short-term path of the comet in a field of view that is optimized for (~10x50) binoculars and finderscopes.

Ephemerides:

Date       Time       RA (2000)    DEC (2000)    delta   radius  elong  phase   PA    magn
2025-07-05 00:00 UT   00 04 30.4   +38 57 56     9.677    9.645   85.2    6.0   244   23.1 
2025-07-05 23:28 UT   00 04 22.3   +38 59 10     9.669    9.651   86.0    6.0   244   23.1 
2025-07-06 00:00 UT   00 04 22.1   +38 59 11     9.669    9.651   86.0    6.0   244   23.1 
2025-07-07 00:00 UT   00 04 13.3   +39 00 24     9.660    9.657   86.8    6.0   243   23.1 
2025-07-08 00:00 UT   00 04 04.0   +39 01 34     9.651    9.662   87.6    6.0   243   23.1 
2025-07-09 00:00 UT   00 03 54.2   +39 02 42     9.643    9.668   88.4    6.0   242   23.1 
2025-07-10 00:00 UT   00 03 43.9   +39 03 47     9.634    9.673   89.2    6.0   242   23.1 
2025-07-11 00:00 UT   00 03 33.2   +39 04 49     9.625    9.679   90.0    6.0   241   23.1 
2025-07-12 00:00 UT   00 03 21.9   +39 05 48     9.617    9.685   90.8    6.0   240   23.1 
2025-07-13 00:00 UT   00 03 10.2   +39 06 44     9.608    9.690   91.6    6.0   240   23.1 
2025-07-14 00:00 UT   00 02 58.0   +39 07 37     9.600    9.696   92.4    6.0   239   23.1 
2025-07-15 00:00 UT   00 02 45.4   +39 08 27     9.591    9.701   93.2    6.0   239   23.1 

    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.