C/2021 P4 (ATLAS)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Nearest approach	13 Jul 2022	10.3	1.114 AU	1.958 AU	09h14m	+27°57'	24.3°	22.1°	81°
Perihelion	30 Jul 2022	10.2	1.078 AU	1.976 AU	09h59m	+14°18'	19.9°	18.7°	105°
Today	4 Jun 2026	27.2	12.745 AU	12.505 AU	23h03m	-40°13'	101.4°	4.5°	250°

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. This lightcurve is being recalculated every 6 hours based on the available COBS/MPC observations (currently 8.3 + 5 log[∆] + 12.2 log[r]). An additional green curve is displayed when an increase in apparent brightness is expected due to forward scattering of sunlight, which occurs when a dust-rich comet is located between the Earth and the Sun. (See Marcus 2007)

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 C/2021 P4 (ATLAS) are:

    e (Eccentricity)                : 0.9964340
    q (Perihelion distance)         : 1.0784150
    i (Inclination)                 : 56.42630
    Ω (Longitude of ascending node) : 347.95690
    ω (Argument of perihelion)      : 175.83940
    L (Longitude of perihelion)     : 345.65324
    B (Latitude of perihelion)      : 3.46558
    T (Time of perihelion passage)  : 2459791.12730
    P (Orbital period in years)     : 5259.04

    Epoch                           : 2026 Jun 03
    Reference                       : MPC194175

    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
2026-06-03 00:00 UT   23 03 39.9   -40 10 41    12.515   12.736  100.3    4.5   250   27.2 
2026-06-04 00:00 UT   23 03 40.8   -40 12 45    12.508   12.743  101.1    4.5   250   27.2 
2026-06-04 09:07 UT   23 03 41.0   -40 13 32    12.505   12.745  101.4    4.5   250   27.2 
2026-06-05 00:00 UT   23 03 41.3   -40 14 50    12.500   12.749  101.9    4.5   251   27.2 
2026-06-06 00:00 UT   23 03 41.4   -40 16 57    12.493   12.756  102.8    4.4   251   27.2 
2026-06-07 00:00 UT   23 03 41.1   -40 19 06    12.485   12.762  103.6    4.4   252   27.2 
2026-06-08 00:00 UT   23 03 40.5   -40 21 16    12.478   12.768  104.4    4.4   252   27.2 
2026-06-09 00:00 UT   23 03 39.5   -40 23 28    12.470   12.775  105.2    4.4   253   27.2 
2026-06-10 00:00 UT   23 03 38.0   -40 25 41    12.463   12.781  106.0    4.4   253   27.2 
2026-06-11 00:00 UT   23 03 36.2   -40 27 56    12.456   12.788  106.9    4.4   254   27.2 
2026-06-12 00:00 UT   23 03 34.0   -40 30 12    12.449   12.794  107.7    4.3   254   27.2 
2026-06-13 00:00 UT   23 03 31.4   -40 32 30    12.442   12.801  108.5    4.3   255   27.2 
2026-06-14 00:00 UT   23 03 28.5   -40 34 49    12.435   12.807  109.3    4.3   256   27.2 

    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.