C/2021 K2 (MASTER)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Nearest approach	13 Jul 2021	18.7	5.480 AU	4.562 AU	19h28m	-49°41'	152.1°	5.0°	1°
Perihelion	9 Sep 2021	18.9	5.464 AU	5.073 AU	18h25m	-41°02'	107.7°	10.1°	81°
Today	7 Jun 2025	23.4	10.759 AU	10.446 AU	17h25m	+51°43'	105.3°	5.2°	186°

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 C/2021 K2 (MASTER) are:

            e (Eccentricity)                : 1.0004780
            q (Perihelion distance)         : 5.4639670
            i (Inclination)                 : 100.87100
            Ω (Longitude of ascending node) : 282.33690
            ω (Argument of perihelion)      : 343.28050
            L (Longitude of perihelion)     : 285.57937
            B (Latitude of perihelion)      : -16.41089
            T (Time of perihelion passage)  : 2459466.76620

            Epoch                           : 2025 Jun 06
            Reference                       : MPEC 2022-O01

            Classification(s):              : Nearly isotropic; New (a > 10000 AU)
        

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 light curve is based on the absolute magnitude and slope parameter as calculated from an MPEC, or the latest values provided by the minor planet center. (8.00 + 5 log[∆] + 10.00 log[r]).

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
2025-06-07 00:00 UT   17 26 15.8   +51 42 20    10.443   10.757  105.4    5.2   186   23.4 
2025-06-07 11:45 UT   17 25 56.2   +51 43 23    10.446   10.759  105.3    5.2   186   23.4 
2025-06-08 00:00 UT   17 25 35.8   +51 44 27    10.449   10.762  105.3    5.2   185   23.4 
2025-06-09 00:00 UT   17 24 55.8   +51 46 26    10.455   10.767  105.2    5.2   184   23.4 
2025-06-10 00:00 UT   17 24 15.8   +51 48 20    10.462   10.772  105.2    5.2   183   23.4 
2025-06-11 00:00 UT   17 23 35.7   +51 50 06    10.468   10.778  105.1    5.2   182   23.4 
2025-06-12 00:00 UT   17 22 55.6   +51 51 47    10.475   10.783  105.0    5.2   181   23.4 
2025-06-13 00:00 UT   17 22 15.5   +51 53 21    10.481   10.788  104.9    5.2   179   23.4 
2025-06-14 00:00 UT   17 21 35.4   +51 54 49    10.488   10.793  104.8    5.2   178   23.4 
2025-06-15 00:00 UT   17 20 55.3   +51 56 10    10.495   10.798  104.7    5.2   177   23.4 
2025-06-16 00:00 UT   17 20 15.3   +51 57 25    10.502   10.804  104.6    5.2   176   23.4 
2025-06-17 00:00 UT   17 19 35.3   +51 58 33    10.509   10.809  104.5    5.2   175   23.4 

    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.