C/2025 K1 (ATLAS)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Perihelion	8 Oct 2025	7.9	0.334 AU	1.292 AU	12h35m	-12°27'	8.1°	25.0°	217°
Nearest approach	24 Nov 2025	10.6	1.193 AU	0.401 AU	09h34m	+63°56'	111.3°	50.4°	274°
Today	10 Dec 2025	12.6	1.475 AU	0.647 AU	01h29m	+56°29'	128.2°	31.6°	107°

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 11.9 + 5 log[∆] + 9.6 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/2025 K1 (ATLAS) are:

    e (Eccentricity)                : 1.0002660
    q (Perihelion distance)         : 0.3342140
    i (Inclination)                 : 147.86420
    Ω (Longitude of ascending node) : 97.55800
    ω (Argument of perihelion)      : 271.02340
    L (Longitude of perihelion)     : 186.34949
    B (Latitude of perihelion)      : -32.13006
    T (Time of perihelion passage)  : 2460956.94030

    Epoch                           : 2025 Dec 09
    Reference                       : MPEC 2025-X35

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

Ephemerides

Date       Time       RA (2000)    DEC (2000)    delta   radius  elong  phase   PA    magn
2025-12-09 00:00 UT   01 36 51.8   +58 29 58     0.616    1.454  129.1   31.7   112   12.4 
2025-12-10 00:00 UT   01 30 27.9   +56 47 56     0.642    1.472  128.4   31.6   108   12.5 
2025-12-10 04:33 UT   01 29 22.9   +56 29 21     0.647    1.475  128.2   31.6   107   12.6 
2025-12-11 00:00 UT   01 25 09.4   +55 12 36     0.668    1.490  127.6   31.6   104   12.7 
2025-12-12 00:00 UT   01 20 42.8   +53 43 41     0.695    1.507  126.7   31.6   101   12.8 
2025-12-13 00:00 UT   01 16 58.1   +52 20 49     0.723    1.525  125.8   31.6    98   12.9 
2025-12-14 00:00 UT   01 13 47.4   +51 03 37     0.751    1.542  124.8   31.6    96   13.1 
2025-12-15 00:00 UT   01 11 04.9   +49 51 41     0.780    1.559  123.8   31.6    93   13.2 
2025-12-16 00:00 UT   01 08 45.9   +48 44 38     0.809    1.577  122.8   31.6    91   13.3 
2025-12-17 00:00 UT   01 06 46.9   +47 42 06     0.838    1.594  121.8   31.7    89   13.4 
2025-12-18 00:00 UT   01 05 04.7   +46 43 44     0.868    1.611  120.7   31.7    88   13.6 
2025-12-19 00:00 UT   01 03 37.2   +45 49 12     0.898    1.628  119.7   31.7    86   13.7 
2025-12-20 00:00 UT   01 02 22.2   +44 58 13     0.928    1.645  118.6   31.7    85   13.8 

    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.