C/2019 K4 (Ye)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Perihelion	15 Jun 2019	16.8	2.276 AU	2.719 AU	01h25m	+42°56'	54.0°	21.2°	271°
Nearest approach	17 Sep 2019	16.0	2.510 AU	1.525 AU	00h13m	+09°07'	165.1°	5.9°	219°
Today	5 Dec 2025	29.7	17.514 AU	17.824 AU	09h56m	-79°59'	70.1°	3.0°	286°

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 11.1 + 5 log[∆] + 10.0 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/2019 K4 (Ye) are:

    e (Eccentricity)                : 0.9986250
    q (Perihelion distance)         : 2.2757280
    i (Inclination)                 : 105.28280
    Ω (Longitude of ascending node) : 180.33940
    ω (Argument of perihelion)      : 140.03270
    L (Longitude of perihelion)     : 192.79690
    B (Latitude of perihelion)      : 38.28946
    T (Time of perihelion passage)  : 2458649.87620
    P (Orbital period in years)     : 67332.77

    Epoch                           : 2025 Nov 12
    Reference                       : MPC119997

    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
2025-12-04 00:00 UT   09 57 17.9   -79 56 05    17.818   17.507   70.0    3.0   285   29.7 
2025-12-05 00:00 UT   09 57 02.1   -79 58 59    17.823   17.513   70.1    3.0   286   29.7 
2025-12-05 04:17 UT   09 56 59.1   -79 59 30    17.824   17.514   70.1    3.0   286   29.7 
2025-12-06 00:00 UT   09 56 44.8   -80 01 51    17.827   17.518   70.2    3.0   287   29.7 
2025-12-07 00:00 UT   09 56 26.2   -80 04 43    17.832   17.523   70.2    3.0   288   29.7 
2025-12-08 00:00 UT   09 56 06.2   -80 07 33    17.836   17.529   70.3    3.0   289   29.7 
2025-12-09 00:00 UT   09 55 44.8   -80 10 22    17.840   17.534   70.4    3.0   290   29.7 
2025-12-10 00:00 UT   09 55 21.9   -80 13 10    17.844   17.540   70.4    3.0   291   29.7 
2025-12-11 00:00 UT   09 54 57.7   -80 15 56    17.848   17.545   70.5    3.0   293   29.7 
2025-12-12 00:00 UT   09 54 32.0   -80 18 41    17.852   17.550   70.6    3.0   294   29.8 
2025-12-13 00:00 UT   09 54 04.9   -80 21 24    17.856   17.556   70.7    3.0   295   29.8 
2025-12-14 00:00 UT   09 53 36.3   -80 24 06    17.860   17.561   70.8    3.0   296   29.8 
2025-12-15 00:00 UT   09 53 06.3   -80 26 46    17.863   17.567   70.9    3.0   297   29.8 

    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.