C/2025 D1 (Groeller)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Today	11 Nov 2026	18.5	14.345 AU	14.257 AU	09h25m	+24°10'	93.1°	4.0°	288°
Nearest approach	3 Feb 2028	18.3	14.124 AU	13.140 AU	08h58m	+13°41'	176.6°	0.2°	32°
Perihelion	23 May 2028	18.5	14.115 AU	14.479 AU	08h42m	+12°13'	67.0°	3.8°	108°

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. 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. (1.2 + 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/2025 D1 (Groeller) are:

    e (Eccentricity)                : 1.0032290
    q (Perihelion distance)         : 14.1146210
    i (Inclination)                 : 84.44710
    Ω (Longitude of ascending node) : 312.90380
    ω (Argument of perihelion)      : 185.99420
    L (Longitude of perihelion)     : 313.48593
    B (Latitude of perihelion)      : -5.96597
    T (Time of perihelion passage)  : 2461915.28810

    Epoch                           : 2026 Nov 11
    Reference                       : MPC194194

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

Ephemerides

Date       Time       RA (2000)    DEC (2000)    delta   radius  elong  phase   PA    magn
2026-11-10 00:00 UT   09 25 18.0   +24 12 09    14.292   14.346   91.1    4.0   288   18.5 
2026-11-11 00:00 UT   09 25 16.6   +24 11 18    14.274   14.346   92.1    4.0   288   18.5 
2026-11-11 23:08 UT   09 25 15.0   +24 10 30    14.257   14.345   93.1    4.0   288   18.5 
2026-11-12 00:00 UT   09 25 14.9   +24 10 28    14.257   14.345   93.1    4.0   288   18.5 
2026-11-13 00:00 UT   09 25 12.9   +24 09 39    14.239   14.344   94.1    3.9   288   18.5 
2026-11-14 00:00 UT   09 25 10.6   +24 08 52    14.221   14.343   95.1    3.9   288   18.5 
2026-11-15 00:00 UT   09 25 08.0   +24 08 06    14.203   14.342   96.1    3.9   287   18.5 
2026-11-16 00:00 UT   09 25 05.1   +24 07 21    14.185   14.342   97.1    3.9   287   18.5 
2026-11-17 00:00 UT   09 25 01.9   +24 06 37    14.167   14.341   98.1    3.9   287   18.5 
2026-11-18 00:00 UT   09 24 58.3   +24 05 55    14.150   14.340   99.1    3.9   287   18.5 
2026-11-19 00:00 UT   09 24 54.5   +24 05 13    14.132   14.339  100.2    3.9   287   18.5 
2026-11-20 00:00 UT   09 24 50.3   +24 04 33    14.114   14.338  101.2    3.9   287   18.5 
2026-11-21 00:00 UT   09 24 45.8   +24 03 54    14.097   14.337  102.2    3.9   286   18.5 

    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.