C/2025 D1 (Groeller)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Today	7 Jan 2026	18.6	14.660 AU	13.809 AU	09h25m	+33°17'	148.9°	2.0°	258°
Nearest approach	3 Feb 2028	18.3	14.126 AU	13.142 AU	08h58m	+13°41'	176.6°	0.2°	32°
Perihelion	21 May 2028	18.5	14.117 AU	14.443 AU	08h41m	+12°16'	69.3°	3.8°	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. 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)                : 1.0031540
    q (Perihelion distance)         : 14.1173640
    i (Inclination)                 : 84.45370
    Ω (Longitude of ascending node) : 312.90220
    ω (Argument of perihelion)      : 185.92760
    L (Longitude of perihelion)     : 313.47714
    B (Latitude of perihelion)      : -5.89975
    T (Time of perihelion passage)  : 2461912.83110

    Epoch                           : 2026 Jan 06
    Reference                       : MPEC 2025-UQ3

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

Ephemerides

Date       Time       RA (2000)    DEC (2000)    delta   radius  elong  phase   PA    magn
2026-01-06 00:00 UT   09 25 35.9   +33 17 08    13.822   14.662  147.6    2.1   260   18.6 
2026-01-07 00:00 UT   09 25 17.6   +33 17 27    13.813   14.661  148.5    2.0   259   18.6 
2026-01-07 11:14 UT   09 25 09.0   +33 17 35    13.809   14.660  148.9    2.0   258   18.6 
2026-01-08 00:00 UT   09 24 59.2   +33 17 45    13.805   14.660  149.4    2.0   257   18.6 
2026-01-09 00:00 UT   09 24 40.5   +33 18 02    13.796   14.659  150.3    1.9   256   18.6 
2026-01-10 00:00 UT   09 24 21.6   +33 18 19    13.788   14.657  151.2    1.9   255   18.6 
2026-01-11 00:00 UT   09 24 02.5   +33 18 35    13.780   14.656  152.0    1.8   253   18.6 
2026-01-12 00:00 UT   09 23 43.2   +33 18 50    13.773   14.655  152.9    1.8   252   18.6 
2026-01-13 00:00 UT   09 23 23.8   +33 19 04    13.765   14.654  153.7    1.7   250   18.6 
2026-01-14 00:00 UT   09 23 04.1   +33 19 18    13.758   14.652  154.5    1.7   249   18.6 
2026-01-15 00:00 UT   09 22 44.3   +33 19 30    13.752   14.651  155.3    1.6   247   18.6 
2026-01-16 00:00 UT   09 22 24.3   +33 19 42    13.745   14.650  156.1    1.6   245   18.5 
2026-01-17 00:00 UT   09 22 04.2   +33 19 53    13.739   14.649  156.9    1.5   243   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.