103P/Hartley
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Nearest approach	26 Sep 2023	9.6	1.089 AU	0.389 AU	06h01m	+34°40'	92.2°	66.9°	270°
Perihelion	12 Oct 2023	9.6	1.066 AU	0.411 AU	07h27m	+21°05'	88.0°	69.3°	279°
Today	7 Jan 2026	27.1	5.485 AU	5.730 AU	14h12m	-16°30'	70.7°	9.7°	288°

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[∆] + 16.6 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 103P/Hartley are:

    e (Eccentricity)                : 0.6933150
    q (Perihelion distance)         : 1.0660840
    i (Inclination)                 : 13.60430
    Ω (Longitude of ascending node) : 219.76150
    ω (Argument of perihelion)      : 181.33400
    L (Longitude of perihelion)     : 221.05809
    B (Latitude of perihelion)      : -0.31375
    T (Time of perihelion passage)  : 2460229.80760
    P (Orbital period in years)     : 6.48

    Epoch                           : 2026 Jan 07
    Reference                       : MPEC 2025-W75

    Classification(s):              : Ecliptic; Jupiter family
    Tisserand (Jupiter)             : 2.642

Ephemerides

Date       Time       RA (2000)    DEC (2000)    delta   radius  elong  phase   PA    magn
2026-01-06 00:00 UT   14 12 13.6   -16 27 15     5.756    5.480   68.9    9.6   288   27.1 
2026-01-07 00:00 UT   14 12 36.8   -16 29 08     5.743    5.483   69.9    9.7   288   27.1 
2026-01-07 22:53 UT   14 12 58.5   -16 30 53     5.730    5.485   70.7    9.7   288   27.1 
2026-01-08 00:00 UT   14 12 59.5   -16 30 58     5.729    5.485   70.8    9.7   288   27.1 
2026-01-09 00:00 UT   14 13 21.7   -16 32 45     5.716    5.487   71.7    9.8   288   27.1 
2026-01-10 00:00 UT   14 13 43.2   -16 34 29     5.702    5.489   72.6    9.8   288   27.1 
2026-01-11 00:00 UT   14 14 04.2   -16 36 11     5.688    5.491   73.6    9.9   289   27.1 
2026-01-12 00:00 UT   14 14 24.6   -16 37 49     5.674    5.494   74.5    9.9   289   27.1 
2026-01-13 00:00 UT   14 14 44.3   -16 39 24     5.660    5.496   75.4   10.0   289   27.1 
2026-01-14 00:00 UT   14 15 03.5   -16 40 56     5.646    5.498   76.4   10.0   289   27.1 
2026-01-15 00:00 UT   14 15 22.1   -16 42 25     5.632    5.500   77.3   10.0   289   27.1 
2026-01-16 00:00 UT   14 15 40.0   -16 43 51     5.618    5.503   78.2   10.1   289   27.1 
2026-01-17 00:00 UT   14 15 57.3   -16 45 13     5.604    5.505   79.2   10.1   289   27.1 

    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.