161P/Hartley-IRAS
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Today	10 May 2026	17.8	2.778 AU	3.356 AU	02h36m	-29°19'	47.7°	15.6°	191°
Nearest approach	2 Oct 2026	9.6	1.483 AU	0.505 AU	23h14m	-05°52'	158.7°	14.2°	65°
Perihelion	27 Nov 2026	10.8	1.265 AU	1.406 AU	19h18m	+19°10'	60.9°	42.9°	51°

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. (8.5 + 5 log[∆] + 15.0 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 161P/Hartley-IRAS are:

    e (Eccentricity)                : 0.8361580
    q (Perihelion distance)         : 1.2651250
    i (Inclination)                 : 95.79030
    Ω (Longitude of ascending node) : 1.47600
    ω (Argument of perihelion)      : 47.07120
    L (Longitude of perihelion)     : 355.28596
    B (Latitude of perihelion)      : 46.75785
    T (Time of perihelion passage)  : 2461372.01290
    P (Orbital period in years)     : 21.46

    Epoch                           : 2026 May 10
    Reference                       : MPC191607

    Classification(s):              : Nearly isotropic; Returning (a < 10000 AU); Halley type (P < 200 years)

Ephemerides

Date       Time       RA (2000)    DEC (2000)    delta   radius  elong  phase   PA    magn
2026-05-09 00:00 UT   02 35 10.2   -29 40 47     3.379    2.795   47.3   15.4   189   17.8 
2026-05-10 00:00 UT   02 35 55.9   -29 29 22     3.367    2.786   47.5   15.5   190   17.8 
2026-05-10 20:59 UT   02 36 35.9   -29 19 29     3.356    2.778   47.7   15.6   191   17.8 
2026-05-11 00:00 UT   02 36 41.7   -29 18 04     3.354    2.777   47.7   15.6   191   17.8 
2026-05-12 00:00 UT   02 37 27.4   -29 06 51     3.341    2.767   47.9   15.7   192   17.8 
2026-05-13 00:00 UT   02 38 13.2   -28 55 46     3.328    2.758   48.1   15.8   193   17.7 
2026-05-14 00:00 UT   02 38 58.9   -28 44 46     3.315    2.749   48.4   15.9   194   17.7 
2026-05-15 00:00 UT   02 39 44.7   -28 33 52     3.302    2.740   48.6   16.1   195   17.7 
2026-05-16 00:00 UT   02 40 30.4   -28 23 05     3.288    2.730   48.8   16.2   196   17.6 
2026-05-17 00:00 UT   02 41 16.1   -28 12 24     3.274    2.721   49.1   16.3   196   17.6 
2026-05-18 00:00 UT   02 42 01.7   -28 01 50     3.260    2.712   49.3   16.4   197   17.6 
2026-05-19 00:00 UT   02 42 47.2   -27 51 22     3.246    2.703   49.6   16.6   198   17.5 
2026-05-20 00:00 UT   02 43 32.7   -27 40 60     3.232    2.693   49.9   16.7   199   17.5 

    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.