C/2021 U5 (Catalina)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Perihelion	27 Jan 2022	17.8	2.359 AU	1.623 AU	10h19m	-27°14'	127.9°	19.2°	329°
Nearest approach	3 Mar 2022	17.6	2.392 AU	1.460 AU	10h16m	-16°58'	154.2°	10.4°	24°
Today	13 Jan 2026	29.3	12.061 AU	12.792 AU	18h13m	+13°02'	40.5°	3.0°	328°

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. (13.0 + 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/2021 U5 (Catalina) are:

    e (Eccentricity)                : 0.9894950
    q (Perihelion distance)         : 2.3590130
    i (Inclination)                 : 39.03930
    Ω (Longitude of ascending node) : 182.65170
    ω (Argument of perihelion)      : 321.48520
    L (Longitude of perihelion)     : 150.92925
    B (Latitude of perihelion)      : -23.09272
    T (Time of perihelion passage)  : 2459606.62630
    P (Orbital period in years)     : 3365.13

    Epoch                           : 2025 Nov 12
    Reference                       : MPEC 2022-WQ9

    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
2026-01-12 00:00 UT   18 12 57.9   +13 00 30    12.789   12.051   39.9    3.0   330   29.3 
2026-01-13 00:00 UT   18 13 19.4   +13 01 34    12.791   12.057   40.2    3.0   329   29.3 
2026-01-13 17:06 UT   18 13 34.6   +13 02 21    12.792   12.061   40.5    3.0   328   29.3 
2026-01-14 00:00 UT   18 13 40.8   +13 02 41    12.792   12.063   40.6    3.0   328   29.3 
2026-01-15 00:00 UT   18 14 02.0   +13 03 50    12.794   12.069   41.0    3.1   326   29.4 
2026-01-16 00:00 UT   18 14 23.2   +13 05 02    12.795   12.075   41.4    3.1   325   29.4 
2026-01-17 00:00 UT   18 14 44.2   +13 06 16    12.796   12.081   41.8    3.1   324   29.4 
2026-01-18 00:00 UT   18 15 05.1   +13 07 33    12.797   12.088   42.3    3.1   323   29.4 
2026-01-19 00:00 UT   18 15 25.8   +13 08 52    12.798   12.094   42.7    3.2   321   29.4 
2026-01-20 00:00 UT   18 15 46.5   +13 10 14    12.799   12.100   43.2    3.2   320   29.4 
2026-01-21 00:00 UT   18 16 06.9   +13 11 39    12.799   12.106   43.6    3.2   319   29.4 
2026-01-22 00:00 UT   18 16 27.2   +13 13 06    12.799   12.112   44.1    3.2   318   29.4 
2026-01-23 00:00 UT   18 16 47.4   +13 14 35    12.799   12.119   44.6    3.3   317   29.4 

    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.