| Parameter |
Value |
| Designation |
C/2020 U3 (Rankin) |
| Type |
C |
| Perihelion (tp_cal, UTC) |
2021-02-05T23:23:23.781120Z |
| Orbit solution date (soln_date, UTC) |
2023-04-24T19:06:41Z |
| Obs used |
178 |
| NEO |
- |
| M1 |
9.700 |
| K1 |
22.000 |
| PC |
- |
| Discovery observation (MPC, UTC) |
2020-10-22T03:37:43.852800Z |
| Discovery magnitude (MPC) |
20.14 G |
| Discovery observatory (MPC) |
G96 · Mt. Lemmon Survey |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
2020-11-22.0000000 |
| e |
0.96479330 |
| q (au) |
2.276177 |
| a (au) |
64.651799 |
| i (deg) |
30.176991 |
| Ω (om, deg) |
282.679092 |
| ω (w, deg) |
124.262013 |
| M (ma, deg) |
359.855954 |
Magnitude
Scatter + Global Linear
$$
M_a = (11.589 + 6.000\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
11.589 |
| n |
6.000 |
| gf |
1.000 |
| gb |
-0.500 |
| k |
1.000 |
| δ90 |
10.000 |
| Parameter |
Symbol |
Range |
Description |
| Absolute magnitude at 1 AU from Sun and Earth |
H0 |
-5 to 20 |
Intrinsic brightness of the comet |
| Photometric slope parameter |
n |
2 to 6 |
Rate of brightness change with heliocentric distance |
| Forward scattering asymmetry factor |
gf |
0.8 to 1 |
Degree of forward scattering |
| Backward scattering asymmetry factor |
gb |
-1 to -0.5 |
Degree of backward scattering |
| Partitioning coefficient |
k |
0.8 to 1 |
Ratio between forward/backward scattering contributions |
| Dust-to-gas brightness ratio |
δ90 |
1 to 10 |
Relative contribution of dust scattering to gas emission |
Reference: EPSC-DPS2025-160
Residuals (Piecewise)
$$\epsilon = a \log_{10} r_{\mathrm{au}} + b$$
| Start (UTC) |
End (UTC) |
a |
b |
| 2020-07-21 |
2021-02-05 |
+3.5360 |
-1.291 |
| 2021-02-07 |
2021-10-31 |
+2.0235 |
-1.913 |
log10 r = log10(heliocentric distance / AU), Δ = geocentric distance (AU)
Ephemeris
| Date/Time (UTC) |
RA (J2000) |
Dec (J2000) |
Nearest HIP |
Dist from HIP (arcmin) |
| 2026-05-12 00:00 |
10:58:27.76 |
-27:16:01.7 |
HIP 53724 |
19.17 |
| 2026-05-12 12:00 |
10:58:25.71 |
-27:14:52.6 |
HIP 53724 |
20.29 |
| 2026-05-13 00:00 |
10:58:23.73 |
-27:13:43.7 |
HIP 53724 |
21.41 |
| 2026-05-13 12:00 |
10:58:21.82 |
-27:12:34.9 |
HIP 53724 |
22.53 |
| 2026-05-14 00:00 |
10:58:19.98 |
-27:11:26.3 |
HIP 53724 |
23.65 |
| 2026-05-14 12:00 |
10:58:18.21 |
-27:10:18.0 |
HIP 53724 |
24.76 |
| 2026-05-15 00:00 |
10:58:16.52 |
-27:09:09.8 |
HIP 53724 |
25.87 |
| 2026-05-15 12:00 |
10:58:14.90 |
-27:08:01.8 |
HIP 53712 |
26.81 |
| 2026-05-16 00:00 |
10:58:13.35 |
-27:06:54.1 |
HIP 53712 |
26.10 |
| 2026-05-16 12:00 |
10:58:11.87 |
-27:05:46.5 |
HIP 53712 |
25.42 |
| 2026-05-17 00:00 |
10:58:10.47 |
-27:04:39.2 |
HIP 53712 |
24.77 |
| 2026-05-17 12:00 |
10:58:09.14 |
-27:03:32.1 |
HIP 53712 |
24.15 |
| 2026-05-18 00:00 |
10:58:07.88 |
-27:02:25.3 |
HIP 53712 |
23.56 |
| 2026-05-18 12:00 |
10:58:06.69 |
-27:01:18.7 |
HIP 53712 |
23.01 |
| 2026-05-19 00:00 |
10:58:05.57 |
-27:00:12.3 |
HIP 53712 |
22.48 |
| 2026-05-19 12:00 |
10:58:04.53 |
-26:59:06.2 |
HIP 53712 |
22.00 |
| 2026-05-20 00:00 |
10:58:03.56 |
-26:58:00.4 |
HIP 53712 |
21.55 |
| 2026-05-20 12:00 |
10:58:02.66 |
-26:56:54.8 |
HIP 53712 |
21.14 |
| 2026-05-21 00:00 |
10:58:01.83 |
-26:55:49.5 |
HIP 53712 |
20.77 |
| 2026-05-21 12:00 |
10:58:01.07 |
-26:54:44.5 |
HIP 53712 |
20.44 |
| 2026-05-22 00:00 |
10:58:00.39 |
-26:53:39.7 |
HIP 53712 |
20.15 |
| 2026-05-22 12:00 |
10:57:59.78 |
-26:52:35.2 |
HIP 53712 |
19.90 |
| 2026-05-23 00:00 |
10:57:59.24 |
-26:51:31.1 |
HIP 53712 |
19.70 |
| 2026-05-23 12:00 |
10:57:58.77 |
-26:50:27.2 |
HIP 53712 |
19.54 |
| 2026-05-24 00:00 |
10:57:58.37 |
-26:49:23.6 |
HIP 53712 |
19.42 |
| 2026-05-24 12:00 |
10:57:58.05 |
-26:48:20.4 |
HIP 53712 |
19.34 |
| 2026-05-25 00:00 |
10:57:57.79 |
-26:47:17.4 |
HIP 53712 |
19.31 |
| 2026-05-25 12:00 |
10:57:57.61 |
-26:46:14.8 |
HIP 53712 |
19.31 |
| 2026-05-26 00:00 |
10:57:57.50 |
-26:45:12.5 |
HIP 53712 |
19.36 |
| 2026-05-26 12:00 |
10:57:57.46 |
-26:44:10.5 |
HIP 53712 |
19.45 |
| 2026-05-27 00:00 |
10:57:57.49 |
-26:43:08.8 |
HIP 53712 |
19.57 |
| 2026-05-27 12:00 |
10:57:57.59 |
-26:42:07.5 |
HIP 53712 |
19.73 |
| 2026-05-28 00:00 |
10:57:57.76 |
-26:41:06.5 |
HIP 53712 |
19.93 |
| 2026-05-28 12:00 |
10:57:58.00 |
-26:40:05.9 |
HIP 53712 |
20.15 |
| 2026-05-29 00:00 |
10:57:58.31 |
-26:39:05.6 |
HIP 53712 |
20.41 |
| 2026-05-29 12:00 |
10:57:58.69 |
-26:38:05.7 |
HIP 53712 |
20.70 |
| 2026-05-30 00:00 |
10:57:59.14 |
-26:37:06.1 |
HIP 53712 |
21.01 |
| 2026-05-30 12:00 |
10:57:59.66 |
-26:36:06.8 |
HIP 53712 |
21.35 |
| 2026-05-31 00:00 |
10:58:00.25 |
-26:35:08.0 |
HIP 53712 |
21.72 |
| 2026-05-31 12:00 |
10:58:00.91 |
-26:34:09.5 |
HIP 53712 |
22.10 |
| 2026-06-01 00:00 |
10:58:01.64 |
-26:33:11.4 |
HIP 53712 |
22.51 |
| 2026-06-01 12:00 |
10:58:02.44 |
-26:32:13.6 |
HIP 53712 |
22.93 |
| 2026-06-02 00:00 |
10:58:03.31 |
-26:31:16.2 |
HIP 53712 |
23.38 |