C/2020 U3 (Rankin)
| 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) |
| 2026-02-03 00:00 |
11:19:31.95 |
-29:37:01.7 |
HIP 55450 |
24.40 |
| 2026-02-03 12:00 |
11:19:25.46 |
-29:37:18.1 |
HIP 55176 |
24.80 |
| 2026-02-04 00:00 |
11:19:18.91 |
-29:37:33.7 |
HIP 55176 |
23.75 |
| 2026-02-04 12:00 |
11:19:12.31 |
-29:37:48.5 |
HIP 55176 |
22.72 |
| 2026-02-05 00:00 |
11:19:05.67 |
-29:38:02.6 |
HIP 55176 |
21.72 |
| 2026-02-05 12:00 |
11:18:58.98 |
-29:38:15.9 |
HIP 55176 |
20.76 |
| 2026-02-06 00:00 |
11:18:52.24 |
-29:38:28.5 |
HIP 55176 |
19.85 |
| 2026-02-06 12:00 |
11:18:45.45 |
-29:38:40.3 |
HIP 55176 |
18.99 |
| 2026-02-07 00:00 |
11:18:38.61 |
-29:38:51.3 |
HIP 55176 |
18.20 |
| 2026-02-07 12:00 |
11:18:31.74 |
-29:39:01.6 |
HIP 55176 |
17.49 |
| 2026-02-08 00:00 |
11:18:24.81 |
-29:39:11.0 |
HIP 55176 |
16.86 |
| 2026-02-08 12:00 |
11:18:17.84 |
-29:39:19.8 |
HIP 55176 |
16.34 |
| 2026-02-09 00:00 |
11:18:10.83 |
-29:39:27.7 |
HIP 55176 |
15.93 |
| 2026-02-09 12:00 |
11:18:03.78 |
-29:39:34.8 |
HIP 55176 |
15.65 |
| 2026-02-10 00:00 |
11:17:56.68 |
-29:39:41.2 |
HIP 55176 |
15.49 |
| 2026-02-10 12:00 |
11:17:49.55 |
-29:39:46.8 |
HIP 55176 |
15.48 |
| 2026-02-11 00:00 |
11:17:42.37 |
-29:39:51.6 |
HIP 55176 |
15.62 |
| 2026-02-11 12:00 |
11:17:35.15 |
-29:39:55.7 |
HIP 55176 |
15.89 |
| 2026-02-12 00:00 |
11:17:27.90 |
-29:39:59.0 |
HIP 55176 |
16.30 |
| 2026-02-12 12:00 |
11:17:20.60 |
-29:40:01.4 |
HIP 55176 |
16.84 |
| 2026-02-13 00:00 |
11:17:13.27 |
-29:40:03.1 |
HIP 55176 |
17.51 |
| 2026-02-13 12:00 |
11:17:05.90 |
-29:40:04.1 |
HIP 55176 |
18.27 |
| 2026-02-14 00:00 |
11:16:58.50 |
-29:40:04.2 |
HIP 55008 |
17.05 |
| 2026-02-14 12:00 |
11:16:51.06 |
-29:40:03.6 |
HIP 55008 |
15.57 |
| 2026-02-15 00:00 |
11:16:43.58 |
-29:40:02.2 |
HIP 55008 |
14.11 |
| 2026-02-15 12:00 |
11:16:36.08 |
-29:40:00.0 |
HIP 55008 |
12.67 |
| 2026-02-16 00:00 |
11:16:28.54 |
-29:39:57.0 |
HIP 55008 |
11.27 |
| 2026-02-16 12:00 |
11:16:20.97 |
-29:39:53.2 |
HIP 55008 |
9.93 |
| 2026-02-17 00:00 |
11:16:13.37 |
-29:39:48.7 |
HIP 55008 |
8.69 |
| 2026-02-17 12:00 |
11:16:05.73 |
-29:39:43.4 |
HIP 55008 |
7.58 |
| 2026-02-18 00:00 |
11:15:58.07 |
-29:39:37.3 |
HIP 55008 |
6.70 |
| 2026-02-18 12:00 |
11:15:50.38 |
-29:39:30.4 |
HIP 55008 |
6.14 |
| 2026-02-19 00:00 |
11:15:42.67 |
-29:39:22.7 |
HIP 55008 |
6.00 |
| 2026-02-19 12:00 |
11:15:34.92 |
-29:39:14.3 |
HIP 55008 |
6.31 |
| 2026-02-20 00:00 |
11:15:27.15 |
-29:39:05.1 |
HIP 55008 |
7.01 |
| 2026-02-20 12:00 |
11:15:19.36 |
-29:38:55.2 |
HIP 54970 |
7.97 |
| 2026-02-21 00:00 |
11:15:11.54 |
-29:38:44.4 |
HIP 54970 |
8.07 |
| 2026-02-21 12:00 |
11:15:03.70 |
-29:38:32.9 |
HIP 54970 |
8.52 |
| 2026-02-22 00:00 |
11:14:55.84 |
-29:38:20.6 |
HIP 54970 |
9.26 |
| 2026-02-22 12:00 |
11:14:47.96 |
-29:38:07.6 |
HIP 54970 |
10.23 |
| 2026-02-23 00:00 |
11:14:40.05 |
-29:37:53.8 |
HIP 54970 |
11.38 |
| 2026-02-23 12:00 |
11:14:32.13 |
-29:37:39.3 |
HIP 54970 |
12.66 |
| 2026-02-24 00:00 |
11:14:24.19 |
-29:37:24.0 |
HIP 54970 |
14.03 |