389P/Siding Spring
| Parameter |
Value |
| Designation |
389P/Siding Spring |
| Type |
P |
| Perihelion (tp_cal, UTC) |
2020-01-02T20:23:08.842560Z |
| Orbit solution date (soln_date, UTC) |
2022-07-31T01:43:35Z |
| Obs used |
103 |
| NEO |
- |
| M1 |
14.300 |
| K1 |
19.500 |
| PC |
0.030 |
| Discovery observation (MPC, UTC) |
2019-09-25T12:36:33.696000Z |
| Discovery magnitude (MPC) |
20.50 w |
| Discovery observatory (MPC) |
F51 · Pan-STARRS 1, Haleakala |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
2013-11-08.0000000 |
| e |
0.70466929 |
| q (au) |
1.659623 |
| a (au) |
5.619542 |
| i (deg) |
160.071918 |
| Ω (om, deg) |
218.811242 |
| ω (w, deg) |
249.490302 |
| M (ma, deg) |
193.763391 |
Magnitude
Scatter + Global Linear
$$
M_a = (14.922 + 6.000\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
14.922 |
| n |
6.000 |
| gf |
1.000 |
| gb |
-0.937 |
| k |
0.999 |
| 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
Ephemeris
| Date/Time (UTC) |
RA (J2000) |
Dec (J2000) |
Nearest HIP |
Dist from HIP (arcmin) |
| 2026-02-03 00:00 |
11:08:26.81 |
+27:13:07.9 |
HIP 54644 |
34.73 |
| 2026-02-03 12:00 |
11:08:12.47 |
+27:15:11.8 |
HIP 54644 |
37.93 |
| 2026-02-04 00:00 |
11:07:58.04 |
+27:17:15.5 |
HIP 54644 |
41.25 |
| 2026-02-04 12:00 |
11:07:43.53 |
+27:19:18.9 |
HIP 54492 |
43.07 |
| 2026-02-05 00:00 |
11:07:28.93 |
+27:21:22.1 |
HIP 54492 |
42.54 |
| 2026-02-05 12:00 |
11:07:14.25 |
+27:23:25.0 |
HIP 54146 |
41.72 |
| 2026-02-06 00:00 |
11:06:59.50 |
+27:25:27.6 |
HIP 54146 |
37.86 |
| 2026-02-06 12:00 |
11:06:44.66 |
+27:27:29.9 |
HIP 54146 |
33.99 |
| 2026-02-07 00:00 |
11:06:29.75 |
+27:29:32.0 |
HIP 54146 |
30.10 |
| 2026-02-07 12:00 |
11:06:14.76 |
+27:31:33.7 |
HIP 54146 |
26.21 |
| 2026-02-08 00:00 |
11:05:59.70 |
+27:33:35.1 |
HIP 54146 |
22.31 |
| 2026-02-08 12:00 |
11:05:44.56 |
+27:35:36.1 |
HIP 54146 |
18.40 |
| 2026-02-09 00:00 |
11:05:29.35 |
+27:37:36.8 |
HIP 54146 |
14.49 |
| 2026-02-09 12:00 |
11:05:14.07 |
+27:39:37.1 |
HIP 54146 |
10.57 |
| 2026-02-10 00:00 |
11:04:58.72 |
+27:41:37.0 |
HIP 54146 |
6.66 |
| 2026-02-10 12:00 |
11:04:43.29 |
+27:43:36.6 |
HIP 54146 |
2.85 |
| 2026-02-11 00:00 |
11:04:27.81 |
+27:45:35.7 |
HIP 54146 |
1.78 |
| 2026-02-11 12:00 |
11:04:12.25 |
+27:47:34.5 |
HIP 54146 |
5.45 |
| 2026-02-12 00:00 |
11:03:56.63 |
+27:49:32.8 |
HIP 54146 |
9.38 |
| 2026-02-12 12:00 |
11:03:40.95 |
+27:51:30.6 |
HIP 54146 |
13.34 |
| 2026-02-13 00:00 |
11:03:25.21 |
+27:53:28.0 |
HIP 53932 |
16.98 |
| 2026-02-13 12:00 |
11:03:09.40 |
+27:55:25.0 |
HIP 53932 |
13.79 |
| 2026-02-14 00:00 |
11:02:53.54 |
+27:57:21.4 |
HIP 53932 |
11.12 |
| 2026-02-14 12:00 |
11:02:37.62 |
+27:59:17.4 |
HIP 53932 |
9.43 |
| 2026-02-15 00:00 |
11:02:21.65 |
+28:01:12.8 |
HIP 53932 |
9.29 |
| 2026-02-15 12:00 |
11:02:05.61 |
+28:03:07.8 |
HIP 53932 |
10.76 |
| 2026-02-16 00:00 |
11:01:49.53 |
+28:05:02.2 |
HIP 53932 |
13.32 |
| 2026-02-16 12:00 |
11:01:33.40 |
+28:06:56.1 |
HIP 53932 |
16.48 |
| 2026-02-17 00:00 |
11:01:17.21 |
+28:08:49.4 |
HIP 53932 |
19.96 |
| 2026-02-17 12:00 |
11:01:00.98 |
+28:10:42.1 |
HIP 53722 |
20.42 |
| 2026-02-18 00:00 |
11:00:44.70 |
+28:12:34.3 |
HIP 53722 |
17.33 |
| 2026-02-18 12:00 |
11:00:28.37 |
+28:14:25.9 |
HIP 53722 |
14.70 |
| 2026-02-19 00:00 |
11:00:12.01 |
+28:16:16.9 |
HIP 53722 |
12.82 |
| 2026-02-19 12:00 |
10:59:55.60 |
+28:18:07.2 |
HIP 53722 |
12.04 |
| 2026-02-20 00:00 |
10:59:39.15 |
+28:19:57.0 |
HIP 53722 |
12.58 |
| 2026-02-20 12:00 |
10:59:22.66 |
+28:21:46.1 |
HIP 53722 |
14.30 |
| 2026-02-21 00:00 |
10:59:06.13 |
+28:23:34.6 |
HIP 53722 |
16.83 |
| 2026-02-21 12:00 |
10:58:49.57 |
+28:25:22.4 |
HIP 53722 |
19.87 |
| 2026-02-22 00:00 |
10:58:32.98 |
+28:27:09.5 |
HIP 53722 |
23.22 |
| 2026-02-22 12:00 |
10:58:16.35 |
+28:28:56.0 |
HIP 53722 |
26.76 |
| 2026-02-23 00:00 |
10:57:59.70 |
+28:30:41.8 |
HIP 53541 |
27.73 |
| 2026-02-23 12:00 |
10:57:43.01 |
+28:32:26.8 |
HIP 53541 |
24.86 |
| 2026-02-24 00:00 |
10:57:26.30 |
+28:34:11.2 |
HIP 53541 |
22.37 |