C/2021 S4 (Tsuchinshan)
| Parameter |
Value |
| Designation |
C/2021 S4 (Tsuchinshan) |
| Type |
C |
| Perihelion (tp_cal, UTC) |
2024-01-02T07:59:01.633920Z |
| Orbit solution date (soln_date, UTC) |
2025-04-11T14:44:24Z |
| Obs used |
1150 |
| NEO |
- |
| M1 |
6.400 |
| K1 |
9.250 |
| PC |
0.030 |
| Discovery observation (MPC, UTC) |
2021-09-29T18:31:15.744000Z |
| Discovery magnitude (MPC) |
20.50 R |
| Discovery observatory (MPC) |
D29 · Purple Mountain Observatory, XuYi Station |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
2023-10-20.0000000 |
| e |
0.95934147 |
| q (au) |
6.689326 |
| a (au) |
164.524534 |
| i (deg) |
17.478958 |
| Ω (om, deg) |
5.490988 |
| ω (w, deg) |
72.869064 |
| M (ma, deg) |
359.965283 |
Magnitude
Scatter + Global Linear
$$
M_a = (0.704 + 6.000\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
0.704 |
| n |
6.000 |
| gf |
0.892 |
| gb |
-0.916 |
| k |
1.000 |
| δ90 |
5.113 |
| 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 |
09:18:23.07 |
+32:34:31.8 |
HIP 45517 |
32.89 |
| 2026-02-03 12:00 |
09:18:11.90 |
+32:34:54.8 |
HIP 45517 |
31.61 |
| 2026-02-04 00:00 |
09:18:00.74 |
+32:35:17.2 |
HIP 45517 |
30.46 |
| 2026-02-04 12:00 |
09:17:49.57 |
+32:35:38.9 |
HIP 45517 |
29.44 |
| 2026-02-05 00:00 |
09:17:38.41 |
+32:36:00.0 |
HIP 45517 |
28.58 |
| 2026-02-05 12:00 |
09:17:27.24 |
+32:36:20.2 |
HIP 45517 |
27.89 |
| 2026-02-06 00:00 |
09:17:16.08 |
+32:36:39.9 |
HIP 45517 |
27.38 |
| 2026-02-06 12:00 |
09:17:04.92 |
+32:36:58.9 |
HIP 45517 |
27.06 |
| 2026-02-07 00:00 |
09:16:53.77 |
+32:37:17.1 |
HIP 45517 |
26.93 |
| 2026-02-07 12:00 |
09:16:42.63 |
+32:37:34.7 |
HIP 45374 |
25.17 |
| 2026-02-08 00:00 |
09:16:31.50 |
+32:37:51.6 |
HIP 45374 |
22.85 |
| 2026-02-08 12:00 |
09:16:20.39 |
+32:38:07.7 |
HIP 45374 |
20.55 |
| 2026-02-09 00:00 |
09:16:09.28 |
+32:38:23.2 |
HIP 45374 |
18.26 |
| 2026-02-09 12:00 |
09:15:58.20 |
+32:38:37.9 |
HIP 45374 |
16.01 |
| 2026-02-10 00:00 |
09:15:47.13 |
+32:38:51.9 |
HIP 45374 |
13.79 |
| 2026-02-10 12:00 |
09:15:36.08 |
+32:39:05.2 |
HIP 45374 |
11.62 |
| 2026-02-11 00:00 |
09:15:25.05 |
+32:39:17.7 |
HIP 45374 |
9.56 |
| 2026-02-11 12:00 |
09:15:14.05 |
+32:39:29.6 |
HIP 45374 |
7.65 |
| 2026-02-12 00:00 |
09:15:03.07 |
+32:39:40.6 |
HIP 45374 |
6.06 |
| 2026-02-12 12:00 |
09:14:52.12 |
+32:39:51.0 |
HIP 45374 |
5.08 |
| 2026-02-13 00:00 |
09:14:41.19 |
+32:40:00.5 |
HIP 45374 |
5.06 |
| 2026-02-13 12:00 |
09:14:30.30 |
+32:40:09.4 |
HIP 45374 |
6.01 |
| 2026-02-14 00:00 |
09:14:19.44 |
+32:40:17.4 |
HIP 45374 |
7.57 |
| 2026-02-14 12:00 |
09:14:08.61 |
+32:40:24.7 |
HIP 45374 |
9.42 |
| 2026-02-15 00:00 |
09:13:57.82 |
+32:40:31.3 |
HIP 45374 |
11.43 |
| 2026-02-15 12:00 |
09:13:47.07 |
+32:40:37.1 |
HIP 45374 |
13.52 |
| 2026-02-16 00:00 |
09:13:36.36 |
+32:40:42.1 |
HIP 45374 |
15.66 |
| 2026-02-16 12:00 |
09:13:25.69 |
+32:40:46.3 |
HIP 45374 |
17.81 |
| 2026-02-17 00:00 |
09:13:15.06 |
+32:40:49.8 |
HIP 45374 |
19.98 |
| 2026-02-17 12:00 |
09:13:04.47 |
+32:40:52.5 |
HIP 45374 |
22.16 |
| 2026-02-18 00:00 |
09:12:53.94 |
+32:40:54.4 |
HIP 45374 |
24.34 |
| 2026-02-18 12:00 |
09:12:43.45 |
+32:40:55.5 |
HIP 45374 |
26.52 |
| 2026-02-19 00:00 |
09:12:33.01 |
+32:40:55.9 |
HIP 45374 |
28.69 |
| 2026-02-19 12:00 |
09:12:22.62 |
+32:40:55.4 |
HIP 45374 |
30.85 |
| 2026-02-20 00:00 |
09:12:12.29 |
+32:40:54.2 |
HIP 45374 |
33.01 |
| 2026-02-20 12:00 |
09:12:02.02 |
+32:40:52.2 |
HIP 44955 |
32.87 |
| 2026-02-21 00:00 |
09:11:51.79 |
+32:40:49.4 |
HIP 44955 |
30.81 |
| 2026-02-21 12:00 |
09:11:41.63 |
+32:40:45.8 |
HIP 44955 |
28.78 |
| 2026-02-22 00:00 |
09:11:31.53 |
+32:40:41.4 |
HIP 44955 |
26.78 |
| 2026-02-22 12:00 |
09:11:21.49 |
+32:40:36.2 |
HIP 44955 |
24.82 |
| 2026-02-23 00:00 |
09:11:11.52 |
+32:40:30.2 |
HIP 44955 |
22.90 |
| 2026-02-23 12:00 |
09:11:01.61 |
+32:40:23.4 |
HIP 44955 |
21.04 |
| 2026-02-24 00:00 |
09:10:51.76 |
+32:40:15.8 |
HIP 44955 |
19.24 |