| Parameter |
Value |
| Designation |
C/2021 S4 (Tsuchinshan) |
| Type |
C |
| Perihelion (tp_cal, UTC) |
2024-01-02T08:26:27.882240Z |
| Orbit solution date (soln_date, UTC) |
2026-03-07T14:42:53Z |
| Obs used |
1156 |
| 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) |
2023-10-25.0000000 |
| e |
0.95933247 |
| q (au) |
6.689317 |
| a (au) |
164.487891 |
| i (deg) |
17.478939 |
| Ω (om, deg) |
5.490839 |
| ω (w, deg) |
72.870717 |
| M (ma, deg) |
359.967599 |
Magnitude
Scatter + Global Linear
$$
M_a = (0.703 + 6.000\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
0.703 |
| n |
6.000 |
| gf |
0.892 |
| gb |
-0.917 |
| 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) |
| 2026-05-12 00:00 |
09:07:09.40 |
+30:10:54.7 |
HIP 44687 |
11.68 |
| 2026-05-12 12:00 |
09:07:17.13 |
+30:09:21.5 |
HIP 44687 |
13.92 |
| 2026-05-13 00:00 |
09:07:24.96 |
+30:07:48.1 |
HIP 44687 |
16.20 |
| 2026-05-13 12:00 |
09:07:32.89 |
+30:06:14.5 |
HIP 44856 |
16.81 |
| 2026-05-14 00:00 |
09:07:40.93 |
+30:04:40.6 |
HIP 44856 |
17.02 |
| 2026-05-14 12:00 |
09:07:49.08 |
+30:03:06.4 |
HIP 44856 |
17.55 |
| 2026-05-15 00:00 |
09:07:57.32 |
+30:01:32.0 |
HIP 44856 |
18.36 |
| 2026-05-15 12:00 |
09:08:05.66 |
+29:59:57.4 |
HIP 44856 |
19.43 |
| 2026-05-16 00:00 |
09:08:14.11 |
+29:58:22.5 |
HIP 44818 |
19.36 |
| 2026-05-16 12:00 |
09:08:22.65 |
+29:56:47.4 |
HIP 44818 |
18.21 |
| 2026-05-17 00:00 |
09:08:31.30 |
+29:55:12.1 |
HIP 44818 |
17.33 |
| 2026-05-17 12:00 |
09:08:40.04 |
+29:53:36.6 |
HIP 44818 |
16.77 |
| 2026-05-18 00:00 |
09:08:48.89 |
+29:52:00.8 |
HIP 44818 |
16.58 |
| 2026-05-18 12:00 |
09:08:57.83 |
+29:50:24.8 |
HIP 44818 |
16.78 |
| 2026-05-19 00:00 |
09:09:06.86 |
+29:48:48.6 |
HIP 44818 |
17.37 |
| 2026-05-19 12:00 |
09:09:16.00 |
+29:47:12.2 |
HIP 44818 |
18.30 |
| 2026-05-20 00:00 |
09:09:25.23 |
+29:45:35.5 |
HIP 44818 |
19.55 |
| 2026-05-20 12:00 |
09:09:34.55 |
+29:43:58.7 |
HIP 44818 |
21.05 |
| 2026-05-21 00:00 |
09:09:43.97 |
+29:42:21.6 |
HIP 44818 |
22.78 |
| 2026-05-21 12:00 |
09:09:53.48 |
+29:40:44.4 |
HIP 44818 |
24.68 |
| 2026-05-22 00:00 |
09:10:03.08 |
+29:39:07.0 |
HIP 44818 |
26.73 |
| 2026-05-22 12:00 |
09:10:12.78 |
+29:37:29.3 |
HIP 44818 |
28.89 |
| 2026-05-23 00:00 |
09:10:22.57 |
+29:35:51.5 |
HIP 44818 |
31.15 |
| 2026-05-23 12:00 |
09:10:32.45 |
+29:34:13.5 |
HIP 45049 |
30.01 |
| 2026-05-24 00:00 |
09:10:42.42 |
+29:32:35.3 |
HIP 45049 |
28.45 |
| 2026-05-24 12:00 |
09:10:52.48 |
+29:30:57.0 |
HIP 45049 |
27.08 |
| 2026-05-25 00:00 |
09:11:02.62 |
+29:29:18.4 |
HIP 45049 |
25.93 |
| 2026-05-25 12:00 |
09:11:12.86 |
+29:27:39.7 |
HIP 45049 |
25.04 |
| 2026-05-26 00:00 |
09:11:23.18 |
+29:26:00.8 |
HIP 45049 |
24.44 |
| 2026-05-26 12:00 |
09:11:33.59 |
+29:24:21.8 |
HIP 45049 |
24.16 |
| 2026-05-27 00:00 |
09:11:44.08 |
+29:22:42.6 |
HIP 45049 |
24.21 |
| 2026-05-27 12:00 |
09:11:54.66 |
+29:21:03.2 |
HIP 45049 |
24.60 |
| 2026-05-28 00:00 |
09:12:05.33 |
+29:19:23.6 |
HIP 45049 |
25.32 |
| 2026-05-28 12:00 |
09:12:16.08 |
+29:17:43.9 |
HIP 45157 |
25.76 |
| 2026-05-29 00:00 |
09:12:26.91 |
+29:16:04.1 |
HIP 45157 |
24.63 |
| 2026-05-29 12:00 |
09:12:37.82 |
+29:14:24.1 |
HIP 45157 |
23.80 |
| 2026-05-30 00:00 |
09:12:48.82 |
+29:12:43.9 |
HIP 45157 |
23.32 |
| 2026-05-30 12:00 |
09:12:59.90 |
+29:11:03.6 |
HIP 45157 |
23.21 |
| 2026-05-31 00:00 |
09:13:11.06 |
+29:09:23.1 |
HIP 45157 |
23.48 |
| 2026-05-31 12:00 |
09:13:22.30 |
+29:07:42.5 |
HIP 45157 |
24.13 |
| 2026-06-01 00:00 |
09:13:33.62 |
+29:06:01.8 |
HIP 45157 |
25.12 |
| 2026-06-01 12:00 |
09:13:45.02 |
+29:04:20.9 |
HIP 45157 |
26.44 |
| 2026-06-02 00:00 |
09:13:56.49 |
+29:02:39.8 |
HIP 45157 |
28.03 |