| 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
$$
M_a = (0.603 + 6.000\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
0.603 |
| n |
6.000 |
| gf |
0.913 |
| gb |
-0.916 |
| k |
1.000 |
| δ90 |
8.803 |
| 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 |
| 2021-09-08 |
2024-01-01 |
+9.2478 |
-7.921 |
| 2024-01-02 |
2026-02-23 |
+17.3082 |
-14.299 |
log10 r = log10(heliocentric distance / AU), Δ = geocentric distance (AU)
Ephemeris
| Date/Time (UTC) |
RA (J2000) |
Dec (J2000) |
Nearest HIP |
Dist from HIP (arcmin) |
| 2026-06-01 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 |
| 2026-06-02 12:00 |
09:14:08.05 |
+29:00:58.7 |
HIP 45157 |
29.87 |
| 2026-06-03 00:00 |
09:14:19.68 |
+28:59:17.4 |
HIP 45157 |
31.90 |
| 2026-06-03 12:00 |
09:14:31.39 |
+28:57:36.0 |
HIP 45157 |
34.11 |
| 2026-06-04 00:00 |
09:14:43.17 |
+28:55:54.4 |
HIP 45157 |
36.46 |
| 2026-06-04 12:00 |
09:14:55.03 |
+28:54:12.7 |
HIP 45157 |
38.93 |
| 2026-06-05 00:00 |
09:15:06.97 |
+28:52:30.9 |
HIP 45617 |
41.06 |
| 2026-06-05 12:00 |
09:15:18.98 |
+28:50:49.0 |
HIP 45617 |
37.94 |
| 2026-06-06 00:00 |
09:15:31.06 |
+28:49:06.9 |
HIP 45617 |
34.82 |
| 2026-06-06 12:00 |
09:15:43.22 |
+28:47:24.8 |
HIP 45617 |
31.68 |
| 2026-06-07 00:00 |
09:15:55.45 |
+28:45:42.5 |
HIP 45617 |
28.53 |
| 2026-06-07 12:00 |
09:16:07.75 |
+28:44:00.1 |
HIP 45617 |
25.37 |
| 2026-06-08 00:00 |
09:16:20.12 |
+28:42:17.6 |
HIP 45617 |
22.20 |
| 2026-06-08 12:00 |
09:16:32.56 |
+28:40:34.9 |
HIP 45617 |
19.03 |
| 2026-06-09 00:00 |
09:16:45.08 |
+28:38:52.2 |
HIP 45617 |
15.87 |
| 2026-06-09 12:00 |
09:16:57.66 |
+28:37:09.3 |
HIP 45617 |
12.72 |
| 2026-06-10 00:00 |
09:17:10.31 |
+28:35:26.4 |
HIP 45617 |
9.62 |
| 2026-06-10 12:00 |
09:17:23.03 |
+28:33:43.3 |
HIP 45617 |
6.67 |
| 2026-06-11 00:00 |
09:17:35.82 |
+28:32:00.2 |
HIP 45617 |
4.22 |
| 2026-06-11 12:00 |
09:17:48.68 |
+28:30:16.9 |
HIP 45617 |
3.58 |
| 2026-06-12 00:00 |
09:18:01.60 |
+28:28:33.6 |
HIP 45617 |
5.45 |
| 2026-06-12 12:00 |
09:18:14.59 |
+28:26:50.1 |
HIP 45617 |
8.30 |
| 2026-06-13 00:00 |
09:18:27.65 |
+28:25:06.6 |
HIP 45617 |
11.42 |
| 2026-06-13 12:00 |
09:18:40.77 |
+28:23:23.0 |
HIP 45617 |
14.66 |
| 2026-06-14 00:00 |
09:18:53.95 |
+28:21:39.3 |
HIP 45767 |
14.66 |
| 2026-06-14 12:00 |
09:19:07.20 |
+28:19:55.5 |
HIP 45767 |
11.41 |
| 2026-06-15 00:00 |
09:19:20.51 |
+28:18:11.6 |
HIP 45767 |
8.26 |
| 2026-06-15 12:00 |
09:19:33.89 |
+28:16:27.7 |
HIP 45767 |
5.40 |
| 2026-06-16 00:00 |
09:19:47.32 |
+28:14:43.6 |
HIP 45767 |
3.66 |
| 2026-06-16 12:00 |
09:20:00.82 |
+28:12:59.5 |
HIP 45767 |
4.60 |
| 2026-06-17 00:00 |
09:20:14.38 |
+28:11:15.4 |
HIP 45767 |
7.26 |
| 2026-06-17 12:00 |
09:20:28.00 |
+28:09:31.1 |
HIP 45767 |
10.41 |
| 2026-06-18 00:00 |
09:20:41.67 |
+28:07:46.8 |
HIP 45767 |
13.73 |
| 2026-06-18 12:00 |
09:20:55.41 |
+28:06:02.4 |
HIP 45767 |
17.12 |
| 2026-06-19 00:00 |
09:21:09.20 |
+28:04:18.0 |
HIP 45767 |
20.55 |
| 2026-06-19 12:00 |
09:21:23.05 |
+28:02:33.5 |
HIP 45767 |
24.02 |
| 2026-06-20 00:00 |
09:21:36.95 |
+28:00:49.0 |
HIP 45988 |
27.25 |
| 2026-06-20 12:00 |
09:21:50.91 |
+27:59:04.4 |
HIP 45988 |
24.16 |
| 2026-06-21 00:00 |
09:22:04.92 |
+27:57:19.8 |
HIP 45988 |
21.22 |
| 2026-06-21 12:00 |
09:22:18.99 |
+27:55:35.1 |
HIP 45988 |
18.49 |
| 2026-06-22 00:00 |
09:22:33.11 |
+27:53:50.3 |
HIP 45988 |
16.08 |