| Parameter |
Value |
| Designation |
C/2021 S4 (Tsuchinshan) |
| Type |
C |
| Perihelion (tp_cal, UTC) |
2024-01-02T08:21:02.681280Z |
| Orbit solution date (soln_date, UTC) |
2026-06-09T11:12:25Z |
| Obs used |
1159 |
| 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) |
2023-10-24.0000000 |
| e |
0.95933414 |
| q (au) |
6.689318 |
| a (au) |
164.494697 |
| i (deg) |
17.478943 |
| Ω (om, deg) |
5.490868 |
| ω (w, deg) |
72.870391 |
| M (ma, deg) |
359.967135 |
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) |
| 2026-07-29 00:00 |
09:41:45.42 |
+25:44:55.6 |
HIP 47550 |
9.97 |
| 2026-07-29 12:00 |
09:42:01.90 |
+25:43:13.4 |
HIP 47602 |
8.94 |
| 2026-07-30 00:00 |
09:42:18.39 |
+25:41:31.2 |
HIP 47602 |
6.14 |
| 2026-07-30 12:00 |
09:42:34.89 |
+25:39:49.2 |
HIP 47602 |
5.38 |
| 2026-07-31 00:00 |
09:42:51.40 |
+25:38:07.2 |
HIP 47602 |
7.32 |
| 2026-07-31 12:00 |
09:43:07.92 |
+25:36:25.4 |
HIP 47602 |
10.57 |
| 2026-08-01 00:00 |
09:43:24.44 |
+25:34:43.8 |
HIP 47602 |
14.27 |
| 2026-08-01 12:00 |
09:43:40.98 |
+25:33:02.2 |
HIP 47749 |
16.00 |
| 2026-08-02 00:00 |
09:43:57.52 |
+25:31:20.8 |
HIP 47749 |
13.48 |
| 2026-08-02 12:00 |
09:44:14.07 |
+25:29:39.5 |
HIP 47749 |
11.89 |
| 2026-08-03 00:00 |
09:44:30.62 |
+25:27:58.3 |
HIP 47749 |
11.59 |
| 2026-08-03 12:00 |
09:44:47.18 |
+25:26:17.3 |
HIP 47749 |
12.70 |
| 2026-08-04 00:00 |
09:45:03.75 |
+25:24:36.4 |
HIP 47749 |
14.90 |
| 2026-08-04 12:00 |
09:45:20.32 |
+25:22:55.7 |
HIP 47749 |
17.78 |
| 2026-08-05 00:00 |
09:45:36.90 |
+25:21:15.0 |
HIP 47749 |
21.08 |
| 2026-08-05 12:00 |
09:45:53.48 |
+25:19:34.6 |
HIP 47749 |
24.63 |
| 2026-08-06 00:00 |
09:46:10.06 |
+25:17:54.2 |
HIP 47749 |
28.33 |
| 2026-08-06 12:00 |
09:46:26.65 |
+25:16:14.0 |
HIP 48107 |
28.67 |
| 2026-08-07 00:00 |
09:46:43.24 |
+25:14:34.0 |
HIP 48107 |
24.68 |
| 2026-08-07 12:00 |
09:46:59.83 |
+25:12:54.1 |
HIP 48107 |
20.73 |
| 2026-08-08 00:00 |
09:47:16.42 |
+25:11:14.4 |
HIP 48107 |
16.86 |
| 2026-08-08 12:00 |
09:47:33.02 |
+25:09:34.8 |
HIP 48107 |
13.12 |
| 2026-08-09 00:00 |
09:47:49.61 |
+25:07:55.4 |
HIP 48107 |
9.68 |
| 2026-08-09 12:00 |
09:48:06.21 |
+25:06:16.1 |
HIP 48107 |
7.00 |
| 2026-08-10 00:00 |
09:48:22.80 |
+25:04:37.0 |
HIP 48107 |
6.16 |
| 2026-08-10 12:00 |
09:48:39.39 |
+25:02:58.1 |
HIP 48107 |
7.78 |
| 2026-08-11 00:00 |
09:48:55.98 |
+25:01:19.4 |
HIP 48107 |
10.80 |
| 2026-08-11 12:00 |
09:49:12.57 |
+24:59:40.8 |
HIP 48107 |
14.36 |
| 2026-08-12 00:00 |
09:49:29.16 |
+24:58:02.4 |
HIP 48107 |
18.15 |
| 2026-08-12 12:00 |
09:49:45.74 |
+24:56:24.2 |
HIP 48107 |
22.05 |
| 2026-08-13 00:00 |
09:50:02.32 |
+24:54:46.1 |
HIP 48248 |
21.13 |
| 2026-08-13 12:00 |
09:50:18.89 |
+24:53:08.3 |
HIP 48248 |
19.52 |
| 2026-08-14 00:00 |
09:50:35.46 |
+24:51:30.6 |
HIP 48248 |
18.68 |
| 2026-08-14 12:00 |
09:50:52.02 |
+24:49:53.2 |
HIP 48248 |
18.73 |
| 2026-08-15 00:00 |
09:51:08.57 |
+24:48:15.9 |
HIP 48248 |
19.66 |
| 2026-08-15 12:00 |
09:51:25.12 |
+24:46:38.8 |
HIP 48248 |
21.34 |
| 2026-08-16 00:00 |
09:51:41.66 |
+24:45:01.9 |
HIP 48390 |
21.44 |
| 2026-08-16 12:00 |
09:51:58.19 |
+24:43:25.3 |
HIP 48390 |
19.71 |
| 2026-08-17 00:00 |
09:52:14.72 |
+24:41:48.8 |
HIP 48390 |
18.73 |
| 2026-08-17 12:00 |
09:52:31.23 |
+24:40:12.5 |
HIP 48390 |
18.61 |
| 2026-08-18 00:00 |
09:52:47.74 |
+24:38:36.5 |
HIP 48390 |
19.38 |
| 2026-08-18 12:00 |
09:53:04.23 |
+24:37:00.7 |
HIP 48390 |
20.94 |
| 2026-08-19 00:00 |
09:53:20.71 |
+24:35:25.0 |
HIP 48390 |
23.11 |