| Parameter |
Value |
| Designation |
C/2025 K4 (Siverd) |
| Type |
C |
| Perihelion (tp_cal, UTC) |
2025-07-28T06:25:56.997120Z |
| Orbit solution date (soln_date, UTC) |
2025-12-12T11:12:30Z |
| Obs used |
29 |
| NEO |
- |
| M1 |
13.800 |
| K1 |
10.000 |
| PC |
- |
| Discovery observation (MPC, UTC) |
2025-05-30T22:52:21.100800Z |
| Discovery magnitude (MPC) |
19.15 o |
| Discovery observatory (MPC) |
M22 · ATLAS South Africa, Sutherland |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
2025-06-16.0000000 |
| e |
0.94157044 |
| q (au) |
2.532201 |
| a (au) |
43.337668 |
| i (deg) |
38.543416 |
| Ω (om, deg) |
297.083175 |
| ω (w, deg) |
326.935879 |
| M (ma, deg) |
359.853978 |
Magnitude
Scatter + Global Linear
$$
M_a = (10.661 + 6.000\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
10.661 |
| n |
6.000 |
| gf |
1.000 |
| gb |
-0.502 |
| k |
1.000 |
| 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) |
| 2026-03-26 00:00 |
21:54:58.59 |
+04:02:39.5 |
HIP 108112 |
19.48 |
| 2026-03-26 12:00 |
21:55:28.13 |
+04:09:07.2 |
HIP 108321 |
20.09 |
| 2026-03-27 00:00 |
21:55:57.55 |
+04:15:35.0 |
HIP 108321 |
18.48 |
| 2026-03-27 12:00 |
21:56:26.84 |
+04:22:02.9 |
HIP 108370 |
14.79 |
| 2026-03-28 00:00 |
21:56:56.02 |
+04:28:30.9 |
HIP 108370 |
15.35 |
| 2026-03-28 12:00 |
21:57:25.06 |
+04:34:59.0 |
HIP 108370 |
21.03 |
| 2026-03-29 00:00 |
21:57:53.99 |
+04:41:27.2 |
HIP 108395 |
19.96 |
| 2026-03-29 12:00 |
21:58:22.79 |
+04:47:55.5 |
HIP 108561 |
15.87 |
| 2026-03-30 00:00 |
21:58:51.46 |
+04:54:23.9 |
HIP 108561 |
11.67 |
| 2026-03-30 12:00 |
21:59:20.01 |
+05:00:52.3 |
HIP 108561 |
14.37 |
| 2026-03-31 00:00 |
21:59:48.43 |
+05:07:20.9 |
HIP 108561 |
21.49 |
| 2026-03-31 12:00 |
22:00:16.73 |
+05:13:49.5 |
HIP 108539 |
27.35 |
| 2026-04-01 00:00 |
22:00:44.90 |
+05:20:18.2 |
HIP 108539 |
27.42 |
| 2026-04-01 12:00 |
22:01:12.95 |
+05:26:47.0 |
HIP 108539 |
30.60 |
| 2026-04-02 00:00 |
22:01:40.86 |
+05:33:15.8 |
HIP 108886 |
26.74 |
| 2026-04-02 12:00 |
22:02:08.65 |
+05:39:44.7 |
HIP 108886 |
23.15 |
| 2026-04-03 00:00 |
22:02:36.31 |
+05:46:13.7 |
HIP 108886 |
23.17 |
| 2026-04-03 12:00 |
22:03:03.84 |
+05:52:42.8 |
HIP 108962 |
22.51 |
| 2026-04-04 00:00 |
22:03:31.24 |
+05:59:11.9 |
HIP 108962 |
19.49 |
| 2026-04-04 12:00 |
22:03:58.51 |
+06:05:41.1 |
HIP 108962 |
20.75 |
| 2026-04-05 00:00 |
22:04:25.65 |
+06:12:10.4 |
HIP 109069 |
23.62 |
| 2026-04-05 12:00 |
22:04:52.66 |
+06:18:39.7 |
HIP 109069 |
23.99 |
| 2026-04-06 00:00 |
22:05:19.54 |
+06:25:09.0 |
HIP 109069 |
27.71 |
| 2026-04-06 12:00 |
22:05:46.29 |
+06:31:38.4 |
HIP 109076 |
27.66 |
| 2026-04-07 00:00 |
22:06:12.90 |
+06:38:07.9 |
HIP 109076 |
22.10 |
| 2026-04-07 12:00 |
22:06:39.38 |
+06:44:37.4 |
HIP 109076 |
19.55 |
| 2026-04-08 00:00 |
22:07:05.73 |
+06:51:06.9 |
HIP 109076 |
21.10 |
| 2026-04-08 12:00 |
22:07:31.94 |
+06:57:36.5 |
HIP 109076 |
26.00 |
| 2026-04-09 00:00 |
22:07:58.01 |
+07:04:06.1 |
HIP 109309 |
19.73 |
| 2026-04-09 12:00 |
22:08:23.95 |
+07:10:35.8 |
HIP 109309 |
10.75 |
| 2026-04-10 00:00 |
22:08:49.76 |
+07:17:05.4 |
HIP 109309 |
3.00 |
| 2026-04-10 12:00 |
22:09:15.42 |
+07:23:35.1 |
HIP 109347 |
6.27 |
| 2026-04-11 00:00 |
22:09:40.95 |
+07:30:04.9 |
HIP 109347 |
8.24 |
| 2026-04-11 12:00 |
22:10:06.34 |
+07:36:34.6 |
HIP 109347 |
16.12 |
| 2026-04-12 00:00 |
22:10:31.59 |
+07:43:04.3 |
HIP 109480 |
11.91 |
| 2026-04-12 12:00 |
22:10:56.70 |
+07:49:34.1 |
HIP 109480 |
5.81 |
| 2026-04-13 00:00 |
22:11:21.66 |
+07:56:03.8 |
HIP 109496 |
7.52 |
| 2026-04-13 12:00 |
22:11:46.49 |
+08:02:33.6 |
HIP 109496 |
13.16 |
| 2026-04-14 00:00 |
22:12:11.17 |
+08:09:03.3 |
HIP 109608 |
18.59 |
| 2026-04-14 12:00 |
22:12:35.72 |
+08:15:33.1 |
HIP 109608 |
13.29 |
| 2026-04-15 00:00 |
22:13:00.11 |
+08:22:02.8 |
HIP 109638 |
12.74 |
| 2026-04-15 12:00 |
22:13:24.36 |
+08:28:32.5 |
HIP 109638 |
12.89 |
| 2026-04-16 00:00 |
22:13:48.47 |
+08:35:02.1 |
HIP 109638 |
18.03 |