| 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 |
-0.500 |
| 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) |
| 2026-06-01 00:00 |
22:38:44.51 |
+18:17:34.1 |
HIP 111745 |
29.55 |
| 2026-06-01 12:00 |
22:38:51.77 |
+18:23:33.4 |
HIP 111745 |
35.78 |
| 2026-06-02 00:00 |
22:38:58.81 |
+18:29:32.0 |
HIP 111981 |
38.86 |
| 2026-06-02 12:00 |
22:39:05.63 |
+18:35:29.8 |
HIP 111981 |
33.75 |
| 2026-06-03 00:00 |
22:39:12.23 |
+18:41:26.9 |
HIP 111981 |
29.11 |
| 2026-06-03 12:00 |
22:39:18.61 |
+18:47:23.1 |
HIP 111981 |
25.18 |
| 2026-06-04 00:00 |
22:39:24.77 |
+18:53:18.6 |
HIP 111981 |
22.33 |
| 2026-06-04 12:00 |
22:39:30.70 |
+18:59:13.3 |
HIP 111981 |
20.96 |
| 2026-06-05 00:00 |
22:39:36.42 |
+19:05:07.1 |
HIP 111981 |
21.36 |
| 2026-06-05 12:00 |
22:39:41.91 |
+19:11:00.2 |
HIP 111935 |
19.89 |
| 2026-06-06 00:00 |
22:39:47.17 |
+19:16:52.4 |
HIP 111935 |
14.39 |
| 2026-06-06 12:00 |
22:39:52.21 |
+19:22:43.7 |
HIP 111935 |
9.58 |
| 2026-06-07 00:00 |
22:39:57.02 |
+19:28:34.2 |
HIP 111935 |
6.97 |
| 2026-06-07 12:00 |
22:40:01.61 |
+19:34:23.7 |
HIP 111884 |
7.33 |
| 2026-06-08 00:00 |
22:40:05.97 |
+19:40:12.4 |
HIP 111884 |
4.51 |
| 2026-06-08 12:00 |
22:40:10.10 |
+19:46:00.2 |
HIP 111884 |
7.47 |
| 2026-06-09 00:00 |
22:40:14.00 |
+19:51:47.0 |
HIP 111943 |
11.40 |
| 2026-06-09 12:00 |
22:40:17.67 |
+19:57:32.9 |
HIP 111943 |
5.81 |
| 2026-06-10 00:00 |
22:40:21.11 |
+20:03:17.8 |
HIP 111943 |
2.38 |
| 2026-06-10 12:00 |
22:40:24.32 |
+20:09:01.7 |
HIP 111956 |
5.60 |
| 2026-06-11 00:00 |
22:40:27.29 |
+20:14:44.7 |
HIP 111956 |
10.36 |
| 2026-06-11 12:00 |
22:40:30.03 |
+20:20:26.6 |
HIP 111956 |
15.79 |
| 2026-06-12 00:00 |
22:40:32.54 |
+20:26:07.5 |
HIP 111956 |
21.36 |
| 2026-06-12 12:00 |
22:40:34.82 |
+20:31:47.4 |
HIP 111973 |
18.06 |
| 2026-06-13 00:00 |
22:40:36.85 |
+20:37:26.2 |
HIP 111973 |
12.48 |
| 2026-06-13 12:00 |
22:40:38.66 |
+20:43:03.9 |
HIP 111973 |
7.08 |
| 2026-06-14 00:00 |
22:40:40.22 |
+20:48:40.5 |
HIP 111973 |
2.94 |
| 2026-06-14 12:00 |
22:40:41.55 |
+20:54:16.0 |
HIP 111973 |
5.52 |
| 2026-06-15 00:00 |
22:40:42.64 |
+20:59:50.4 |
HIP 111973 |
10.72 |
| 2026-06-15 12:00 |
22:40:43.50 |
+21:05:23.6 |
HIP 112057 |
15.88 |
| 2026-06-16 00:00 |
22:40:44.11 |
+21:10:55.7 |
HIP 112057 |
15.00 |
| 2026-06-16 12:00 |
22:40:44.49 |
+21:16:26.5 |
HIP 112057 |
16.14 |
| 2026-06-17 00:00 |
22:40:44.63 |
+21:21:56.2 |
HIP 112063 |
16.09 |
| 2026-06-17 12:00 |
22:40:44.53 |
+21:27:24.6 |
HIP 112063 |
15.69 |
| 2026-06-18 00:00 |
22:40:44.19 |
+21:32:51.8 |
HIP 112063 |
17.17 |
| 2026-06-18 12:00 |
22:40:43.61 |
+21:38:17.8 |
HIP 112063 |
20.10 |
| 2026-06-19 00:00 |
22:40:42.79 |
+21:43:42.5 |
HIP 112063 |
23.95 |
| 2026-06-19 12:00 |
22:40:41.73 |
+21:49:05.9 |
HIP 112075 |
25.26 |
| 2026-06-20 00:00 |
22:40:40.43 |
+21:54:28.0 |
HIP 112075 |
22.28 |
| 2026-06-20 12:00 |
22:40:38.89 |
+21:59:48.7 |
HIP 112075 |
20.38 |
| 2026-06-21 00:00 |
22:40:37.11 |
+22:05:08.2 |
HIP 112075 |
19.83 |
| 2026-06-21 12:00 |
22:40:35.09 |
+22:10:26.2 |
HIP 112075 |
20.75 |
| 2026-06-22 00:00 |
22:40:32.84 |
+22:15:42.9 |
HIP 112058 |
19.33 |