| Parameter |
Value |
| Designation |
C/2025 F2 (SWAN) |
| Type |
C |
| Perihelion (tp_cal, UTC) |
2025-05-01T03:51:29.594880Z |
| Orbit solution date (soln_date, UTC) |
2025-09-30T14:13:43Z |
| Obs used |
375 |
| NEO |
- |
| M1 |
12.300 |
| K1 |
13.000 |
| PC |
- |
| Discovery observation (MPC, UTC) |
2025-03-22T12:00:00Z |
| Discovery magnitude (MPC) |
- |
| Discovery observatory (MPC) |
249 · SOHO |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
2025-03-31.0000000 |
| e |
1.00013474 |
| q (au) |
0.333496 |
| a (au) |
-2475.174637 |
| i (deg) |
90.364801 |
| Ω (om, deg) |
329.839874 |
| ω (w, deg) |
153.835634 |
| M (ma, deg) |
-0.000249 |
Magnitude
Scatter + Global Linear
$$
M_a = (12.159 + 3.735\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
12.159 |
| n |
3.735 |
| gf |
0.800 |
| gb |
-0.536 |
| k |
0.800 |
| δ90 |
9.999 |
| 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 |
| 2024-09-03 |
2025-04-05 |
+5.8025 |
+0.079 |
| 2025-04-05 |
2025-04-21 |
-13.4640 |
-2.999 |
| 2025-04-21 |
2025-04-29 |
-20.8594 |
-6.023 |
log10 r = log10(heliocentric distance / AU), Δ = geocentric distance (AU)
Ephemeris
| Date/Time (UTC) |
RA (J2000) |
Dec (J2000) |
Nearest HIP |
Dist from HIP (arcmin) |
| 2026-09-25 00:00 |
00:17:04.86 |
-65:21:21.9 |
HIP 1396 |
18.47 |
| 2026-09-25 12:00 |
00:16:19.61 |
-65:21:27.3 |
HIP 1396 |
19.56 |
| 2026-09-26 00:00 |
00:15:34.46 |
-65:21:29.6 |
HIP 1396 |
21.67 |
| 2026-09-26 12:00 |
00:14:49.41 |
-65:21:28.9 |
HIP 1396 |
24.53 |
| 2026-09-27 00:00 |
00:14:04.45 |
-65:21:25.1 |
HIP 809 |
25.68 |
| 2026-09-27 12:00 |
00:13:19.62 |
-65:21:18.4 |
HIP 809 |
21.01 |
| 2026-09-28 00:00 |
00:12:34.90 |
-65:21:08.6 |
HIP 809 |
16.35 |
| 2026-09-28 12:00 |
00:11:50.30 |
-65:20:55.8 |
HIP 809 |
11.71 |
| 2026-09-29 00:00 |
00:11:05.84 |
-65:20:40.1 |
HIP 809 |
7.10 |
| 2026-09-29 12:00 |
00:10:21.51 |
-65:20:21.3 |
HIP 809 |
2.67 |
| 2026-09-30 00:00 |
00:09:37.34 |
-65:19:59.6 |
HIP 809 |
2.60 |
| 2026-09-30 12:00 |
00:08:53.31 |
-65:19:35.0 |
HIP 809 |
7.00 |
| 2026-10-01 00:00 |
00:08:09.45 |
-65:19:07.4 |
HIP 809 |
11.57 |
| 2026-10-01 12:00 |
00:07:25.75 |
-65:18:36.9 |
HIP 809 |
16.14 |
| 2026-10-02 00:00 |
00:06:42.22 |
-65:18:03.4 |
HIP 809 |
20.72 |
| 2026-10-02 12:00 |
00:05:58.87 |
-65:17:27.1 |
HIP 809 |
25.28 |
| 2026-10-03 00:00 |
00:05:15.71 |
-65:16:47.9 |
HIP 809 |
29.84 |
| 2026-10-03 12:00 |
00:04:32.74 |
-65:16:05.8 |
HIP 284 |
34.16 |
| 2026-10-04 00:00 |
00:03:49.97 |
-65:15:20.9 |
HIP 118322 |
31.13 |
| 2026-10-04 12:00 |
00:03:07.40 |
-65:14:33.1 |
HIP 118322 |
28.35 |
| 2026-10-05 00:00 |
00:02:25.04 |
-65:13:42.5 |
HIP 118322 |
26.11 |
| 2026-10-05 12:00 |
00:01:42.90 |
-65:12:49.1 |
HIP 118270 |
23.79 |
| 2026-10-06 00:00 |
00:01:00.99 |
-65:11:52.9 |
HIP 118270 |
22.14 |
| 2026-10-06 12:00 |
00:00:19.30 |
-65:10:54.0 |
HIP 118270 |
21.37 |
| 2026-10-07 00:00 |
23:59:37.84 |
-65:09:52.2 |
HIP 118270 |
21.56 |
| 2026-10-07 12:00 |
23:58:56.63 |
-65:08:47.8 |
HIP 118270 |
22.68 |
| 2026-10-08 00:00 |
23:58:15.66 |
-65:07:40.6 |
HIP 118270 |
24.59 |
| 2026-10-08 12:00 |
23:57:34.95 |
-65:06:30.8 |
HIP 118270 |
27.13 |
| 2026-10-09 00:00 |
23:56:54.49 |
-65:05:18.3 |
HIP 118270 |
30.14 |
| 2026-10-09 12:00 |
23:56:14.29 |
-65:04:03.1 |
HIP 117661 |
32.59 |
| 2026-10-10 00:00 |
23:55:34.36 |
-65:02:45.3 |
HIP 117661 |
28.29 |
| 2026-10-10 12:00 |
23:54:54.71 |
-65:01:24.8 |
HIP 117661 |
24.02 |
| 2026-10-11 00:00 |
23:54:15.33 |
-65:00:01.8 |
HIP 117661 |
19.81 |
| 2026-10-11 12:00 |
23:53:36.24 |
-64:58:36.3 |
HIP 117661 |
15.69 |
| 2026-10-12 00:00 |
23:52:57.43 |
-64:57:08.2 |
HIP 117661 |
11.75 |
| 2026-10-12 12:00 |
23:52:18.91 |
-64:55:37.5 |
HIP 117661 |
8.21 |
| 2026-10-13 00:00 |
23:51:40.69 |
-64:54:04.4 |
HIP 117661 |
5.86 |
| 2026-10-13 12:00 |
23:51:02.77 |
-64:52:28.8 |
HIP 117661 |
6.20 |
| 2026-10-14 00:00 |
23:50:25.16 |
-64:50:50.8 |
HIP 117661 |
8.91 |
| 2026-10-14 12:00 |
23:49:47.85 |
-64:49:10.4 |
HIP 117661 |
12.52 |
| 2026-10-15 00:00 |
23:49:10.86 |
-64:47:27.5 |
HIP 117661 |
16.45 |
| 2026-10-15 12:00 |
23:48:34.18 |
-64:45:42.4 |
HIP 117253 |
17.28 |
| 2026-10-16 00:00 |
23:47:57.83 |
-64:43:54.8 |
HIP 117253 |
13.23 |