C/2025 F2 (SWAN)
| 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) |
| 2026-02-03 00:00 |
23:41:34.64 |
-56:59:28.5 |
HIP 116734 |
17.77 |
| 2026-02-03 12:00 |
23:42:04.60 |
-56:54:39.0 |
HIP 116734 |
22.35 |
| 2026-02-04 00:00 |
23:42:34.57 |
-56:49:51.3 |
HIP 116935 |
27.27 |
| 2026-02-04 12:00 |
23:43:04.56 |
-56:45:05.4 |
HIP 116935 |
23.53 |
| 2026-02-05 00:00 |
23:43:34.57 |
-56:40:21.3 |
HIP 117160 |
18.41 |
| 2026-02-05 12:00 |
23:44:04.59 |
-56:35:39.1 |
HIP 117160 |
12.17 |
| 2026-02-06 00:00 |
23:44:34.62 |
-56:30:58.7 |
HIP 117160 |
5.99 |
| 2026-02-06 12:00 |
23:45:04.67 |
-56:26:20.1 |
HIP 117160 |
1.22 |
| 2026-02-07 00:00 |
23:45:34.73 |
-56:21:43.3 |
HIP 117160 |
6.66 |
| 2026-02-07 12:00 |
23:46:04.79 |
-56:17:08.3 |
HIP 117160 |
12.80 |
| 2026-02-08 00:00 |
23:46:34.87 |
-56:12:35.2 |
HIP 117160 |
18.96 |
| 2026-02-08 12:00 |
23:47:04.96 |
-56:08:03.9 |
HIP 117276 |
19.59 |
| 2026-02-09 00:00 |
23:47:35.06 |
-56:03:34.4 |
HIP 117276 |
16.21 |
| 2026-02-09 12:00 |
23:48:05.17 |
-55:59:06.7 |
HIP 117276 |
14.79 |
| 2026-02-10 00:00 |
23:48:35.29 |
-55:54:40.9 |
HIP 117545 |
14.25 |
| 2026-02-10 12:00 |
23:49:05.41 |
-55:50:16.9 |
HIP 117545 |
10.14 |
| 2026-02-11 00:00 |
23:49:35.54 |
-55:45:54.7 |
HIP 117545 |
8.73 |
| 2026-02-11 12:00 |
23:50:05.67 |
-55:41:34.3 |
HIP 117545 |
11.08 |
| 2026-02-12 00:00 |
23:50:35.81 |
-55:37:15.8 |
HIP 117545 |
15.55 |
| 2026-02-12 12:00 |
23:51:05.96 |
-55:32:59.0 |
HIP 117648 |
19.45 |
| 2026-02-13 00:00 |
23:51:36.10 |
-55:28:44.2 |
HIP 117648 |
14.75 |
| 2026-02-13 12:00 |
23:52:06.25 |
-55:24:31.1 |
HIP 117648 |
11.41 |
| 2026-02-14 00:00 |
23:52:36.40 |
-55:20:19.9 |
HIP 117648 |
10.77 |
| 2026-02-14 12:00 |
23:53:06.56 |
-55:16:10.5 |
HIP 117648 |
13.19 |
| 2026-02-15 00:00 |
23:53:36.71 |
-55:12:03.0 |
HIP 117648 |
17.43 |
| 2026-02-15 12:00 |
23:54:06.86 |
-55:07:57.2 |
HIP 117648 |
22.46 |
| 2026-02-16 00:00 |
23:54:37.01 |
-55:03:53.4 |
HIP 117648 |
27.86 |
| 2026-02-16 12:00 |
23:55:07.16 |
-54:59:51.3 |
HIP 118039 |
31.75 |
| 2026-02-17 00:00 |
23:55:37.31 |
-54:55:51.1 |
HIP 118039 |
34.18 |
| 2026-02-17 12:00 |
23:56:07.45 |
-54:51:52.8 |
HIP 118248 |
28.54 |
| 2026-02-18 00:00 |
23:56:37.59 |
-54:47:56.3 |
HIP 118248 |
22.93 |
| 2026-02-18 12:00 |
23:57:07.73 |
-54:44:01.6 |
HIP 118248 |
17.49 |
| 2026-02-19 00:00 |
23:57:37.85 |
-54:40:08.8 |
HIP 118248 |
12.42 |
| 2026-02-19 12:00 |
23:58:07.97 |
-54:36:17.9 |
HIP 118248 |
8.37 |
| 2026-02-20 00:00 |
23:58:38.09 |
-54:32:28.8 |
HIP 118248 |
7.27 |
| 2026-02-20 12:00 |
23:59:08.19 |
-54:28:41.5 |
HIP 118248 |
10.11 |
| 2026-02-21 00:00 |
23:59:38.29 |
-54:24:56.1 |
HIP 118248 |
14.75 |
| 2026-02-21 12:00 |
00:00:08.37 |
-54:21:12.6 |
HIP 118248 |
19.96 |
| 2026-02-22 00:00 |
00:00:38.44 |
-54:17:30.9 |
HIP 118248 |
25.37 |
| 2026-02-22 12:00 |
00:01:08.50 |
-54:13:51.1 |
HIP 118248 |
30.88 |
| 2026-02-23 00:00 |
00:01:38.55 |
-54:10:13.1 |
HIP 346 |
28.53 |
| 2026-02-23 12:00 |
00:02:08.58 |
-54:06:37.0 |
HIP 346 |
22.89 |
| 2026-02-24 00:00 |
00:02:38.60 |
-54:03:02.8 |
HIP 346 |
17.29 |