C/2025 R2 (SWAN)
Metadata
| Parameter | Value |
|---|---|
| Designation | C/2025 R2 (SWAN) |
| Type | C |
| Perihelion (tp_cal, UTC) | 2025-09-12T20:17:34.578240Z |
| Orbit solution date (soln_date, UTC) | 2026-01-13T08:12:19Z |
| Obs used | 2225 |
| NEO | - |
| M1 | 13.900 |
| K1 | 10.500 |
| PC | - |
| Discovery observation (MPC, UTC) | 2025-09-11T23:33:15.552000Z |
| Discovery magnitude (MPC) | 7.50 V |
| Discovery observatory (MPC) | 247 · Roving Observer |
Osculating Elements
| Parameter | Value |
|---|---|
| Epoch (epoch_cal, TDB) | 2025-11-08.0000000 |
| e | 0.99417555 |
| q (au) | 0.504084 |
| a (au) | 86.546179 |
| i (deg) | 4.472969 |
| Ω (om, deg) | 335.326912 |
| ω (w, deg) | 308.357358 |
| M (ma, deg) | 0.068741 |
Magnitude
Scatter + Global Linear
$$ M_a = (12.899 + 4.820\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta $$ $$ \theta = 180^\circ - \alpha $$ $$ \Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b) $$ $$ \Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1 $$
Model Parameters
| Parameter | Value |
|---|---|
| H0 | 12.899 |
| n | 4.820 |
| gf | 0.999 |
| gb | -1.000 |
| k | 0.910 |
| δ90 | 9.997 |
| 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 |
|---|---|---|---|
| 2025-09-12 | 2026-01-23 | -0.9094 | -0.911 |
log10 r = log10(heliocentric distance / AU), Δ = geocentric distance (AU)
Finding Chart
Ephemeris
| Date/Time (UTC) | RA (J2000) | Dec (J2000) | Nearest HIP | Dist from HIP (arcmin) |
|---|---|---|---|---|
| 2026-02-03 00:00 | 01:44:53.50 | +15:24:16.0 | HIP 8073 | 27.63 |
| 2026-02-03 12:00 | 01:45:32.65 | +15:27:16.8 | HIP 8262 | 20.08 |
| 2026-02-04 00:00 | 01:46:11.78 | +15:30:17.4 | HIP 8262 | 12.94 |
| 2026-02-04 12:00 | 01:46:50.87 | +15:33:17.8 | HIP 8262 | 11.28 |
| 2026-02-05 00:00 | 01:47:29.93 | +15:36:17.9 | HIP 8262 | 16.80 |
| 2026-02-05 12:00 | 01:48:08.95 | +15:39:17.8 | HIP 8262 | 25.13 |
| 2026-02-06 00:00 | 01:48:47.95 | +15:42:17.4 | HIP 8262 | 34.27 |
| 2026-02-06 12:00 | 01:49:26.92 | +15:45:16.8 | HIP 8414 | 35.51 |
| 2026-02-07 00:00 | 01:50:05.86 | +15:48:15.9 | HIP 8568 | 36.64 |
| 2026-02-07 12:00 | 01:50:44.78 | +15:51:14.8 | HIP 8667 | 35.12 |
| 2026-02-08 00:00 | 01:51:23.66 | +15:54:13.5 | HIP 8782 | 29.12 |
| 2026-02-08 12:00 | 01:52:02.52 | +15:57:11.9 | HIP 8782 | 25.13 |
| 2026-02-09 00:00 | 01:52:41.36 | +16:00:10.0 | HIP 8782 | 24.65 |
| 2026-02-09 12:00 | 01:53:20.16 | +16:03:07.9 | HIP 8782 | 27.85 |
| 2026-02-10 00:00 | 01:53:58.94 | +16:06:05.6 | HIP 8782 | 33.68 |
| 2026-02-10 12:00 | 01:54:37.70 | +16:09:03.0 | HIP 9076 | 32.72 |
| 2026-02-11 00:00 | 01:55:16.43 | +16:12:00.2 | HIP 9076 | 24.77 |
| 2026-02-11 12:00 | 01:55:55.14 | +16:14:57.1 | HIP 9076 | 18.65 |
| 2026-02-12 00:00 | 01:56:33.82 | +16:17:53.8 | HIP 9076 | 16.50 |
| 2026-02-12 12:00 | 01:57:12.48 | +16:20:50.2 | HIP 9076 | 19.65 |
| 2026-02-13 00:00 | 01:57:51.12 | +16:23:46.4 | HIP 9228 | 13.72 |
| 2026-02-13 12:00 | 01:58:29.73 | +16:26:42.3 | HIP 9228 | 5.77 |
| 2026-02-14 00:00 | 01:59:08.32 | +16:29:37.9 | HIP 9228 | 8.18 |
| 2026-02-14 12:00 | 01:59:46.89 | +16:32:33.3 | HIP 9228 | 16.98 |
| 2026-02-15 00:00 | 02:00:25.44 | +16:35:28.5 | HIP 9434 | 10.74 |
| 2026-02-15 12:00 | 02:01:03.96 | +16:38:23.4 | HIP 9434 | 4.69 |
| 2026-02-16 00:00 | 02:01:42.46 | +16:41:18.0 | HIP 9434 | 10.77 |
| 2026-02-16 12:00 | 02:02:20.95 | +16:44:12.3 | HIP 9434 | 19.91 |
| 2026-02-17 00:00 | 02:02:59.41 | +16:47:06.4 | HIP 9613 | 26.38 |
| 2026-02-17 12:00 | 02:03:37.85 | +16:50:00.2 | HIP 9613 | 22.21 |
| 2026-02-18 00:00 | 02:04:16.27 | +16:52:53.8 | HIP 9613 | 21.82 |
| 2026-02-18 12:00 | 02:04:54.66 | +16:55:47.0 | HIP 9820 | 21.19 |
| 2026-02-19 00:00 | 02:05:33.04 | +16:58:40.0 | HIP 9820 | 13.30 |
| 2026-02-19 12:00 | 02:06:11.40 | +17:01:32.7 | HIP 9839 | 6.79 |
| 2026-02-20 00:00 | 02:06:49.73 | +17:04:25.1 | HIP 9839 | 3.41 |
| 2026-02-20 12:00 | 02:07:28.05 | +17:07:17.3 | HIP 9839 | 12.70 |
| 2026-02-21 00:00 | 02:08:06.34 | +17:10:09.1 | HIP 10050 | 18.61 |
| 2026-02-21 12:00 | 02:08:44.61 | +17:13:00.7 | HIP 10050 | 9.19 |
| 2026-02-22 00:00 | 02:09:22.86 | +17:15:51.9 | HIP 10050 | 2.39 |
| 2026-02-22 12:00 | 02:10:01.09 | +17:18:42.9 | HIP 10050 | 10.49 |
| 2026-02-23 00:00 | 02:10:39.30 | +17:21:33.5 | HIP 10050 | 19.92 |
| 2026-02-23 12:00 | 02:11:17.48 | +17:24:23.9 | HIP 10050 | 29.42 |
| 2026-02-24 00:00 | 02:11:55.65 | +17:27:13.9 | HIP 10295 | 35.38 |