C/2025 R2 (SWAN)
Metadata
| Parameter | Value |
|---|---|
| Designation | C/2025 R2 (SWAN) |
| Type | C |
| Perihelion (tp_cal, UTC) | 2025-09-12T20:18:11.635200Z |
| Orbit solution date (soln_date, UTC) | 2026-04-14T13:42:19Z |
| Obs used | 2411 |
| NEO | - |
| M1 | 13.900 |
| K1 | 9.750 |
| 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) | 2025-11-12.0000000 |
| e | 0.99419610 |
| q (au) | 0.504084 |
| a (au) | 86.852676 |
| i (deg) | 4.472975 |
| Ω (om, deg) | 335.325998 |
| ω (w, deg) | 308.358648 |
| M (ma, deg) | 0.073248 |
Magnitude
Scatter + Global Linear
$$ M_a = (12.752 + 5.000\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta $$ $$ \theta = 180^\circ - \alpha $$ $$ \Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b) $$ $$ \Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1 $$
Model Parameters
| Parameter | Value |
|---|---|
| H0 | 12.752 |
| n | 5.000 |
| gf | 1.000 |
| gb | -1.000 |
| k | 0.934 |
| 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
Residuals (Piecewise)
$$\epsilon = a \log_{10} r_{\mathrm{au}} + b$$
| Start (UTC) | End (UTC) | a | b |
|---|---|---|---|
| 2025-09-12 | 2026-03-09 | -1.6782 | -0.950 |
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) |
|---|---|---|---|---|
| 2026-05-12 00:00 | 03:44:34.26 | +23:25:33.0 | HIP 17497 | 10.18 |
| 2026-05-12 12:00 | 03:45:07.43 | +23:27:18.0 | HIP 17497 | 11.76 |
| 2026-05-13 00:00 | 03:45:40.54 | +23:29:02.6 | HIP 17497 | 17.16 |
| 2026-05-13 12:00 | 03:46:13.60 | +23:30:46.7 | HIP 17684 | 19.41 |
| 2026-05-14 00:00 | 03:46:46.60 | +23:32:30.4 | HIP 17684 | 13.12 |
| 2026-05-14 12:00 | 03:47:19.55 | +23:34:13.6 | HIP 17684 | 9.40 |
| 2026-05-15 00:00 | 03:47:52.45 | +23:35:56.3 | HIP 17684 | 11.14 |
| 2026-05-15 12:00 | 03:48:25.29 | +23:37:38.6 | HIP 17776 | 12.40 |
| 2026-05-16 00:00 | 03:48:58.07 | +23:39:20.4 | HIP 17900 | 10.94 |
| 2026-05-16 12:00 | 03:49:30.80 | +23:41:01.8 | HIP 17900 | 3.37 |
| 2026-05-17 00:00 | 03:50:03.47 | +23:42:42.7 | HIP 17900 | 4.57 |
| 2026-05-17 12:00 | 03:50:36.08 | +23:44:23.1 | HIP 17923 | 10.89 |
| 2026-05-18 00:00 | 03:51:08.64 | +23:46:03.1 | HIP 18018 | 8.28 |
| 2026-05-18 12:00 | 03:51:41.13 | +23:47:42.6 | HIP 18018 | 10.88 |
| 2026-05-19 00:00 | 03:52:13.57 | +23:49:21.6 | HIP 18018 | 16.85 |
| 2026-05-19 12:00 | 03:52:45.94 | +23:51:00.2 | HIP 18018 | 23.75 |
| 2026-05-20 00:00 | 03:53:18.25 | +23:52:38.4 | HIP 18018 | 30.95 |
| 2026-05-20 12:00 | 03:53:50.51 | +23:54:16.0 | HIP 18263 | 28.47 |
| 2026-05-21 00:00 | 03:54:22.70 | +23:55:53.2 | HIP 18263 | 25.73 |
| 2026-05-21 12:00 | 03:54:54.83 | +23:57:30.0 | HIP 18263 | 25.04 |
| 2026-05-22 00:00 | 03:55:26.89 | +23:59:06.3 | HIP 18263 | 26.54 |
| 2026-05-22 12:00 | 03:55:58.89 | +24:00:42.1 | HIP 18263 | 29.89 |
| 2026-05-23 00:00 | 03:56:30.83 | +24:02:17.5 | HIP 18559 | 25.26 |
| 2026-05-23 12:00 | 03:57:02.71 | +24:03:52.4 | HIP 18559 | 17.87 |
| 2026-05-24 00:00 | 03:57:34.52 | +24:05:26.9 | HIP 18559 | 10.60 |
| 2026-05-24 12:00 | 03:58:06.26 | +24:07:00.9 | HIP 18559 | 3.97 |
| 2026-05-25 00:00 | 03:58:37.94 | +24:08:34.4 | HIP 18559 | 5.37 |
| 2026-05-25 12:00 | 03:59:09.55 | +24:10:07.5 | HIP 18559 | 12.28 |
| 2026-05-26 00:00 | 03:59:41.10 | +24:11:40.2 | HIP 18559 | 19.52 |
| 2026-05-26 12:00 | 04:00:12.58 | +24:13:12.4 | HIP 18559 | 26.81 |
| 2026-05-27 00:00 | 04:00:43.99 | +24:14:44.2 | HIP 18559 | 34.10 |
| 2026-05-27 12:00 | 04:01:15.33 | +24:16:15.5 | HIP 18559 | 41.38 |
| 2026-05-28 00:00 | 04:01:46.61 | +24:17:46.3 | HIP 19009 | 37.15 |
| 2026-05-28 12:00 | 04:02:17.82 | +24:19:16.8 | HIP 19009 | 31.05 |
| 2026-05-29 00:00 | 04:02:48.96 | +24:20:46.7 | HIP 19009 | 25.59 |
| 2026-05-29 12:00 | 04:03:20.03 | +24:22:16.3 | HIP 19009 | 21.23 |
| 2026-05-30 00:00 | 04:03:51.03 | +24:23:45.3 | HIP 19009 | 18.74 |
| 2026-05-30 12:00 | 04:04:21.96 | +24:25:14.0 | HIP 19009 | 18.87 |
| 2026-05-31 00:00 | 04:04:52.82 | +24:26:42.2 | HIP 19009 | 21.54 |
| 2026-05-31 12:00 | 04:05:23.61 | +24:28:10.0 | HIP 19137 | 18.32 |
| 2026-06-01 00:00 | 04:05:54.33 | +24:29:37.3 | HIP 19137 | 14.50 |
| 2026-06-01 12:00 | 04:06:24.98 | +24:31:04.2 | HIP 19137 | 13.66 |
| 2026-06-02 00:00 | 04:06:55.56 | +24:32:30.7 | HIP 19137 | 16.25 |