C/2025 R2 (SWAN)
Metadata
| Parameter | Value |
|---|---|
| Designation | C/2025 R2 (SWAN) |
| Type | C |
| Perihelion (tp_cal, UTC) | 2025-09-12T20:18:10.952640Z |
| Orbit solution date (soln_date, UTC) | 2026-07-06T12:12:28Z |
| Obs used | 2441 |
| NEO | - |
| M1 | 13.900 |
| K1 | 9.500 |
| 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) | 2025-11-12.0000000 |
| e | 0.99419572 |
| q (au) | 0.504085 |
| a (au) | 86.846983 |
| i (deg) | 4.472975 |
| Ω (om, deg) | 335.326008 |
| ω (w, deg) | 308.358635 |
| M (ma, deg) | 0.073255 |
Magnitude
Scatter + Global Linear
$$ M_a = (12.783 + 5.090\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta $$ $$ \theta = 180^\circ - \alpha $$ $$ \Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b) $$ $$ \Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1 $$
Model Parameters
| Parameter | Value |
|---|---|
| H0 | 12.783 |
| n | 5.090 |
| gf | 1.000 |
| gb | -0.999 |
| k | 0.936 |
| 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 | 2026-03-09 | -1.8779 | -0.979 |
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) |
|---|---|---|---|---|
| 2026-09-20 00:00 | 05:10:22.57 | +27:38:33.0 | HIP 24035 | 4.84 |
| 2026-09-20 12:00 | 05:10:20.38 | +27:38:57.6 | HIP 24035 | 4.36 |
| 2026-09-21 00:00 | 05:10:17.95 | +27:39:21.8 | HIP 24035 | 3.89 |
| 2026-09-21 12:00 | 05:10:15.30 | +27:39:45.8 | HIP 24035 | 3.43 |
| 2026-09-22 00:00 | 05:10:12.43 | +27:40:09.5 | HIP 24035 | 3.02 |
| 2026-09-22 12:00 | 05:10:09.32 | +27:40:33.0 | HIP 24035 | 2.72 |
| 2026-09-23 00:00 | 05:10:05.99 | +27:40:56.2 | HIP 24035 | 2.61 |
| 2026-09-23 12:00 | 05:10:02.43 | +27:41:19.1 | HIP 24035 | 2.74 |
| 2026-09-24 00:00 | 05:09:58.64 | +27:41:41.7 | HIP 24035 | 3.13 |
| 2026-09-24 12:00 | 05:09:54.62 | +27:42:04.0 | HIP 24035 | 3.72 |
| 2026-09-25 00:00 | 05:09:50.38 | +27:42:26.0 | HIP 24035 | 4.46 |
| 2026-09-25 12:00 | 05:09:45.91 | +27:42:47.8 | HIP 24035 | 5.32 |
| 2026-09-26 00:00 | 05:09:41.21 | +27:43:09.2 | HIP 24035 | 6.28 |
| 2026-09-26 12:00 | 05:09:36.28 | +27:43:30.4 | HIP 24035 | 7.30 |
| 2026-09-27 00:00 | 05:09:31.13 | +27:43:51.2 | HIP 24035 | 8.40 |
| 2026-09-27 12:00 | 05:09:25.75 | +27:44:11.8 | HIP 24035 | 9.55 |
| 2026-09-28 00:00 | 05:09:20.14 | +27:44:32.0 | HIP 24035 | 10.77 |
| 2026-09-28 12:00 | 05:09:14.30 | +27:44:51.9 | HIP 24035 | 12.04 |
| 2026-09-29 00:00 | 05:09:08.24 | +27:45:11.5 | HIP 24035 | 13.36 |
| 2026-09-29 12:00 | 05:09:01.94 | +27:45:30.7 | HIP 24035 | 14.73 |
| 2026-09-30 00:00 | 05:08:55.42 | +27:45:49.6 | HIP 24035 | 16.16 |
| 2026-09-30 12:00 | 05:08:48.67 | +27:46:08.2 | HIP 24035 | 17.64 |
| 2026-10-01 00:00 | 05:08:41.70 | +27:46:26.5 | HIP 24035 | 19.17 |
| 2026-10-01 12:00 | 05:08:34.50 | +27:46:44.4 | HIP 24035 | 20.75 |
| 2026-10-02 00:00 | 05:08:27.07 | +27:47:02.0 | HIP 24035 | 22.38 |
| 2026-10-02 12:00 | 05:08:19.41 | +27:47:19.2 | HIP 24019 | 23.85 |
| 2026-10-03 00:00 | 05:08:11.53 | +27:47:36.0 | HIP 24019 | 25.09 |
| 2026-10-03 12:00 | 05:08:03.41 | +27:47:52.5 | HIP 24019 | 26.44 |
| 2026-10-04 00:00 | 05:07:55.08 | +27:48:08.6 | HIP 24019 | 27.89 |
| 2026-10-04 12:00 | 05:07:46.51 | +27:48:24.4 | HIP 24019 | 29.43 |
| 2026-10-05 00:00 | 05:07:37.72 | +27:48:39.8 | HIP 23721 | 28.56 |
| 2026-10-05 12:00 | 05:07:28.71 | +27:48:54.7 | HIP 23721 | 26.91 |
| 2026-10-06 00:00 | 05:07:19.47 | +27:49:09.3 | HIP 23721 | 25.28 |
| 2026-10-06 12:00 | 05:07:10.01 | +27:49:23.6 | HIP 23721 | 23.69 |
| 2026-10-07 00:00 | 05:07:00.32 | +27:49:37.4 | HIP 23721 | 22.17 |
| 2026-10-07 12:00 | 05:06:50.40 | +27:49:50.8 | HIP 23721 | 20.73 |
| 2026-10-08 00:00 | 05:06:40.27 | +27:50:03.8 | HIP 23721 | 19.42 |
| 2026-10-08 12:00 | 05:06:29.91 | +27:50:16.4 | HIP 23721 | 18.28 |
| 2026-10-09 00:00 | 05:06:19.33 | +27:50:28.6 | HIP 23721 | 17.36 |
| 2026-10-09 12:00 | 05:06:08.53 | +27:50:40.3 | HIP 23721 | 16.73 |
| 2026-10-10 00:00 | 05:05:57.51 | +27:50:51.7 | HIP 23721 | 16.43 |
| 2026-10-10 12:00 | 05:05:46.27 | +27:51:02.6 | HIP 23721 | 16.51 |
| 2026-10-11 00:00 | 05:05:34.81 | +27:51:13.0 | HIP 23614 | 15.73 |