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) |
|---|---|---|---|---|
| 2026-07-29 00:00 | 04:54:43.69 | +26:35:24.2 | HIP 22802 | 14.27 |
| 2026-07-29 12:00 | 04:55:01.93 | +26:36:10.9 | HIP 22802 | 15.72 |
| 2026-07-30 00:00 | 04:55:20.02 | +26:36:57.3 | HIP 22802 | 18.01 |
| 2026-07-30 12:00 | 04:55:37.97 | +26:37:43.5 | HIP 22802 | 20.84 |
| 2026-07-31 00:00 | 04:55:55.76 | +26:38:29.4 | HIP 23018 | 22.05 |
| 2026-07-31 12:00 | 04:56:13.40 | +26:39:15.1 | HIP 23018 | 20.32 |
| 2026-08-01 00:00 | 04:56:30.89 | +26:40:00.6 | HIP 23018 | 19.29 |
| 2026-08-01 12:00 | 04:56:48.23 | +26:40:45.8 | HIP 23018 | 19.06 |
| 2026-08-02 00:00 | 04:57:05.42 | +26:41:30.8 | HIP 23018 | 19.62 |
| 2026-08-02 12:00 | 04:57:22.45 | +26:42:15.6 | HIP 23018 | 20.91 |
| 2026-08-03 00:00 | 04:57:39.33 | +26:43:00.2 | HIP 23018 | 22.78 |
| 2026-08-03 12:00 | 04:57:56.05 | +26:43:44.5 | HIP 23018 | 25.08 |
| 2026-08-04 00:00 | 04:58:12.61 | +26:44:28.6 | HIP 23018 | 27.69 |
| 2026-08-04 12:00 | 04:58:29.01 | +26:45:12.4 | HIP 23018 | 30.52 |
| 2026-08-05 00:00 | 04:58:45.26 | +26:45:56.1 | HIP 23209 | 33.17 |
| 2026-08-05 12:00 | 04:59:01.35 | +26:46:39.5 | HIP 23209 | 32.74 |
| 2026-08-06 00:00 | 04:59:17.27 | +26:47:22.7 | HIP 23349 | 31.20 |
| 2026-08-06 12:00 | 04:59:33.04 | +26:48:05.7 | HIP 23349 | 28.58 |
| 2026-08-07 00:00 | 04:59:48.64 | +26:48:48.4 | HIP 23349 | 26.21 |
| 2026-08-07 12:00 | 05:00:04.08 | +26:49:31.0 | HIP 23349 | 24.17 |
| 2026-08-08 00:00 | 05:00:19.35 | +26:50:13.3 | HIP 23395 | 21.41 |
| 2026-08-08 12:00 | 05:00:34.46 | +26:50:55.4 | HIP 23395 | 18.88 |
| 2026-08-09 00:00 | 05:00:49.41 | +26:51:37.4 | HIP 23395 | 16.70 |
| 2026-08-09 12:00 | 05:01:04.18 | +26:52:19.0 | HIP 23395 | 15.01 |
| 2026-08-10 00:00 | 05:01:18.79 | +26:53:00.5 | HIP 23395 | 13.96 |
| 2026-08-10 12:00 | 05:01:33.22 | +26:53:41.8 | HIP 23395 | 13.66 |
| 2026-08-11 00:00 | 05:01:47.49 | +26:54:22.9 | HIP 23395 | 14.14 |
| 2026-08-11 12:00 | 05:02:01.58 | +26:55:03.7 | HIP 23395 | 15.29 |
| 2026-08-12 00:00 | 05:02:15.50 | +26:55:44.4 | HIP 23395 | 16.97 |
| 2026-08-12 12:00 | 05:02:29.25 | +26:56:24.8 | HIP 23395 | 19.01 |
| 2026-08-13 00:00 | 05:02:42.82 | +26:57:05.1 | HIP 23395 | 21.30 |
| 2026-08-13 12:00 | 05:02:56.22 | +26:57:45.1 | HIP 23395 | 23.74 |
| 2026-08-14 00:00 | 05:03:09.44 | +26:58:24.9 | HIP 23634 | 23.14 |
| 2026-08-14 12:00 | 05:03:22.48 | +26:59:04.6 | HIP 23634 | 20.51 |
| 2026-08-15 00:00 | 05:03:35.34 | +26:59:44.0 | HIP 23634 | 18.02 |
| 2026-08-15 12:00 | 05:03:48.03 | +27:00:23.2 | HIP 23634 | 15.73 |
| 2026-08-16 00:00 | 05:04:00.53 | +27:01:02.3 | HIP 23634 | 13.71 |
| 2026-08-16 12:00 | 05:04:12.86 | +27:01:41.1 | HIP 23634 | 12.05 |
| 2026-08-17 00:00 | 05:04:25.00 | +27:02:19.8 | HIP 23634 | 10.91 |
| 2026-08-17 12:00 | 05:04:36.96 | +27:02:58.2 | HIP 23634 | 10.41 |
| 2026-08-18 00:00 | 05:04:48.74 | +27:03:36.5 | HIP 23634 | 10.62 |
| 2026-08-18 12:00 | 05:05:00.33 | +27:04:14.5 | HIP 23634 | 11.46 |
| 2026-08-19 00:00 | 05:05:11.73 | +27:04:52.4 | HIP 23634 | 12.80 |