C/2025 A6 (Lemmon)
Metadata
| Parameter | Value |
|---|---|
| Designation | C/2025 A6 (Lemmon) |
| Type | C |
| Perihelion (tp_cal, UTC) | 2025-11-08T12:55:33.208320Z |
| Orbit solution date (soln_date, UTC) | 2026-01-07T15:42:42Z |
| Obs used | 1622 |
| NEO | - |
| M1 | 10.600 |
| K1 | 11.250 |
| PC | - |
| Discovery observation (MPC, UTC) | 2025-01-03T08:12:42.537600Z |
| Discovery magnitude (MPC) | 21.65 G |
| Discovery observatory (MPC) | G96 · Mt. Lemmon Survey |
Osculating Elements
| Parameter | Value |
|---|---|
| Epoch (epoch_cal, TDB) | 2025-09-12.0000000 |
| e | 0.99561380 |
| q (au) | 0.529889 |
| a (au) | 120.808144 |
| i (deg) | 143.663681 |
| Ω (om, deg) | 108.097777 |
| ω (w, deg) | 132.970340 |
| M (ma, deg) | 359.957291 |
Magnitude
Scatter + Global Linear
$$ M_a = (9.077 + 6.000\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta $$ $$ \theta = 180^\circ - \alpha $$ $$ \Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b) $$ $$ \Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1 $$
Model Parameters
| Parameter | Value |
|---|---|
| H0 | 9.077 |
| n | 6.000 |
| gf | 1.000 |
| gb | -0.506 |
| k | 0.800 |
| 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 |
|---|---|---|---|
| 2024-11-12 | 2025-09-20 | +3.7943 | -1.389 |
| 2025-09-20 | 2025-11-08 | -5.6216 | -0.486 |
| 2025-11-08 | 2026-02-08 | -8.4130 | -2.224 |
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 | 16:58:26.86 | -50:47:45.5 | HIP 83057 | 9.40 |
| 2026-02-03 12:00 | 16:57:56.51 | -50:59:03.0 | HIP 83023 | 13.56 |
| 2026-02-04 00:00 | 16:57:25.28 | -51:10:22.4 | HIP 83023 | 5.41 |
| 2026-02-04 12:00 | 16:56:53.16 | -51:21:43.5 | HIP 83023 | 13.48 |
| 2026-02-05 00:00 | 16:56:20.13 | -51:33:06.5 | HIP 82866 | 20.85 |
| 2026-02-05 12:00 | 16:55:46.16 | -51:44:31.2 | HIP 82866 | 9.80 |
| 2026-02-06 00:00 | 16:55:11.23 | -51:55:57.6 | HIP 82866 | 8.66 |
| 2026-02-06 12:00 | 16:54:35.33 | -52:07:25.7 | HIP 82661 | 7.44 |
| 2026-02-07 00:00 | 16:53:58.42 | -52:18:55.4 | HIP 82661 | 14.25 |
| 2026-02-07 12:00 | 16:53:20.48 | -52:30:26.7 | HIP 82816 | 21.35 |
| 2026-02-08 00:00 | 16:52:41.50 | -52:41:59.6 | HIP 82555 | 18.05 |
| 2026-02-08 12:00 | 16:52:01.44 | -52:53:34.1 | HIP 82555 | 7.52 |
| 2026-02-09 00:00 | 16:51:20.28 | -53:05:09.9 | HIP 82555 | 11.47 |
| 2026-02-09 12:00 | 16:50:38.00 | -53:16:47.2 | HIP 82555 | 23.60 |
| 2026-02-10 00:00 | 16:49:54.56 | -53:28:25.8 | HIP 82348 | 12.36 |
| 2026-02-10 12:00 | 16:49:09.95 | -53:40:05.6 | HIP 82348 | 3.57 |
| 2026-02-11 00:00 | 16:48:24.14 | -53:51:46.7 | HIP 82365 | 14.95 |
| 2026-02-11 12:00 | 16:47:37.10 | -54:03:28.8 | HIP 82118 | 16.23 |
| 2026-02-12 00:00 | 16:46:48.80 | -54:15:12.0 | HIP 82118 | 2.90 |
| 2026-02-12 12:00 | 16:45:59.21 | -54:26:56.2 | HIP 82118 | 11.40 |
| 2026-02-13 00:00 | 16:45:08.30 | -54:38:41.2 | HIP 81859 | 19.07 |
| 2026-02-13 12:00 | 16:44:16.05 | -54:50:27.0 | HIP 81859 | 10.31 |
| 2026-02-14 00:00 | 16:43:22.42 | -55:02:13.4 | HIP 81797 | 11.00 |
| 2026-02-14 12:00 | 16:42:27.39 | -55:14:00.3 | HIP 81797 | 4.45 |
| 2026-02-15 00:00 | 16:41:30.92 | -55:25:47.7 | HIP 81700 | 8.09 |
| 2026-02-15 12:00 | 16:40:32.98 | -55:37:35.4 | HIP 81780 | 14.85 |
| 2026-02-16 00:00 | 16:39:33.53 | -55:49:23.3 | HIP 81352 | 23.63 |
| 2026-02-16 12:00 | 16:38:32.56 | -56:01:11.3 | HIP 81469 | 14.39 |
| 2026-02-17 00:00 | 16:37:30.01 | -56:12:59.1 | HIP 81469 | 7.82 |
| 2026-02-17 12:00 | 16:36:25.87 | -56:24:46.7 | HIP 81371 | 10.17 |
| 2026-02-18 00:00 | 16:35:20.09 | -56:36:33.9 | HIP 81371 | 14.86 |
| 2026-02-18 12:00 | 16:34:12.64 | -56:48:20.6 | HIP 81021 | 13.22 |
| 2026-02-19 00:00 | 16:33:03.49 | -57:00:06.5 | HIP 80976 | 15.90 |
| 2026-02-19 12:00 | 16:31:52.61 | -57:11:51.6 | HIP 80976 | 3.11 |
| 2026-02-20 00:00 | 16:30:39.95 | -57:23:35.5 | HIP 80976 | 15.23 |
| 2026-02-20 12:00 | 16:29:25.48 | -57:35:18.2 | HIP 80788 | 10.42 |
| 2026-02-21 00:00 | 16:28:09.16 | -57:46:59.4 | HIP 80706 | 4.51 |
| 2026-02-21 12:00 | 16:26:50.97 | -57:58:38.9 | HIP 80578 | 8.96 |
| 2026-02-22 00:00 | 16:25:30.87 | -58:10:16.5 | HIP 80578 | 13.28 |
| 2026-02-22 12:00 | 16:24:08.81 | -58:21:52.0 | HIP 80336 | 14.50 |
| 2026-02-23 00:00 | 16:22:44.77 | -58:33:25.1 | HIP 80336 | 10.36 |
| 2026-02-23 12:00 | 16:21:18.70 | -58:44:55.7 | HIP 80336 | 22.78 |
| 2026-02-24 00:00 | 16:19:50.57 | -58:56:23.4 | HIP 79993 | 7.87 |