C/2025 A6 (Lemmon)
Metadata
| Parameter | Value |
|---|---|
| Designation | C/2025 A6 (Lemmon) |
| Type | C |
| Perihelion (tp_cal, UTC) | 2025-11-08T12:56:51.607680Z |
| Orbit solution date (soln_date, UTC) | 2026-03-31T09:42:18Z |
| Obs used | 1816 |
| NEO | - |
| M1 | 10.500 |
| K1 | 10.250 |
| 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) | 2025-10-01.0000000 |
| e | 0.99558347 |
| q (au) | 0.529886 |
| a (au) | 119.977825 |
| i (deg) | 143.663587 |
| Ω (om, deg) | 108.097769 |
| ω (w, deg) | 132.971452 |
| M (ma, deg) | 359.971096 |
Magnitude
Scatter + Global Linear
$$ M_a = (8.652 + 5.370\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta $$ $$ \theta = 180^\circ - \alpha $$ $$ \Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b) $$ $$ \Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1 $$
Model Parameters
| Parameter | Value |
|---|---|
| H0 | 8.652 |
| n | 5.370 |
| gf | 1.000 |
| gb | -0.500 |
| 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 | +5.3966 | -1.008 |
| 2025-09-20 | 2025-11-08 | -4.0196 | -0.130 |
| 2025-11-08 | 2026-01-23 | -7.1282 | -1.913 |
| 2026-01-23 | 2026-03-24 | +10.5694 | -5.744 |
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) |
|---|---|---|---|---|
| 2026-03-26 00:00 | 13:41:49.92 | -65:07:33.8 | HIP 67049 | 23.06 |
| 2026-03-26 12:00 | 13:38:28.29 | -65:04:26.8 | HIP 66457 | 10.61 |
| 2026-03-27 00:00 | 13:35:07.41 | -65:00:56.8 | HIP 66333 | 8.80 |
| 2026-03-27 12:00 | 13:31:47.40 | -64:57:04.2 | HIP 65904 | 13.10 |
| 2026-03-28 00:00 | 13:28:28.40 | -64:52:48.9 | HIP 65783 | 12.97 |
| 2026-03-28 12:00 | 13:25:10.53 | -64:48:11.2 | HIP 65383 | 9.73 |
| 2026-03-29 00:00 | 13:21:53.93 | -64:43:11.3 | HIP 65147 | 10.47 |
| 2026-03-29 12:00 | 13:18:38.70 | -64:37:49.5 | HIP 65147 | 15.48 |
| 2026-03-30 00:00 | 13:15:24.97 | -64:32:06.0 | HIP 64546 | 16.99 |
| 2026-03-30 12:00 | 13:12:12.84 | -64:26:01.2 | HIP 64301 | 11.02 |
| 2026-03-31 00:00 | 13:09:02.43 | -64:19:35.2 | HIP 64301 | 16.24 |
| 2026-03-31 12:00 | 13:05:53.82 | -64:12:48.5 | HIP 63847 | 5.39 |
| 2026-04-01 00:00 | 13:02:47.12 | -64:05:41.5 | HIP 63847 | 17.16 |
| 2026-04-01 12:00 | 12:59:42.42 | -63:58:14.4 | HIP 63470 | 15.67 |
| 2026-04-02 00:00 | 12:56:39.79 | -63:50:27.6 | HIP 63260 | 13.27 |
| 2026-04-02 12:00 | 12:53:39.32 | -63:42:21.7 | HIP 63041 | 10.17 |
| 2026-04-03 00:00 | 12:50:41.07 | -63:33:56.9 | HIP 62400 | 22.56 |
| 2026-04-03 12:00 | 12:47:45.12 | -63:25:13.7 | HIP 62400 | 8.29 |
| 2026-04-04 00:00 | 12:44:51.52 | -63:16:12.6 | HIP 62115 | 12.91 |
| 2026-04-04 12:00 | 12:42:00.32 | -63:06:54.0 | HIP 62027 | 6.59 |
| 2026-04-05 00:00 | 12:39:11.59 | -62:57:18.4 | HIP 61978 | 19.57 |
| 2026-04-05 12:00 | 12:36:25.35 | -62:47:26.3 | HIP 61506 | 3.80 |
| 2026-04-06 00:00 | 12:33:41.66 | -62:37:18.0 | HIP 61187 | 12.42 |
| 2026-04-06 12:00 | 12:31:00.53 | -62:26:54.2 | HIP 61187 | 9.10 |
| 2026-04-07 00:00 | 12:28:22.01 | -62:16:15.3 | HIP 60859 | 11.72 |
| 2026-04-07 12:00 | 12:25:46.11 | -62:05:21.8 | HIP 60488 | 16.36 |
| 2026-04-08 00:00 | 12:23:12.86 | -61:54:14.1 | HIP 60488 | 5.89 |
| 2026-04-08 12:00 | 12:20:42.26 | -61:42:52.9 | HIP 60288 | 12.91 |
| 2026-04-09 00:00 | 12:18:14.33 | -61:31:18.5 | HIP 59982 | 3.24 |
| 2026-04-09 12:00 | 12:15:49.07 | -61:19:31.6 | HIP 59799 | 11.74 |
| 2026-04-10 00:00 | 12:13:26.49 | -61:07:32.5 | HIP 59583 | 3.85 |
| 2026-04-10 12:00 | 12:11:06.58 | -60:55:21.8 | HIP 59601 | 16.87 |
| 2026-04-11 00:00 | 12:08:49.35 | -60:43:00.0 | HIP 59200 | 8.38 |
| 2026-04-11 12:00 | 12:06:34.78 | -60:30:27.6 | HIP 59251 | 19.63 |
| 2026-04-12 00:00 | 12:04:22.86 | -60:17:45.0 | HIP 58736 | 13.64 |
| 2026-04-12 12:00 | 12:02:13.57 | -60:04:52.8 | HIP 58699 | 5.68 |
| 2026-04-13 00:00 | 12:00:06.91 | -59:51:51.4 | HIP 58565 | 6.40 |
| 2026-04-13 12:00 | 11:58:02.86 | -59:38:41.3 | HIP 58367 | 3.15 |
| 2026-04-14 00:00 | 11:56:01.39 | -59:25:22.9 | HIP 58107 | 12.72 |
| 2026-04-14 12:00 | 11:54:02.48 | -59:11:56.8 | HIP 58107 | 8.22 |
| 2026-04-15 00:00 | 11:52:06.10 | -58:58:23.4 | HIP 58048 | 25.35 |
| 2026-04-15 12:00 | 11:50:12.24 | -58:44:43.1 | HIP 57739 | 27.56 |
| 2026-04-16 00:00 | 11:48:20.86 | -58:30:56.4 | HIP 57546 | 12.31 |