C/2025 A6 (Lemmon)
Metadata
| Parameter | Value |
|---|---|
| Designation | C/2025 A6 (Lemmon) |
| Type | C |
| Perihelion (tp_cal, UTC) | 2025-11-08T12:57:13.985280Z |
| Orbit solution date (soln_date, UTC) | 2026-05-28T12:12:15Z |
| Obs used | 2011 |
| NEO | - |
| M1 | 10.400 |
| K1 | 9.250 |
| PC | - |
| Discovery observation (MPC, UTC) | 2025-01-03T08:12:42.537600Z |
| Discovery magnitude (MPC) | 21.65 G |
| Discovery observatory (MPC) | G96 · University of Arizona Mt. Lemmon Survey |
Osculating Elements
| Parameter | Value |
|---|---|
| Epoch (epoch_cal, TDB) | 2025-10-21.0000000 |
| e | 0.99555136 |
| q (au) | 0.529897 |
| a (au) | 119.114259 |
| i (deg) | 143.663695 |
| Ω (om, deg) | 108.097912 |
| ω (w, deg) | 132.970610 |
| M (ma, deg) | 359.985944 |
Magnitude
Scatter + Global Linear
$$ M_a = (8.664 + 5.317\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta $$ $$ \theta = 180^\circ - \alpha $$ $$ \Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b) $$ $$ \Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1 $$
Model Parameters
| Parameter | Value |
|---|---|
| H0 | 8.664 |
| n | 5.317 |
| gf | 1.000 |
| gb | -0.524 |
| 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 | +5.7589 | -0.986 |
| 2025-09-20 | 2025-11-08 | -3.7659 | -0.119 |
| 2025-11-08 | 2026-01-21 | -6.9254 | -1.857 |
| 2026-01-21 | 2026-05-27 | +10.3491 | -5.473 |
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) |
|---|---|---|---|---|
| 2026-06-01 00:00 | 10:46:47.54 | -39:14:01.7 | HIP 52589 | 28.29 |
| 2026-06-01 12:00 | 10:46:46.15 | -39:05:19.6 | HIP 52589 | 22.19 |
| 2026-06-02 00:00 | 10:46:45.15 | -38:56:43.1 | HIP 52589 | 18.43 |
| 2026-06-02 12:00 | 10:46:44.55 | -38:48:12.2 | HIP 52589 | 18.36 |
| 2026-06-03 00:00 | 10:46:44.35 | -38:39:46.8 | HIP 52832 | 16.77 |
| 2026-06-03 12:00 | 10:46:44.52 | -38:31:27.0 | HIP 52745 | 16.85 |
| 2026-06-04 00:00 | 10:46:45.06 | -38:23:12.6 | HIP 52745 | 8.85 |
| 2026-06-04 12:00 | 10:46:45.98 | -38:15:03.8 | HIP 52745 | 2.88 |
| 2026-06-05 00:00 | 10:46:47.25 | -38:07:00.3 | HIP 52745 | 8.32 |
| 2026-06-05 12:00 | 10:46:48.88 | -37:59:02.3 | HIP 52745 | 16.03 |
| 2026-06-06 00:00 | 10:46:50.86 | -37:51:09.7 | HIP 52778 | 20.95 |
| 2026-06-06 12:00 | 10:46:53.18 | -37:43:22.5 | HIP 52778 | 13.64 |
| 2026-06-07 00:00 | 10:46:55.83 | -37:35:40.5 | HIP 52778 | 7.40 |
| 2026-06-07 12:00 | 10:46:58.82 | -37:28:03.9 | HIP 52778 | 6.42 |
| 2026-06-08 00:00 | 10:47:02.13 | -37:20:32.5 | HIP 52778 | 11.90 |
| 2026-06-08 12:00 | 10:47:05.76 | -37:13:06.3 | HIP 52778 | 18.77 |
| 2026-06-09 00:00 | 10:47:09.70 | -37:05:45.4 | HIP 52635 | 18.43 |
| 2026-06-09 12:00 | 10:47:13.95 | -36:58:29.6 | HIP 52635 | 16.96 |
| 2026-06-10 00:00 | 10:47:18.50 | -36:51:19.0 | HIP 52635 | 18.55 |
| 2026-06-10 12:00 | 10:47:23.35 | -36:44:13.5 | HIP 52635 | 22.49 |
| 2026-06-11 00:00 | 10:47:28.50 | -36:37:13.0 | HIP 52635 | 27.72 |
| 2026-06-11 12:00 | 10:47:33.93 | -36:30:17.7 | HIP 52923 | 26.65 |
| 2026-06-12 00:00 | 10:47:39.64 | -36:23:27.3 | HIP 52923 | 22.59 |
| 2026-06-12 12:00 | 10:47:45.63 | -36:16:41.9 | HIP 52923 | 20.11 |
| 2026-06-13 00:00 | 10:47:51.89 | -36:10:01.5 | HIP 52923 | 19.73 |
| 2026-06-13 12:00 | 10:47:58.43 | -36:03:26.0 | HIP 52900 | 15.98 |
| 2026-06-14 00:00 | 10:48:05.22 | -35:56:55.5 | HIP 52900 | 13.12 |
| 2026-06-14 12:00 | 10:48:12.28 | -35:50:29.8 | HIP 52900 | 13.23 |
| 2026-06-15 00:00 | 10:48:19.58 | -35:44:08.9 | HIP 52900 | 16.17 |
| 2026-06-15 12:00 | 10:48:27.14 | -35:37:52.8 | HIP 52960 | 20.69 |
| 2026-06-16 00:00 | 10:48:34.95 | -35:31:41.5 | HIP 52960 | 23.26 |
| 2026-06-16 12:00 | 10:48:42.99 | -35:25:35.0 | HIP 52960 | 27.03 |
| 2026-06-17 00:00 | 10:48:51.27 | -35:19:33.1 | HIP 52960 | 31.53 |
| 2026-06-17 12:00 | 10:48:59.79 | -35:13:36.0 | HIP 53077 | 32.92 |
| 2026-06-18 00:00 | 10:49:08.53 | -35:07:43.5 | HIP 52784 | 33.12 |
| 2026-06-18 12:00 | 10:49:17.50 | -35:01:55.6 | HIP 52784 | 30.09 |
| 2026-06-19 00:00 | 10:49:26.68 | -34:56:12.2 | HIP 52784 | 28.16 |
| 2026-06-19 12:00 | 10:49:36.09 | -34:50:33.5 | HIP 53011 | 25.57 |
| 2026-06-20 00:00 | 10:49:45.70 | -34:44:59.2 | HIP 53011 | 19.88 |
| 2026-06-20 12:00 | 10:49:55.52 | -34:39:29.4 | HIP 53011 | 14.39 |
| 2026-06-21 00:00 | 10:50:05.55 | -34:34:04.0 | HIP 53011 | 9.36 |
| 2026-06-21 12:00 | 10:50:15.78 | -34:28:43.1 | HIP 53011 | 5.90 |
| 2026-06-22 00:00 | 10:50:26.20 | -34:23:26.5 | HIP 53011 | 6.84 |