C/2023 H5 (Lemmon)
Metadata
| Parameter | Value |
|---|---|
| Designation | C/2023 H5 (Lemmon) |
| Type | C |
| Perihelion (tp_cal, UTC) | 2025-06-30T05:10:00.736320Z |
| Orbit solution date (soln_date, UTC) | 2026-07-28T14:12:17Z |
| Obs used | 2693 |
| NEO | - |
| M1 | 8.400 |
| K1 | 8.000 |
| PC | 0.030 |
| Discovery observation (MPC, UTC) | 2023-04-19T04:23:52.540800Z |
| Discovery magnitude (MPC) | 20.29 G |
| Discovery observatory (MPC) | G96 · University of Arizona Mt. Lemmon Survey |
Osculating Elements
| Parameter | Value |
|---|---|
| Epoch (epoch_cal, TDB) | 2025-01-25.0000000 |
| e | 1.00039773 |
| q (au) | 4.312677 |
| a (au) | -10843.236885 |
| i (deg) | 97.856545 |
| Ω (om, deg) | 159.479522 |
| ω (w, deg) | 60.089524 |
| M (ma, deg) | -0.000136 |
Magnitude
Scatter + Global Linear
$$ M_a = (7.597 + 4.323\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta $$ $$ \theta = 180^\circ - \alpha $$ $$ \Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b) $$ $$ \Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1 $$
Model Parameters
| Parameter | Value |
|---|---|
| H0 | 7.597 |
| n | 4.323 |
| gf | 0.922 |
| gb | -0.782 |
| k | 0.972 |
| δ90 | 6.936 |
| 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 |
|---|---|---|---|
| 2022-12-01 | 2024-01-19 | +6.2497 | -4.969 |
| 2024-01-19 | 2024-06-26 | +4.6525 | -3.597 |
| 2024-06-26 | 2025-06-30 | -3.4214 | +2.131 |
| 2025-06-30 | 2026-07-27 | +9.3970 | -5.773 |
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 | 21:24:41.02 | +66:56:37.7 | HIP 105605 | 7.79 |
| 2026-07-29 12:00 | 21:23:59.56 | +66:54:28.9 | HIP 105605 | 4.62 |
| 2026-07-30 00:00 | 21:23:18.12 | +66:52:16.6 | HIP 105605 | 4.98 |
| 2026-07-30 12:00 | 21:22:36.68 | +66:50:00.8 | HIP 105605 | 8.47 |
| 2026-07-31 00:00 | 21:21:55.27 | +66:47:41.6 | HIP 105605 | 12.77 |
| 2026-07-31 12:00 | 21:21:13.89 | +66:45:18.8 | HIP 105605 | 17.32 |
| 2026-08-01 00:00 | 21:20:32.54 | +66:42:52.6 | HIP 105122 | 17.76 |
| 2026-08-01 12:00 | 21:19:51.24 | +66:40:22.8 | HIP 105122 | 13.25 |
| 2026-08-02 00:00 | 21:19:09.99 | +66:37:49.5 | HIP 105122 | 9.02 |
| 2026-08-02 12:00 | 21:18:28.80 | +66:35:12.7 | HIP 105122 | 5.83 |
| 2026-08-03 00:00 | 21:17:47.69 | +66:32:32.3 | HIP 105122 | 5.83 |
| 2026-08-03 12:00 | 21:17:06.64 | +66:29:48.4 | HIP 105122 | 9.09 |
| 2026-08-04 00:00 | 21:16:25.69 | +66:27:01.0 | HIP 105122 | 13.45 |
| 2026-08-04 12:00 | 21:15:44.83 | +66:24:10.0 | HIP 105122 | 18.15 |
| 2026-08-05 00:00 | 21:15:04.06 | +66:21:15.5 | HIP 105187 | 21.89 |
| 2026-08-05 12:00 | 21:14:23.41 | +66:18:17.5 | HIP 104543 | 24.48 |
| 2026-08-06 00:00 | 21:13:42.87 | +66:15:15.9 | HIP 104543 | 19.64 |
| 2026-08-06 12:00 | 21:13:02.46 | +66:12:10.8 | HIP 104543 | 14.96 |
| 2026-08-07 00:00 | 21:12:22.17 | +66:09:02.1 | HIP 104543 | 10.67 |
| 2026-08-07 12:00 | 21:11:42.03 | +66:05:49.9 | HIP 104543 | 7.55 |
| 2026-08-08 00:00 | 21:11:02.03 | +66:02:34.1 | HIP 104543 | 7.38 |
| 2026-08-08 12:00 | 21:10:22.19 | +65:59:14.8 | HIP 104543 | 10.35 |
| 2026-08-09 00:00 | 21:09:42.50 | +65:55:51.9 | HIP 104543 | 14.70 |
| 2026-08-09 12:00 | 21:09:02.99 | +65:52:25.5 | HIP 104502 | 13.05 |
| 2026-08-10 00:00 | 21:08:23.65 | +65:48:55.6 | HIP 104502 | 13.18 |
| 2026-08-10 12:00 | 21:07:44.50 | +65:45:22.2 | HIP 104502 | 15.29 |
| 2026-08-11 00:00 | 21:07:05.53 | +65:41:45.2 | HIP 104502 | 18.73 |
| 2026-08-11 12:00 | 21:06:26.77 | +65:38:04.7 | HIP 104462 | 20.92 |
| 2026-08-12 00:00 | 21:05:48.21 | +65:34:20.7 | HIP 104462 | 23.97 |
| 2026-08-12 12:00 | 21:05:09.86 | +65:30:33.2 | HIP 104462 | 27.76 |
| 2026-08-13 00:00 | 21:04:31.73 | +65:26:42.2 | HIP 103974 | 23.82 |
| 2026-08-13 12:00 | 21:03:53.82 | +65:22:47.8 | HIP 103974 | 19.69 |
| 2026-08-14 00:00 | 21:03:16.15 | +65:18:49.9 | HIP 103974 | 16.36 |
| 2026-08-14 12:00 | 21:02:38.71 | +65:14:48.5 | HIP 103974 | 14.46 |
| 2026-08-15 00:00 | 21:02:01.52 | +65:10:43.7 | HIP 103974 | 14.57 |
| 2026-08-15 12:00 | 21:01:24.58 | +65:06:35.5 | HIP 103974 | 16.70 |
| 2026-08-16 00:00 | 21:00:47.90 | +65:02:23.9 | HIP 103974 | 20.24 |
| 2026-08-16 12:00 | 21:00:11.48 | +64:58:08.8 | HIP 103974 | 24.61 |
| 2026-08-17 00:00 | 20:59:35.32 | +64:53:50.4 | HIP 103974 | 29.46 |
| 2026-08-17 12:00 | 20:58:59.45 | +64:49:28.7 | HIP 103307 | 27.80 |
| 2026-08-18 00:00 | 20:58:23.84 | +64:45:03.6 | HIP 103307 | 22.05 |
| 2026-08-18 12:00 | 20:57:48.53 | +64:40:35.2 | HIP 103307 | 16.33 |
| 2026-08-19 00:00 | 20:57:13.50 | +64:36:03.5 | HIP 103307 | 10.74 |