C/2023 H5 (Lemmon)
Metadata
| Parameter | Value |
|---|---|
| Designation | C/2023 H5 (Lemmon) |
| Type | C |
| Perihelion (tp_cal, UTC) | 2025-06-30T05:14:37.199040Z |
| Orbit solution date (soln_date, UTC) | 2026-08-25T08:42:10Z |
| Obs used | 2731 |
| 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) | 2025-02-02.0000000 |
| e | 1.00040332 |
| q (au) | 4.312668 |
| a (au) | -10692.859977 |
| i (deg) | 97.856350 |
| Ω (om, deg) | 159.479374 |
| ω (w, deg) | 60.090059 |
| M (ma, deg) | -0.000132 |
Magnitude
Scatter + Global Linear
$$ M_a = (7.036 + 4.455\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta $$ $$ \theta = 180^\circ - \alpha $$ $$ \Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b) $$ $$ \Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1 $$
Model Parameters
| Parameter | Value |
|---|---|
| H0 | 7.036 |
| n | 4.455 |
| gf | 0.900 |
| gb | -0.798 |
| k | 0.984 |
| δ90 | 6.301 |
| 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 | +5.8337 | -4.661 |
| 2024-01-19 | 2024-06-26 | +4.9869 | -3.864 |
| 2024-06-26 | 2025-06-30 | -3.7375 | +2.333 |
| 2025-06-30 | 2026-09-19 | +6.9605 | -4.190 |
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) |
|---|---|---|---|---|
| 2026-09-20 00:00 | 20:31:58.25 | +58:10:43.3 | HIP 101184 | 12.80 |
| 2026-09-20 12:00 | 20:31:46.67 | +58:03:34.0 | HIP 101184 | 16.66 |
| 2026-09-21 00:00 | 20:31:35.44 | +57:56:23.3 | HIP 101458 | 19.20 |
| 2026-09-21 12:00 | 20:31:24.58 | +57:49:11.3 | HIP 101458 | 18.72 |
| 2026-09-22 00:00 | 20:31:14.07 | +57:41:58.1 | HIP 101230 | 18.71 |
| 2026-09-22 12:00 | 20:31:03.92 | +57:34:43.6 | HIP 101230 | 11.50 |
| 2026-09-23 00:00 | 20:30:54.13 | +57:27:28.0 | HIP 101230 | 4.75 |
| 2026-09-23 12:00 | 20:30:44.69 | +57:20:11.2 | HIP 101230 | 4.65 |
| 2026-09-24 00:00 | 20:30:35.59 | +57:12:53.2 | HIP 101230 | 11.40 |
| 2026-09-24 12:00 | 20:30:26.85 | +57:05:34.2 | HIP 101234 | 13.65 |
| 2026-09-25 00:00 | 20:30:18.46 | +56:58:14.2 | HIP 101234 | 8.81 |
| 2026-09-25 12:00 | 20:30:10.41 | +56:50:53.1 | HIP 101234 | 8.86 |
| 2026-09-26 00:00 | 20:30:02.71 | +56:43:31.0 | HIP 101234 | 13.77 |
| 2026-09-26 12:00 | 20:29:55.34 | +56:36:08.0 | HIP 101285 | 18.62 |
| 2026-09-27 00:00 | 20:29:48.32 | +56:28:44.0 | HIP 101266 | 16.49 |
| 2026-09-27 12:00 | 20:29:41.63 | +56:21:19.2 | HIP 101266 | 15.69 |
| 2026-09-28 00:00 | 20:29:35.27 | +56:13:53.5 | HIP 101084 | 9.87 |
| 2026-09-28 12:00 | 20:29:29.25 | +56:06:27.0 | HIP 101084 | 2.38 |
| 2026-09-29 00:00 | 20:29:23.56 | +55:58:59.8 | HIP 101084 | 5.12 |
| 2026-09-29 12:00 | 20:29:18.20 | +55:51:31.8 | HIP 101084 | 12.62 |
| 2026-09-30 00:00 | 20:29:13.17 | +55:44:03.0 | HIP 101084 | 20.14 |
| 2026-09-30 12:00 | 20:29:08.46 | +55:36:33.6 | HIP 101287 | 22.71 |
| 2026-10-01 00:00 | 20:29:04.08 | +55:29:03.5 | HIP 101231 | 20.51 |
| 2026-10-01 12:00 | 20:29:00.01 | +55:21:32.9 | HIP 101231 | 18.77 |
| 2026-10-02 00:00 | 20:28:56.27 | +55:14:01.6 | HIP 101171 | 19.40 |
| 2026-10-02 12:00 | 20:28:52.84 | +55:06:29.8 | HIP 101171 | 14.91 |
| 2026-10-03 00:00 | 20:28:49.73 | +54:58:57.4 | HIP 101171 | 13.46 |
| 2026-10-03 12:00 | 20:28:46.93 | +54:51:24.6 | HIP 101171 | 15.90 |
| 2026-10-04 00:00 | 20:28:44.44 | +54:43:51.3 | HIP 101163 | 13.94 |
| 2026-10-04 12:00 | 20:28:42.26 | +54:36:17.6 | HIP 101163 | 14.67 |
| 2026-10-05 00:00 | 20:28:40.39 | +54:28:43.5 | HIP 101163 | 18.70 |
| 2026-10-05 12:00 | 20:28:38.83 | +54:21:09.1 | HIP 101163 | 24.45 |
| 2026-10-06 00:00 | 20:28:37.57 | +54:13:34.4 | HIP 101222 | 30.56 |
| 2026-10-06 12:00 | 20:28:36.61 | +54:05:59.3 | HIP 101124 | 26.39 |
| 2026-10-07 00:00 | 20:28:35.95 | +53:58:24.0 | HIP 101124 | 19.92 |
| 2026-10-07 12:00 | 20:28:35.58 | +53:50:48.5 | HIP 101124 | 14.53 |
| 2026-10-08 00:00 | 20:28:35.52 | +53:43:12.9 | HIP 101124 | 11.82 |
| 2026-10-08 12:00 | 20:28:35.74 | +53:35:37.0 | HIP 101124 | 13.52 |
| 2026-10-09 00:00 | 20:28:36.26 | +53:28:01.1 | HIP 101085 | 9.71 |
| 2026-10-09 12:00 | 20:28:37.07 | +53:20:25.1 | HIP 101085 | 7.68 |
| 2026-10-10 00:00 | 20:28:38.16 | +53:12:49.0 | HIP 101085 | 11.77 |
| 2026-10-10 12:00 | 20:28:39.54 | +53:05:12.9 | HIP 101085 | 18.26 |
| 2026-10-11 00:00 | 20:28:41.21 | +52:57:36.9 | HIP 101085 | 25.36 |