242P/Spahr
Metadata
| Parameter | Value |
|---|---|
| Designation | 242P/Spahr |
| Type | P |
| Perihelion (tp_cal, UTC) | 2025-01-06T00:15:17.516160Z |
| Orbit solution date (soln_date, UTC) | 2026-05-08T13:42:13Z |
| Obs used | 1557 |
| NEO | - |
| M1 | 11.100 |
| K1 | 7.250 |
| PC | - |
Osculating Elements
| Parameter | Value |
|---|---|
| Epoch (epoch_cal, TDB) | 2020-03-03.0000000 |
| e | 0.27787117 |
| q (au) | 3.954577 |
| a (au) | 5.476276 |
| i (deg) | 32.479961 |
| Ω (om, deg) | 180.502312 |
| ω (w, deg) | 246.294601 |
| M (ma, deg) | 223.870592 |
Magnitude
Scatter + Global Linear
$$ M_a = (11.528 + 2.000\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta $$ $$ \theta = 180^\circ - \alpha $$ $$ \Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b) $$ $$ \Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1 $$
Model Parameters
| Parameter | Value |
|---|---|
| H0 | 11.528 |
| n | 2.000 |
| gf | 1.000 |
| gb | -0.512 |
| k | 1.000 |
| 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 |
|---|---|---|---|
| 2023-07-28 | 2025-01-05 | +22.5723 | -13.313 |
| 2025-01-06 | 2026-04-07 | -14.1768 | +8.451 |
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 | 08:11:02.43 | -01:47:19.7 | HIP 40080 | 13.61 |
| 2026-06-01 12:00 | 08:11:28.52 | -01:46:10.3 | HIP 40080 | 12.78 |
| 2026-06-02 00:00 | 08:11:54.68 | -01:45:02.2 | HIP 40080 | 15.16 |
| 2026-06-02 12:00 | 08:12:20.91 | -01:43:55.4 | HIP 40080 | 19.63 |
| 2026-06-03 00:00 | 08:12:47.21 | -01:42:49.8 | HIP 40080 | 25.11 |
| 2026-06-03 12:00 | 08:13:13.59 | -01:41:45.6 | HIP 40080 | 31.08 |
| 2026-06-04 00:00 | 08:13:40.03 | -01:40:42.6 | HIP 40263 | 31.09 |
| 2026-06-04 12:00 | 08:14:06.54 | -01:39:41.0 | HIP 40263 | 31.76 |
| 2026-06-05 00:00 | 08:14:33.13 | -01:38:40.6 | HIP 40457 | 29.00 |
| 2026-06-05 12:00 | 08:14:59.78 | -01:37:41.4 | HIP 40457 | 24.88 |
| 2026-06-06 00:00 | 08:15:26.49 | -01:36:43.6 | HIP 40457 | 22.11 |
| 2026-06-06 12:00 | 08:15:53.28 | -01:35:47.0 | HIP 40457 | 21.24 |
| 2026-06-07 00:00 | 08:16:20.13 | -01:34:51.7 | HIP 40598 | 21.34 |
| 2026-06-07 12:00 | 08:16:47.04 | -01:33:57.6 | HIP 40598 | 18.21 |
| 2026-06-08 00:00 | 08:17:14.02 | -01:33:04.8 | HIP 40598 | 17.29 |
| 2026-06-08 12:00 | 08:17:41.06 | -01:32:13.3 | HIP 40649 | 16.23 |
| 2026-06-09 00:00 | 08:18:08.17 | -01:31:23.0 | HIP 40649 | 17.30 |
| 2026-06-09 12:00 | 08:18:35.34 | -01:30:34.0 | HIP 40649 | 20.68 |
| 2026-06-10 00:00 | 08:19:02.57 | -01:29:46.3 | HIP 40649 | 25.49 |
| 2026-06-10 12:00 | 08:19:29.86 | -01:28:59.7 | HIP 40941 | 28.50 |
| 2026-06-11 00:00 | 08:19:57.20 | -01:28:14.5 | HIP 40941 | 22.21 |
| 2026-06-11 12:00 | 08:20:24.61 | -01:27:30.5 | HIP 40941 | 16.36 |
| 2026-06-12 00:00 | 08:20:52.08 | -01:26:47.7 | HIP 40941 | 11.69 |
| 2026-06-12 12:00 | 08:21:19.60 | -01:26:06.2 | HIP 40941 | 10.02 |
| 2026-06-13 00:00 | 08:21:47.18 | -01:25:25.9 | HIP 40941 | 12.62 |
| 2026-06-13 12:00 | 08:22:14.82 | -01:24:46.8 | HIP 40941 | 17.73 |
| 2026-06-14 00:00 | 08:22:42.51 | -01:24:09.0 | HIP 41166 | 19.29 |
| 2026-06-14 12:00 | 08:23:10.25 | -01:23:32.4 | HIP 41166 | 13.12 |
| 2026-06-15 00:00 | 08:23:38.05 | -01:22:57.0 | HIP 41166 | 8.28 |
| 2026-06-15 12:00 | 08:24:05.90 | -01:22:22.8 | HIP 41166 | 7.88 |
| 2026-06-16 00:00 | 08:24:33.80 | -01:21:49.9 | HIP 41166 | 12.37 |
| 2026-06-16 12:00 | 08:25:01.75 | -01:21:18.2 | HIP 41209 | 14.33 |
| 2026-06-17 00:00 | 08:25:29.75 | -01:20:47.7 | HIP 41209 | 18.49 |
| 2026-06-17 12:00 | 08:25:57.81 | -01:20:18.4 | HIP 41417 | 15.42 |
| 2026-06-18 00:00 | 08:26:25.90 | -01:19:50.3 | HIP 41417 | 9.50 |
| 2026-06-18 12:00 | 08:26:54.05 | -01:19:23.4 | HIP 41417 | 6.48 |
| 2026-06-19 00:00 | 08:27:22.24 | -01:18:57.6 | HIP 41417 | 9.67 |
| 2026-06-19 12:00 | 08:27:50.48 | -01:18:33.1 | HIP 41417 | 15.66 |
| 2026-06-20 00:00 | 08:28:18.76 | -01:18:09.8 | HIP 41417 | 22.31 |
| 2026-06-20 12:00 | 08:28:47.08 | -01:17:47.6 | HIP 41645 | 22.93 |
| 2026-06-21 00:00 | 08:29:15.45 | -01:17:26.6 | HIP 41645 | 20.20 |
| 2026-06-21 12:00 | 08:29:43.86 | -01:17:06.8 | HIP 41645 | 19.79 |
| 2026-06-22 00:00 | 08:30:12.30 | -01:16:48.1 | HIP 41645 | 21.86 |