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
$$ M_a = (5.655 + 6.000\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta $$ $$ \theta = 180^\circ - \alpha $$ $$ \Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b) $$ $$ \Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1 $$
Model Parameters
| Parameter | Value |
|---|---|
| H0 | 5.655 |
| n | 6.000 |
| gf | 0.999 |
| gb | -0.504 |
| 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 | 2025-01-06 | +12.5528 | -7.426 |
| 2025-01-07 | 2026-04-06 | -16.2587 | +9.534 |
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) |
|---|---|---|---|---|
| 2026-05-12 00:00 | 07:54:49.92 | -02:51:51.2 | HIP 38728 | 24.18 |
| 2026-05-12 12:00 | 07:55:12.28 | -02:49:47.8 | HIP 38728 | 23.48 |
| 2026-05-13 00:00 | 07:55:34.75 | -02:47:45.7 | HIP 38728 | 24.24 |
| 2026-05-13 12:00 | 07:55:57.33 | -02:45:45.1 | HIP 38728 | 26.35 |
| 2026-05-14 00:00 | 07:56:20.02 | -02:43:45.8 | HIP 38728 | 29.53 |
| 2026-05-14 12:00 | 07:56:42.83 | -02:41:47.9 | HIP 38728 | 33.48 |
| 2026-05-15 00:00 | 07:57:05.74 | -02:39:51.4 | HIP 38714 | 36.65 |
| 2026-05-15 12:00 | 07:57:28.77 | -02:37:56.2 | HIP 38714 | 39.20 |
| 2026-05-16 00:00 | 07:57:51.90 | -02:36:02.5 | HIP 38714 | 42.50 |
| 2026-05-16 12:00 | 07:58:15.14 | -02:34:10.1 | HIP 39172 | 41.66 |
| 2026-05-17 00:00 | 07:58:38.48 | -02:32:19.1 | HIP 39172 | 37.54 |
| 2026-05-17 12:00 | 07:59:01.93 | -02:30:29.4 | HIP 39172 | 33.98 |
| 2026-05-18 00:00 | 07:59:25.48 | -02:28:41.2 | HIP 39172 | 31.19 |
| 2026-05-18 12:00 | 07:59:49.14 | -02:26:54.3 | HIP 39172 | 29.41 |
| 2026-05-19 00:00 | 08:00:12.89 | -02:25:08.8 | HIP 39172 | 28.84 |
| 2026-05-19 12:00 | 08:00:36.75 | -02:23:24.6 | HIP 39292 | 22.66 |
| 2026-05-20 00:00 | 08:01:00.70 | -02:21:41.9 | HIP 39292 | 16.43 |
| 2026-05-20 12:00 | 08:01:24.75 | -02:20:00.5 | HIP 39292 | 10.19 |
| 2026-05-21 00:00 | 08:01:48.90 | -02:18:20.4 | HIP 39292 | 3.94 |
| 2026-05-21 12:00 | 08:02:13.14 | -02:16:41.8 | HIP 39292 | 2.38 |
| 2026-05-22 00:00 | 08:02:37.48 | -02:15:04.5 | HIP 39337 | 7.25 |
| 2026-05-22 12:00 | 08:03:01.91 | -02:13:28.5 | HIP 39337 | 9.81 |
| 2026-05-23 00:00 | 08:03:26.43 | -02:11:53.9 | HIP 39337 | 14.84 |
| 2026-05-23 12:00 | 08:03:51.05 | -02:10:20.7 | HIP 39486 | 20.02 |
| 2026-05-24 00:00 | 08:04:15.75 | -02:08:48.8 | HIP 39486 | 17.65 |
| 2026-05-24 12:00 | 08:04:40.54 | -02:07:18.3 | HIP 39486 | 17.44 |
| 2026-05-25 00:00 | 08:05:05.42 | -02:05:49.1 | HIP 39486 | 19.47 |
| 2026-05-25 12:00 | 08:05:30.39 | -02:04:21.2 | HIP 39486 | 23.18 |
| 2026-05-26 00:00 | 08:05:55.44 | -02:02:54.7 | HIP 39672 | 22.11 |
| 2026-05-26 12:00 | 08:06:20.58 | -02:01:29.5 | HIP 39672 | 22.18 |
| 2026-05-27 00:00 | 08:06:45.80 | -02:00:05.7 | HIP 39701 | 21.26 |
| 2026-05-27 12:00 | 08:07:11.11 | -01:58:43.2 | HIP 39701 | 20.41 |
| 2026-05-28 00:00 | 08:07:36.49 | -01:57:22.0 | HIP 39857 | 16.14 |
| 2026-05-28 12:00 | 08:08:01.96 | -01:56:02.1 | HIP 39857 | 11.82 |
| 2026-05-29 00:00 | 08:08:27.51 | -01:54:43.5 | HIP 39857 | 10.16 |
| 2026-05-29 12:00 | 08:08:53.14 | -01:53:26.3 | HIP 39857 | 12.29 |
| 2026-05-30 00:00 | 08:09:18.84 | -01:52:10.4 | HIP 39857 | 16.86 |
| 2026-05-30 12:00 | 08:09:44.63 | -01:50:55.7 | HIP 39962 | 19.84 |
| 2026-05-31 00:00 | 08:10:10.49 | -01:49:42.4 | HIP 40080 | 22.20 |
| 2026-05-31 12:00 | 08:10:36.42 | -01:48:30.4 | HIP 40080 | 17.19 |
| 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 |