1P/Halley
Metadata
| Parameter | Value |
|---|---|
| Designation | 1P/Halley |
| Type | P |
| Perihelion (tp_cal, UTC) | 1986-02-08T11:22:00.431040Z |
| Orbit solution date (soln_date, UTC) | 2025-11-21T15:57:34Z |
| Obs used | 8518 |
| NEO | Yes |
| M1 | 5.500 |
| K1 | 8.000 |
| PC | 0.030 |
Osculating Elements
| Parameter | Value |
|---|---|
| Epoch (epoch_cal, TDB) | 1968-01-20.0000000 |
| e | 0.96793600 |
| q (au) | 0.574864 |
| a (au) | 17.928635 |
| i (deg) | 162.190530 |
| Ω (om, deg) | 59.098947 |
| ω (w, deg) | 112.241431 |
| M (ma, deg) | 274.382337 |
Description
The first predicted periodic comet; the earliest known record appears in China’s Shiji (Records of the Grand Historian) in 240 BCE.
Magnitude
Scatter + Global Linear
$$ M_a = (3.660 + 3.868\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta $$ $$ \theta = 180^\circ - \alpha $$ $$ \Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b) $$ $$ \Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1 $$
Model Parameters
| Parameter | Value |
|---|---|
| H0 | 3.660 |
| n | 3.868 |
| gf | 1.000 |
| gb | -0.500 |
| 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 |
|---|---|---|---|
| 1981-12-02 | 1985-11-05 | +6.7285 | -0.429 |
| 1985-11-05 | 1986-01-28 | +2.0431 | +0.389 |
| 1986-02-15 | 1986-07-09 | -2.8084 | -0.457 |
| 1986-07-09 | 1988-04-30 | +0.7924 | -1.679 |
| 1988-04-30 | 1990-10-11 | -1.4554 | +0.636 |
| 1990-10-11 | 2003-03-08 | +16.4369 | -19.774 |
log10 r = log10(heliocentric distance / AU), Δ = geocentric distance (AU)
Ephemeris
| Date/Time (UTC) | RA (J2000) | Dec (J2000) | Nearest HIP | Dist from HIP (arcmin) |
|---|---|---|---|---|
| 2026-02-03 00:00 | 08:13:50.38 | +02:37:19.1 | HIP 40186 | 23.41 |
| 2026-02-03 12:00 | 08:13:46.93 | +02:37:33.8 | HIP 40186 | 22.55 |
| 2026-02-04 00:00 | 08:13:43.49 | +02:37:48.5 | HIP 40186 | 21.70 |
| 2026-02-04 12:00 | 08:13:40.05 | +02:38:03.4 | HIP 40186 | 20.86 |
| 2026-02-05 00:00 | 08:13:36.62 | +02:38:18.4 | HIP 40186 | 20.02 |
| 2026-02-05 12:00 | 08:13:33.20 | +02:38:33.5 | HIP 40186 | 19.18 |
| 2026-02-06 00:00 | 08:13:29.78 | +02:38:48.7 | HIP 40186 | 18.35 |
| 2026-02-06 12:00 | 08:13:26.38 | +02:39:04.0 | HIP 40186 | 17.52 |
| 2026-02-07 00:00 | 08:13:22.98 | +02:39:19.4 | HIP 40186 | 16.71 |
| 2026-02-07 12:00 | 08:13:19.59 | +02:39:34.9 | HIP 40186 | 15.90 |
| 2026-02-08 00:00 | 08:13:16.22 | +02:39:50.5 | HIP 40186 | 15.09 |
| 2026-02-08 12:00 | 08:13:12.85 | +02:40:06.2 | HIP 40186 | 14.30 |
| 2026-02-09 00:00 | 08:13:09.49 | +02:40:22.0 | HIP 40186 | 13.53 |
| 2026-02-09 12:00 | 08:13:06.13 | +02:40:37.9 | HIP 40186 | 12.76 |
| 2026-02-10 00:00 | 08:13:02.79 | +02:40:53.9 | HIP 40186 | 12.01 |
| 2026-02-10 12:00 | 08:12:59.46 | +02:41:10.0 | HIP 40186 | 11.28 |
| 2026-02-11 00:00 | 08:12:56.15 | +02:41:26.2 | HIP 40186 | 10.57 |
| 2026-02-11 12:00 | 08:12:52.84 | +02:41:42.4 | HIP 40186 | 9.89 |
| 2026-02-12 00:00 | 08:12:49.54 | +02:41:58.8 | HIP 40186 | 9.23 |
| 2026-02-12 12:00 | 08:12:46.26 | +02:42:15.3 | HIP 40186 | 8.62 |
| 2026-02-13 00:00 | 08:12:42.98 | +02:42:31.8 | HIP 40186 | 8.05 |
| 2026-02-13 12:00 | 08:12:39.72 | +02:42:48.4 | HIP 40186 | 7.54 |
| 2026-02-14 00:00 | 08:12:36.47 | +02:43:05.1 | HIP 40186 | 7.10 |
| 2026-02-14 12:00 | 08:12:33.23 | +02:43:21.9 | HIP 40186 | 6.73 |
| 2026-02-15 00:00 | 08:12:30.01 | +02:43:38.8 | HIP 40186 | 6.45 |
| 2026-02-15 12:00 | 08:12:26.80 | +02:43:55.7 | HIP 40186 | 6.28 |
| 2026-02-16 00:00 | 08:12:23.60 | +02:44:12.8 | HIP 40186 | 6.22 |
| 2026-02-16 12:00 | 08:12:20.42 | +02:44:29.9 | HIP 40186 | 6.27 |
| 2026-02-17 00:00 | 08:12:17.25 | +02:44:47.0 | HIP 40186 | 6.43 |
| 2026-02-17 12:00 | 08:12:14.09 | +02:45:04.3 | HIP 40186 | 6.69 |
| 2026-02-18 00:00 | 08:12:10.95 | +02:45:21.6 | HIP 40186 | 7.03 |
| 2026-02-18 12:00 | 08:12:07.82 | +02:45:39.0 | HIP 40186 | 7.45 |
| 2026-02-19 00:00 | 08:12:04.71 | +02:45:56.5 | HIP 40186 | 7.93 |
| 2026-02-19 12:00 | 08:12:01.62 | +02:46:14.0 | HIP 40186 | 8.47 |
| 2026-02-20 00:00 | 08:11:58.53 | +02:46:31.6 | HIP 40186 | 9.04 |
| 2026-02-20 12:00 | 08:11:55.47 | +02:46:49.3 | HIP 40186 | 9.64 |
| 2026-02-21 00:00 | 08:11:52.42 | +02:47:07.0 | HIP 40186 | 10.27 |
| 2026-02-21 12:00 | 08:11:49.39 | +02:47:24.8 | HIP 40186 | 10.93 |
| 2026-02-22 00:00 | 08:11:46.37 | +02:47:42.7 | HIP 40186 | 11.59 |
| 2026-02-22 12:00 | 08:11:43.37 | +02:48:00.6 | HIP 40186 | 12.27 |
| 2026-02-23 00:00 | 08:11:40.39 | +02:48:18.6 | HIP 40186 | 12.96 |
| 2026-02-23 12:00 | 08:11:37.42 | +02:48:36.6 | HIP 40186 | 13.66 |
| 2026-02-24 00:00 | 08:11:34.47 | +02:48:54.7 | HIP 40186 | 14.37 |