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
$$ M_a = (3.661 + 3.876\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta $$ $$ \theta = 180^\circ - \alpha $$ $$ \Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b) $$ $$ \Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1 $$
Model Parameters
| Parameter | Value |
|---|---|
| H0 | 3.661 |
| n | 3.876 |
| 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 | +6.7140 | -0.431 |
| 1985-11-05 | 1986-01-28 | +2.0297 | +0.388 |
| 1986-02-15 | 1986-07-08 | -2.7942 | -0.455 |
| 1986-07-08 | 1987-12-12 | +0.0819 | -1.319 |
| 1987-12-12 | 2003-03-08 | +3.7502 | -4.319 |
log10 r = log10(heliocentric distance / AU), Δ = geocentric distance (AU)
Ephemeris
| Date/Time (UTC) | RA (J2000) | Dec (J2000) | Nearest HIP | Dist from HIP (arcmin) |
|---|---|---|---|---|
| 2026-05-12 00:00 | 08:08:51.40 | +03:31:37.6 | HIP 39924 | 16.54 |
| 2026-05-12 12:00 | 08:08:52.43 | +03:31:48.0 | HIP 39924 | 16.29 |
| 2026-05-13 00:00 | 08:08:53.49 | +03:31:58.2 | HIP 39924 | 16.05 |
| 2026-05-13 12:00 | 08:08:54.58 | +03:32:08.3 | HIP 39924 | 15.81 |
| 2026-05-14 00:00 | 08:08:55.68 | +03:32:18.2 | HIP 39924 | 15.57 |
| 2026-05-14 12:00 | 08:08:56.82 | +03:32:28.1 | HIP 39924 | 15.34 |
| 2026-05-15 00:00 | 08:08:57.98 | +03:32:37.8 | HIP 39924 | 15.11 |
| 2026-05-15 12:00 | 08:08:59.16 | +03:32:47.3 | HIP 39924 | 14.88 |
| 2026-05-16 00:00 | 08:09:00.37 | +03:32:56.8 | HIP 39924 | 14.66 |
| 2026-05-16 12:00 | 08:09:01.60 | +03:33:06.1 | HIP 39924 | 14.45 |
| 2026-05-17 00:00 | 08:09:02.86 | +03:33:15.2 | HIP 39924 | 14.24 |
| 2026-05-17 12:00 | 08:09:04.15 | +03:33:24.3 | HIP 39924 | 14.04 |
| 2026-05-18 00:00 | 08:09:05.45 | +03:33:33.2 | HIP 39924 | 13.84 |
| 2026-05-18 12:00 | 08:09:06.78 | +03:33:41.9 | HIP 39924 | 13.66 |
| 2026-05-19 00:00 | 08:09:08.14 | +03:33:50.5 | HIP 39924 | 13.48 |
| 2026-05-19 12:00 | 08:09:09.52 | +03:33:59.0 | HIP 39924 | 13.32 |
| 2026-05-20 00:00 | 08:09:10.92 | +03:34:07.4 | HIP 39924 | 13.16 |
| 2026-05-20 12:00 | 08:09:12.35 | +03:34:15.6 | HIP 39924 | 13.01 |
| 2026-05-21 00:00 | 08:09:13.80 | +03:34:23.7 | HIP 39924 | 12.88 |
| 2026-05-21 12:00 | 08:09:15.27 | +03:34:31.6 | HIP 39924 | 12.76 |
| 2026-05-22 00:00 | 08:09:16.76 | +03:34:39.4 | HIP 39924 | 12.65 |
| 2026-05-22 12:00 | 08:09:18.28 | +03:34:47.1 | HIP 39924 | 12.56 |
| 2026-05-23 00:00 | 08:09:19.83 | +03:34:54.6 | HIP 39924 | 12.49 |
| 2026-05-23 12:00 | 08:09:21.39 | +03:35:02.0 | HIP 39924 | 12.42 |
| 2026-05-24 00:00 | 08:09:22.98 | +03:35:09.2 | HIP 39924 | 12.38 |
| 2026-05-24 12:00 | 08:09:24.59 | +03:35:16.3 | HIP 39924 | 12.35 |
| 2026-05-25 00:00 | 08:09:26.22 | +03:35:23.3 | HIP 39924 | 12.34 |
| 2026-05-25 12:00 | 08:09:27.87 | +03:35:30.1 | HIP 39924 | 12.35 |
| 2026-05-26 00:00 | 08:09:29.55 | +03:35:36.8 | HIP 39924 | 12.38 |
| 2026-05-26 12:00 | 08:09:31.24 | +03:35:43.4 | HIP 39924 | 12.43 |
| 2026-05-27 00:00 | 08:09:32.96 | +03:35:49.8 | HIP 39924 | 12.50 |
| 2026-05-27 12:00 | 08:09:34.70 | +03:35:56.0 | HIP 39924 | 12.58 |
| 2026-05-28 00:00 | 08:09:36.47 | +03:36:02.2 | HIP 39924 | 12.69 |
| 2026-05-28 12:00 | 08:09:38.25 | +03:36:08.1 | HIP 39924 | 12.81 |
| 2026-05-29 00:00 | 08:09:40.05 | +03:36:14.0 | HIP 39924 | 12.96 |
| 2026-05-29 12:00 | 08:09:41.88 | +03:36:19.7 | HIP 39924 | 13.13 |
| 2026-05-30 00:00 | 08:09:43.73 | +03:36:25.2 | HIP 39924 | 13.31 |
| 2026-05-30 12:00 | 08:09:45.59 | +03:36:30.7 | HIP 39924 | 13.51 |
| 2026-05-31 00:00 | 08:09:47.48 | +03:36:35.9 | HIP 39924 | 13.73 |
| 2026-05-31 12:00 | 08:09:49.39 | +03:36:41.1 | HIP 39924 | 13.97 |
| 2026-06-01 00:00 | 08:09:51.31 | +03:36:46.1 | HIP 39924 | 14.23 |
| 2026-06-01 12:00 | 08:09:53.26 | +03:36:50.9 | HIP 39924 | 14.50 |
| 2026-06-02 00:00 | 08:09:55.23 | +03:36:55.6 | HIP 39924 | 14.79 |