C/1991 L4 (Helin-Alu)
| Parameter |
Value |
| Designation |
C/1991 L4 (Helin-Alu) |
| Type |
C |
| Perihelion (tp_cal, UTC) |
1992-02-19T22:39:07.948800Z |
| Orbit solution date (soln_date, UTC) |
2021-04-15T23:29:41Z |
| Obs used |
80 |
| NEO |
- |
| M1 |
10.100 |
| K1 |
4.500 |
| PC |
- |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
1992-06-10.0000000 |
| e |
1.00017877 |
| q (au) |
4.849875 |
| a (au) |
-27129.680481 |
| i (deg) |
49.292514 |
| Ω (om, deg) |
253.650707 |
| ω (w, deg) |
30.794475 |
| M (ma, deg) |
0.000024 |
Magnitude
Scatter + Global Linear
$$
M_a = (0.872 + 6.000\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
0.872 |
| n |
6.000 |
| gf |
1.000 |
| gb |
-0.501 |
| 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
Ephemeris
| Date/Time (UTC) |
RA (J2000) |
Dec (J2000) |
Nearest HIP |
Dist from HIP (arcmin) |
| 2026-02-03 00:00 |
04:32:17.51 |
+24:55:49.4 |
HIP 21103 |
15.07 |
| 2026-02-03 12:00 |
04:32:16.55 |
+24:55:44.5 |
HIP 21103 |
14.91 |
| 2026-02-04 00:00 |
04:32:15.62 |
+24:55:39.5 |
HIP 21103 |
14.75 |
| 2026-02-04 12:00 |
04:32:14.71 |
+24:55:34.7 |
HIP 21103 |
14.60 |
| 2026-02-05 00:00 |
04:32:13.81 |
+24:55:29.8 |
HIP 21103 |
14.45 |
| 2026-02-05 12:00 |
04:32:12.93 |
+24:55:25.0 |
HIP 21103 |
14.31 |
| 2026-02-06 00:00 |
04:32:12.08 |
+24:55:20.2 |
HIP 21103 |
14.17 |
| 2026-02-06 12:00 |
04:32:11.24 |
+24:55:15.5 |
HIP 21103 |
14.04 |
| 2026-02-07 00:00 |
04:32:10.43 |
+24:55:10.7 |
HIP 21103 |
13.91 |
| 2026-02-07 12:00 |
04:32:09.63 |
+24:55:06.1 |
HIP 21103 |
13.79 |
| 2026-02-08 00:00 |
04:32:08.85 |
+24:55:01.4 |
HIP 21103 |
13.68 |
| 2026-02-08 12:00 |
04:32:08.09 |
+24:54:56.8 |
HIP 21103 |
13.57 |
| 2026-02-09 00:00 |
04:32:07.36 |
+24:54:52.2 |
HIP 21103 |
13.46 |
| 2026-02-09 12:00 |
04:32:06.64 |
+24:54:47.7 |
HIP 21103 |
13.37 |
| 2026-02-10 00:00 |
04:32:05.94 |
+24:54:43.2 |
HIP 21103 |
13.27 |
| 2026-02-10 12:00 |
04:32:05.26 |
+24:54:38.8 |
HIP 21103 |
13.18 |
| 2026-02-11 00:00 |
04:32:04.61 |
+24:54:34.3 |
HIP 21103 |
13.10 |
| 2026-02-11 12:00 |
04:32:03.97 |
+24:54:29.9 |
HIP 21103 |
13.02 |
| 2026-02-12 00:00 |
04:32:03.35 |
+24:54:25.6 |
HIP 21103 |
12.95 |
| 2026-02-12 12:00 |
04:32:02.76 |
+24:54:21.3 |
HIP 21103 |
12.88 |
| 2026-02-13 00:00 |
04:32:02.18 |
+24:54:17.0 |
HIP 21103 |
12.81 |
| 2026-02-13 12:00 |
04:32:01.62 |
+24:54:12.8 |
HIP 21103 |
12.75 |
| 2026-02-14 00:00 |
04:32:01.09 |
+24:54:08.6 |
HIP 21103 |
12.70 |
| 2026-02-14 12:00 |
04:32:00.57 |
+24:54:04.5 |
HIP 21103 |
12.65 |
| 2026-02-15 00:00 |
04:32:00.08 |
+24:54:00.3 |
HIP 21103 |
12.60 |
| 2026-02-15 12:00 |
04:31:59.61 |
+24:53:56.3 |
HIP 21103 |
12.56 |
| 2026-02-16 00:00 |
04:31:59.15 |
+24:53:52.2 |
HIP 21103 |
12.52 |
| 2026-02-16 12:00 |
04:31:58.72 |
+24:53:48.2 |
HIP 21103 |
12.49 |
| 2026-02-17 00:00 |
04:31:58.31 |
+24:53:44.3 |
HIP 21103 |
12.46 |
| 2026-02-17 12:00 |
04:31:57.92 |
+24:53:40.4 |
HIP 21103 |
12.44 |
| 2026-02-18 00:00 |
04:31:57.55 |
+24:53:36.5 |
HIP 21103 |
12.42 |
| 2026-02-18 12:00 |
04:31:57.20 |
+24:53:32.7 |
HIP 21103 |
12.40 |
| 2026-02-19 00:00 |
04:31:56.87 |
+24:53:28.9 |
HIP 21103 |
12.39 |
| 2026-02-19 12:00 |
04:31:56.56 |
+24:53:25.1 |
HIP 21103 |
12.38 |
| 2026-02-20 00:00 |
04:31:56.28 |
+24:53:21.4 |
HIP 21103 |
12.37 |
| 2026-02-20 12:00 |
04:31:56.01 |
+24:53:17.8 |
HIP 21103 |
12.37 |
| 2026-02-21 00:00 |
04:31:55.76 |
+24:53:14.1 |
HIP 21103 |
12.37 |
| 2026-02-21 12:00 |
04:31:55.54 |
+24:53:10.5 |
HIP 21103 |
12.38 |
| 2026-02-22 00:00 |
04:31:55.34 |
+24:53:07.0 |
HIP 21103 |
12.39 |
| 2026-02-22 12:00 |
04:31:55.15 |
+24:53:03.5 |
HIP 21103 |
12.40 |
| 2026-02-23 00:00 |
04:31:54.99 |
+24:53:00.0 |
HIP 21103 |
12.42 |
| 2026-02-23 12:00 |
04:31:54.85 |
+24:52:56.6 |
HIP 21103 |
12.43 |
| 2026-02-24 00:00 |
04:31:54.73 |
+24:52:53.3 |
HIP 21103 |
12.45 |