| 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) |
| 2026-05-12 00:00 |
04:35:09.45 |
+24:52:31.3 |
HIP 21275 |
28.50 |
| 2026-05-12 12:00 |
04:35:11.70 |
+24:52:33.8 |
HIP 21275 |
28.86 |
| 2026-05-13 00:00 |
04:35:13.96 |
+24:52:36.4 |
HIP 21275 |
29.21 |
| 2026-05-13 12:00 |
04:35:16.23 |
+24:52:39.0 |
HIP 21275 |
29.58 |
| 2026-05-14 00:00 |
04:35:18.50 |
+24:52:41.6 |
HIP 21275 |
29.95 |
| 2026-05-14 12:00 |
04:35:20.78 |
+24:52:44.2 |
HIP 21275 |
30.32 |
| 2026-05-15 00:00 |
04:35:23.06 |
+24:52:46.8 |
HIP 21275 |
30.70 |
| 2026-05-15 12:00 |
04:35:25.35 |
+24:52:49.5 |
HIP 21275 |
31.09 |
| 2026-05-16 00:00 |
04:35:27.64 |
+24:52:52.2 |
HIP 21275 |
31.48 |
| 2026-05-16 12:00 |
04:35:29.94 |
+24:52:54.9 |
HIP 21275 |
31.88 |
| 2026-05-17 00:00 |
04:35:32.24 |
+24:52:57.7 |
HIP 21275 |
32.28 |
| 2026-05-17 12:00 |
04:35:34.55 |
+24:53:00.4 |
HIP 21275 |
32.68 |
| 2026-05-18 00:00 |
04:35:36.86 |
+24:53:03.2 |
HIP 21275 |
33.09 |
| 2026-05-18 12:00 |
04:35:39.18 |
+24:53:06.0 |
HIP 21275 |
33.50 |
| 2026-05-19 00:00 |
04:35:41.50 |
+24:53:08.8 |
HIP 21275 |
33.92 |
| 2026-05-19 12:00 |
04:35:43.82 |
+24:53:11.6 |
HIP 21275 |
34.34 |
| 2026-05-20 00:00 |
04:35:46.15 |
+24:53:14.5 |
HIP 21275 |
34.77 |
| 2026-05-20 12:00 |
04:35:48.48 |
+24:53:17.4 |
HIP 21275 |
35.20 |
| 2026-05-21 00:00 |
04:35:50.82 |
+24:53:20.2 |
HIP 21275 |
35.63 |
| 2026-05-21 12:00 |
04:35:53.16 |
+24:53:23.1 |
HIP 21275 |
36.06 |
| 2026-05-22 00:00 |
04:35:55.50 |
+24:53:26.1 |
HIP 21275 |
36.50 |
| 2026-05-22 12:00 |
04:35:57.85 |
+24:53:29.0 |
HIP 21591 |
36.17 |
| 2026-05-23 00:00 |
04:36:00.19 |
+24:53:32.0 |
HIP 21591 |
35.76 |
| 2026-05-23 12:00 |
04:36:02.54 |
+24:53:34.9 |
HIP 21591 |
35.35 |
| 2026-05-24 00:00 |
04:36:04.90 |
+24:53:37.9 |
HIP 21591 |
34.94 |
| 2026-05-24 12:00 |
04:36:07.25 |
+24:53:40.9 |
HIP 21591 |
34.54 |
| 2026-05-25 00:00 |
04:36:09.61 |
+24:53:43.9 |
HIP 21591 |
34.14 |
| 2026-05-25 12:00 |
04:36:11.97 |
+24:53:47.0 |
HIP 21591 |
33.74 |
| 2026-05-26 00:00 |
04:36:14.33 |
+24:53:50.0 |
HIP 21591 |
33.35 |
| 2026-05-26 12:00 |
04:36:16.70 |
+24:53:53.1 |
HIP 21591 |
32.96 |
| 2026-05-27 00:00 |
04:36:19.06 |
+24:53:56.1 |
HIP 21591 |
32.58 |
| 2026-05-27 12:00 |
04:36:21.43 |
+24:53:59.2 |
HIP 21591 |
32.20 |
| 2026-05-28 00:00 |
04:36:23.80 |
+24:54:02.3 |
HIP 21591 |
31.82 |
| 2026-05-28 12:00 |
04:36:26.17 |
+24:54:05.5 |
HIP 21591 |
31.45 |
| 2026-05-29 00:00 |
04:36:28.54 |
+24:54:08.6 |
HIP 21591 |
31.09 |
| 2026-05-29 12:00 |
04:36:30.91 |
+24:54:11.7 |
HIP 21591 |
30.72 |
| 2026-05-30 00:00 |
04:36:33.28 |
+24:54:14.9 |
HIP 21591 |
30.37 |
| 2026-05-30 12:00 |
04:36:35.66 |
+24:54:18.1 |
HIP 21591 |
30.02 |
| 2026-05-31 00:00 |
04:36:38.03 |
+24:54:21.2 |
HIP 21591 |
29.68 |
| 2026-05-31 12:00 |
04:36:40.41 |
+24:54:24.4 |
HIP 21591 |
29.34 |
| 2026-06-01 00:00 |
04:36:42.78 |
+24:54:27.6 |
HIP 21591 |
29.01 |
| 2026-06-01 12:00 |
04:36:45.16 |
+24:54:30.8 |
HIP 21591 |
28.68 |
| 2026-06-02 00:00 |
04:36:47.53 |
+24:54:34.1 |
HIP 21591 |
28.36 |