| Parameter |
Value |
| Designation |
C/1989 T1 (Helin-Roman-Alu) |
| Type |
C |
| Perihelion (tp_cal, UTC) |
1989-12-15T22:37:06.297600Z |
| Orbit solution date (soln_date, UTC) |
2021-04-15T23:29:38Z |
| Obs used |
120 |
| NEO |
- |
| M1 |
12.500 |
| K1 |
13.750 |
| PC |
- |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
1989-11-17.0000000 |
| e |
0.99061399 |
| q (au) |
1.047319 |
| a (au) |
111.582949 |
| i (deg) |
46.036538 |
| Ω (om, deg) |
8.519172 |
| ω (w, deg) |
68.125993 |
| M (ma, deg) |
359.975798 |
Magnitude
Scatter + Global Linear
$$
M_a = (10.273 + 3.956\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
10.273 |
| n |
3.956 |
| 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 |
| 1989-10-01 |
1989-12-07 |
+5.1672 |
-0.345 |
| 1989-12-16 |
1990-11-17 |
-15.8129 |
+1.431 |
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 |
14:24:13.88 |
-53:24:02.1 |
HIP 70515 |
11.75 |
| 2026-05-12 12:00 |
14:24:10.69 |
-53:23:50.9 |
HIP 70515 |
12.26 |
| 2026-05-13 00:00 |
14:24:07.50 |
-53:23:39.6 |
HIP 70515 |
12.77 |
| 2026-05-13 12:00 |
14:24:04.32 |
-53:23:28.2 |
HIP 70363 |
13.11 |
| 2026-05-14 00:00 |
14:24:01.15 |
-53:23:16.5 |
HIP 70363 |
12.84 |
| 2026-05-14 12:00 |
14:23:57.98 |
-53:23:04.8 |
HIP 70363 |
12.58 |
| 2026-05-15 00:00 |
14:23:54.83 |
-53:22:52.8 |
HIP 70363 |
12.34 |
| 2026-05-15 12:00 |
14:23:51.68 |
-53:22:40.8 |
HIP 70363 |
12.12 |
| 2026-05-16 00:00 |
14:23:48.54 |
-53:22:28.5 |
HIP 70363 |
11.90 |
| 2026-05-16 12:00 |
14:23:45.41 |
-53:22:16.2 |
HIP 70363 |
11.71 |
| 2026-05-17 00:00 |
14:23:42.28 |
-53:22:03.6 |
HIP 70363 |
11.53 |
| 2026-05-17 12:00 |
14:23:39.17 |
-53:21:51.0 |
HIP 70363 |
11.37 |
| 2026-05-18 00:00 |
14:23:36.07 |
-53:21:38.2 |
HIP 70363 |
11.22 |
| 2026-05-18 12:00 |
14:23:32.97 |
-53:21:25.2 |
HIP 70363 |
11.10 |
| 2026-05-19 00:00 |
14:23:29.89 |
-53:21:12.1 |
HIP 70363 |
10.99 |
| 2026-05-19 12:00 |
14:23:26.81 |
-53:20:58.9 |
HIP 70363 |
10.91 |
| 2026-05-20 00:00 |
14:23:23.75 |
-53:20:45.5 |
HIP 70363 |
10.84 |
| 2026-05-20 12:00 |
14:23:20.70 |
-53:20:32.0 |
HIP 70363 |
10.80 |
| 2026-05-21 00:00 |
14:23:17.65 |
-53:20:18.4 |
HIP 70363 |
10.78 |
| 2026-05-21 12:00 |
14:23:14.62 |
-53:20:04.6 |
HIP 70363 |
10.78 |
| 2026-05-22 00:00 |
14:23:11.60 |
-53:19:50.7 |
HIP 70363 |
10.80 |
| 2026-05-22 12:00 |
14:23:08.60 |
-53:19:36.6 |
HIP 70363 |
10.84 |
| 2026-05-23 00:00 |
14:23:05.60 |
-53:19:22.5 |
HIP 70363 |
10.90 |
| 2026-05-23 12:00 |
14:23:02.62 |
-53:19:08.1 |
HIP 70363 |
10.99 |
| 2026-05-24 00:00 |
14:22:59.65 |
-53:18:53.7 |
HIP 70363 |
11.09 |
| 2026-05-24 12:00 |
14:22:56.69 |
-53:18:39.1 |
HIP 70363 |
11.21 |
| 2026-05-25 00:00 |
14:22:53.74 |
-53:18:24.4 |
HIP 70363 |
11.35 |
| 2026-05-25 12:00 |
14:22:50.81 |
-53:18:09.6 |
HIP 70363 |
11.51 |
| 2026-05-26 00:00 |
14:22:47.89 |
-53:17:54.7 |
HIP 70363 |
11.68 |
| 2026-05-26 12:00 |
14:22:44.98 |
-53:17:39.6 |
HIP 70363 |
11.87 |
| 2026-05-27 00:00 |
14:22:42.09 |
-53:17:24.4 |
HIP 70363 |
12.08 |
| 2026-05-27 12:00 |
14:22:39.21 |
-53:17:09.1 |
HIP 70363 |
12.30 |
| 2026-05-28 00:00 |
14:22:36.34 |
-53:16:53.7 |
HIP 70363 |
12.53 |
| 2026-05-28 12:00 |
14:22:33.49 |
-53:16:38.2 |
HIP 70207 |
12.16 |
| 2026-05-29 00:00 |
14:22:30.65 |
-53:16:22.5 |
HIP 70207 |
11.72 |
| 2026-05-29 12:00 |
14:22:27.83 |
-53:16:06.7 |
HIP 70207 |
11.28 |
| 2026-05-30 00:00 |
14:22:25.02 |
-53:15:50.9 |
HIP 70207 |
10.85 |
| 2026-05-30 12:00 |
14:22:22.23 |
-53:15:34.9 |
HIP 70207 |
10.42 |
| 2026-05-31 00:00 |
14:22:19.45 |
-53:15:18.7 |
HIP 70207 |
10.00 |
| 2026-05-31 12:00 |
14:22:16.69 |
-53:15:02.5 |
HIP 70207 |
9.58 |
| 2026-06-01 00:00 |
14:22:13.94 |
-53:14:46.2 |
HIP 70207 |
9.17 |
| 2026-06-01 12:00 |
14:22:11.21 |
-53:14:29.8 |
HIP 70207 |
8.77 |
| 2026-06-02 00:00 |
14:22:08.50 |
-53:14:13.2 |
HIP 70207 |
8.38 |