| Parameter |
Value |
| Designation |
C/1998 J1 (SOHO) |
| Type |
C |
| Perihelion (tp_cal, UTC) |
1998-05-08T14:51:07.577280Z |
| Orbit solution date (soln_date, UTC) |
2021-04-15T23:29:53Z |
| Obs used |
318 |
| NEO |
- |
| M1 |
6.500 |
| K1 |
7.500 |
| PC |
0.030 |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
1998-06-09.0000000 |
| e |
1.00017217 |
| q (au) |
0.153214 |
| a (au) |
-889.893232 |
| i (deg) |
62.931830 |
| Ω (om, deg) |
351.648559 |
| ω (w, deg) |
110.557189 |
| M (ma, deg) |
0.001165 |
Magnitude
Scatter + Global Linear
$$
M_a = (6.621 + 2.438\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
6.621 |
| n |
2.438 |
| gf |
0.800 |
| gb |
-0.500 |
| k |
0.800 |
| δ90 |
1.000 |
| 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 |
| 1998-05-08 |
1998-05-20 |
+3.7861 |
+1.870 |
| 1998-05-20 |
1998-05-31 |
-2.0767 |
+0.554 |
| 1998-05-31 |
1998-07-02 |
+0.2386 |
-0.078 |
| 1998-07-02 |
1998-08-15 |
+14.9567 |
-2.015 |
log10 r = log10(heliocentric distance / AU), Δ = geocentric distance (AU)
Ephemeris
| Date/Time (UTC) |
RA (J2000) |
Dec (J2000) |
Nearest HIP |
Dist from HIP (arcmin) |
| 2026-09-20 00:00 |
22:03:21.77 |
-79:19:49.4 |
HIP 108615 |
9.13 |
| 2026-09-20 12:00 |
22:03:11.86 |
-79:19:37.7 |
HIP 108615 |
8.63 |
| 2026-09-21 00:00 |
22:03:02.02 |
-79:19:25.7 |
HIP 108615 |
8.14 |
| 2026-09-21 12:00 |
22:02:52.23 |
-79:19:13.4 |
HIP 108615 |
7.65 |
| 2026-09-22 00:00 |
22:02:42.49 |
-79:19:00.9 |
HIP 108615 |
7.17 |
| 2026-09-22 12:00 |
22:02:32.82 |
-79:18:48.1 |
HIP 108615 |
6.69 |
| 2026-09-23 00:00 |
22:02:23.20 |
-79:18:35.0 |
HIP 108615 |
6.21 |
| 2026-09-23 12:00 |
22:02:13.64 |
-79:18:21.7 |
HIP 108615 |
5.74 |
| 2026-09-24 00:00 |
22:02:04.14 |
-79:18:08.1 |
HIP 108615 |
5.27 |
| 2026-09-24 12:00 |
22:01:54.70 |
-79:17:54.2 |
HIP 108615 |
4.81 |
| 2026-09-25 00:00 |
22:01:45.33 |
-79:17:40.1 |
HIP 108615 |
4.37 |
| 2026-09-25 12:00 |
22:01:36.02 |
-79:17:25.7 |
HIP 108615 |
3.93 |
| 2026-09-26 00:00 |
22:01:26.77 |
-79:17:11.1 |
HIP 108615 |
3.52 |
| 2026-09-26 12:00 |
22:01:17.58 |
-79:16:56.2 |
HIP 108615 |
3.13 |
| 2026-09-27 00:00 |
22:01:08.46 |
-79:16:41.1 |
HIP 108615 |
2.78 |
| 2026-09-27 12:00 |
22:00:59.40 |
-79:16:25.7 |
HIP 108615 |
2.48 |
| 2026-09-28 00:00 |
22:00:50.41 |
-79:16:10.1 |
HIP 108615 |
2.26 |
| 2026-09-28 12:00 |
22:00:41.49 |
-79:15:54.2 |
HIP 108615 |
2.14 |
| 2026-09-29 00:00 |
22:00:32.63 |
-79:15:38.0 |
HIP 108615 |
2.13 |
| 2026-09-29 12:00 |
22:00:23.85 |
-79:15:21.7 |
HIP 108615 |
2.23 |
| 2026-09-30 00:00 |
22:00:15.13 |
-79:15:05.0 |
HIP 108615 |
2.44 |
| 2026-09-30 12:00 |
22:00:06.48 |
-79:14:48.2 |
HIP 108615 |
2.72 |
| 2026-10-01 00:00 |
21:59:57.90 |
-79:14:31.0 |
HIP 108615 |
3.06 |
| 2026-10-01 12:00 |
21:59:49.39 |
-79:14:13.7 |
HIP 108615 |
3.44 |
| 2026-10-02 00:00 |
21:59:40.96 |
-79:13:56.1 |
HIP 108615 |
3.85 |
| 2026-10-02 12:00 |
21:59:32.60 |
-79:13:38.3 |
HIP 108615 |
4.28 |
| 2026-10-03 00:00 |
21:59:24.31 |
-79:13:20.2 |
HIP 108615 |
4.72 |
| 2026-10-03 12:00 |
21:59:16.09 |
-79:13:01.9 |
HIP 108615 |
5.17 |
| 2026-10-04 00:00 |
21:59:07.95 |
-79:12:43.3 |
HIP 108615 |
5.63 |
| 2026-10-04 12:00 |
21:58:59.88 |
-79:12:24.5 |
HIP 108615 |
6.10 |
| 2026-10-05 00:00 |
21:58:51.89 |
-79:12:05.5 |
HIP 108615 |
6.57 |
| 2026-10-05 12:00 |
21:58:43.98 |
-79:11:46.3 |
HIP 108615 |
7.04 |
| 2026-10-06 00:00 |
21:58:36.15 |
-79:11:26.8 |
HIP 108615 |
7.52 |
| 2026-10-06 12:00 |
21:58:28.39 |
-79:11:07.1 |
HIP 108615 |
8.00 |
| 2026-10-07 00:00 |
21:58:20.71 |
-79:10:47.2 |
HIP 108615 |
8.48 |
| 2026-10-07 12:00 |
21:58:13.11 |
-79:10:27.1 |
HIP 108615 |
8.97 |
| 2026-10-08 00:00 |
21:58:05.59 |
-79:10:06.7 |
HIP 108615 |
9.45 |
| 2026-10-08 12:00 |
21:57:58.15 |
-79:09:46.1 |
HIP 108449 |
9.19 |
| 2026-10-09 00:00 |
21:57:50.80 |
-79:09:25.3 |
HIP 108449 |
8.88 |
| 2026-10-09 12:00 |
21:57:43.52 |
-79:09:04.3 |
HIP 108449 |
8.57 |
| 2026-10-10 00:00 |
21:57:36.33 |
-79:08:43.1 |
HIP 108449 |
8.28 |
| 2026-10-10 12:00 |
21:57:29.22 |
-79:08:21.7 |
HIP 108449 |
8.00 |
| 2026-10-11 00:00 |
21:57:22.19 |
-79:08:00.0 |
HIP 108449 |
7.74 |