C/1998 J1 (SOHO)
| 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) |
| 2026-02-03 00:00 |
22:07:05.15 |
-77:29:06.2 |
HIP 108799 |
18.30 |
| 2026-02-03 12:00 |
22:07:14.75 |
-77:28:52.5 |
HIP 108799 |
18.62 |
| 2026-02-04 00:00 |
22:07:24.37 |
-77:28:39.0 |
HIP 108799 |
18.95 |
| 2026-02-04 12:00 |
22:07:34.01 |
-77:28:25.7 |
HIP 108799 |
19.29 |
| 2026-02-05 00:00 |
22:07:43.66 |
-77:28:12.7 |
HIP 109323 |
19.01 |
| 2026-02-05 12:00 |
22:07:53.33 |
-77:27:59.9 |
HIP 109323 |
18.70 |
| 2026-02-06 00:00 |
22:08:03.02 |
-77:27:47.3 |
HIP 109323 |
18.40 |
| 2026-02-06 12:00 |
22:08:12.72 |
-77:27:35.0 |
HIP 109323 |
18.12 |
| 2026-02-07 00:00 |
22:08:22.43 |
-77:27:22.9 |
HIP 109323 |
17.86 |
| 2026-02-07 12:00 |
22:08:32.16 |
-77:27:11.0 |
HIP 109323 |
17.62 |
| 2026-02-08 00:00 |
22:08:41.90 |
-77:26:59.4 |
HIP 109323 |
17.40 |
| 2026-02-08 12:00 |
22:08:51.66 |
-77:26:48.0 |
HIP 109323 |
17.19 |
| 2026-02-09 00:00 |
22:09:01.42 |
-77:26:36.9 |
HIP 109323 |
17.01 |
| 2026-02-09 12:00 |
22:09:11.20 |
-77:26:26.0 |
HIP 109323 |
16.84 |
| 2026-02-10 00:00 |
22:09:20.99 |
-77:26:15.3 |
HIP 109323 |
16.70 |
| 2026-02-10 12:00 |
22:09:30.78 |
-77:26:04.9 |
HIP 109323 |
16.59 |
| 2026-02-11 00:00 |
22:09:40.59 |
-77:25:54.7 |
HIP 109323 |
16.49 |
| 2026-02-11 12:00 |
22:09:50.41 |
-77:25:44.8 |
HIP 109323 |
16.42 |
| 2026-02-12 00:00 |
22:10:00.23 |
-77:25:35.1 |
HIP 109323 |
16.37 |
| 2026-02-12 12:00 |
22:10:10.06 |
-77:25:25.6 |
HIP 109848 |
16.04 |
| 2026-02-13 00:00 |
22:10:19.90 |
-77:25:16.4 |
HIP 109848 |
15.58 |
| 2026-02-13 12:00 |
22:10:29.75 |
-77:25:07.5 |
HIP 109848 |
15.12 |
| 2026-02-14 00:00 |
22:10:39.60 |
-77:24:58.8 |
HIP 109848 |
14.67 |
| 2026-02-14 12:00 |
22:10:49.46 |
-77:24:50.3 |
HIP 109848 |
14.23 |
| 2026-02-15 00:00 |
22:10:59.32 |
-77:24:42.1 |
HIP 109848 |
13.79 |
| 2026-02-15 12:00 |
22:11:09.18 |
-77:24:34.1 |
HIP 109848 |
13.35 |
| 2026-02-16 00:00 |
22:11:19.05 |
-77:24:26.4 |
HIP 109848 |
12.93 |
| 2026-02-16 12:00 |
22:11:28.93 |
-77:24:19.0 |
HIP 109848 |
12.51 |
| 2026-02-17 00:00 |
22:11:38.80 |
-77:24:11.7 |
HIP 109848 |
12.09 |
| 2026-02-17 12:00 |
22:11:48.68 |
-77:24:04.8 |
HIP 109848 |
11.69 |
| 2026-02-18 00:00 |
22:11:58.56 |
-77:23:58.1 |
HIP 109848 |
11.30 |
| 2026-02-18 12:00 |
22:12:08.44 |
-77:23:51.6 |
HIP 109848 |
10.92 |
| 2026-02-19 00:00 |
22:12:18.31 |
-77:23:45.4 |
HIP 109848 |
10.54 |
| 2026-02-19 12:00 |
22:12:28.19 |
-77:23:39.4 |
HIP 109848 |
10.19 |
| 2026-02-20 00:00 |
22:12:38.07 |
-77:23:33.7 |
HIP 109848 |
9.84 |
| 2026-02-20 12:00 |
22:12:47.94 |
-77:23:28.3 |
HIP 109848 |
9.52 |
| 2026-02-21 00:00 |
22:12:57.81 |
-77:23:23.1 |
HIP 109848 |
9.21 |
| 2026-02-21 12:00 |
22:13:07.68 |
-77:23:18.1 |
HIP 109848 |
8.92 |
| 2026-02-22 00:00 |
22:13:17.54 |
-77:23:13.4 |
HIP 109848 |
8.65 |
| 2026-02-22 12:00 |
22:13:27.40 |
-77:23:09.0 |
HIP 109848 |
8.40 |
| 2026-02-23 00:00 |
22:13:37.26 |
-77:23:04.8 |
HIP 109848 |
8.18 |
| 2026-02-23 12:00 |
22:13:47.11 |
-77:23:00.9 |
HIP 109848 |
7.98 |
| 2026-02-24 00:00 |
22:13:56.95 |
-77:22:57.2 |
HIP 109848 |
7.82 |