38P/Stephan-Oterma
| Parameter |
Value |
| Designation |
38P/Stephan-Oterma |
| Type |
P |
| Perihelion (tp_cal, UTC) |
2018-11-10T23:41:26.018880Z |
| Orbit solution date (soln_date, UTC) |
2024-12-04T09:13:02Z |
| Obs used |
3293 |
| NEO |
- |
| M1 |
11.600 |
| K1 |
9.500 |
| PC |
0.030 |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
2018-05-28.0000000 |
| e |
0.85928734 |
| q (au) |
1.588509 |
| a (au) |
11.289028 |
| i (deg) |
18.352950 |
| Ω (om, deg) |
78.000299 |
| ω (w, deg) |
359.588512 |
| M (ma, deg) |
355.660875 |
Magnitude
Scatter + Global Linear
$$
M_a = (10.407 + 3.946\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
10.407 |
| n |
3.946 |
| gf |
1.000 |
| gb |
-1.000 |
| 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 |
| 2017-06-24 |
2018-11-10 |
+2.7150 |
-1.674 |
| 2018-11-11 |
2020-05-21 |
+1.0438 |
-0.761 |
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 |
16:03:37.73 |
-14:19:55.9 |
HIP 78567 |
24.07 |
| 2026-02-03 12:00 |
16:03:41.04 |
-14:19:57.1 |
HIP 78567 |
24.56 |
| 2026-02-04 00:00 |
16:03:44.29 |
-14:19:58.0 |
HIP 78567 |
25.07 |
| 2026-02-04 12:00 |
16:03:47.47 |
-14:19:58.7 |
HIP 78567 |
25.59 |
| 2026-02-05 00:00 |
16:03:50.60 |
-14:19:59.2 |
HIP 78567 |
26.10 |
| 2026-02-05 12:00 |
16:03:53.66 |
-14:19:59.5 |
HIP 78567 |
26.63 |
| 2026-02-06 00:00 |
16:03:56.66 |
-14:19:59.5 |
HIP 78567 |
27.15 |
| 2026-02-06 12:00 |
16:03:59.59 |
-14:19:59.3 |
HIP 78567 |
27.67 |
| 2026-02-07 00:00 |
16:04:02.46 |
-14:19:58.9 |
HIP 78567 |
28.19 |
| 2026-02-07 12:00 |
16:04:05.27 |
-14:19:58.3 |
HIP 78567 |
28.71 |
| 2026-02-08 00:00 |
16:04:08.02 |
-14:19:57.5 |
HIP 78567 |
29.23 |
| 2026-02-08 12:00 |
16:04:10.70 |
-14:19:56.4 |
HIP 78567 |
29.75 |
| 2026-02-09 00:00 |
16:04:13.31 |
-14:19:55.1 |
HIP 78567 |
30.25 |
| 2026-02-09 12:00 |
16:04:15.86 |
-14:19:53.6 |
HIP 78567 |
30.76 |
| 2026-02-10 00:00 |
16:04:18.35 |
-14:19:51.9 |
HIP 78567 |
31.26 |
| 2026-02-10 12:00 |
16:04:20.77 |
-14:19:50.0 |
HIP 78917 |
31.69 |
| 2026-02-11 00:00 |
16:04:23.13 |
-14:19:47.8 |
HIP 78917 |
31.12 |
| 2026-02-11 12:00 |
16:04:25.42 |
-14:19:45.4 |
HIP 78917 |
30.56 |
| 2026-02-12 00:00 |
16:04:27.64 |
-14:19:42.8 |
HIP 78917 |
30.02 |
| 2026-02-12 12:00 |
16:04:29.80 |
-14:19:40.0 |
HIP 78917 |
29.50 |
| 2026-02-13 00:00 |
16:04:31.89 |
-14:19:37.0 |
HIP 78917 |
28.99 |
| 2026-02-13 12:00 |
16:04:33.92 |
-14:19:33.8 |
HIP 78917 |
28.50 |
| 2026-02-14 00:00 |
16:04:35.88 |
-14:19:30.3 |
HIP 78917 |
28.02 |
| 2026-02-14 12:00 |
16:04:37.77 |
-14:19:26.6 |
HIP 78917 |
27.56 |
| 2026-02-15 00:00 |
16:04:39.59 |
-14:19:22.7 |
HIP 78917 |
27.12 |
| 2026-02-15 12:00 |
16:04:41.35 |
-14:19:18.6 |
HIP 78917 |
26.69 |
| 2026-02-16 00:00 |
16:04:43.04 |
-14:19:14.3 |
HIP 78917 |
26.28 |
| 2026-02-16 12:00 |
16:04:44.67 |
-14:19:09.8 |
HIP 78917 |
25.89 |
| 2026-02-17 00:00 |
16:04:46.22 |
-14:19:05.0 |
HIP 78917 |
25.51 |
| 2026-02-17 12:00 |
16:04:47.71 |
-14:19:00.1 |
HIP 78917 |
25.15 |
| 2026-02-18 00:00 |
16:04:49.13 |
-14:18:54.9 |
HIP 78917 |
24.80 |
| 2026-02-18 12:00 |
16:04:50.48 |
-14:18:49.6 |
HIP 78917 |
24.48 |
| 2026-02-19 00:00 |
16:04:51.77 |
-14:18:44.0 |
HIP 78917 |
24.16 |
| 2026-02-19 12:00 |
16:04:52.98 |
-14:18:38.2 |
HIP 78917 |
23.87 |
| 2026-02-20 00:00 |
16:04:54.13 |
-14:18:32.2 |
HIP 78917 |
23.59 |
| 2026-02-20 12:00 |
16:04:55.21 |
-14:18:26.0 |
HIP 78917 |
23.33 |
| 2026-02-21 00:00 |
16:04:56.22 |
-14:18:19.6 |
HIP 78917 |
23.09 |
| 2026-02-21 12:00 |
16:04:57.16 |
-14:18:13.0 |
HIP 78917 |
22.86 |
| 2026-02-22 00:00 |
16:04:58.03 |
-14:18:06.1 |
HIP 78917 |
22.66 |
| 2026-02-22 12:00 |
16:04:58.84 |
-14:17:59.1 |
HIP 78917 |
22.46 |
| 2026-02-23 00:00 |
16:04:59.57 |
-14:17:51.9 |
HIP 78917 |
22.29 |
| 2026-02-23 12:00 |
16:05:00.24 |
-14:17:44.5 |
HIP 78917 |
22.14 |
| 2026-02-24 00:00 |
16:05:00.83 |
-14:17:36.9 |
HIP 78917 |
22.00 |