C/2018 W2 (Africano)
| Parameter |
Value |
| Designation |
C/2018 W2 (Africano) |
| Type |
C |
| Perihelion (tp_cal, UTC) |
2019-09-05T17:29:59.596800Z |
| Orbit solution date (soln_date, UTC) |
2021-08-24T14:05:51Z |
| Obs used |
1995 |
| NEO |
- |
| M1 |
13.400 |
| K1 |
4.500 |
| PC |
- |
| Discovery observation (MPC, UTC) |
2018-11-27T12:43:12.864000Z |
| Discovery magnitude (MPC) |
18.30 G |
| Discovery observatory (MPC) |
G96 · Mt. Lemmon Survey |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
2019-07-27.0000000 |
| e |
1.00075966 |
| q (au) |
1.454668 |
| a (au) |
-1914.899581 |
| i (deg) |
116.615771 |
| Ω (om, deg) |
181.849455 |
| ω (w, deg) |
157.972854 |
| M (ma, deg) |
-0.000479 |
Magnitude
Scatter + Global Linear
$$
M_a = (13.119 + 2.000\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
13.119 |
| n |
2.000 |
| gf |
0.994 |
| gb |
-0.500 |
| k |
0.800 |
| δ90 |
1.652 |
| 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 |
| 2018-08-24 |
2018-11-28 |
-98.3101 |
+57.174 |
| 2018-11-28 |
2019-09-05 |
+4.8234 |
-2.497 |
| 2019-09-05 |
2020-06-15 |
-2.6714 |
+0.118 |
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 |
12:42:32.97 |
-57:37:52.4 |
HIP 61873 |
14.22 |
| 2026-02-03 12:00 |
12:42:26.55 |
-57:38:37.4 |
HIP 61873 |
13.38 |
| 2026-02-04 00:00 |
12:42:20.04 |
-57:39:21.9 |
HIP 61873 |
12.57 |
| 2026-02-04 12:00 |
12:42:13.43 |
-57:40:05.8 |
HIP 61873 |
11.81 |
| 2026-02-05 00:00 |
12:42:06.74 |
-57:40:49.2 |
HIP 61873 |
11.10 |
| 2026-02-05 12:00 |
12:41:59.96 |
-57:41:32.0 |
HIP 61873 |
10.45 |
| 2026-02-06 00:00 |
12:41:53.09 |
-57:42:14.2 |
HIP 61873 |
9.88 |
| 2026-02-06 12:00 |
12:41:46.13 |
-57:42:55.9 |
HIP 61873 |
9.41 |
| 2026-02-07 00:00 |
12:41:39.09 |
-57:43:37.0 |
HIP 61873 |
9.05 |
| 2026-02-07 12:00 |
12:41:31.96 |
-57:44:17.5 |
HIP 61873 |
8.81 |
| 2026-02-08 00:00 |
12:41:24.73 |
-57:44:57.3 |
HIP 61873 |
8.71 |
| 2026-02-08 12:00 |
12:41:17.43 |
-57:45:36.6 |
HIP 61873 |
8.75 |
| 2026-02-09 00:00 |
12:41:10.03 |
-57:46:15.3 |
HIP 61873 |
8.93 |
| 2026-02-09 12:00 |
12:41:02.55 |
-57:46:53.4 |
HIP 61873 |
9.25 |
| 2026-02-10 00:00 |
12:40:54.99 |
-57:47:30.9 |
HIP 61873 |
9.70 |
| 2026-02-10 12:00 |
12:40:47.34 |
-57:48:07.7 |
HIP 61873 |
10.25 |
| 2026-02-11 00:00 |
12:40:39.61 |
-57:48:43.9 |
HIP 61769 |
10.06 |
| 2026-02-11 12:00 |
12:40:31.79 |
-57:49:19.5 |
HIP 61769 |
8.86 |
| 2026-02-12 00:00 |
12:40:23.90 |
-57:49:54.5 |
HIP 61769 |
7.66 |
| 2026-02-12 12:00 |
12:40:15.91 |
-57:50:28.8 |
HIP 61769 |
6.46 |
| 2026-02-13 00:00 |
12:40:07.85 |
-57:51:02.5 |
HIP 61769 |
5.26 |
| 2026-02-13 12:00 |
12:39:59.71 |
-57:51:35.5 |
HIP 61769 |
4.06 |
| 2026-02-14 00:00 |
12:39:51.49 |
-57:52:07.9 |
HIP 61769 |
2.88 |
| 2026-02-14 12:00 |
12:39:43.18 |
-57:52:39.6 |
HIP 61769 |
1.75 |
| 2026-02-15 00:00 |
12:39:34.80 |
-57:53:10.7 |
HIP 61769 |
0.93 |
| 2026-02-15 12:00 |
12:39:26.34 |
-57:53:41.0 |
HIP 61769 |
1.31 |
| 2026-02-16 00:00 |
12:39:17.80 |
-57:54:10.8 |
HIP 61769 |
2.38 |
| 2026-02-16 12:00 |
12:39:09.19 |
-57:54:39.8 |
HIP 61769 |
3.56 |
| 2026-02-17 00:00 |
12:39:00.50 |
-57:55:08.1 |
HIP 61769 |
4.79 |
| 2026-02-17 12:00 |
12:38:51.73 |
-57:55:35.8 |
HIP 61659 |
5.18 |
| 2026-02-18 00:00 |
12:38:42.89 |
-57:56:02.8 |
HIP 61659 |
4.07 |
| 2026-02-18 12:00 |
12:38:33.98 |
-57:56:29.1 |
HIP 61659 |
3.07 |
| 2026-02-19 00:00 |
12:38:24.99 |
-57:56:54.6 |
HIP 61659 |
2.37 |
| 2026-02-19 12:00 |
12:38:15.94 |
-57:57:19.5 |
HIP 61659 |
2.24 |
| 2026-02-20 00:00 |
12:38:06.81 |
-57:57:43.7 |
HIP 61659 |
2.78 |
| 2026-02-20 12:00 |
12:37:57.61 |
-57:58:07.2 |
HIP 61659 |
3.71 |
| 2026-02-21 00:00 |
12:37:48.34 |
-57:58:29.9 |
HIP 61659 |
4.82 |
| 2026-02-21 12:00 |
12:37:39.00 |
-57:58:51.9 |
HIP 61659 |
6.01 |
| 2026-02-22 00:00 |
12:37:29.60 |
-57:59:13.2 |
HIP 61613 |
6.13 |
| 2026-02-22 12:00 |
12:37:20.13 |
-57:59:33.8 |
HIP 61613 |
6.04 |
| 2026-02-23 00:00 |
12:37:10.59 |
-57:59:53.7 |
HIP 61613 |
6.24 |
| 2026-02-23 12:00 |
12:37:00.99 |
-58:00:12.8 |
HIP 61613 |
6.71 |
| 2026-02-24 00:00 |
12:36:51.32 |
-58:00:31.2 |
HIP 61613 |
7.40 |