| 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 |
2018-12-01 |
-96.0365 |
+55.664 |
| 2018-12-01 |
2019-09-05 |
+4.8869 |
-2.512 |
| 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) |
| 2026-03-26 00:00 |
12:25:51.79 |
-57:55:19.2 |
HIP 60497 |
13.50 |
| 2026-03-26 12:00 |
12:25:40.15 |
-57:54:49.8 |
HIP 60497 |
11.95 |
| 2026-03-27 00:00 |
12:25:28.51 |
-57:54:19.7 |
HIP 60497 |
10.43 |
| 2026-03-27 12:00 |
12:25:16.88 |
-57:53:48.8 |
HIP 60497 |
8.95 |
| 2026-03-28 00:00 |
12:25:05.26 |
-57:53:17.1 |
HIP 60497 |
7.54 |
| 2026-03-28 12:00 |
12:24:53.64 |
-57:52:44.6 |
HIP 60497 |
6.24 |
| 2026-03-29 00:00 |
12:24:42.03 |
-57:52:11.4 |
HIP 60497 |
5.13 |
| 2026-03-29 12:00 |
12:24:30.42 |
-57:51:37.4 |
HIP 60497 |
4.39 |
| 2026-03-30 00:00 |
12:24:18.83 |
-57:51:02.6 |
HIP 60497 |
4.21 |
| 2026-03-30 12:00 |
12:24:07.24 |
-57:50:27.1 |
HIP 60497 |
4.66 |
| 2026-03-31 00:00 |
12:23:55.67 |
-57:49:50.8 |
HIP 60497 |
5.59 |
| 2026-03-31 12:00 |
12:23:44.11 |
-57:49:13.8 |
HIP 60497 |
6.81 |
| 2026-04-01 00:00 |
12:23:32.57 |
-57:48:36.0 |
HIP 60497 |
8.19 |
| 2026-04-01 12:00 |
12:23:21.04 |
-57:47:57.5 |
HIP 60379 |
8.51 |
| 2026-04-02 00:00 |
12:23:09.52 |
-57:47:18.2 |
HIP 60379 |
7.25 |
| 2026-04-02 12:00 |
12:22:58.03 |
-57:46:38.2 |
HIP 60379 |
6.18 |
| 2026-04-03 00:00 |
12:22:46.55 |
-57:45:57.4 |
HIP 60379 |
5.40 |
| 2026-04-03 12:00 |
12:22:35.09 |
-57:45:15.9 |
HIP 60379 |
5.08 |
| 2026-04-04 00:00 |
12:22:23.65 |
-57:44:33.6 |
HIP 60379 |
5.28 |
| 2026-04-04 12:00 |
12:22:12.23 |
-57:43:50.7 |
HIP 60379 |
5.96 |
| 2026-04-05 00:00 |
12:22:00.83 |
-57:43:07.0 |
HIP 60379 |
6.98 |
| 2026-04-05 12:00 |
12:21:49.46 |
-57:42:22.5 |
HIP 60379 |
8.22 |
| 2026-04-06 00:00 |
12:21:38.11 |
-57:41:37.4 |
HIP 60379 |
9.60 |
| 2026-04-06 12:00 |
12:21:26.78 |
-57:40:51.5 |
HIP 60379 |
11.06 |
| 2026-04-07 00:00 |
12:21:15.49 |
-57:40:04.9 |
HIP 60379 |
12.57 |
| 2026-04-07 12:00 |
12:21:04.22 |
-57:39:17.6 |
HIP 60379 |
14.13 |
| 2026-04-08 00:00 |
12:20:52.98 |
-57:38:29.6 |
HIP 60379 |
15.72 |
| 2026-04-08 12:00 |
12:20:41.76 |
-57:37:40.9 |
HIP 60379 |
17.32 |
| 2026-04-09 00:00 |
12:20:30.58 |
-57:36:51.5 |
HIP 60379 |
18.95 |
| 2026-04-09 12:00 |
12:20:19.43 |
-57:36:01.3 |
HIP 60246 |
19.17 |
| 2026-04-10 00:00 |
12:20:08.32 |
-57:35:10.5 |
HIP 60246 |
19.02 |
| 2026-04-10 12:00 |
12:19:57.23 |
-57:34:19.0 |
HIP 60246 |
19.01 |
| 2026-04-11 00:00 |
12:19:46.18 |
-57:33:26.8 |
HIP 60246 |
19.15 |
| 2026-04-11 12:00 |
12:19:35.17 |
-57:32:34.0 |
HIP 60246 |
19.43 |
| 2026-04-12 00:00 |
12:19:24.19 |
-57:31:40.4 |
HIP 60246 |
19.84 |
| 2026-04-12 12:00 |
12:19:13.26 |
-57:30:46.2 |
HIP 59990 |
18.86 |
| 2026-04-13 00:00 |
12:19:02.36 |
-57:29:51.3 |
HIP 59990 |
17.42 |
| 2026-04-13 12:00 |
12:18:51.50 |
-57:28:55.7 |
HIP 59990 |
16.04 |
| 2026-04-14 00:00 |
12:18:40.68 |
-57:27:59.5 |
HIP 59990 |
14.71 |
| 2026-04-14 12:00 |
12:18:29.90 |
-57:27:02.6 |
HIP 59990 |
13.47 |
| 2026-04-15 00:00 |
12:18:19.16 |
-57:26:05.1 |
HIP 59990 |
12.35 |
| 2026-04-15 12:00 |
12:18:08.47 |
-57:25:06.9 |
HIP 59990 |
11.36 |
| 2026-04-16 00:00 |
12:17:57.83 |
-57:24:08.1 |
HIP 59990 |
10.56 |