| 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 · University of Arizona 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) |
| 2026-09-20 00:00 |
12:21:35.27 |
-52:08:06.4 |
HIP 60218 |
6.60 |
| 2026-09-20 12:00 |
12:21:43.99 |
-52:08:12.7 |
HIP 60218 |
7.87 |
| 2026-09-21 00:00 |
12:21:52.72 |
-52:08:19.6 |
HIP 60218 |
9.16 |
| 2026-09-21 12:00 |
12:22:01.45 |
-52:08:27.0 |
HIP 60218 |
10.47 |
| 2026-09-22 00:00 |
12:22:10.19 |
-52:08:34.9 |
HIP 60374 |
10.59 |
| 2026-09-22 12:00 |
12:22:18.93 |
-52:08:43.4 |
HIP 60374 |
9.82 |
| 2026-09-23 00:00 |
12:22:27.68 |
-52:08:52.5 |
HIP 60374 |
9.18 |
| 2026-09-23 12:00 |
12:22:36.43 |
-52:09:02.1 |
HIP 60374 |
8.69 |
| 2026-09-24 00:00 |
12:22:45.19 |
-52:09:12.3 |
HIP 60374 |
8.38 |
| 2026-09-24 12:00 |
12:22:53.95 |
-52:09:23.0 |
HIP 60374 |
8.28 |
| 2026-09-25 00:00 |
12:23:02.71 |
-52:09:34.2 |
HIP 60374 |
8.38 |
| 2026-09-25 12:00 |
12:23:11.47 |
-52:09:46.0 |
HIP 60374 |
8.69 |
| 2026-09-26 00:00 |
12:23:20.24 |
-52:09:58.3 |
HIP 60374 |
9.19 |
| 2026-09-26 12:00 |
12:23:29.01 |
-52:10:11.2 |
HIP 60374 |
9.84 |
| 2026-09-27 00:00 |
12:23:37.77 |
-52:10:24.6 |
HIP 60540 |
9.46 |
| 2026-09-27 12:00 |
12:23:46.54 |
-52:10:38.6 |
HIP 60540 |
8.09 |
| 2026-09-28 00:00 |
12:23:55.31 |
-52:10:53.1 |
HIP 60540 |
6.73 |
| 2026-09-28 12:00 |
12:24:04.08 |
-52:11:08.1 |
HIP 60540 |
5.36 |
| 2026-09-29 00:00 |
12:24:12.85 |
-52:11:23.6 |
HIP 60540 |
4.00 |
| 2026-09-29 12:00 |
12:24:21.62 |
-52:11:39.7 |
HIP 60540 |
2.64 |
| 2026-09-30 00:00 |
12:24:30.38 |
-52:11:56.3 |
HIP 60540 |
1.30 |
| 2026-09-30 12:00 |
12:24:39.14 |
-52:12:13.5 |
HIP 60540 |
0.42 |
| 2026-10-01 00:00 |
12:24:47.91 |
-52:12:31.1 |
HIP 60540 |
1.56 |
| 2026-10-01 12:00 |
12:24:56.66 |
-52:12:49.3 |
HIP 60540 |
2.92 |
| 2026-10-02 00:00 |
12:25:05.42 |
-52:13:08.0 |
HIP 60540 |
4.29 |
| 2026-10-02 12:00 |
12:25:14.17 |
-52:13:27.3 |
HIP 60540 |
5.66 |
| 2026-10-03 00:00 |
12:25:22.91 |
-52:13:47.0 |
HIP 60540 |
7.04 |
| 2026-10-03 12:00 |
12:25:31.65 |
-52:14:07.3 |
HIP 60540 |
8.42 |
| 2026-10-04 00:00 |
12:25:40.38 |
-52:14:28.1 |
HIP 60540 |
9.80 |
| 2026-10-04 12:00 |
12:25:49.11 |
-52:14:49.4 |
HIP 60540 |
11.18 |
| 2026-10-05 00:00 |
12:25:57.84 |
-52:15:11.3 |
HIP 60540 |
12.57 |
| 2026-10-05 12:00 |
12:26:06.55 |
-52:15:33.6 |
HIP 60540 |
13.95 |
| 2026-10-06 00:00 |
12:26:15.26 |
-52:15:56.4 |
HIP 60692 |
14.84 |
| 2026-10-06 12:00 |
12:26:23.96 |
-52:16:19.8 |
HIP 60692 |
15.22 |
| 2026-10-07 00:00 |
12:26:32.65 |
-52:16:43.7 |
HIP 60692 |
15.73 |
| 2026-10-07 12:00 |
12:26:41.33 |
-52:17:08.1 |
HIP 60692 |
16.34 |
| 2026-10-08 00:00 |
12:26:50.00 |
-52:17:32.9 |
HIP 60692 |
17.05 |
| 2026-10-08 12:00 |
12:26:58.66 |
-52:17:58.3 |
HIP 60835 |
17.17 |
| 2026-10-09 00:00 |
12:27:07.31 |
-52:18:24.2 |
HIP 60899 |
15.85 |
| 2026-10-09 12:00 |
12:27:15.95 |
-52:18:50.6 |
HIP 60899 |
14.53 |
| 2026-10-10 00:00 |
12:27:24.58 |
-52:19:17.5 |
HIP 60899 |
13.23 |
| 2026-10-10 12:00 |
12:27:33.19 |
-52:19:44.8 |
HIP 60899 |
11.95 |
| 2026-10-11 00:00 |
12:27:41.79 |
-52:20:12.7 |
HIP 60899 |
10.70 |