| 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) |
| 2026-05-12 00:00 |
12:10:06.50 |
-56:20:56.3 |
HIP 59360 |
7.46 |
| 2026-05-12 12:00 |
12:09:59.33 |
-56:19:32.3 |
HIP 59360 |
9.17 |
| 2026-05-13 00:00 |
12:09:52.24 |
-56:18:08.0 |
HIP 59360 |
10.88 |
| 2026-05-13 12:00 |
12:09:45.23 |
-56:16:43.5 |
HIP 59360 |
12.58 |
| 2026-05-14 00:00 |
12:09:38.30 |
-56:15:18.6 |
HIP 59360 |
14.29 |
| 2026-05-14 12:00 |
12:09:31.46 |
-56:13:53.5 |
HIP 59360 |
15.99 |
| 2026-05-15 00:00 |
12:09:24.70 |
-56:12:28.1 |
HIP 59360 |
17.69 |
| 2026-05-15 12:00 |
12:09:18.02 |
-56:11:02.4 |
HIP 59360 |
19.39 |
| 2026-05-16 00:00 |
12:09:11.43 |
-56:09:36.5 |
HIP 59360 |
21.09 |
| 2026-05-16 12:00 |
12:09:04.92 |
-56:08:10.4 |
HIP 59360 |
22.78 |
| 2026-05-17 00:00 |
12:08:58.49 |
-56:06:44.0 |
HIP 59231 |
23.05 |
| 2026-05-17 12:00 |
12:08:52.15 |
-56:05:17.3 |
HIP 59231 |
21.60 |
| 2026-05-18 00:00 |
12:08:45.90 |
-56:03:50.5 |
HIP 59231 |
20.18 |
| 2026-05-18 12:00 |
12:08:39.73 |
-56:02:23.4 |
HIP 59231 |
18.81 |
| 2026-05-19 00:00 |
12:08:33.65 |
-56:00:56.2 |
HIP 59231 |
17.48 |
| 2026-05-19 12:00 |
12:08:27.65 |
-55:59:28.7 |
HIP 59231 |
16.22 |
| 2026-05-20 00:00 |
12:08:21.74 |
-55:58:01.0 |
HIP 59231 |
15.03 |
| 2026-05-20 12:00 |
12:08:15.91 |
-55:56:33.2 |
HIP 59231 |
13.94 |
| 2026-05-21 00:00 |
12:08:10.17 |
-55:55:05.2 |
HIP 59231 |
12.97 |
| 2026-05-21 12:00 |
12:08:04.52 |
-55:53:37.0 |
HIP 59231 |
12.14 |
| 2026-05-22 00:00 |
12:07:58.96 |
-55:52:08.7 |
HIP 59231 |
11.48 |
| 2026-05-22 12:00 |
12:07:53.48 |
-55:50:40.2 |
HIP 59231 |
11.03 |
| 2026-05-23 00:00 |
12:07:48.09 |
-55:49:11.5 |
HIP 59231 |
10.81 |
| 2026-05-23 12:00 |
12:07:42.79 |
-55:47:42.7 |
HIP 59231 |
10.83 |
| 2026-05-24 00:00 |
12:07:37.57 |
-55:46:13.8 |
HIP 59231 |
11.09 |
| 2026-05-24 12:00 |
12:07:32.44 |
-55:44:44.8 |
HIP 59231 |
11.57 |
| 2026-05-25 00:00 |
12:07:27.40 |
-55:43:15.6 |
HIP 59231 |
12.24 |
| 2026-05-25 12:00 |
12:07:22.45 |
-55:41:46.4 |
HIP 59231 |
13.08 |
| 2026-05-26 00:00 |
12:07:17.59 |
-55:40:17.0 |
HIP 59231 |
14.04 |
| 2026-05-26 12:00 |
12:07:12.81 |
-55:38:47.5 |
HIP 59231 |
15.12 |
| 2026-05-27 00:00 |
12:07:08.13 |
-55:37:18.0 |
HIP 59231 |
16.27 |
| 2026-05-27 12:00 |
12:07:03.53 |
-55:35:48.3 |
HIP 59231 |
17.50 |
| 2026-05-28 00:00 |
12:06:59.02 |
-55:34:18.6 |
HIP 59231 |
18.77 |
| 2026-05-28 12:00 |
12:06:54.59 |
-55:32:48.8 |
HIP 59231 |
20.09 |
| 2026-05-29 00:00 |
12:06:50.26 |
-55:31:19.0 |
HIP 58883 |
19.53 |
| 2026-05-29 12:00 |
12:06:46.02 |
-55:29:49.1 |
HIP 58883 |
18.59 |
| 2026-05-30 00:00 |
12:06:41.86 |
-55:28:19.1 |
HIP 58883 |
17.75 |
| 2026-05-30 12:00 |
12:06:37.79 |
-55:26:49.1 |
HIP 58883 |
17.03 |
| 2026-05-31 00:00 |
12:06:33.81 |
-55:25:19.1 |
HIP 58883 |
16.45 |
| 2026-05-31 12:00 |
12:06:29.92 |
-55:23:49.1 |
HIP 58883 |
16.02 |
| 2026-06-01 00:00 |
12:06:26.12 |
-55:22:19.0 |
HIP 58883 |
15.76 |
| 2026-06-01 12:00 |
12:06:22.40 |
-55:20:48.9 |
HIP 58883 |
15.67 |
| 2026-06-02 00:00 |
12:06:18.78 |
-55:19:18.8 |
HIP 58883 |
15.75 |