| Parameter |
Value |
| Designation |
C/2019 S4 (Lemmon) |
| Type |
C |
| Perihelion (tp_cal, UTC) |
2020-04-07T22:29:16.782720Z |
| Orbit solution date (soln_date, UTC) |
2021-09-20T00:12:43Z |
| Obs used |
267 |
| NEO |
- |
| M1 |
8.600 |
| K1 |
13.500 |
| PC |
- |
| Discovery observation (MPC, UTC) |
2019-09-17T10:53:32.640000Z |
| Discovery magnitude (MPC) |
20.30 G |
| Discovery observatory (MPC) |
G96 · Mt. Lemmon Survey |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
2020-02-18.0000000 |
| e |
0.98581834 |
| q (au) |
3.441733 |
| a (au) |
242.688906 |
| i (deg) |
92.025259 |
| Ω (om, deg) |
63.169569 |
| ω (w, deg) |
71.354510 |
| M (ma, deg) |
359.986982 |
Magnitude
Scatter + Global Linear
$$
M_a = (6.827 + 6.000\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
6.827 |
| n |
6.000 |
| 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 |
| 2019-09-17 |
2020-04-01 |
+21.5169 |
-10.890 |
| 2020-05-29 |
2020-10-30 |
-14.1476 |
+7.524 |
| 2020-10-30 |
2021-09-12 |
+6.0879 |
-4.406 |
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 |
16:01:25.94 |
-37:39:12.1 |
HIP 78533 |
9.67 |
| 2026-03-26 12:00 |
16:01:20.27 |
-37:39:48.1 |
HIP 78533 |
10.88 |
| 2026-03-27 00:00 |
16:01:14.52 |
-37:40:23.7 |
HIP 78533 |
12.11 |
| 2026-03-27 12:00 |
16:01:08.70 |
-37:40:59.1 |
HIP 78533 |
13.36 |
| 2026-03-28 00:00 |
16:01:02.81 |
-37:41:34.1 |
HIP 78533 |
14.62 |
| 2026-03-28 12:00 |
16:00:56.84 |
-37:42:08.7 |
HIP 78533 |
15.89 |
| 2026-03-29 00:00 |
16:00:50.81 |
-37:42:43.1 |
HIP 78533 |
17.18 |
| 2026-03-29 12:00 |
16:00:44.69 |
-37:43:17.1 |
HIP 78533 |
18.49 |
| 2026-03-30 00:00 |
16:00:38.51 |
-37:43:50.8 |
HIP 78308 |
19.43 |
| 2026-03-30 12:00 |
16:00:32.25 |
-37:44:24.2 |
HIP 78308 |
18.84 |
| 2026-03-31 00:00 |
16:00:25.92 |
-37:44:57.2 |
HIP 78308 |
18.32 |
| 2026-03-31 12:00 |
16:00:19.53 |
-37:45:29.9 |
HIP 78308 |
17.88 |
| 2026-04-01 00:00 |
16:00:13.06 |
-37:46:02.2 |
HIP 78308 |
17.52 |
| 2026-04-01 12:00 |
16:00:06.52 |
-37:46:34.2 |
HIP 78308 |
17.25 |
| 2026-04-02 00:00 |
15:59:59.91 |
-37:47:05.9 |
HIP 78308 |
17.08 |
| 2026-04-02 12:00 |
15:59:53.23 |
-37:47:37.2 |
HIP 78308 |
17.02 |
| 2026-04-03 00:00 |
15:59:46.48 |
-37:48:08.2 |
HIP 78308 |
17.07 |
| 2026-04-03 12:00 |
15:59:39.67 |
-37:48:38.8 |
HIP 78308 |
17.23 |
| 2026-04-04 00:00 |
15:59:32.78 |
-37:49:09.1 |
HIP 78308 |
17.50 |
| 2026-04-04 12:00 |
15:59:25.83 |
-37:49:39.0 |
HIP 78308 |
17.87 |
| 2026-04-05 00:00 |
15:59:18.81 |
-37:50:08.6 |
HIP 78308 |
18.35 |
| 2026-04-05 12:00 |
15:59:11.73 |
-37:50:37.8 |
HIP 78308 |
18.93 |
| 2026-04-06 00:00 |
15:59:04.58 |
-37:51:06.6 |
HIP 78308 |
19.60 |
| 2026-04-06 12:00 |
15:58:57.36 |
-37:51:35.1 |
HIP 78308 |
20.35 |
| 2026-04-07 00:00 |
15:58:50.08 |
-37:52:03.2 |
HIP 78308 |
21.19 |
| 2026-04-07 12:00 |
15:58:42.74 |
-37:52:31.0 |
HIP 78308 |
22.09 |
| 2026-04-08 00:00 |
15:58:35.33 |
-37:52:58.4 |
HIP 78094 |
22.62 |
| 2026-04-08 12:00 |
15:58:27.86 |
-37:53:25.4 |
HIP 78094 |
21.25 |
| 2026-04-09 00:00 |
15:58:20.32 |
-37:53:52.0 |
HIP 78094 |
19.89 |
| 2026-04-09 12:00 |
15:58:12.73 |
-37:54:18.3 |
HIP 78094 |
18.54 |
| 2026-04-10 00:00 |
15:58:05.07 |
-37:54:44.2 |
HIP 78094 |
17.23 |
| 2026-04-10 12:00 |
15:57:57.35 |
-37:55:09.7 |
HIP 78094 |
15.94 |
| 2026-04-11 00:00 |
15:57:49.57 |
-37:55:34.9 |
HIP 78094 |
14.70 |
| 2026-04-11 12:00 |
15:57:41.73 |
-37:55:59.7 |
HIP 78094 |
13.52 |
| 2026-04-12 00:00 |
15:57:33.83 |
-37:56:24.0 |
HIP 78094 |
12.42 |
| 2026-04-12 12:00 |
15:57:25.87 |
-37:56:48.0 |
HIP 78094 |
11.44 |
| 2026-04-13 00:00 |
15:57:17.85 |
-37:57:11.7 |
HIP 78094 |
10.59 |
| 2026-04-13 12:00 |
15:57:09.78 |
-37:57:34.9 |
HIP 78094 |
9.93 |
| 2026-04-14 00:00 |
15:57:01.64 |
-37:57:57.7 |
HIP 78094 |
9.51 |
| 2026-04-14 12:00 |
15:56:53.46 |
-37:58:20.2 |
HIP 78053 |
9.01 |
| 2026-04-15 00:00 |
15:56:45.21 |
-37:58:42.2 |
HIP 78053 |
7.56 |
| 2026-04-15 12:00 |
15:56:36.91 |
-37:59:03.9 |
HIP 78053 |
6.21 |
| 2026-04-16 00:00 |
15:56:28.56 |
-37:59:25.2 |
HIP 78053 |
5.06 |