C/2019 S4 (Lemmon)
| 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 |
2020-12-21 |
-9.1806 |
+4.741 |
| 2020-12-21 |
2021-05-21 |
+5.8572 |
-4.412 |
| 2021-05-21 |
2021-09-12 |
+14.1273 |
-10.004 |
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 |
16:03:57.40 |
-36:18:04.0 |
HIP 120121 |
27.85 |
| 2026-02-03 12:00 |
16:03:59.98 |
-36:18:58.7 |
HIP 120121 |
28.52 |
| 2026-02-04 00:00 |
16:04:02.49 |
-36:19:53.5 |
HIP 120121 |
29.22 |
| 2026-02-04 12:00 |
16:04:04.93 |
-36:20:48.1 |
HIP 120121 |
29.94 |
| 2026-02-05 00:00 |
16:04:07.29 |
-36:21:42.7 |
HIP 120121 |
30.67 |
| 2026-02-05 12:00 |
16:04:09.57 |
-36:22:37.3 |
HIP 78652 |
30.88 |
| 2026-02-06 00:00 |
16:04:11.79 |
-36:23:31.8 |
HIP 78652 |
30.17 |
| 2026-02-06 12:00 |
16:04:13.92 |
-36:24:26.2 |
HIP 78652 |
29.46 |
| 2026-02-07 00:00 |
16:04:15.98 |
-36:25:20.5 |
HIP 78652 |
28.77 |
| 2026-02-07 12:00 |
16:04:17.96 |
-36:26:14.8 |
HIP 78652 |
28.09 |
| 2026-02-08 00:00 |
16:04:19.87 |
-36:27:09.0 |
HIP 78652 |
27.42 |
| 2026-02-08 12:00 |
16:04:21.70 |
-36:28:03.1 |
HIP 78652 |
26.77 |
| 2026-02-09 00:00 |
16:04:23.45 |
-36:28:57.1 |
HIP 78652 |
26.13 |
| 2026-02-09 12:00 |
16:04:25.12 |
-36:29:51.1 |
HIP 78652 |
25.51 |
| 2026-02-10 00:00 |
16:04:26.72 |
-36:30:44.9 |
HIP 78652 |
24.89 |
| 2026-02-10 12:00 |
16:04:28.24 |
-36:31:38.7 |
HIP 78652 |
24.30 |
| 2026-02-11 00:00 |
16:04:29.67 |
-36:32:32.4 |
HIP 78652 |
23.72 |
| 2026-02-11 12:00 |
16:04:31.04 |
-36:33:26.0 |
HIP 78652 |
23.15 |
| 2026-02-12 00:00 |
16:04:32.32 |
-36:34:19.5 |
HIP 78652 |
22.60 |
| 2026-02-12 12:00 |
16:04:33.52 |
-36:35:12.9 |
HIP 78652 |
22.07 |
| 2026-02-13 00:00 |
16:04:34.64 |
-36:36:06.2 |
HIP 78652 |
21.55 |
| 2026-02-13 12:00 |
16:04:35.68 |
-36:36:59.4 |
HIP 78652 |
21.05 |
| 2026-02-14 00:00 |
16:04:36.65 |
-36:37:52.6 |
HIP 78652 |
20.57 |
| 2026-02-14 12:00 |
16:04:37.53 |
-36:38:45.6 |
HIP 78652 |
20.10 |
| 2026-02-15 00:00 |
16:04:38.33 |
-36:39:38.4 |
HIP 78652 |
19.66 |
| 2026-02-15 12:00 |
16:04:39.05 |
-36:40:31.2 |
HIP 78652 |
19.23 |
| 2026-02-16 00:00 |
16:04:39.69 |
-36:41:23.9 |
HIP 78652 |
18.83 |
| 2026-02-16 12:00 |
16:04:40.25 |
-36:42:16.4 |
HIP 78652 |
18.44 |
| 2026-02-17 00:00 |
16:04:40.72 |
-36:43:08.9 |
HIP 78652 |
18.08 |
| 2026-02-17 12:00 |
16:04:41.12 |
-36:44:01.2 |
HIP 78652 |
17.74 |
| 2026-02-18 00:00 |
16:04:41.43 |
-36:44:53.3 |
HIP 78652 |
17.42 |
| 2026-02-18 12:00 |
16:04:41.66 |
-36:45:45.4 |
HIP 78652 |
17.13 |
| 2026-02-19 00:00 |
16:04:41.81 |
-36:46:37.3 |
HIP 78652 |
16.86 |
| 2026-02-19 12:00 |
16:04:41.87 |
-36:47:29.1 |
HIP 78652 |
16.61 |
| 2026-02-20 00:00 |
16:04:41.86 |
-36:48:20.7 |
HIP 78652 |
16.40 |
| 2026-02-20 12:00 |
16:04:41.75 |
-36:49:12.2 |
HIP 78652 |
16.21 |
| 2026-02-21 00:00 |
16:04:41.57 |
-36:50:03.6 |
HIP 78652 |
16.04 |
| 2026-02-21 12:00 |
16:04:41.31 |
-36:50:54.8 |
HIP 78652 |
15.91 |
| 2026-02-22 00:00 |
16:04:40.96 |
-36:51:45.9 |
HIP 78652 |
15.80 |
| 2026-02-22 12:00 |
16:04:40.52 |
-36:52:36.8 |
HIP 78652 |
15.72 |
| 2026-02-23 00:00 |
16:04:40.01 |
-36:53:27.6 |
HIP 78652 |
15.68 |
| 2026-02-23 12:00 |
16:04:39.41 |
-36:54:18.2 |
HIP 78652 |
15.66 |
| 2026-02-24 00:00 |
16:04:38.73 |
-36:55:08.7 |
HIP 78652 |
15.67 |