C/2020 R4 (ATLAS)
| Parameter |
Value |
| Designation |
C/2020 R4 (ATLAS) |
| Type |
C |
| Perihelion (tp_cal, UTC) |
2021-03-01T22:27:03.700800Z |
| Orbit solution date (soln_date, UTC) |
2022-06-06T17:33:25Z |
| Obs used |
2399 |
| NEO |
- |
| M1 |
12.800 |
| K1 |
11.750 |
| PC |
0.030 |
| Discovery observation (MPC, UTC) |
2020-09-12T11:53:38.889600Z |
| Discovery magnitude (MPC) |
19.71 o |
| Discovery observatory (MPC) |
T08 · ATLAS-MLO, Mauna Loa |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
2021-03-13.0000000 |
| e |
0.98936453 |
| q (au) |
1.028587 |
| a (au) |
96.712911 |
| i (deg) |
164.463346 |
| Ω (om, deg) |
323.272439 |
| ω (w, deg) |
46.707930 |
| M (ma, deg) |
0.011466 |
Magnitude
Scatter + Global Linear
$$
M_a = (12.395 + 6.000\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
12.395 |
| n |
6.000 |
| gf |
1.000 |
| gb |
-0.526 |
| k |
0.800 |
| 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 |
| 2020-08-29 |
2020-11-08 |
-8.7561 |
+3.767 |
| 2020-11-08 |
2020-12-10 |
+11.5646 |
-2.872 |
| 2020-12-10 |
2021-01-05 |
+28.0663 |
-6.809 |
| 2021-01-05 |
2021-02-27 |
-11.7027 |
-1.609 |
| 2021-03-04 |
2021-04-25 |
+19.4111 |
-2.321 |
| 2021-04-25 |
2021-06-04 |
+1.2854 |
-0.645 |
| 2021-06-04 |
2022-03-01 |
-6.4189 |
+0.769 |
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 |
08:27:56.28 |
+14:00:28.4 |
HIP 41578 |
15.73 |
| 2026-02-03 12:00 |
08:27:47.06 |
+14:01:00.1 |
HIP 41578 |
16.86 |
| 2026-02-04 00:00 |
08:27:37.86 |
+14:01:31.9 |
HIP 41578 |
18.21 |
| 2026-02-04 12:00 |
08:27:28.68 |
+14:02:03.7 |
HIP 41578 |
19.73 |
| 2026-02-05 00:00 |
08:27:19.51 |
+14:02:35.5 |
HIP 41578 |
21.38 |
| 2026-02-05 12:00 |
08:27:10.37 |
+14:03:07.4 |
HIP 41578 |
23.14 |
| 2026-02-06 00:00 |
08:27:01.24 |
+14:03:39.2 |
HIP 41578 |
24.98 |
| 2026-02-06 12:00 |
08:26:52.14 |
+14:04:11.0 |
HIP 41578 |
26.87 |
| 2026-02-07 00:00 |
08:26:43.05 |
+14:04:42.8 |
HIP 41578 |
28.82 |
| 2026-02-07 12:00 |
08:26:33.99 |
+14:05:14.6 |
HIP 41578 |
30.81 |
| 2026-02-08 00:00 |
08:26:24.96 |
+14:05:46.4 |
HIP 41197 |
29.39 |
| 2026-02-08 12:00 |
08:26:15.94 |
+14:06:18.2 |
HIP 41197 |
27.19 |
| 2026-02-09 00:00 |
08:26:06.95 |
+14:06:50.0 |
HIP 41197 |
25.00 |
| 2026-02-09 12:00 |
08:25:57.99 |
+14:07:21.7 |
HIP 41197 |
22.83 |
| 2026-02-10 00:00 |
08:25:49.05 |
+14:07:53.4 |
HIP 41197 |
20.68 |
| 2026-02-10 12:00 |
08:25:40.14 |
+14:08:25.1 |
HIP 41197 |
18.56 |
| 2026-02-11 00:00 |
08:25:31.26 |
+14:08:56.8 |
HIP 41197 |
16.47 |
| 2026-02-11 12:00 |
08:25:22.40 |
+14:09:28.5 |
HIP 41197 |
14.42 |
| 2026-02-12 00:00 |
08:25:13.57 |
+14:10:00.1 |
HIP 41197 |
12.44 |
| 2026-02-12 12:00 |
08:25:04.78 |
+14:10:31.7 |
HIP 41197 |
10.55 |
| 2026-02-13 00:00 |
08:24:56.01 |
+14:11:03.3 |
HIP 41197 |
8.81 |
| 2026-02-13 12:00 |
08:24:47.28 |
+14:11:34.8 |
HIP 41197 |
7.32 |
| 2026-02-14 00:00 |
08:24:38.58 |
+14:12:06.2 |
HIP 41197 |
6.26 |
| 2026-02-14 12:00 |
08:24:29.91 |
+14:12:37.7 |
HIP 41197 |
5.86 |
| 2026-02-15 00:00 |
08:24:21.27 |
+14:13:09.0 |
HIP 41197 |
6.22 |
| 2026-02-15 12:00 |
08:24:12.67 |
+14:13:40.4 |
HIP 41197 |
7.24 |
| 2026-02-16 00:00 |
08:24:04.10 |
+14:14:11.6 |
HIP 41197 |
8.67 |
| 2026-02-16 12:00 |
08:23:55.57 |
+14:14:42.9 |
HIP 41197 |
10.35 |
| 2026-02-17 00:00 |
08:23:47.08 |
+14:15:14.0 |
HIP 41197 |
12.16 |
| 2026-02-17 12:00 |
08:23:38.62 |
+14:15:45.1 |
HIP 41197 |
14.05 |
| 2026-02-18 00:00 |
08:23:30.20 |
+14:16:16.1 |
HIP 41197 |
15.99 |
| 2026-02-18 12:00 |
08:23:21.82 |
+14:16:47.1 |
HIP 41197 |
17.96 |
| 2026-02-19 00:00 |
08:23:13.48 |
+14:17:18.0 |
HIP 41197 |
19.94 |
| 2026-02-19 12:00 |
08:23:05.18 |
+14:17:48.8 |
HIP 40982 |
18.64 |
| 2026-02-20 00:00 |
08:22:56.92 |
+14:18:19.5 |
HIP 40982 |
16.61 |
| 2026-02-20 12:00 |
08:22:48.70 |
+14:18:50.2 |
HIP 40982 |
14.60 |
| 2026-02-21 00:00 |
08:22:40.52 |
+14:19:20.8 |
HIP 40982 |
12.62 |
| 2026-02-21 12:00 |
08:22:32.39 |
+14:19:51.3 |
HIP 40982 |
10.67 |
| 2026-02-22 00:00 |
08:22:24.30 |
+14:20:21.7 |
HIP 40982 |
8.77 |
| 2026-02-22 12:00 |
08:22:16.25 |
+14:20:52.0 |
HIP 40982 |
6.95 |
| 2026-02-23 00:00 |
08:22:08.25 |
+14:21:22.2 |
HIP 40982 |
5.29 |
| 2026-02-23 12:00 |
08:22:00.29 |
+14:21:52.4 |
HIP 40982 |
3.95 |
| 2026-02-24 00:00 |
08:21:52.38 |
+14:22:22.4 |
HIP 40982 |
3.36 |