| Parameter |
Value |
| Designation |
C/2020 P1 (NEOWISE) |
| Type |
C |
| Perihelion (tp_cal, UTC) |
2020-10-20T04:17:44.208960Z |
| Orbit solution date (soln_date, UTC) |
2021-04-15T23:34:09Z |
| Obs used |
136 |
| NEO |
- |
| M1 |
15.300 |
| K1 |
5.250 |
| PC |
- |
| Discovery observation (MPC, UTC) |
2020-08-02T15:00:32.832000Z |
| Discovery magnitude (MPC) |
19.00 R |
| Discovery observatory (MPC) |
C51 · WISE |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
2020-09-09.0000000 |
| e |
1.00029689 |
| q (au) |
0.342183 |
| a (au) |
-1152.562177 |
| i (deg) |
45.053817 |
| Ω (om, deg) |
53.539366 |
| ω (w, deg) |
8.894962 |
| M (ma, deg) |
-0.001037 |
Magnitude
Scatter + Global Linear
$$
M_a = (14.493 + 2.000\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
14.493 |
| n |
2.000 |
| gf |
1.000 |
| gb |
-0.500 |
| 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 |
| 2020-08-02 |
2020-09-20 |
+1.4276 |
-0.325 |
| 2020-09-20 |
2020-10-05 |
-8.5024 |
-2.547 |
log10 r = log10(heliocentric distance / AU), Δ = geocentric distance (AU)
Ephemeris
| Date/Time (UTC) |
RA (J2000) |
Dec (J2000) |
Nearest HIP |
Dist from HIP (arcmin) |
| 2026-07-29 00:00 |
14:57:07.94 |
-11:32:29.2 |
HIP 73133 |
9.54 |
| 2026-07-29 12:00 |
14:57:07.03 |
-11:32:37.8 |
HIP 73133 |
9.54 |
| 2026-07-30 00:00 |
14:57:06.17 |
-11:32:46.5 |
HIP 73133 |
9.55 |
| 2026-07-30 12:00 |
14:57:05.37 |
-11:32:55.5 |
HIP 73133 |
9.58 |
| 2026-07-31 00:00 |
14:57:04.62 |
-11:33:04.7 |
HIP 73133 |
9.63 |
| 2026-07-31 12:00 |
14:57:03.93 |
-11:33:14.2 |
HIP 73133 |
9.69 |
| 2026-08-01 00:00 |
14:57:03.29 |
-11:33:23.9 |
HIP 73133 |
9.77 |
| 2026-08-01 12:00 |
14:57:02.71 |
-11:33:33.8 |
HIP 73133 |
9.86 |
| 2026-08-02 00:00 |
14:57:02.18 |
-11:33:44.0 |
HIP 73133 |
9.96 |
| 2026-08-02 12:00 |
14:57:01.70 |
-11:33:54.4 |
HIP 73133 |
10.08 |
| 2026-08-03 00:00 |
14:57:01.28 |
-11:34:05.0 |
HIP 73133 |
10.20 |
| 2026-08-03 12:00 |
14:57:00.92 |
-11:34:15.8 |
HIP 73133 |
10.34 |
| 2026-08-04 00:00 |
14:57:00.61 |
-11:34:26.9 |
HIP 73133 |
10.49 |
| 2026-08-04 12:00 |
14:57:00.35 |
-11:34:38.2 |
HIP 73133 |
10.64 |
| 2026-08-05 00:00 |
14:57:00.15 |
-11:34:49.8 |
HIP 73133 |
10.81 |
| 2026-08-05 12:00 |
14:57:00.00 |
-11:35:01.5 |
HIP 73133 |
10.98 |
| 2026-08-06 00:00 |
14:56:59.91 |
-11:35:13.5 |
HIP 73133 |
11.17 |
| 2026-08-06 12:00 |
14:56:59.87 |
-11:35:25.8 |
HIP 73133 |
11.36 |
| 2026-08-07 00:00 |
14:56:59.89 |
-11:35:38.2 |
HIP 73133 |
11.56 |
| 2026-08-07 12:00 |
14:56:59.96 |
-11:35:50.9 |
HIP 73133 |
11.76 |
| 2026-08-08 00:00 |
14:57:00.08 |
-11:36:03.8 |
HIP 73133 |
11.98 |
| 2026-08-08 12:00 |
14:57:00.26 |
-11:36:16.9 |
HIP 73133 |
12.20 |
| 2026-08-09 00:00 |
14:57:00.50 |
-11:36:30.2 |
HIP 73133 |
12.43 |
| 2026-08-09 12:00 |
14:57:00.78 |
-11:36:43.8 |
HIP 73133 |
12.67 |
| 2026-08-10 00:00 |
14:57:01.13 |
-11:36:57.6 |
HIP 73133 |
12.91 |
| 2026-08-10 12:00 |
14:57:01.52 |
-11:37:11.6 |
HIP 73133 |
13.16 |
| 2026-08-11 00:00 |
14:57:01.97 |
-11:37:25.8 |
HIP 73133 |
13.42 |
| 2026-08-11 12:00 |
14:57:02.47 |
-11:37:40.2 |
HIP 73133 |
13.69 |
| 2026-08-12 00:00 |
14:57:03.03 |
-11:37:54.9 |
HIP 73133 |
13.96 |
| 2026-08-12 12:00 |
14:57:03.64 |
-11:38:09.8 |
HIP 73133 |
14.24 |
| 2026-08-13 00:00 |
14:57:04.31 |
-11:38:24.9 |
HIP 73133 |
14.53 |
| 2026-08-13 12:00 |
14:57:05.02 |
-11:38:40.2 |
HIP 73133 |
14.83 |
| 2026-08-14 00:00 |
14:57:05.80 |
-11:38:55.7 |
HIP 73133 |
15.13 |
| 2026-08-14 12:00 |
14:57:06.62 |
-11:39:11.4 |
HIP 73133 |
15.45 |
| 2026-08-15 00:00 |
14:57:07.50 |
-11:39:27.3 |
HIP 73133 |
15.77 |
| 2026-08-15 12:00 |
14:57:08.43 |
-11:39:43.4 |
HIP 73133 |
16.10 |
| 2026-08-16 00:00 |
14:57:09.41 |
-11:39:59.8 |
HIP 73133 |
16.44 |
| 2026-08-16 12:00 |
14:57:10.45 |
-11:40:16.3 |
HIP 73133 |
16.78 |
| 2026-08-17 00:00 |
14:57:11.54 |
-11:40:33.1 |
HIP 73133 |
17.14 |
| 2026-08-17 12:00 |
14:57:12.68 |
-11:40:50.0 |
HIP 73133 |
17.51 |
| 2026-08-18 00:00 |
14:57:13.87 |
-11:41:07.2 |
HIP 73133 |
17.88 |
| 2026-08-18 12:00 |
14:57:15.12 |
-11:41:24.6 |
HIP 73133 |
18.26 |
| 2026-08-19 00:00 |
14:57:16.41 |
-11:41:42.1 |
HIP 73133 |
18.66 |