| Parameter |
Value |
| Designation |
C/2021 A10 (NEOWISE) |
| Type |
C |
| Perihelion (tp_cal, UTC) |
2021-03-15T06:26:00.660480Z |
| Orbit solution date (soln_date, UTC) |
2021-07-01T22:12:55Z |
| Obs used |
116 |
| NEO |
- |
| M1 |
19.600 |
| K1 |
4.500 |
| PC |
- |
| Discovery observation (MPC, UTC) |
2021-01-12T03:54:10.368000Z |
| Discovery magnitude (MPC) |
19.00 R |
| Discovery observatory (MPC) |
C51 · WISE |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
2021-01-29.0000000 |
| e |
0.98633128 |
| q (au) |
1.268515 |
| a (au) |
92.804201 |
| i (deg) |
151.524714 |
| Ω (om, deg) |
188.347864 |
| ω (w, deg) |
82.268366 |
| M (ma, deg) |
359.950095 |
Magnitude
Scatter + Global Linear
$$
M_a = (19.470 + 2.456\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
19.470 |
| n |
2.456 |
| gf |
0.896 |
| gb |
-0.500 |
| k |
0.800 |
| δ90 |
1.149 |
| 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
Ephemeris
| Date/Time (UTC) |
RA (J2000) |
Dec (J2000) |
Nearest HIP |
Dist from HIP (arcmin) |
| 2026-09-20 00:00 |
21:58:07.68 |
-36:33:49.8 |
HIP 108411 |
6.65 |
| 2026-09-20 12:00 |
21:57:59.27 |
-36:34:02.9 |
HIP 108411 |
5.35 |
| 2026-09-21 00:00 |
21:57:50.91 |
-36:34:15.5 |
HIP 108411 |
4.35 |
| 2026-09-21 12:00 |
21:57:42.59 |
-36:34:27.5 |
HIP 108411 |
3.88 |
| 2026-09-22 00:00 |
21:57:34.32 |
-36:34:39.0 |
HIP 108411 |
4.11 |
| 2026-09-22 12:00 |
21:57:26.10 |
-36:34:49.9 |
HIP 108411 |
4.93 |
| 2026-09-23 00:00 |
21:57:17.92 |
-36:35:00.3 |
HIP 108411 |
6.10 |
| 2026-09-23 12:00 |
21:57:09.80 |
-36:35:10.1 |
HIP 108411 |
7.44 |
| 2026-09-24 00:00 |
21:57:01.73 |
-36:35:19.3 |
HIP 108411 |
8.88 |
| 2026-09-24 12:00 |
21:56:53.70 |
-36:35:28.1 |
HIP 108411 |
10.37 |
| 2026-09-25 00:00 |
21:56:45.73 |
-36:35:36.2 |
HIP 108411 |
11.88 |
| 2026-09-25 12:00 |
21:56:37.81 |
-36:35:43.8 |
HIP 108261 |
12.98 |
| 2026-09-26 00:00 |
21:56:29.95 |
-36:35:50.9 |
HIP 108261 |
12.12 |
| 2026-09-26 12:00 |
21:56:22.13 |
-36:35:57.5 |
HIP 108261 |
11.42 |
| 2026-09-27 00:00 |
21:56:14.37 |
-36:36:03.4 |
HIP 108261 |
10.90 |
| 2026-09-27 12:00 |
21:56:06.66 |
-36:36:08.9 |
HIP 108261 |
10.57 |
| 2026-09-28 00:00 |
21:55:59.01 |
-36:36:13.8 |
HIP 108261 |
10.46 |
| 2026-09-28 12:00 |
21:55:51.42 |
-36:36:18.2 |
HIP 108261 |
10.57 |
| 2026-09-29 00:00 |
21:55:43.87 |
-36:36:22.0 |
HIP 108186 |
10.00 |
| 2026-09-29 12:00 |
21:55:36.39 |
-36:36:25.3 |
HIP 108186 |
8.99 |
| 2026-09-30 00:00 |
21:55:28.96 |
-36:36:28.1 |
HIP 108186 |
8.12 |
| 2026-09-30 12:00 |
21:55:21.59 |
-36:36:30.3 |
HIP 108186 |
7.46 |
| 2026-10-01 00:00 |
21:55:14.28 |
-36:36:32.0 |
HIP 108186 |
7.04 |
| 2026-10-01 12:00 |
21:55:07.02 |
-36:36:33.2 |
HIP 108186 |
6.90 |
| 2026-10-02 00:00 |
21:54:59.82 |
-36:36:33.9 |
HIP 108186 |
7.06 |
| 2026-10-02 12:00 |
21:54:52.68 |
-36:36:34.0 |
HIP 108186 |
7.48 |
| 2026-10-03 00:00 |
21:54:45.61 |
-36:36:33.6 |
HIP 108186 |
8.13 |
| 2026-10-03 12:00 |
21:54:38.59 |
-36:36:32.7 |
HIP 108186 |
8.94 |
| 2026-10-04 00:00 |
21:54:31.63 |
-36:36:31.2 |
HIP 108186 |
9.87 |
| 2026-10-04 12:00 |
21:54:24.74 |
-36:36:29.2 |
HIP 108186 |
10.89 |
| 2026-10-05 00:00 |
21:54:17.90 |
-36:36:26.7 |
HIP 108186 |
11.96 |
| 2026-10-05 12:00 |
21:54:11.13 |
-36:36:23.7 |
HIP 108186 |
13.08 |
| 2026-10-06 00:00 |
21:54:04.42 |
-36:36:20.2 |
HIP 108186 |
14.22 |
| 2026-10-06 12:00 |
21:53:57.78 |
-36:36:16.2 |
HIP 108186 |
15.38 |
| 2026-10-07 00:00 |
21:53:51.20 |
-36:36:11.6 |
HIP 108186 |
16.56 |
| 2026-10-07 12:00 |
21:53:44.68 |
-36:36:06.5 |
HIP 108186 |
17.74 |
| 2026-10-08 00:00 |
21:53:38.23 |
-36:36:01.0 |
HIP 108035 |
18.39 |
| 2026-10-08 12:00 |
21:53:31.84 |
-36:35:54.9 |
HIP 108035 |
18.20 |
| 2026-10-09 00:00 |
21:53:25.52 |
-36:35:48.3 |
HIP 108035 |
18.12 |
| 2026-10-09 12:00 |
21:53:19.27 |
-36:35:41.2 |
HIP 108035 |
18.13 |
| 2026-10-10 00:00 |
21:53:13.08 |
-36:35:33.6 |
HIP 108035 |
18.23 |
| 2026-10-10 12:00 |
21:53:06.96 |
-36:35:25.5 |
HIP 108035 |
18.43 |
| 2026-10-11 00:00 |
21:53:00.91 |
-36:35:16.9 |
HIP 108035 |
18.71 |