| 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) |
| 2026-07-29 00:00 |
22:14:47.50 |
-35:21:43.3 |
HIP 109978 |
23.47 |
| 2026-07-29 12:00 |
22:14:38.55 |
-35:22:46.2 |
HIP 109662 |
21.56 |
| 2026-07-30 00:00 |
22:14:29.57 |
-35:23:48.9 |
HIP 109662 |
19.61 |
| 2026-07-30 12:00 |
22:14:20.55 |
-35:24:51.3 |
HIP 109662 |
17.69 |
| 2026-07-31 00:00 |
22:14:11.49 |
-35:25:53.5 |
HIP 109662 |
15.82 |
| 2026-07-31 12:00 |
22:14:02.41 |
-35:26:55.3 |
HIP 109662 |
14.01 |
| 2026-08-01 00:00 |
22:13:53.29 |
-35:27:56.8 |
HIP 109662 |
12.29 |
| 2026-08-01 12:00 |
22:13:44.13 |
-35:28:58.0 |
HIP 109662 |
10.71 |
| 2026-08-02 00:00 |
22:13:34.95 |
-35:29:58.9 |
HIP 109662 |
9.34 |
| 2026-08-02 12:00 |
22:13:25.73 |
-35:30:59.5 |
HIP 109662 |
8.28 |
| 2026-08-03 00:00 |
22:13:16.49 |
-35:31:59.8 |
HIP 109662 |
7.69 |
| 2026-08-03 12:00 |
22:13:07.21 |
-35:32:59.8 |
HIP 109662 |
7.65 |
| 2026-08-04 00:00 |
22:12:57.91 |
-35:33:59.4 |
HIP 109662 |
8.18 |
| 2026-08-04 12:00 |
22:12:48.57 |
-35:34:58.7 |
HIP 109662 |
9.19 |
| 2026-08-05 00:00 |
22:12:39.21 |
-35:35:57.7 |
HIP 109662 |
10.54 |
| 2026-08-05 12:00 |
22:12:29.82 |
-35:36:56.3 |
HIP 109662 |
12.12 |
| 2026-08-06 00:00 |
22:12:20.41 |
-35:37:54.6 |
HIP 109662 |
13.85 |
| 2026-08-06 12:00 |
22:12:10.97 |
-35:38:52.5 |
HIP 109662 |
15.68 |
| 2026-08-07 00:00 |
22:12:01.50 |
-35:39:50.1 |
HIP 109662 |
17.58 |
| 2026-08-07 12:00 |
22:11:52.01 |
-35:40:47.3 |
HIP 109662 |
19.53 |
| 2026-08-08 00:00 |
22:11:42.50 |
-35:41:44.1 |
HIP 109662 |
21.51 |
| 2026-08-08 12:00 |
22:11:32.96 |
-35:42:40.6 |
HIP 109433 |
22.51 |
| 2026-08-09 00:00 |
22:11:23.41 |
-35:43:36.7 |
HIP 109433 |
20.49 |
| 2026-08-09 12:00 |
22:11:13.83 |
-35:44:32.4 |
HIP 109433 |
18.51 |
| 2026-08-10 00:00 |
22:11:04.23 |
-35:45:27.7 |
HIP 109433 |
16.58 |
| 2026-08-10 12:00 |
22:10:54.61 |
-35:46:22.6 |
HIP 109433 |
14.71 |
| 2026-08-11 00:00 |
22:10:44.98 |
-35:47:17.2 |
HIP 109433 |
12.93 |
| 2026-08-11 12:00 |
22:10:35.32 |
-35:48:11.3 |
HIP 109433 |
11.29 |
| 2026-08-12 00:00 |
22:10:25.65 |
-35:49:05.0 |
HIP 109433 |
9.86 |
| 2026-08-12 12:00 |
22:10:15.97 |
-35:49:58.3 |
HIP 109433 |
8.73 |
| 2026-08-13 00:00 |
22:10:06.27 |
-35:50:51.2 |
HIP 109433 |
8.05 |
| 2026-08-13 12:00 |
22:09:56.55 |
-35:51:43.7 |
HIP 109433 |
7.91 |
| 2026-08-14 00:00 |
22:09:46.82 |
-35:52:35.8 |
HIP 109433 |
8.36 |
| 2026-08-14 12:00 |
22:09:37.08 |
-35:53:27.4 |
HIP 109329 |
8.63 |
| 2026-08-15 00:00 |
22:09:27.33 |
-35:54:18.6 |
HIP 109329 |
6.48 |
| 2026-08-15 12:00 |
22:09:17.56 |
-35:55:09.3 |
HIP 109329 |
4.33 |
| 2026-08-16 00:00 |
22:09:07.79 |
-35:55:59.7 |
HIP 109329 |
2.19 |
| 2026-08-16 12:00 |
22:08:58.01 |
-35:56:49.5 |
HIP 109329 |
0.17 |
| 2026-08-17 00:00 |
22:08:48.22 |
-35:57:39.0 |
HIP 109329 |
2.12 |
| 2026-08-17 12:00 |
22:08:38.42 |
-35:58:27.9 |
HIP 109329 |
4.26 |
| 2026-08-18 00:00 |
22:08:28.62 |
-35:59:16.5 |
HIP 109329 |
6.40 |
| 2026-08-18 12:00 |
22:08:18.81 |
-36:00:04.5 |
HIP 109329 |
8.54 |
| 2026-08-19 00:00 |
22:08:08.99 |
-36:00:52.1 |
HIP 109334 |
10.56 |