| Parameter |
Value |
| Designation |
C/2017 C1 (NEOWISE) |
| Type |
C |
| Perihelion (tp_cal, UTC) |
2017-01-18T22:42:46.506240Z |
| Orbit solution date (soln_date, UTC) |
2021-04-15T23:33:29Z |
| Obs used |
60 |
| NEO |
- |
| M1 |
18.100 |
| K1 |
8.500 |
| PC |
- |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
2017-03-06.0000000 |
| e |
0.92781552 |
| q (au) |
1.501755 |
| a (au) |
20.804403 |
| i (deg) |
65.752241 |
| Ω (om, deg) |
357.457191 |
| ω (w, deg) |
110.204316 |
| M (ma, deg) |
0.478338 |
Magnitude
Scatter + Global Linear
$$
M_a = (17.436 + 6.000\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
17.436 |
| n |
6.000 |
| gf |
1.000 |
| gb |
-0.703 |
| 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
Ephemeris
| Date/Time (UTC) |
RA (J2000) |
Dec (J2000) |
Nearest HIP |
Dist from HIP (arcmin) |
| 2026-07-29 00:00 |
10:53:11.40 |
-85:01:08.5 |
HIP 52020 |
22.46 |
| 2026-07-29 12:00 |
10:54:00.01 |
-85:00:24.8 |
HIP 52020 |
23.74 |
| 2026-07-30 00:00 |
10:54:48.68 |
-84:59:41.5 |
HIP 53702 |
24.80 |
| 2026-07-30 12:00 |
10:55:37.39 |
-84:58:58.5 |
HIP 53702 |
23.86 |
| 2026-07-31 00:00 |
10:56:26.15 |
-84:58:15.9 |
HIP 53702 |
22.95 |
| 2026-07-31 12:00 |
10:57:14.95 |
-84:57:33.7 |
HIP 53702 |
22.10 |
| 2026-08-01 00:00 |
10:58:03.81 |
-84:56:51.9 |
HIP 53702 |
21.29 |
| 2026-08-01 12:00 |
10:58:52.71 |
-84:56:10.4 |
HIP 53702 |
20.55 |
| 2026-08-02 00:00 |
10:59:41.65 |
-84:55:29.4 |
HIP 53702 |
19.87 |
| 2026-08-02 12:00 |
11:00:30.65 |
-84:54:48.7 |
HIP 53702 |
19.26 |
| 2026-08-03 00:00 |
11:01:19.69 |
-84:54:08.4 |
HIP 53702 |
18.73 |
| 2026-08-03 12:00 |
11:02:08.78 |
-84:53:28.5 |
HIP 53702 |
18.28 |
| 2026-08-04 00:00 |
11:02:57.91 |
-84:52:48.9 |
HIP 53702 |
17.93 |
| 2026-08-04 12:00 |
11:03:47.10 |
-84:52:09.8 |
HIP 53702 |
17.68 |
| 2026-08-05 00:00 |
11:04:36.32 |
-84:51:31.0 |
HIP 53702 |
17.52 |
| 2026-08-05 12:00 |
11:05:25.60 |
-84:50:52.7 |
HIP 53702 |
17.48 |
| 2026-08-06 00:00 |
11:06:14.92 |
-84:50:14.7 |
HIP 53702 |
17.53 |
| 2026-08-06 12:00 |
11:07:04.29 |
-84:49:37.1 |
HIP 53702 |
17.69 |
| 2026-08-07 00:00 |
11:07:53.70 |
-84:49:00.0 |
HIP 53702 |
17.95 |
| 2026-08-07 12:00 |
11:08:43.16 |
-84:48:23.1 |
HIP 53702 |
18.31 |
| 2026-08-08 00:00 |
11:09:32.67 |
-84:47:46.7 |
HIP 53702 |
18.76 |
| 2026-08-08 12:00 |
11:10:22.22 |
-84:47:10.7 |
HIP 53702 |
19.29 |
| 2026-08-09 00:00 |
11:11:11.82 |
-84:46:35.1 |
HIP 53702 |
19.90 |
| 2026-08-09 12:00 |
11:12:01.46 |
-84:46:00.0 |
HIP 53702 |
20.58 |
| 2026-08-10 00:00 |
11:12:51.15 |
-84:45:25.2 |
HIP 54391 |
20.51 |
| 2026-08-10 12:00 |
11:13:40.88 |
-84:44:50.8 |
HIP 55746 |
19.97 |
| 2026-08-11 00:00 |
11:14:30.65 |
-84:44:16.8 |
HIP 55746 |
19.50 |
| 2026-08-11 12:00 |
11:15:20.48 |
-84:43:43.2 |
HIP 55746 |
19.08 |
| 2026-08-12 00:00 |
11:16:10.34 |
-84:43:10.0 |
HIP 55746 |
18.73 |
| 2026-08-12 12:00 |
11:17:00.25 |
-84:42:37.2 |
HIP 55746 |
18.45 |
| 2026-08-13 00:00 |
11:17:50.20 |
-84:42:04.9 |
HIP 55746 |
18.24 |
| 2026-08-13 12:00 |
11:18:40.19 |
-84:41:32.9 |
HIP 55746 |
18.10 |
| 2026-08-14 00:00 |
11:19:30.22 |
-84:41:01.4 |
HIP 55746 |
18.05 |
| 2026-08-14 12:00 |
11:20:20.30 |
-84:40:30.3 |
HIP 55746 |
18.07 |
| 2026-08-15 00:00 |
11:21:10.42 |
-84:39:59.6 |
HIP 55746 |
18.17 |
| 2026-08-15 12:00 |
11:22:00.57 |
-84:39:29.3 |
HIP 55746 |
18.34 |
| 2026-08-16 00:00 |
11:22:50.77 |
-84:38:59.4 |
HIP 55746 |
18.59 |
| 2026-08-16 12:00 |
11:23:41.01 |
-84:38:29.9 |
HIP 55746 |
18.90 |
| 2026-08-17 00:00 |
11:24:31.28 |
-84:38:00.9 |
HIP 55746 |
19.29 |
| 2026-08-17 12:00 |
11:25:21.60 |
-84:37:32.2 |
HIP 55746 |
19.74 |
| 2026-08-18 00:00 |
11:26:11.95 |
-84:37:04.0 |
HIP 55746 |
20.24 |
| 2026-08-18 12:00 |
11:27:02.34 |
-84:36:36.2 |
HIP 55746 |
20.81 |
| 2026-08-19 00:00 |
11:27:52.78 |
-84:36:08.8 |
HIP 55746 |
21.42 |