| Parameter |
Value |
| Designation |
C/2016 U1 (NEOWISE) |
| Type |
C |
| Perihelion (tp_cal, UTC) |
2017-01-14T00:24:03.925440Z |
| Orbit solution date (soln_date, UTC) |
2021-04-15T23:33:28Z |
| Obs used |
366 |
| NEO |
- |
| M1 |
13.100 |
| K1 |
12.250 |
| PC |
0.030 |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
2016-12-12.0000000 |
| e |
1.00025297 |
| q (au) |
0.319170 |
| a (au) |
-1261.677714 |
| i (deg) |
46.434833 |
| Ω (om, deg) |
61.428521 |
| ω (w, deg) |
162.748270 |
| M (ma, deg) |
-0.000726 |
Magnitude
Scatter + Global Linear
$$
M_a = (15.005 + 6.000\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
15.005 |
| n |
6.000 |
| gf |
1.000 |
| gb |
-0.984 |
| k |
0.993 |
| δ90 |
9.928 |
| 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 |
| 2016-10-21 |
2017-01-12 |
-0.0100 |
-1.052 |
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 |
03:04:09.05 |
-04:55:35.2 |
HIP 14197 |
17.43 |
| 2026-07-29 12:00 |
03:04:10.03 |
-04:55:55.5 |
HIP 14197 |
17.52 |
| 2026-07-30 00:00 |
03:04:10.97 |
-04:56:15.9 |
HIP 14197 |
17.60 |
| 2026-07-30 12:00 |
03:04:11.88 |
-04:56:36.6 |
HIP 14197 |
17.69 |
| 2026-07-31 00:00 |
03:04:12.75 |
-04:56:57.5 |
HIP 14282 |
17.72 |
| 2026-07-31 12:00 |
03:04:13.59 |
-04:57:18.5 |
HIP 14282 |
17.39 |
| 2026-08-01 00:00 |
03:04:14.38 |
-04:57:39.8 |
HIP 14282 |
17.06 |
| 2026-08-01 12:00 |
03:04:15.14 |
-04:58:01.2 |
HIP 14282 |
16.73 |
| 2026-08-02 00:00 |
03:04:15.87 |
-04:58:22.9 |
HIP 14282 |
16.40 |
| 2026-08-02 12:00 |
03:04:16.55 |
-04:58:44.7 |
HIP 14282 |
16.06 |
| 2026-08-03 00:00 |
03:04:17.20 |
-04:59:06.8 |
HIP 14282 |
15.73 |
| 2026-08-03 12:00 |
03:04:17.81 |
-04:59:29.0 |
HIP 14282 |
15.39 |
| 2026-08-04 00:00 |
03:04:18.39 |
-04:59:51.4 |
HIP 14282 |
15.05 |
| 2026-08-04 12:00 |
03:04:18.93 |
-05:00:14.0 |
HIP 14282 |
14.71 |
| 2026-08-05 00:00 |
03:04:19.43 |
-05:00:36.8 |
HIP 14282 |
14.37 |
| 2026-08-05 12:00 |
03:04:19.89 |
-05:00:59.8 |
HIP 14282 |
14.02 |
| 2026-08-06 00:00 |
03:04:20.31 |
-05:01:23.0 |
HIP 14282 |
13.68 |
| 2026-08-06 12:00 |
03:04:20.70 |
-05:01:46.3 |
HIP 14282 |
13.33 |
| 2026-08-07 00:00 |
03:04:21.05 |
-05:02:09.9 |
HIP 14282 |
12.97 |
| 2026-08-07 12:00 |
03:04:21.36 |
-05:02:33.6 |
HIP 14282 |
12.62 |
| 2026-08-08 00:00 |
03:04:21.63 |
-05:02:57.5 |
HIP 14282 |
12.26 |
| 2026-08-08 12:00 |
03:04:21.87 |
-05:03:21.5 |
HIP 14282 |
11.90 |
| 2026-08-09 00:00 |
03:04:22.06 |
-05:03:45.8 |
HIP 14282 |
11.53 |
| 2026-08-09 12:00 |
03:04:22.22 |
-05:04:10.2 |
HIP 14282 |
11.17 |
| 2026-08-10 00:00 |
03:04:22.34 |
-05:04:34.8 |
HIP 14282 |
10.80 |
| 2026-08-10 12:00 |
03:04:22.42 |
-05:04:59.5 |
HIP 14282 |
10.42 |
| 2026-08-11 00:00 |
03:04:22.47 |
-05:05:24.5 |
HIP 14282 |
10.05 |
| 2026-08-11 12:00 |
03:04:22.47 |
-05:05:49.6 |
HIP 14282 |
9.66 |
| 2026-08-12 00:00 |
03:04:22.44 |
-05:06:14.8 |
HIP 14282 |
9.28 |
| 2026-08-12 12:00 |
03:04:22.37 |
-05:06:40.2 |
HIP 14282 |
8.89 |
| 2026-08-13 00:00 |
03:04:22.26 |
-05:07:05.8 |
HIP 14282 |
8.50 |
| 2026-08-13 12:00 |
03:04:22.11 |
-05:07:31.6 |
HIP 14282 |
8.11 |
| 2026-08-14 00:00 |
03:04:21.92 |
-05:07:57.5 |
HIP 14282 |
7.71 |
| 2026-08-14 12:00 |
03:04:21.69 |
-05:08:23.5 |
HIP 14282 |
7.31 |
| 2026-08-15 00:00 |
03:04:21.43 |
-05:08:49.7 |
HIP 14282 |
6.91 |
| 2026-08-15 12:00 |
03:04:21.12 |
-05:09:16.1 |
HIP 14282 |
6.50 |
| 2026-08-16 00:00 |
03:04:20.78 |
-05:09:42.6 |
HIP 14282 |
6.09 |
| 2026-08-16 12:00 |
03:04:20.40 |
-05:10:09.2 |
HIP 14282 |
5.68 |
| 2026-08-17 00:00 |
03:04:19.98 |
-05:10:36.0 |
HIP 14282 |
5.27 |
| 2026-08-17 12:00 |
03:04:19.52 |
-05:11:02.9 |
HIP 14282 |
4.86 |
| 2026-08-18 00:00 |
03:04:19.02 |
-05:11:30.0 |
HIP 14282 |
4.45 |
| 2026-08-18 12:00 |
03:04:18.49 |
-05:11:57.2 |
HIP 14282 |
4.05 |
| 2026-08-19 00:00 |
03:04:17.91 |
-05:12:24.5 |
HIP 14282 |
3.65 |