C/2015 X8 (NEOWISE)
| Parameter |
Value |
| Designation |
C/2015 X8 (NEOWISE) |
| Type |
C |
| Perihelion (tp_cal, UTC) |
2015-10-23T02:58:51.087360Z |
| Orbit solution date (soln_date, UTC) |
2021-04-15T23:33:20Z |
| Obs used |
116 |
| NEO |
Yes |
| M1 |
16.200 |
| K1 |
4.500 |
| PC |
0.030 |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
2016-01-22.0000000 |
| e |
0.93911400 |
| q (au) |
1.190273 |
| a (au) |
19.549200 |
| i (deg) |
155.281698 |
| Ω (om, deg) |
191.111870 |
| ω (w, deg) |
20.400527 |
| M (ma, deg) |
1.036236 |
Magnitude
Scatter + Global Linear
$$
M_a = (15.395 + 4.524\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
15.395 |
| n |
4.524 |
| gf |
0.999 |
| gb |
-0.984 |
| k |
0.971 |
| 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) |
| 2026-02-03 00:00 |
00:26:57.54 |
+01:51:24.2 |
HIP 2047 |
16.07 |
| 2026-02-03 12:00 |
00:27:00.27 |
+01:51:40.3 |
HIP 2047 |
16.63 |
| 2026-02-04 00:00 |
00:27:03.02 |
+01:51:56.7 |
HIP 2047 |
17.20 |
| 2026-02-04 12:00 |
00:27:05.81 |
+01:52:13.3 |
HIP 2212 |
16.96 |
| 2026-02-05 00:00 |
00:27:08.63 |
+01:52:30.1 |
HIP 2212 |
16.24 |
| 2026-02-05 12:00 |
00:27:11.49 |
+01:52:47.1 |
HIP 2212 |
15.52 |
| 2026-02-06 00:00 |
00:27:14.37 |
+01:53:04.3 |
HIP 2212 |
14.80 |
| 2026-02-06 12:00 |
00:27:17.29 |
+01:53:21.7 |
HIP 2212 |
14.07 |
| 2026-02-07 00:00 |
00:27:20.23 |
+01:53:39.2 |
HIP 2212 |
13.35 |
| 2026-02-07 12:00 |
00:27:23.21 |
+01:53:57.0 |
HIP 2212 |
12.62 |
| 2026-02-08 00:00 |
00:27:26.22 |
+01:54:14.9 |
HIP 2212 |
11.90 |
| 2026-02-08 12:00 |
00:27:29.26 |
+01:54:33.1 |
HIP 2212 |
11.18 |
| 2026-02-09 00:00 |
00:27:32.33 |
+01:54:51.4 |
HIP 2212 |
10.46 |
| 2026-02-09 12:00 |
00:27:35.43 |
+01:55:09.9 |
HIP 2212 |
9.76 |
| 2026-02-10 00:00 |
00:27:38.55 |
+01:55:28.6 |
HIP 2212 |
9.07 |
| 2026-02-10 12:00 |
00:27:41.71 |
+01:55:47.5 |
HIP 2212 |
8.41 |
| 2026-02-11 00:00 |
00:27:44.90 |
+01:56:06.5 |
HIP 2212 |
7.78 |
| 2026-02-11 12:00 |
00:27:48.11 |
+01:56:25.8 |
HIP 2212 |
7.19 |
| 2026-02-12 00:00 |
00:27:51.36 |
+01:56:45.2 |
HIP 2212 |
6.65 |
| 2026-02-12 12:00 |
00:27:54.63 |
+01:57:04.7 |
HIP 2212 |
6.19 |
| 2026-02-13 00:00 |
00:27:57.93 |
+01:57:24.5 |
HIP 2212 |
5.82 |
| 2026-02-13 12:00 |
00:28:01.26 |
+01:57:44.4 |
HIP 2212 |
5.57 |
| 2026-02-14 00:00 |
00:28:04.61 |
+01:58:04.5 |
HIP 2212 |
5.45 |
| 2026-02-14 12:00 |
00:28:07.99 |
+01:58:24.7 |
HIP 2212 |
5.48 |
| 2026-02-15 00:00 |
00:28:11.40 |
+01:58:45.2 |
HIP 2212 |
5.67 |
| 2026-02-15 12:00 |
00:28:14.84 |
+01:59:05.7 |
HIP 2212 |
5.99 |
| 2026-02-16 00:00 |
00:28:18.30 |
+01:59:26.5 |
HIP 2212 |
6.44 |
| 2026-02-16 12:00 |
00:28:21.79 |
+01:59:47.4 |
HIP 2212 |
6.98 |
| 2026-02-17 00:00 |
00:28:25.30 |
+02:00:08.4 |
HIP 2212 |
7.61 |
| 2026-02-17 12:00 |
00:28:28.84 |
+02:00:29.6 |
HIP 2212 |
8.30 |
| 2026-02-18 00:00 |
00:28:32.40 |
+02:00:51.0 |
HIP 2212 |
9.05 |
| 2026-02-18 12:00 |
00:28:35.99 |
+02:01:12.5 |
HIP 2212 |
9.83 |
| 2026-02-19 00:00 |
00:28:39.60 |
+02:01:34.1 |
HIP 2212 |
10.66 |
| 2026-02-19 12:00 |
00:28:43.24 |
+02:01:55.9 |
HIP 2212 |
11.51 |
| 2026-02-20 00:00 |
00:28:46.90 |
+02:02:17.9 |
HIP 2212 |
12.39 |
| 2026-02-20 12:00 |
00:28:50.58 |
+02:02:39.9 |
HIP 2212 |
13.28 |
| 2026-02-21 00:00 |
00:28:54.29 |
+02:03:02.1 |
HIP 2212 |
14.20 |
| 2026-02-21 12:00 |
00:28:58.02 |
+02:03:24.5 |
HIP 2212 |
15.13 |
| 2026-02-22 00:00 |
00:29:01.77 |
+02:03:47.0 |
HIP 2212 |
16.08 |
| 2026-02-22 12:00 |
00:29:05.54 |
+02:04:09.6 |
HIP 2212 |
17.04 |
| 2026-02-23 00:00 |
00:29:09.34 |
+02:04:32.3 |
HIP 2212 |
18.01 |
| 2026-02-23 12:00 |
00:29:13.16 |
+02:04:55.2 |
HIP 2212 |
18.99 |
| 2026-02-24 00:00 |
00:29:17.00 |
+02:05:18.2 |
HIP 2212 |
19.98 |