| Parameter |
Value |
| Designation |
C/2015 YG1 (NEOWISE) |
| Type |
C |
| Perihelion (tp_cal, UTC) |
2015-09-28T23:19:05.626560Z |
| Orbit solution date (soln_date, UTC) |
2021-04-15T23:33:21Z |
| Obs used |
222 |
| NEO |
- |
| M1 |
12.100 |
| K1 |
10.500 |
| PC |
0.030 |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
2016-02-05.0000000 |
| e |
0.87923622 |
| q (au) |
2.073411 |
| a (au) |
17.169149 |
| i (deg) |
57.336038 |
| Ω (om, deg) |
350.511863 |
| ω (w, deg) |
102.791763 |
| M (ma, deg) |
1.787583 |
Magnitude
Scatter + Global Linear
$$
M_a = (H_0 + n\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
- |
| n |
- |
| gf |
- |
| gb |
- |
| k |
- |
| δ90 |
- |
| 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) |
| 2026-05-12 00:00 |
13:25:03.79 |
-75:12:59.1 |
HIP 65468 |
19.74 |
| 2026-05-12 12:00 |
13:24:46.06 |
-75:12:17.1 |
HIP 65468 |
19.08 |
| 2026-05-13 00:00 |
13:24:28.45 |
-75:11:34.4 |
HIP 65468 |
18.49 |
| 2026-05-13 12:00 |
13:24:10.95 |
-75:10:51.0 |
HIP 65468 |
17.97 |
| 2026-05-14 00:00 |
13:23:53.57 |
-75:10:07.1 |
HIP 65468 |
17.53 |
| 2026-05-14 12:00 |
13:23:36.31 |
-75:09:22.5 |
HIP 65468 |
17.16 |
| 2026-05-15 00:00 |
13:23:19.17 |
-75:08:37.3 |
HIP 65468 |
16.89 |
| 2026-05-15 12:00 |
13:23:02.16 |
-75:07:51.5 |
HIP 65468 |
16.70 |
| 2026-05-16 00:00 |
13:22:45.27 |
-75:07:05.1 |
HIP 65468 |
16.61 |
| 2026-05-16 12:00 |
13:22:28.51 |
-75:06:18.1 |
HIP 65468 |
16.61 |
| 2026-05-17 00:00 |
13:22:11.88 |
-75:05:30.5 |
HIP 65468 |
16.71 |
| 2026-05-17 12:00 |
13:21:55.38 |
-75:04:42.3 |
HIP 65468 |
16.91 |
| 2026-05-18 00:00 |
13:21:39.01 |
-75:03:53.5 |
HIP 64972 |
17.00 |
| 2026-05-18 12:00 |
13:21:22.77 |
-75:03:04.2 |
HIP 64972 |
15.71 |
| 2026-05-19 00:00 |
13:21:06.67 |
-75:02:14.3 |
HIP 64972 |
14.43 |
| 2026-05-19 12:00 |
13:20:50.70 |
-75:01:23.9 |
HIP 64972 |
13.15 |
| 2026-05-20 00:00 |
13:20:34.88 |
-75:00:32.9 |
HIP 64972 |
11.88 |
| 2026-05-20 12:00 |
13:20:19.19 |
-74:59:41.4 |
HIP 64972 |
10.63 |
| 2026-05-21 00:00 |
13:20:03.64 |
-74:58:49.3 |
HIP 64972 |
9.39 |
| 2026-05-21 12:00 |
13:19:48.24 |
-74:57:56.7 |
HIP 64972 |
8.17 |
| 2026-05-22 00:00 |
13:19:32.97 |
-74:57:03.6 |
HIP 64972 |
6.99 |
| 2026-05-22 12:00 |
13:19:17.85 |
-74:56:09.9 |
HIP 64972 |
5.87 |
| 2026-05-23 00:00 |
13:19:02.88 |
-74:55:15.8 |
HIP 64972 |
4.85 |
| 2026-05-23 12:00 |
13:18:48.05 |
-74:54:21.1 |
HIP 64972 |
4.00 |
| 2026-05-24 00:00 |
13:18:33.37 |
-74:53:26.0 |
HIP 64972 |
3.45 |
| 2026-05-24 12:00 |
13:18:18.84 |
-74:52:30.4 |
HIP 64972 |
3.36 |
| 2026-05-25 00:00 |
13:18:04.46 |
-74:51:34.2 |
HIP 64972 |
3.75 |
| 2026-05-25 12:00 |
13:17:50.23 |
-74:50:37.7 |
HIP 64972 |
4.51 |
| 2026-05-26 00:00 |
13:17:36.15 |
-74:49:40.6 |
HIP 64972 |
5.48 |
| 2026-05-26 12:00 |
13:17:22.22 |
-74:48:43.1 |
HIP 64972 |
6.57 |
| 2026-05-27 00:00 |
13:17:08.45 |
-74:47:45.1 |
HIP 64972 |
7.73 |
| 2026-05-27 12:00 |
13:16:54.83 |
-74:46:46.7 |
HIP 64972 |
8.92 |
| 2026-05-28 00:00 |
13:16:41.36 |
-74:45:47.8 |
HIP 64972 |
10.15 |
| 2026-05-28 12:00 |
13:16:28.05 |
-74:44:48.5 |
HIP 64972 |
11.39 |
| 2026-05-29 00:00 |
13:16:14.89 |
-74:43:48.8 |
HIP 64972 |
12.64 |
| 2026-05-29 12:00 |
13:16:01.89 |
-74:42:48.7 |
HIP 64972 |
13.91 |
| 2026-05-30 00:00 |
13:15:49.05 |
-74:41:48.1 |
HIP 64972 |
15.17 |
| 2026-05-30 12:00 |
13:15:36.37 |
-74:40:47.1 |
HIP 64972 |
16.45 |
| 2026-05-31 00:00 |
13:15:23.84 |
-74:39:45.8 |
HIP 64972 |
17.72 |
| 2026-05-31 12:00 |
13:15:11.48 |
-74:38:44.0 |
HIP 64972 |
19.00 |
| 2026-06-01 00:00 |
13:14:59.28 |
-74:37:41.9 |
HIP 64972 |
20.28 |
| 2026-06-01 12:00 |
13:14:47.23 |
-74:36:39.3 |
HIP 64972 |
21.56 |
| 2026-06-02 00:00 |
13:14:35.35 |
-74:35:36.4 |
HIP 64972 |
22.84 |