| Parameter |
Value |
| Designation |
C/1995 Y1 (Hyakutake) |
| Type |
C |
| Perihelion (tp_cal, UTC) |
1996-02-24T06:53:53.528640Z |
| Orbit solution date (soln_date, UTC) |
2021-04-15T23:29:47Z |
| Obs used |
259 |
| NEO |
- |
| M1 |
9.900 |
| K1 |
15.000 |
| PC |
0.030 |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
1996-02-24.0000000 |
| e |
1.00026947 |
| q (au) |
1.054617 |
| a (au) |
-3913.664483 |
| i (deg) |
54.466072 |
| Ω (om, deg) |
195.761478 |
| ω (w, deg) |
46.348701 |
| M (ma, deg) |
-0.000001 |
Magnitude
Scatter + Global Linear
$$
M_a = (6.861 + 6.000\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
6.861 |
| n |
6.000 |
| gf |
1.000 |
| gb |
-0.998 |
| k |
1.000 |
| 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
Residuals (Piecewise)
$$\epsilon = a \log_{10} r_{\mathrm{au}} + b$$
| Start (UTC) |
End (UTC) |
a |
b |
| 1995-12-27 |
1996-01-15 |
-32.9619 |
+4.433 |
| 1996-01-15 |
1996-02-24 |
+5.8871 |
-0.300 |
| 1996-02-24 |
1996-07-18 |
+2.0313 |
-0.181 |
| 1996-07-18 |
1996-10-05 |
+7.6754 |
-1.742 |
log10 r = log10(heliocentric distance / AU), Δ = geocentric distance (AU)
Ephemeris
| Date/Time (UTC) |
RA (J2000) |
Dec (J2000) |
Nearest HIP |
Dist from HIP (arcmin) |
| 2026-05-12 00:00 |
02:41:42.23 |
-09:16:05.1 |
HIP 12444 |
24.75 |
| 2026-05-12 12:00 |
02:41:44.35 |
-09:15:58.6 |
HIP 12444 |
25.27 |
| 2026-05-13 00:00 |
02:41:46.46 |
-09:15:52.2 |
HIP 12444 |
25.78 |
| 2026-05-13 12:00 |
02:41:48.58 |
-09:15:46.0 |
HIP 12444 |
26.30 |
| 2026-05-14 00:00 |
02:41:50.69 |
-09:15:39.8 |
HIP 12444 |
26.81 |
| 2026-05-14 12:00 |
02:41:52.79 |
-09:15:33.8 |
HIP 12444 |
27.32 |
| 2026-05-15 00:00 |
02:41:54.89 |
-09:15:28.0 |
HIP 12444 |
27.83 |
| 2026-05-15 12:00 |
02:41:57.00 |
-09:15:22.2 |
HIP 12444 |
28.34 |
| 2026-05-16 00:00 |
02:41:59.09 |
-09:15:16.6 |
HIP 12444 |
28.85 |
| 2026-05-16 12:00 |
02:42:01.18 |
-09:15:11.1 |
HIP 12444 |
29.36 |
| 2026-05-17 00:00 |
02:42:03.27 |
-09:15:05.7 |
HIP 12760 |
29.05 |
| 2026-05-17 12:00 |
02:42:05.36 |
-09:15:00.5 |
HIP 12760 |
28.53 |
| 2026-05-18 00:00 |
02:42:07.44 |
-09:14:55.4 |
HIP 12760 |
28.01 |
| 2026-05-18 12:00 |
02:42:09.52 |
-09:14:50.4 |
HIP 12760 |
27.49 |
| 2026-05-19 00:00 |
02:42:11.59 |
-09:14:45.6 |
HIP 12760 |
26.97 |
| 2026-05-19 12:00 |
02:42:13.66 |
-09:14:40.9 |
HIP 12760 |
26.45 |
| 2026-05-20 00:00 |
02:42:15.72 |
-09:14:36.3 |
HIP 12760 |
25.94 |
| 2026-05-20 12:00 |
02:42:17.78 |
-09:14:31.9 |
HIP 12760 |
25.43 |
| 2026-05-21 00:00 |
02:42:19.84 |
-09:14:27.6 |
HIP 12760 |
24.91 |
| 2026-05-21 12:00 |
02:42:21.89 |
-09:14:23.4 |
HIP 12760 |
24.40 |
| 2026-05-22 00:00 |
02:42:23.93 |
-09:14:19.3 |
HIP 12760 |
23.89 |
| 2026-05-22 12:00 |
02:42:25.97 |
-09:14:15.4 |
HIP 12760 |
23.39 |
| 2026-05-23 00:00 |
02:42:28.00 |
-09:14:11.6 |
HIP 12760 |
22.88 |
| 2026-05-23 12:00 |
02:42:30.03 |
-09:14:08.0 |
HIP 12760 |
22.38 |
| 2026-05-24 00:00 |
02:42:32.05 |
-09:14:04.5 |
HIP 12760 |
21.88 |
| 2026-05-24 12:00 |
02:42:34.07 |
-09:14:01.1 |
HIP 12760 |
21.38 |
| 2026-05-25 00:00 |
02:42:36.08 |
-09:13:57.8 |
HIP 12760 |
20.88 |
| 2026-05-25 12:00 |
02:42:38.08 |
-09:13:54.7 |
HIP 12760 |
20.38 |
| 2026-05-26 00:00 |
02:42:40.08 |
-09:13:51.7 |
HIP 12760 |
19.89 |
| 2026-05-26 12:00 |
02:42:42.07 |
-09:13:48.9 |
HIP 12760 |
19.40 |
| 2026-05-27 00:00 |
02:42:44.05 |
-09:13:46.2 |
HIP 12760 |
18.90 |
| 2026-05-27 12:00 |
02:42:46.03 |
-09:13:43.6 |
HIP 12760 |
18.42 |
| 2026-05-28 00:00 |
02:42:48.00 |
-09:13:41.2 |
HIP 12760 |
17.93 |
| 2026-05-28 12:00 |
02:42:49.97 |
-09:13:38.9 |
HIP 12760 |
17.45 |
| 2026-05-29 00:00 |
02:42:51.93 |
-09:13:36.7 |
HIP 12760 |
16.96 |
| 2026-05-29 12:00 |
02:42:53.88 |
-09:13:34.7 |
HIP 12760 |
16.48 |
| 2026-05-30 00:00 |
02:42:55.82 |
-09:13:32.7 |
HIP 12760 |
16.01 |
| 2026-05-30 12:00 |
02:42:57.76 |
-09:13:31.0 |
HIP 12760 |
15.53 |
| 2026-05-31 00:00 |
02:42:59.69 |
-09:13:29.3 |
HIP 12760 |
15.06 |
| 2026-05-31 12:00 |
02:43:01.61 |
-09:13:27.8 |
HIP 12760 |
14.59 |
| 2026-06-01 00:00 |
02:43:03.52 |
-09:13:26.5 |
HIP 12760 |
14.12 |
| 2026-06-01 12:00 |
02:43:05.43 |
-09:13:25.3 |
HIP 12760 |
13.66 |
| 2026-06-02 00:00 |
02:43:07.33 |
-09:13:24.2 |
HIP 12760 |
13.19 |