| 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) |
| 2026-07-29 00:00 |
02:45:24.74 |
-09:25:42.0 |
HIP 12760 |
25.87 |
| 2026-07-29 12:00 |
02:45:25.06 |
-09:25:55.2 |
HIP 12760 |
26.06 |
| 2026-07-30 00:00 |
02:45:25.37 |
-09:26:08.5 |
HIP 12760 |
26.25 |
| 2026-07-30 12:00 |
02:45:25.66 |
-09:26:21.8 |
HIP 12760 |
26.44 |
| 2026-07-31 00:00 |
02:45:25.93 |
-09:26:35.3 |
HIP 12760 |
26.63 |
| 2026-07-31 12:00 |
02:45:26.18 |
-09:26:48.8 |
HIP 12945 |
26.80 |
| 2026-08-01 00:00 |
02:45:26.42 |
-09:27:02.5 |
HIP 12945 |
26.58 |
| 2026-08-01 12:00 |
02:45:26.64 |
-09:27:16.2 |
HIP 12945 |
26.37 |
| 2026-08-02 00:00 |
02:45:26.84 |
-09:27:30.0 |
HIP 12945 |
26.15 |
| 2026-08-02 12:00 |
02:45:27.02 |
-09:27:43.9 |
HIP 12945 |
25.94 |
| 2026-08-03 00:00 |
02:45:27.19 |
-09:27:57.9 |
HIP 12945 |
25.73 |
| 2026-08-03 12:00 |
02:45:27.34 |
-09:28:12.0 |
HIP 12945 |
25.52 |
| 2026-08-04 00:00 |
02:45:27.47 |
-09:28:26.1 |
HIP 12945 |
25.31 |
| 2026-08-04 12:00 |
02:45:27.58 |
-09:28:40.4 |
HIP 12945 |
25.11 |
| 2026-08-05 00:00 |
02:45:27.68 |
-09:28:54.7 |
HIP 12945 |
24.90 |
| 2026-08-05 12:00 |
02:45:27.75 |
-09:29:09.1 |
HIP 12945 |
24.70 |
| 2026-08-06 00:00 |
02:45:27.81 |
-09:29:23.6 |
HIP 12945 |
24.50 |
| 2026-08-06 12:00 |
02:45:27.85 |
-09:29:38.2 |
HIP 12945 |
24.31 |
| 2026-08-07 00:00 |
02:45:27.88 |
-09:29:52.8 |
HIP 12945 |
24.12 |
| 2026-08-07 12:00 |
02:45:27.88 |
-09:30:07.5 |
HIP 12945 |
23.93 |
| 2026-08-08 00:00 |
02:45:27.87 |
-09:30:22.3 |
HIP 12945 |
23.74 |
| 2026-08-08 12:00 |
02:45:27.84 |
-09:30:37.2 |
HIP 12945 |
23.55 |
| 2026-08-09 00:00 |
02:45:27.79 |
-09:30:52.2 |
HIP 12945 |
23.37 |
| 2026-08-09 12:00 |
02:45:27.73 |
-09:31:07.2 |
HIP 12945 |
23.19 |
| 2026-08-10 00:00 |
02:45:27.64 |
-09:31:22.3 |
HIP 12945 |
23.02 |
| 2026-08-10 12:00 |
02:45:27.54 |
-09:31:37.5 |
HIP 12945 |
22.85 |
| 2026-08-11 00:00 |
02:45:27.42 |
-09:31:52.7 |
HIP 12945 |
22.68 |
| 2026-08-11 12:00 |
02:45:27.28 |
-09:32:08.0 |
HIP 12945 |
22.52 |
| 2026-08-12 00:00 |
02:45:27.13 |
-09:32:23.4 |
HIP 12945 |
22.36 |
| 2026-08-12 12:00 |
02:45:26.95 |
-09:32:38.9 |
HIP 12945 |
22.20 |
| 2026-08-13 00:00 |
02:45:26.76 |
-09:32:54.4 |
HIP 12945 |
22.05 |
| 2026-08-13 12:00 |
02:45:26.55 |
-09:33:10.0 |
HIP 12945 |
21.90 |
| 2026-08-14 00:00 |
02:45:26.32 |
-09:33:25.6 |
HIP 12945 |
21.76 |
| 2026-08-14 12:00 |
02:45:26.07 |
-09:33:41.3 |
HIP 12945 |
21.63 |
| 2026-08-15 00:00 |
02:45:25.81 |
-09:33:57.1 |
HIP 12945 |
21.49 |
| 2026-08-15 12:00 |
02:45:25.53 |
-09:34:12.9 |
HIP 12945 |
21.37 |
| 2026-08-16 00:00 |
02:45:25.23 |
-09:34:28.8 |
HIP 12945 |
21.25 |
| 2026-08-16 12:00 |
02:45:24.91 |
-09:34:44.8 |
HIP 12945 |
21.13 |
| 2026-08-17 00:00 |
02:45:24.57 |
-09:35:00.8 |
HIP 12945 |
21.02 |
| 2026-08-17 12:00 |
02:45:24.22 |
-09:35:16.9 |
HIP 12945 |
20.92 |
| 2026-08-18 00:00 |
02:45:23.85 |
-09:35:33.0 |
HIP 12945 |
20.82 |
| 2026-08-18 12:00 |
02:45:23.46 |
-09:35:49.1 |
HIP 12945 |
20.73 |
| 2026-08-19 00:00 |
02:45:23.05 |
-09:36:05.4 |
HIP 12945 |
20.64 |