| 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) |
| 2026-09-20 00:00 |
02:44:22.05 |
-09:54:20.0 |
HIP 12945 |
32.01 |
| 2026-09-20 12:00 |
02:44:20.60 |
-09:54:37.1 |
HIP 12945 |
32.42 |
| 2026-09-21 00:00 |
02:44:19.13 |
-09:54:54.2 |
HIP 12945 |
32.82 |
| 2026-09-21 12:00 |
02:44:17.65 |
-09:55:11.2 |
HIP 12945 |
33.24 |
| 2026-09-22 00:00 |
02:44:16.15 |
-09:55:28.2 |
HIP 12945 |
33.66 |
| 2026-09-22 12:00 |
02:44:14.65 |
-09:55:45.2 |
HIP 12945 |
34.08 |
| 2026-09-23 00:00 |
02:44:13.13 |
-09:56:02.1 |
HIP 12945 |
34.50 |
| 2026-09-23 12:00 |
02:44:11.59 |
-09:56:19.0 |
HIP 12945 |
34.93 |
| 2026-09-24 00:00 |
02:44:10.05 |
-09:56:35.9 |
HIP 12945 |
35.37 |
| 2026-09-24 12:00 |
02:44:08.49 |
-09:56:52.7 |
HIP 12660 |
35.00 |
| 2026-09-25 00:00 |
02:44:06.92 |
-09:57:09.5 |
HIP 12660 |
34.54 |
| 2026-09-25 12:00 |
02:44:05.33 |
-09:57:26.2 |
HIP 12660 |
34.09 |
| 2026-09-26 00:00 |
02:44:03.73 |
-09:57:42.9 |
HIP 12660 |
33.63 |
| 2026-09-26 12:00 |
02:44:02.13 |
-09:57:59.6 |
HIP 12660 |
33.17 |
| 2026-09-27 00:00 |
02:44:00.51 |
-09:58:16.2 |
HIP 12660 |
32.70 |
| 2026-09-27 12:00 |
02:43:58.87 |
-09:58:32.8 |
HIP 12660 |
32.24 |
| 2026-09-28 00:00 |
02:43:57.23 |
-09:58:49.3 |
HIP 12660 |
31.78 |
| 2026-09-28 12:00 |
02:43:55.57 |
-09:59:05.8 |
HIP 12660 |
31.32 |
| 2026-09-29 00:00 |
02:43:53.90 |
-09:59:22.2 |
HIP 12660 |
30.86 |
| 2026-09-29 12:00 |
02:43:52.22 |
-09:59:38.6 |
HIP 12660 |
30.39 |
| 2026-09-30 00:00 |
02:43:50.53 |
-09:59:54.9 |
HIP 12660 |
29.93 |
| 2026-09-30 12:00 |
02:43:48.83 |
-10:00:11.2 |
HIP 12660 |
29.47 |
| 2026-10-01 00:00 |
02:43:47.12 |
-10:00:27.5 |
HIP 12660 |
29.01 |
| 2026-10-01 12:00 |
02:43:45.39 |
-10:00:43.6 |
HIP 12660 |
28.55 |
| 2026-10-02 00:00 |
02:43:43.66 |
-10:00:59.7 |
HIP 12660 |
28.09 |
| 2026-10-02 12:00 |
02:43:41.91 |
-10:01:15.8 |
HIP 12660 |
27.63 |
| 2026-10-03 00:00 |
02:43:40.16 |
-10:01:31.8 |
HIP 12660 |
27.17 |
| 2026-10-03 12:00 |
02:43:38.39 |
-10:01:47.8 |
HIP 12660 |
26.72 |
| 2026-10-04 00:00 |
02:43:36.61 |
-10:02:03.6 |
HIP 12660 |
26.26 |
| 2026-10-04 12:00 |
02:43:34.82 |
-10:02:19.5 |
HIP 12660 |
25.81 |
| 2026-10-05 00:00 |
02:43:33.02 |
-10:02:35.2 |
HIP 12660 |
25.36 |
| 2026-10-05 12:00 |
02:43:31.21 |
-10:02:50.9 |
HIP 12660 |
24.91 |
| 2026-10-06 00:00 |
02:43:29.40 |
-10:03:06.5 |
HIP 12660 |
24.46 |
| 2026-10-06 12:00 |
02:43:27.57 |
-10:03:22.1 |
HIP 12660 |
24.02 |
| 2026-10-07 00:00 |
02:43:25.73 |
-10:03:37.6 |
HIP 12660 |
23.58 |
| 2026-10-07 12:00 |
02:43:23.88 |
-10:03:53.0 |
HIP 12660 |
23.14 |
| 2026-10-08 00:00 |
02:43:22.02 |
-10:04:08.4 |
HIP 12660 |
22.70 |
| 2026-10-08 12:00 |
02:43:20.16 |
-10:04:23.6 |
HIP 12660 |
22.27 |
| 2026-10-09 00:00 |
02:43:18.28 |
-10:04:38.9 |
HIP 12660 |
21.85 |
| 2026-10-09 12:00 |
02:43:16.40 |
-10:04:54.0 |
HIP 12660 |
21.42 |
| 2026-10-10 00:00 |
02:43:14.51 |
-10:05:09.0 |
HIP 12660 |
21.01 |
| 2026-10-10 12:00 |
02:43:12.60 |
-10:05:24.0 |
HIP 12660 |
20.60 |
| 2026-10-11 00:00 |
02:43:10.69 |
-10:05:38.9 |
HIP 12660 |
20.19 |