C/2017 Y2 (PANSTARRS)
| Parameter |
Value |
| Designation |
C/2017 Y2 (PANSTARRS) |
| Type |
C |
| Perihelion (tp_cal, UTC) |
2020-11-04T13:33:04.429440Z |
| Orbit solution date (soln_date, UTC) |
2024-02-25T22:12:25Z |
| Obs used |
961 |
| NEO |
- |
| M1 |
8.600 |
| K1 |
8.000 |
| PC |
0.030 |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
2020-09-02.0000000 |
| e |
1.00096403 |
| q (au) |
4.632068 |
| a (au) |
-4804.896119 |
| i (deg) |
128.421418 |
| Ω (om, deg) |
65.986420 |
| ω (w, deg) |
147.860404 |
| M (ma, deg) |
-0.000188 |
Magnitude
Scatter + Global Linear
$$
M_a = (8.195 + 3.722\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
8.195 |
| n |
3.722 |
| gf |
0.963 |
| gb |
-0.841 |
| k |
0.994 |
| 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 |
| 2017-12-24 |
2020-10-30 |
+1.7402 |
-1.104 |
| 2020-11-05 |
2022-02-23 |
-10.1087 |
+6.757 |
| 2022-02-23 |
2022-07-31 |
+14.3389 |
-12.242 |
log10 r = log10(heliocentric distance / AU), Δ = geocentric distance (AU)
Ephemeris
| Date/Time (UTC) |
RA (J2000) |
Dec (J2000) |
Nearest HIP |
Dist from HIP (arcmin) |
| 2026-02-03 00:00 |
10:14:23.38 |
-46:39:27.9 |
HIP 50128 |
5.97 |
| 2026-02-03 12:00 |
10:14:08.98 |
-46:39:27.9 |
HIP 50128 |
4.70 |
| 2026-02-04 00:00 |
10:13:54.54 |
-46:39:26.9 |
HIP 50098 |
4.44 |
| 2026-02-04 12:00 |
10:13:40.07 |
-46:39:24.7 |
HIP 50098 |
4.16 |
| 2026-02-05 00:00 |
10:13:25.56 |
-46:39:21.4 |
HIP 50098 |
5.23 |
| 2026-02-05 12:00 |
10:13:11.03 |
-46:39:16.9 |
HIP 50098 |
7.07 |
| 2026-02-06 00:00 |
10:12:56.46 |
-46:39:11.3 |
HIP 50098 |
9.24 |
| 2026-02-06 12:00 |
10:12:41.87 |
-46:39:04.6 |
HIP 50098 |
11.56 |
| 2026-02-07 00:00 |
10:12:27.25 |
-46:38:56.8 |
HIP 50098 |
13.95 |
| 2026-02-07 12:00 |
10:12:12.61 |
-46:38:47.9 |
HIP 49872 |
12.69 |
| 2026-02-08 00:00 |
10:11:57.94 |
-46:38:37.8 |
HIP 49872 |
10.24 |
| 2026-02-08 12:00 |
10:11:43.24 |
-46:38:26.5 |
HIP 49872 |
7.82 |
| 2026-02-09 00:00 |
10:11:28.53 |
-46:38:14.2 |
HIP 49872 |
5.49 |
| 2026-02-09 12:00 |
10:11:13.79 |
-46:38:00.7 |
HIP 49872 |
3.44 |
| 2026-02-10 00:00 |
10:10:59.04 |
-46:37:46.0 |
HIP 49872 |
2.53 |
| 2026-02-10 12:00 |
10:10:44.26 |
-46:37:30.3 |
HIP 49872 |
3.72 |
| 2026-02-11 00:00 |
10:10:29.47 |
-46:37:13.4 |
HIP 49872 |
5.85 |
| 2026-02-11 12:00 |
10:10:14.67 |
-46:36:55.3 |
HIP 49872 |
8.22 |
| 2026-02-12 00:00 |
10:09:59.85 |
-46:36:36.1 |
HIP 49808 |
8.42 |
| 2026-02-12 12:00 |
10:09:45.02 |
-46:36:15.8 |
HIP 49808 |
8.66 |
| 2026-02-13 00:00 |
10:09:30.17 |
-46:35:54.3 |
HIP 49808 |
9.59 |
| 2026-02-13 12:00 |
10:09:15.32 |
-46:35:31.7 |
HIP 49808 |
11.04 |
| 2026-02-14 00:00 |
10:09:00.45 |
-46:35:08.0 |
HIP 49808 |
12.85 |
| 2026-02-14 12:00 |
10:08:45.58 |
-46:34:43.2 |
HIP 49808 |
14.88 |
| 2026-02-15 00:00 |
10:08:30.71 |
-46:34:17.2 |
HIP 49808 |
17.06 |
| 2026-02-15 12:00 |
10:08:15.83 |
-46:33:50.0 |
HIP 49808 |
19.34 |
| 2026-02-16 00:00 |
10:08:00.94 |
-46:33:21.8 |
HIP 49808 |
21.68 |
| 2026-02-16 12:00 |
10:07:46.06 |
-46:32:52.4 |
HIP 49584 |
21.81 |
| 2026-02-17 00:00 |
10:07:31.17 |
-46:32:21.8 |
HIP 49584 |
20.92 |
| 2026-02-17 12:00 |
10:07:16.29 |
-46:31:50.2 |
HIP 49584 |
20.31 |
| 2026-02-18 00:00 |
10:07:01.40 |
-46:31:17.4 |
HIP 49584 |
20.01 |
| 2026-02-18 12:00 |
10:06:46.53 |
-46:30:43.5 |
HIP 49584 |
20.04 |
| 2026-02-19 00:00 |
10:06:31.65 |
-46:30:08.5 |
HIP 49584 |
20.39 |
| 2026-02-19 12:00 |
10:06:16.78 |
-46:29:32.4 |
HIP 49584 |
21.05 |
| 2026-02-20 00:00 |
10:06:01.92 |
-46:28:55.2 |
HIP 49584 |
22.00 |
| 2026-02-20 12:00 |
10:05:47.07 |
-46:28:16.8 |
HIP 49584 |
23.19 |
| 2026-02-21 00:00 |
10:05:32.23 |
-46:27:37.3 |
HIP 49584 |
24.60 |
| 2026-02-21 12:00 |
10:05:17.41 |
-46:26:56.8 |
HIP 49259 |
23.01 |
| 2026-02-22 00:00 |
10:05:02.59 |
-46:26:15.1 |
HIP 49259 |
21.20 |
| 2026-02-22 12:00 |
10:04:47.79 |
-46:25:32.4 |
HIP 49259 |
19.61 |
| 2026-02-23 00:00 |
10:04:33.01 |
-46:24:48.6 |
HIP 49259 |
18.27 |
| 2026-02-23 12:00 |
10:04:18.24 |
-46:24:03.6 |
HIP 49259 |
17.25 |
| 2026-02-24 00:00 |
10:04:03.50 |
-46:23:17.6 |
HIP 49259 |
16.61 |