| Parameter |
Value |
| Designation |
C/2017 X1 (PANSTARRS) |
| Type |
C |
| Perihelion (tp_cal, UTC) |
2018-06-14T10:45:05.999040Z |
| Orbit solution date (soln_date, UTC) |
2021-09-04T23:42:57Z |
| Obs used |
127 |
| NEO |
- |
| M1 |
7.000 |
| K1 |
13.500 |
| PC |
0.030 |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
2018-02-14.0000000 |
| e |
0.85110910 |
| q (au) |
4.662645 |
| a (au) |
31.315852 |
| i (deg) |
31.310998 |
| Ω (om, deg) |
251.126772 |
| ω (w, deg) |
283.106326 |
| M (ma, deg) |
359.322581 |
Magnitude
Scatter + Global Linear
$$
M_a = (5.561 + 6.000\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
5.561 |
| n |
6.000 |
| gf |
1.000 |
| gb |
-1.000 |
| 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 |
| 2017-02-12 |
2018-06-07 |
+17.3813 |
-12.086 |
| 2018-07-17 |
2019-07-25 |
-2.0175 |
+1.329 |
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 |
19:23:41.78 |
+02:09:48.9 |
HIP 95443 |
26.65 |
| 2026-09-20 12:00 |
19:23:40.35 |
+02:09:13.5 |
HIP 95443 |
26.46 |
| 2026-09-21 00:00 |
19:23:38.98 |
+02:08:38.1 |
HIP 95443 |
26.28 |
| 2026-09-21 12:00 |
19:23:37.66 |
+02:08:02.7 |
HIP 95443 |
26.11 |
| 2026-09-22 00:00 |
19:23:36.40 |
+02:07:27.4 |
HIP 95443 |
25.94 |
| 2026-09-22 12:00 |
19:23:35.19 |
+02:06:52.1 |
HIP 95443 |
25.78 |
| 2026-09-23 00:00 |
19:23:34.05 |
+02:06:16.8 |
HIP 95443 |
25.62 |
| 2026-09-23 12:00 |
19:23:32.95 |
+02:05:41.5 |
HIP 95443 |
25.47 |
| 2026-09-24 00:00 |
19:23:31.92 |
+02:05:06.2 |
HIP 95443 |
25.32 |
| 2026-09-24 12:00 |
19:23:30.94 |
+02:04:31.0 |
HIP 95207 |
24.93 |
| 2026-09-25 00:00 |
19:23:30.01 |
+02:03:55.8 |
HIP 95207 |
24.43 |
| 2026-09-25 12:00 |
19:23:29.15 |
+02:03:20.7 |
HIP 95207 |
23.95 |
| 2026-09-26 00:00 |
19:23:28.34 |
+02:02:45.6 |
HIP 95207 |
23.48 |
| 2026-09-26 12:00 |
19:23:27.58 |
+02:02:10.5 |
HIP 95207 |
23.04 |
| 2026-09-27 00:00 |
19:23:26.88 |
+02:01:35.5 |
HIP 95207 |
22.62 |
| 2026-09-27 12:00 |
19:23:26.24 |
+02:01:00.5 |
HIP 95207 |
22.22 |
| 2026-09-28 00:00 |
19:23:25.66 |
+02:00:25.6 |
HIP 95207 |
21.84 |
| 2026-09-28 12:00 |
19:23:25.14 |
+01:59:50.8 |
HIP 95207 |
21.48 |
| 2026-09-29 00:00 |
19:23:24.67 |
+01:59:16.0 |
HIP 95207 |
21.15 |
| 2026-09-29 12:00 |
19:23:24.25 |
+01:58:41.2 |
HIP 95207 |
20.85 |
| 2026-09-30 00:00 |
19:23:23.90 |
+01:58:06.6 |
HIP 95207 |
20.57 |
| 2026-09-30 12:00 |
19:23:23.60 |
+01:57:32.0 |
HIP 95207 |
20.32 |
| 2026-10-01 00:00 |
19:23:23.36 |
+01:56:57.4 |
HIP 95207 |
20.09 |
| 2026-10-01 12:00 |
19:23:23.18 |
+01:56:23.0 |
HIP 95207 |
19.90 |
| 2026-10-02 00:00 |
19:23:23.05 |
+01:55:48.6 |
HIP 95207 |
19.73 |
| 2026-10-02 12:00 |
19:23:22.98 |
+01:55:14.3 |
HIP 95207 |
19.59 |
| 2026-10-03 00:00 |
19:23:22.97 |
+01:54:40.1 |
HIP 95207 |
19.49 |
| 2026-10-03 12:00 |
19:23:23.01 |
+01:54:06.0 |
HIP 95207 |
19.41 |
| 2026-10-04 00:00 |
19:23:23.12 |
+01:53:31.9 |
HIP 95207 |
19.36 |
| 2026-10-04 12:00 |
19:23:23.28 |
+01:52:58.0 |
HIP 95207 |
19.35 |
| 2026-10-05 00:00 |
19:23:23.49 |
+01:52:24.1 |
HIP 95207 |
19.37 |
| 2026-10-05 12:00 |
19:23:23.77 |
+01:51:50.4 |
HIP 95207 |
19.41 |
| 2026-10-06 00:00 |
19:23:24.10 |
+01:51:16.7 |
HIP 95207 |
19.49 |
| 2026-10-06 12:00 |
19:23:24.49 |
+01:50:43.2 |
HIP 95207 |
19.60 |
| 2026-10-07 00:00 |
19:23:24.94 |
+01:50:09.8 |
HIP 95207 |
19.74 |
| 2026-10-07 12:00 |
19:23:25.45 |
+01:49:36.5 |
HIP 95207 |
19.91 |
| 2026-10-08 00:00 |
19:23:26.01 |
+01:49:03.3 |
HIP 95207 |
20.11 |
| 2026-10-08 12:00 |
19:23:26.63 |
+01:48:30.2 |
HIP 95207 |
20.33 |
| 2026-10-09 00:00 |
19:23:27.31 |
+01:47:57.2 |
HIP 95207 |
20.58 |
| 2026-10-09 12:00 |
19:23:28.05 |
+01:47:24.4 |
HIP 95207 |
20.86 |
| 2026-10-10 00:00 |
19:23:28.84 |
+01:46:51.7 |
HIP 95207 |
21.17 |
| 2026-10-10 12:00 |
19:23:29.69 |
+01:46:19.1 |
HIP 95443 |
21.28 |
| 2026-10-11 00:00 |
19:23:30.60 |
+01:45:46.7 |
HIP 95443 |
21.16 |