| Parameter |
Value |
| Designation |
C/2017 T2 (PANSTARRS) |
| Type |
C |
| Perihelion (tp_cal, UTC) |
2020-05-04T22:47:55.688640Z |
| Orbit solution date (soln_date, UTC) |
2024-07-30T14:57:25Z |
| Obs used |
6922 |
| NEO |
- |
| M1 |
10.200 |
| K1 |
4.500 |
| PC |
- |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
2019-12-13.0000000 |
| e |
0.99967750 |
| q (au) |
1.615095 |
| a (au) |
5008.050241 |
| i (deg) |
57.231440 |
| Ω (om, deg) |
64.378780 |
| ω (w, deg) |
92.993316 |
| M (ma, deg) |
359.999600 |
Magnitude
Scatter + Global Linear
$$
M_a = (10.827 + 2.000\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
10.827 |
| n |
2.000 |
| gf |
0.999 |
| gb |
-0.653 |
| k |
0.800 |
| 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 |
| 2017-09-15 |
2019-08-05 |
+4.1328 |
-3.262 |
| 2019-08-05 |
2020-01-09 |
-1.8797 |
+0.423 |
| 2020-01-09 |
2020-05-04 |
+5.4565 |
-2.847 |
| 2020-05-05 |
2020-08-08 |
+15.7863 |
-4.493 |
| 2020-08-08 |
2021-10-04 |
+3.9198 |
-1.129 |
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 |
20:20:04.83 |
-67:36:41.4 |
HIP 100078 |
16.31 |
| 2026-05-12 12:00 |
20:20:00.90 |
-67:38:04.0 |
HIP 100078 |
17.14 |
| 2026-05-13 00:00 |
20:19:56.83 |
-67:39:26.5 |
HIP 100078 |
18.04 |
| 2026-05-13 12:00 |
20:19:52.60 |
-67:40:49.0 |
HIP 100078 |
19.00 |
| 2026-05-14 00:00 |
20:19:48.22 |
-67:42:11.4 |
HIP 100078 |
20.00 |
| 2026-05-14 12:00 |
20:19:43.68 |
-67:43:33.7 |
HIP 100078 |
21.05 |
| 2026-05-15 00:00 |
20:19:38.99 |
-67:44:55.9 |
HIP 100078 |
22.14 |
| 2026-05-15 12:00 |
20:19:34.14 |
-67:46:18.0 |
HIP 100078 |
23.25 |
| 2026-05-16 00:00 |
20:19:29.14 |
-67:47:40.0 |
HIP 99994 |
24.31 |
| 2026-05-16 12:00 |
20:19:23.98 |
-67:49:01.9 |
HIP 99994 |
25.21 |
| 2026-05-17 00:00 |
20:19:18.68 |
-67:50:23.6 |
HIP 99994 |
26.15 |
| 2026-05-17 12:00 |
20:19:13.21 |
-67:51:45.2 |
HIP 99994 |
27.13 |
| 2026-05-18 00:00 |
20:19:07.60 |
-67:53:06.7 |
HIP 99994 |
28.14 |
| 2026-05-18 12:00 |
20:19:01.83 |
-67:54:28.1 |
HIP 99994 |
29.18 |
| 2026-05-19 00:00 |
20:18:55.90 |
-67:55:49.2 |
HIP 99994 |
30.25 |
| 2026-05-19 12:00 |
20:18:49.82 |
-67:57:10.2 |
HIP 99994 |
31.34 |
| 2026-05-20 00:00 |
20:18:43.59 |
-67:58:31.1 |
HIP 100063 |
31.08 |
| 2026-05-20 12:00 |
20:18:37.21 |
-67:59:51.8 |
HIP 100063 |
29.68 |
| 2026-05-21 00:00 |
20:18:30.68 |
-68:01:12.2 |
HIP 100063 |
28.28 |
| 2026-05-21 12:00 |
20:18:23.99 |
-68:02:32.5 |
HIP 100063 |
26.90 |
| 2026-05-22 00:00 |
20:18:17.15 |
-68:03:52.6 |
HIP 100063 |
25.53 |
| 2026-05-22 12:00 |
20:18:10.17 |
-68:05:12.5 |
HIP 100063 |
24.17 |
| 2026-05-23 00:00 |
20:18:03.03 |
-68:06:32.2 |
HIP 100063 |
22.83 |
| 2026-05-23 12:00 |
20:17:55.74 |
-68:07:51.6 |
HIP 100063 |
21.52 |
| 2026-05-24 00:00 |
20:17:48.30 |
-68:09:10.9 |
HIP 100063 |
20.24 |
| 2026-05-24 12:00 |
20:17:40.71 |
-68:10:29.8 |
HIP 100063 |
18.99 |
| 2026-05-25 00:00 |
20:17:32.97 |
-68:11:48.6 |
HIP 100063 |
17.78 |
| 2026-05-25 12:00 |
20:17:25.08 |
-68:13:07.1 |
HIP 100063 |
16.63 |
| 2026-05-26 00:00 |
20:17:17.04 |
-68:14:25.3 |
HIP 99850 |
15.23 |
| 2026-05-26 12:00 |
20:17:08.86 |
-68:15:43.3 |
HIP 99850 |
13.75 |
| 2026-05-27 00:00 |
20:17:00.53 |
-68:17:01.0 |
HIP 99850 |
12.28 |
| 2026-05-27 12:00 |
20:16:52.05 |
-68:18:18.5 |
HIP 99850 |
10.80 |
| 2026-05-28 00:00 |
20:16:43.42 |
-68:19:35.6 |
HIP 99850 |
9.33 |
| 2026-05-28 12:00 |
20:16:34.65 |
-68:20:52.5 |
HIP 99850 |
7.88 |
| 2026-05-29 00:00 |
20:16:25.74 |
-68:22:09.1 |
HIP 99850 |
6.44 |
| 2026-05-29 12:00 |
20:16:16.67 |
-68:23:25.3 |
HIP 99850 |
5.05 |
| 2026-05-30 00:00 |
20:16:07.47 |
-68:24:41.3 |
HIP 99850 |
3.74 |
| 2026-05-30 12:00 |
20:15:58.12 |
-68:25:56.9 |
HIP 99850 |
2.66 |
| 2026-05-31 00:00 |
20:15:48.62 |
-68:27:12.3 |
HIP 99850 |
2.18 |
| 2026-05-31 12:00 |
20:15:38.99 |
-68:28:27.2 |
HIP 99850 |
2.66 |
| 2026-06-01 00:00 |
20:15:29.21 |
-68:29:41.9 |
HIP 99850 |
3.75 |
| 2026-06-01 12:00 |
20:15:19.28 |
-68:30:56.2 |
HIP 99850 |
5.07 |
| 2026-06-02 00:00 |
20:15:09.22 |
-68:32:10.2 |
HIP 99850 |
6.48 |