| Parameter |
Value |
| Designation |
C/2019 A9 (PANSTARRS) |
| Type |
C |
| Perihelion (tp_cal, UTC) |
2019-07-26T12:36:17.003520Z |
| Orbit solution date (soln_date, UTC) |
2021-04-15T23:33:51Z |
| Obs used |
199 |
| NEO |
- |
| M1 |
10.300 |
| K1 |
17.500 |
| PC |
- |
| Discovery observation (MPC, UTC) |
2019-01-14T06:23:34.368000Z |
| Discovery magnitude (MPC) |
20.30 i |
| Discovery observatory (MPC) |
F51 · Pan-STARRS 1, Haleakala |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
2019-03-25.0000000 |
| e |
0.96326067 |
| q (au) |
1.426376 |
| a (au) |
38.824214 |
| i (deg) |
84.341078 |
| Ω (om, deg) |
278.368440 |
| ω (w, deg) |
237.802336 |
| M (ma, deg) |
359.496725 |
Magnitude
Scatter + Global Linear
$$
M_a = (10.529 + 6.000\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
10.529 |
| n |
6.000 |
| gf |
1.000 |
| gb |
-0.500 |
| 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 |
| 2018-12-18 |
2019-04-22 |
+6.0772 |
-2.366 |
| 2019-08-05 |
2020-06-16 |
+2.0655 |
-3.527 |
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 |
18:28:19.82 |
+06:25:32.4 |
HIP 90534 |
1.06 |
| 2026-09-20 12:00 |
18:28:18.96 |
+06:24:53.1 |
HIP 90534 |
1.00 |
| 2026-09-21 00:00 |
18:28:18.15 |
+06:24:13.7 |
HIP 90534 |
1.34 |
| 2026-09-21 12:00 |
18:28:17.40 |
+06:23:34.4 |
HIP 90534 |
1.87 |
| 2026-09-22 00:00 |
18:28:16.71 |
+06:22:55.1 |
HIP 90534 |
2.47 |
| 2026-09-22 12:00 |
18:28:16.07 |
+06:22:15.8 |
HIP 90534 |
3.09 |
| 2026-09-23 00:00 |
18:28:15.48 |
+06:21:36.5 |
HIP 90534 |
3.73 |
| 2026-09-23 12:00 |
18:28:14.95 |
+06:20:57.3 |
HIP 90534 |
4.36 |
| 2026-09-24 00:00 |
18:28:14.48 |
+06:20:18.1 |
HIP 90534 |
5.00 |
| 2026-09-24 12:00 |
18:28:14.06 |
+06:19:38.9 |
HIP 90534 |
5.64 |
| 2026-09-25 00:00 |
18:28:13.70 |
+06:18:59.8 |
HIP 90534 |
6.28 |
| 2026-09-25 12:00 |
18:28:13.39 |
+06:18:20.7 |
HIP 90534 |
6.91 |
| 2026-09-26 00:00 |
18:28:13.14 |
+06:17:41.6 |
HIP 90497 |
7.02 |
| 2026-09-26 12:00 |
18:28:12.94 |
+06:17:02.6 |
HIP 90497 |
6.44 |
| 2026-09-27 00:00 |
18:28:12.80 |
+06:16:23.7 |
HIP 90497 |
5.89 |
| 2026-09-27 12:00 |
18:28:12.72 |
+06:15:44.8 |
HIP 90497 |
5.37 |
| 2026-09-28 00:00 |
18:28:12.69 |
+06:15:06.0 |
HIP 90497 |
4.88 |
| 2026-09-28 12:00 |
18:28:12.71 |
+06:14:27.2 |
HIP 90497 |
4.46 |
| 2026-09-29 00:00 |
18:28:12.79 |
+06:13:48.5 |
HIP 90497 |
4.10 |
| 2026-09-29 12:00 |
18:28:12.93 |
+06:13:09.9 |
HIP 90497 |
3.83 |
| 2026-09-30 00:00 |
18:28:13.12 |
+06:12:31.3 |
HIP 90497 |
3.67 |
| 2026-09-30 12:00 |
18:28:13.36 |
+06:11:52.8 |
HIP 90497 |
3.63 |
| 2026-10-01 00:00 |
18:28:13.66 |
+06:11:14.4 |
HIP 90497 |
3.72 |
| 2026-10-01 12:00 |
18:28:14.02 |
+06:10:36.1 |
HIP 90497 |
3.93 |
| 2026-10-02 00:00 |
18:28:14.42 |
+06:09:57.8 |
HIP 90497 |
4.24 |
| 2026-10-02 12:00 |
18:28:14.89 |
+06:09:19.7 |
HIP 90497 |
4.63 |
| 2026-10-03 00:00 |
18:28:15.41 |
+06:08:41.6 |
HIP 90497 |
5.08 |
| 2026-10-03 12:00 |
18:28:15.98 |
+06:08:03.6 |
HIP 90497 |
5.58 |
| 2026-10-04 00:00 |
18:28:16.61 |
+06:07:25.8 |
HIP 90497 |
6.12 |
| 2026-10-04 12:00 |
18:28:17.29 |
+06:06:48.0 |
HIP 90497 |
6.69 |
| 2026-10-05 00:00 |
18:28:18.03 |
+06:06:10.3 |
HIP 90497 |
7.27 |
| 2026-10-05 12:00 |
18:28:18.82 |
+06:05:32.7 |
HIP 90497 |
7.88 |
| 2026-10-06 00:00 |
18:28:19.66 |
+06:04:55.3 |
HIP 90497 |
8.50 |
| 2026-10-06 12:00 |
18:28:20.56 |
+06:04:17.9 |
HIP 90497 |
9.13 |
| 2026-10-07 00:00 |
18:28:21.52 |
+06:03:40.7 |
HIP 90497 |
9.77 |
| 2026-10-07 12:00 |
18:28:22.52 |
+06:03:03.6 |
HIP 90497 |
10.42 |
| 2026-10-08 00:00 |
18:28:23.59 |
+06:02:26.6 |
HIP 90497 |
11.08 |
| 2026-10-08 12:00 |
18:28:24.70 |
+06:01:49.8 |
HIP 90497 |
11.75 |
| 2026-10-09 00:00 |
18:28:25.87 |
+06:01:13.1 |
HIP 90497 |
12.42 |
| 2026-10-09 12:00 |
18:28:27.09 |
+06:00:36.5 |
HIP 90497 |
13.09 |
| 2026-10-10 00:00 |
18:28:28.37 |
+06:00:00.0 |
HIP 90497 |
13.78 |
| 2026-10-10 12:00 |
18:28:29.70 |
+05:59:23.7 |
HIP 90497 |
14.47 |
| 2026-10-11 00:00 |
18:28:31.08 |
+05:58:47.6 |
HIP 90500 |
14.90 |