| Parameter |
Value |
| Designation |
C/2017 O1 (ASASSN) |
| Type |
C |
| Perihelion (tp_cal, UTC) |
2017-10-14T18:50:39.171840Z |
| Orbit solution date (soln_date, UTC) |
2022-07-31T01:42:28Z |
| Obs used |
2877 |
| NEO |
- |
| M1 |
12.400 |
| K1 |
8.750 |
| PC |
- |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
2017-10-13.0000000 |
| e |
0.99642549 |
| q (au) |
1.498687 |
| a (au) |
419.270415 |
| i (deg) |
39.848413 |
| Ω (om, deg) |
25.809488 |
| ω (w, deg) |
20.907853 |
| M (ma, deg) |
359.999795 |
Magnitude
Scatter + Global Linear
$$
M_a = (12.630 + 2.000\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
12.630 |
| n |
2.000 |
| 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 |
| 2017-07-20 |
2017-10-14 |
-12.1999 |
+1.263 |
| 2017-10-14 |
2019-03-12 |
+7.6667 |
-2.172 |
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 |
13:13:16.93 |
-01:20:36.8 |
HIP 64460 |
26.07 |
| 2026-05-12 12:00 |
13:13:12.76 |
-01:20:20.8 |
HIP 64460 |
26.04 |
| 2026-05-13 00:00 |
13:13:08.62 |
-01:20:05.1 |
HIP 64460 |
26.05 |
| 2026-05-13 12:00 |
13:13:04.50 |
-01:19:49.5 |
HIP 64460 |
26.10 |
| 2026-05-14 00:00 |
13:13:00.41 |
-01:19:34.2 |
HIP 64460 |
26.19 |
| 2026-05-14 12:00 |
13:12:56.34 |
-01:19:19.1 |
HIP 64351 |
26.12 |
| 2026-05-15 00:00 |
13:12:52.31 |
-01:19:04.2 |
HIP 64351 |
25.39 |
| 2026-05-15 12:00 |
13:12:48.30 |
-01:18:49.6 |
HIP 64351 |
24.69 |
| 2026-05-16 00:00 |
13:12:44.31 |
-01:18:35.1 |
HIP 64351 |
24.01 |
| 2026-05-16 12:00 |
13:12:40.36 |
-01:18:20.9 |
HIP 64351 |
23.35 |
| 2026-05-17 00:00 |
13:12:36.43 |
-01:18:07.0 |
HIP 64351 |
22.73 |
| 2026-05-17 12:00 |
13:12:32.54 |
-01:17:53.2 |
HIP 64351 |
22.14 |
| 2026-05-18 00:00 |
13:12:28.67 |
-01:17:39.7 |
HIP 64351 |
21.59 |
| 2026-05-18 12:00 |
13:12:24.83 |
-01:17:26.4 |
HIP 64351 |
21.06 |
| 2026-05-19 00:00 |
13:12:21.02 |
-01:17:13.4 |
HIP 64351 |
20.57 |
| 2026-05-19 12:00 |
13:12:17.24 |
-01:17:00.6 |
HIP 64351 |
20.12 |
| 2026-05-20 00:00 |
13:12:13.49 |
-01:16:48.0 |
HIP 64351 |
19.71 |
| 2026-05-20 12:00 |
13:12:09.77 |
-01:16:35.7 |
HIP 64351 |
19.34 |
| 2026-05-21 00:00 |
13:12:06.08 |
-01:16:23.6 |
HIP 64351 |
19.01 |
| 2026-05-21 12:00 |
13:12:02.42 |
-01:16:11.7 |
HIP 64351 |
18.72 |
| 2026-05-22 00:00 |
13:11:58.79 |
-01:16:00.1 |
HIP 64351 |
18.48 |
| 2026-05-22 12:00 |
13:11:55.20 |
-01:15:48.7 |
HIP 64351 |
18.28 |
| 2026-05-23 00:00 |
13:11:51.63 |
-01:15:37.6 |
HIP 64351 |
18.12 |
| 2026-05-23 12:00 |
13:11:48.10 |
-01:15:26.7 |
HIP 64351 |
18.00 |
| 2026-05-24 00:00 |
13:11:44.60 |
-01:15:16.0 |
HIP 64351 |
17.93 |
| 2026-05-24 12:00 |
13:11:41.13 |
-01:15:05.6 |
HIP 64351 |
17.90 |
| 2026-05-25 00:00 |
13:11:37.69 |
-01:14:55.5 |
HIP 64351 |
17.91 |
| 2026-05-25 12:00 |
13:11:34.29 |
-01:14:45.5 |
HIP 64351 |
17.96 |
| 2026-05-26 00:00 |
13:11:30.92 |
-01:14:35.9 |
HIP 64351 |
18.04 |
| 2026-05-26 12:00 |
13:11:27.58 |
-01:14:26.5 |
HIP 64351 |
18.17 |
| 2026-05-27 00:00 |
13:11:24.28 |
-01:14:17.3 |
HIP 64351 |
18.32 |
| 2026-05-27 12:00 |
13:11:21.01 |
-01:14:08.4 |
HIP 64351 |
18.51 |
| 2026-05-28 00:00 |
13:11:17.77 |
-01:13:59.7 |
HIP 64351 |
18.73 |
| 2026-05-28 12:00 |
13:11:14.57 |
-01:13:51.2 |
HIP 64351 |
18.98 |
| 2026-05-29 00:00 |
13:11:11.40 |
-01:13:43.1 |
HIP 64351 |
19.25 |
| 2026-05-29 12:00 |
13:11:08.27 |
-01:13:35.1 |
HIP 64351 |
19.55 |
| 2026-05-30 00:00 |
13:11:05.17 |
-01:13:27.4 |
HIP 64351 |
19.86 |
| 2026-05-30 12:00 |
13:11:02.11 |
-01:13:20.0 |
HIP 64351 |
20.20 |
| 2026-05-31 00:00 |
13:10:59.08 |
-01:13:12.8 |
HIP 64351 |
20.55 |
| 2026-05-31 12:00 |
13:10:56.08 |
-01:13:05.9 |
HIP 64351 |
20.92 |
| 2026-06-01 00:00 |
13:10:53.12 |
-01:12:59.2 |
HIP 64351 |
21.30 |
| 2026-06-01 12:00 |
13:10:50.20 |
-01:12:52.8 |
HIP 64351 |
21.69 |
| 2026-06-02 00:00 |
13:10:47.31 |
-01:12:46.7 |
HIP 64351 |
22.10 |