C/2017 O1 (ASASSN)
| 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 |
-0.997 |
| 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 |
+7.6648 |
-2.171 |
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 |
13:26:47.66 |
-02:35:43.6 |
HIP 65714 |
27.29 |
| 2026-02-03 12:00 |
13:26:45.99 |
-02:35:29.4 |
HIP 65714 |
27.52 |
| 2026-02-04 00:00 |
13:26:44.28 |
-02:35:14.9 |
HIP 65714 |
27.77 |
| 2026-02-04 12:00 |
13:26:42.53 |
-02:35:00.2 |
HIP 65714 |
28.03 |
| 2026-02-05 00:00 |
13:26:40.73 |
-02:34:45.3 |
HIP 65714 |
28.31 |
| 2026-02-05 12:00 |
13:26:38.89 |
-02:34:30.2 |
HIP 65714 |
28.60 |
| 2026-02-06 00:00 |
13:26:37.00 |
-02:34:14.8 |
HIP 65714 |
28.91 |
| 2026-02-06 12:00 |
13:26:35.08 |
-02:33:59.2 |
HIP 65478 |
28.83 |
| 2026-02-07 00:00 |
13:26:33.11 |
-02:33:43.4 |
HIP 65478 |
28.30 |
| 2026-02-07 12:00 |
13:26:31.09 |
-02:33:27.4 |
HIP 65478 |
27.76 |
| 2026-02-08 00:00 |
13:26:29.04 |
-02:33:11.1 |
HIP 65478 |
27.21 |
| 2026-02-08 12:00 |
13:26:26.94 |
-02:32:54.7 |
HIP 65478 |
26.65 |
| 2026-02-09 00:00 |
13:26:24.79 |
-02:32:38.0 |
HIP 65478 |
26.08 |
| 2026-02-09 12:00 |
13:26:22.61 |
-02:32:21.1 |
HIP 65478 |
25.50 |
| 2026-02-10 00:00 |
13:26:20.38 |
-02:32:03.9 |
HIP 65478 |
24.92 |
| 2026-02-10 12:00 |
13:26:18.12 |
-02:31:46.6 |
HIP 65478 |
24.32 |
| 2026-02-11 00:00 |
13:26:15.81 |
-02:31:29.1 |
HIP 65478 |
23.72 |
| 2026-02-11 12:00 |
13:26:13.45 |
-02:31:11.3 |
HIP 65478 |
23.12 |
| 2026-02-12 00:00 |
13:26:11.06 |
-02:30:53.3 |
HIP 65478 |
22.50 |
| 2026-02-12 12:00 |
13:26:08.63 |
-02:30:35.2 |
HIP 65478 |
21.89 |
| 2026-02-13 00:00 |
13:26:06.15 |
-02:30:16.8 |
HIP 65478 |
21.26 |
| 2026-02-13 12:00 |
13:26:03.63 |
-02:29:58.2 |
HIP 65478 |
20.63 |
| 2026-02-14 00:00 |
13:26:01.07 |
-02:29:39.4 |
HIP 65478 |
20.00 |
| 2026-02-14 12:00 |
13:25:58.47 |
-02:29:20.4 |
HIP 65478 |
19.36 |
| 2026-02-15 00:00 |
13:25:55.84 |
-02:29:01.2 |
HIP 65478 |
18.73 |
| 2026-02-15 12:00 |
13:25:53.16 |
-02:28:41.9 |
HIP 65478 |
18.09 |
| 2026-02-16 00:00 |
13:25:50.44 |
-02:28:22.3 |
HIP 65478 |
17.45 |
| 2026-02-16 12:00 |
13:25:47.68 |
-02:28:02.6 |
HIP 65478 |
16.81 |
| 2026-02-17 00:00 |
13:25:44.88 |
-02:27:42.6 |
HIP 65478 |
16.18 |
| 2026-02-17 12:00 |
13:25:42.04 |
-02:27:22.5 |
HIP 65478 |
15.55 |
| 2026-02-18 00:00 |
13:25:39.16 |
-02:27:02.2 |
HIP 65478 |
14.93 |
| 2026-02-18 12:00 |
13:25:36.25 |
-02:26:41.7 |
HIP 65478 |
14.32 |
| 2026-02-19 00:00 |
13:25:33.29 |
-02:26:21.0 |
HIP 65478 |
13.73 |
| 2026-02-19 12:00 |
13:25:30.30 |
-02:26:00.1 |
HIP 65478 |
13.15 |
| 2026-02-20 00:00 |
13:25:27.27 |
-02:25:39.1 |
HIP 65478 |
12.59 |
| 2026-02-20 12:00 |
13:25:24.20 |
-02:25:17.9 |
HIP 65478 |
12.06 |
| 2026-02-21 00:00 |
13:25:21.10 |
-02:24:56.5 |
HIP 65478 |
11.57 |
| 2026-02-21 12:00 |
13:25:17.95 |
-02:24:35.0 |
HIP 65478 |
11.11 |
| 2026-02-22 00:00 |
13:25:14.77 |
-02:24:13.3 |
HIP 65478 |
10.71 |
| 2026-02-22 12:00 |
13:25:11.56 |
-02:23:51.4 |
HIP 65478 |
10.35 |
| 2026-02-23 00:00 |
13:25:08.30 |
-02:23:29.4 |
HIP 65478 |
10.07 |
| 2026-02-23 12:00 |
13:25:05.02 |
-02:23:07.2 |
HIP 65478 |
9.85 |
| 2026-02-24 00:00 |
13:25:01.69 |
-02:22:44.8 |
HIP 65478 |
9.71 |