C/2018 X2 (Fitzsimmons)
| Parameter |
Value |
| Designation |
C/2018 X2 (Fitzsimmons) |
| Type |
C |
| Perihelion (tp_cal, UTC) |
2019-07-08T12:50:12.180480Z |
| Orbit solution date (soln_date, UTC) |
2021-04-15T23:33:48Z |
| Obs used |
390 |
| NEO |
- |
| M1 |
10.600 |
| K1 |
12.750 |
| PC |
0.030 |
| Discovery observation (MPC, UTC) |
2018-12-08T11:10:09.696000Z |
| Discovery magnitude (MPC) |
19.10 c |
| Discovery observatory (MPC) |
T05 · ATLAS-HKO, Haleakala |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
2019-02-10.0000000 |
| e |
0.98628022 |
| q (au) |
2.125879 |
| a (au) |
154.949983 |
| i (deg) |
23.068234 |
| Ω (om, deg) |
340.833210 |
| ω (w, deg) |
162.047045 |
| M (ma, deg) |
359.924099 |
Magnitude
Scatter + Global Linear
$$
M_a = (10.225 + 5.892\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
10.225 |
| n |
5.892 |
| gf |
0.999 |
| gb |
-0.500 |
| k |
0.800 |
| δ90 |
2.698 |
| 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
Ephemeris
| Date/Time (UTC) |
RA (J2000) |
Dec (J2000) |
Nearest HIP |
Dist from HIP (arcmin) |
| 2026-02-03 00:00 |
19:25:46.39 |
-40:34:49.1 |
HIP 95347 |
21.60 |
| 2026-02-03 12:00 |
19:25:55.02 |
-40:34:45.7 |
HIP 95667 |
22.30 |
| 2026-02-04 00:00 |
19:26:03.62 |
-40:34:42.4 |
HIP 95667 |
20.97 |
| 2026-02-04 12:00 |
19:26:12.19 |
-40:34:39.5 |
HIP 95667 |
19.69 |
| 2026-02-05 00:00 |
19:26:20.73 |
-40:34:36.8 |
HIP 95667 |
18.47 |
| 2026-02-05 12:00 |
19:26:29.24 |
-40:34:34.3 |
HIP 95667 |
17.31 |
| 2026-02-06 00:00 |
19:26:37.72 |
-40:34:32.1 |
HIP 95667 |
16.23 |
| 2026-02-06 12:00 |
19:26:46.17 |
-40:34:30.2 |
HIP 95667 |
15.24 |
| 2026-02-07 00:00 |
19:26:54.58 |
-40:34:28.5 |
HIP 95667 |
14.37 |
| 2026-02-07 12:00 |
19:27:02.97 |
-40:34:27.0 |
HIP 95667 |
13.63 |
| 2026-02-08 00:00 |
19:27:11.31 |
-40:34:25.9 |
HIP 95667 |
13.03 |
| 2026-02-08 12:00 |
19:27:19.63 |
-40:34:25.0 |
HIP 95667 |
12.61 |
| 2026-02-09 00:00 |
19:27:27.91 |
-40:34:24.3 |
HIP 95667 |
12.37 |
| 2026-02-09 12:00 |
19:27:36.15 |
-40:34:23.9 |
HIP 95667 |
12.32 |
| 2026-02-10 00:00 |
19:27:44.36 |
-40:34:23.8 |
HIP 95667 |
12.46 |
| 2026-02-10 12:00 |
19:27:52.54 |
-40:34:23.9 |
HIP 95667 |
12.79 |
| 2026-02-11 00:00 |
19:28:00.68 |
-40:34:24.3 |
HIP 95667 |
13.28 |
| 2026-02-11 12:00 |
19:28:08.78 |
-40:34:24.9 |
HIP 95667 |
13.93 |
| 2026-02-12 00:00 |
19:28:16.84 |
-40:34:25.9 |
HIP 95667 |
14.69 |
| 2026-02-12 12:00 |
19:28:24.87 |
-40:34:27.0 |
HIP 95667 |
15.56 |
| 2026-02-13 00:00 |
19:28:32.85 |
-40:34:28.5 |
HIP 95714 |
16.44 |
| 2026-02-13 12:00 |
19:28:40.80 |
-40:34:30.1 |
HIP 95789 |
16.44 |
| 2026-02-14 00:00 |
19:28:48.71 |
-40:34:32.1 |
HIP 95789 |
16.15 |
| 2026-02-14 12:00 |
19:28:56.58 |
-40:34:34.3 |
HIP 95789 |
15.99 |
| 2026-02-15 00:00 |
19:29:04.41 |
-40:34:36.8 |
HIP 95789 |
15.97 |
| 2026-02-15 12:00 |
19:29:12.20 |
-40:34:39.5 |
HIP 95789 |
16.08 |
| 2026-02-16 00:00 |
19:29:19.95 |
-40:34:42.5 |
HIP 95789 |
16.32 |
| 2026-02-16 12:00 |
19:29:27.66 |
-40:34:45.8 |
HIP 95789 |
16.68 |
| 2026-02-17 00:00 |
19:29:35.32 |
-40:34:49.3 |
HIP 95954 |
15.55 |
| 2026-02-17 12:00 |
19:29:42.95 |
-40:34:53.1 |
HIP 95954 |
14.34 |
| 2026-02-18 00:00 |
19:29:50.53 |
-40:34:57.2 |
HIP 95954 |
13.17 |
| 2026-02-18 12:00 |
19:29:58.06 |
-40:35:01.5 |
HIP 95954 |
12.08 |
| 2026-02-19 00:00 |
19:30:05.55 |
-40:35:06.1 |
HIP 95954 |
11.08 |
| 2026-02-19 12:00 |
19:30:13.00 |
-40:35:10.9 |
HIP 95954 |
10.18 |
| 2026-02-20 00:00 |
19:30:20.40 |
-40:35:16.0 |
HIP 95954 |
9.42 |
| 2026-02-20 12:00 |
19:30:27.76 |
-40:35:21.4 |
HIP 95954 |
8.83 |
| 2026-02-21 00:00 |
19:30:35.07 |
-40:35:27.0 |
HIP 95954 |
8.44 |
| 2026-02-21 12:00 |
19:30:42.34 |
-40:35:32.9 |
HIP 95954 |
8.28 |
| 2026-02-22 00:00 |
19:30:49.56 |
-40:35:39.1 |
HIP 95954 |
8.35 |
| 2026-02-22 12:00 |
19:30:56.73 |
-40:35:45.5 |
HIP 95954 |
8.64 |
| 2026-02-23 00:00 |
19:31:03.85 |
-40:35:52.2 |
HIP 95954 |
9.13 |
| 2026-02-23 12:00 |
19:31:10.93 |
-40:35:59.1 |
HIP 95954 |
9.79 |
| 2026-02-24 00:00 |
19:31:17.96 |
-40:36:06.3 |
HIP 95954 |
10.57 |