| 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) |
| 2026-03-26 00:00 |
19:36:38.03 |
-40:50:57.4 |
HIP 96361 |
20.54 |
| 2026-03-26 12:00 |
19:36:41.46 |
-40:51:19.5 |
HIP 96361 |
20.65 |
| 2026-03-27 00:00 |
19:36:44.82 |
-40:51:41.7 |
HIP 96361 |
20.78 |
| 2026-03-27 12:00 |
19:36:48.11 |
-40:52:04.2 |
HIP 96361 |
20.93 |
| 2026-03-28 00:00 |
19:36:51.34 |
-40:52:26.9 |
HIP 96361 |
21.08 |
| 2026-03-28 12:00 |
19:36:54.49 |
-40:52:49.8 |
HIP 96361 |
21.25 |
| 2026-03-29 00:00 |
19:36:57.58 |
-40:53:12.9 |
HIP 96361 |
21.42 |
| 2026-03-29 12:00 |
19:37:00.59 |
-40:53:36.2 |
HIP 96361 |
21.61 |
| 2026-03-30 00:00 |
19:37:03.54 |
-40:53:59.7 |
HIP 96361 |
21.80 |
| 2026-03-30 12:00 |
19:37:06.42 |
-40:54:23.4 |
HIP 96361 |
22.00 |
| 2026-03-31 00:00 |
19:37:09.23 |
-40:54:47.3 |
HIP 96361 |
22.20 |
| 2026-03-31 12:00 |
19:37:11.97 |
-40:55:11.4 |
HIP 96361 |
22.41 |
| 2026-04-01 00:00 |
19:37:14.64 |
-40:55:35.7 |
HIP 96361 |
22.62 |
| 2026-04-01 12:00 |
19:37:17.24 |
-40:56:00.2 |
HIP 96650 |
22.82 |
| 2026-04-02 00:00 |
19:37:19.77 |
-40:56:24.9 |
HIP 96650 |
22.20 |
| 2026-04-02 12:00 |
19:37:22.22 |
-40:56:49.8 |
HIP 96650 |
21.59 |
| 2026-04-03 00:00 |
19:37:24.61 |
-40:57:14.8 |
HIP 96650 |
20.99 |
| 2026-04-03 12:00 |
19:37:26.93 |
-40:57:40.1 |
HIP 96650 |
20.40 |
| 2026-04-04 00:00 |
19:37:29.18 |
-40:58:05.5 |
HIP 96650 |
19.82 |
| 2026-04-04 12:00 |
19:37:31.35 |
-40:58:31.2 |
HIP 96650 |
19.26 |
| 2026-04-05 00:00 |
19:37:33.46 |
-40:58:57.0 |
HIP 96650 |
18.70 |
| 2026-04-05 12:00 |
19:37:35.49 |
-40:59:23.0 |
HIP 96650 |
18.16 |
| 2026-04-06 00:00 |
19:37:37.45 |
-40:59:49.1 |
HIP 96650 |
17.63 |
| 2026-04-06 12:00 |
19:37:39.34 |
-41:00:15.5 |
HIP 96650 |
17.12 |
| 2026-04-07 00:00 |
19:37:41.16 |
-41:00:42.0 |
HIP 96650 |
16.62 |
| 2026-04-07 12:00 |
19:37:42.90 |
-41:01:08.7 |
HIP 96650 |
16.14 |
| 2026-04-08 00:00 |
19:37:44.58 |
-41:01:35.6 |
HIP 96650 |
15.67 |
| 2026-04-08 12:00 |
19:37:46.18 |
-41:02:02.6 |
HIP 96650 |
15.22 |
| 2026-04-09 00:00 |
19:37:47.71 |
-41:02:29.9 |
HIP 96650 |
14.78 |
| 2026-04-09 12:00 |
19:37:49.16 |
-41:02:57.2 |
HIP 96650 |
14.37 |
| 2026-04-10 00:00 |
19:37:50.55 |
-41:03:24.8 |
HIP 96650 |
13.98 |
| 2026-04-10 12:00 |
19:37:51.86 |
-41:03:52.5 |
HIP 96650 |
13.60 |
| 2026-04-11 00:00 |
19:37:53.09 |
-41:04:20.4 |
HIP 96650 |
13.26 |
| 2026-04-11 12:00 |
19:37:54.26 |
-41:04:48.4 |
HIP 96650 |
12.93 |
| 2026-04-12 00:00 |
19:37:55.35 |
-41:05:16.6 |
HIP 96650 |
12.63 |
| 2026-04-12 12:00 |
19:37:56.37 |
-41:05:44.9 |
HIP 96650 |
12.36 |
| 2026-04-13 00:00 |
19:37:57.31 |
-41:06:13.4 |
HIP 96650 |
12.12 |
| 2026-04-13 12:00 |
19:37:58.18 |
-41:06:42.1 |
HIP 96650 |
11.91 |
| 2026-04-14 00:00 |
19:37:58.98 |
-41:07:10.9 |
HIP 96650 |
11.72 |
| 2026-04-14 12:00 |
19:37:59.70 |
-41:07:39.8 |
HIP 96650 |
11.58 |
| 2026-04-15 00:00 |
19:38:00.35 |
-41:08:08.9 |
HIP 96650 |
11.46 |
| 2026-04-15 12:00 |
19:38:00.92 |
-41:08:38.1 |
HIP 96650 |
11.39 |
| 2026-04-16 00:00 |
19:38:01.42 |
-41:09:07.5 |
HIP 96650 |
11.34 |