| Parameter |
Value |
| Designation |
C/2015 X4 (Elenin) |
| Type |
C |
| Perihelion (tp_cal, UTC) |
2015-11-03T11:14:21.828480Z |
| Orbit solution date (soln_date, UTC) |
2022-05-19T21:12:39Z |
| Obs used |
607 |
| NEO |
- |
| M1 |
13.000 |
| K1 |
4.500 |
| PC |
- |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
2016-02-01.0000000 |
| e |
0.81280434 |
| q (au) |
3.394686 |
| a (au) |
18.134427 |
| i (deg) |
29.504921 |
| Ω (om, deg) |
262.635812 |
| ω (w, deg) |
176.329174 |
| M (ma, deg) |
1.142681 |
Magnitude
Scatter + Global Linear
$$
M_a = (11.919 + 2.000\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
11.919 |
| n |
2.000 |
| gf |
0.806 |
| gb |
-0.500 |
| k |
0.997 |
| δ90 |
1.000 |
| 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 |
| 2014-12-22 |
2015-11-02 |
+10.5196 |
-3.568 |
| 2015-12-02 |
2017-03-24 |
-2.7904 |
+1.550 |
log10 r = log10(heliocentric distance / AU), Δ = geocentric distance (AU)
Ephemeris
| Date/Time (UTC) |
RA (J2000) |
Dec (J2000) |
Nearest HIP |
Dist from HIP (arcmin) |
| 2026-03-26 00:00 |
14:56:41.59 |
-35:14:17.9 |
HIP 73123 |
0.10 |
| 2026-03-26 12:00 |
14:56:37.02 |
-35:14:17.1 |
HIP 73123 |
0.98 |
| 2026-03-27 00:00 |
14:56:32.41 |
-35:14:15.9 |
HIP 73123 |
1.93 |
| 2026-03-27 12:00 |
14:56:27.75 |
-35:14:14.4 |
HIP 73123 |
2.88 |
| 2026-03-28 00:00 |
14:56:23.05 |
-35:14:12.5 |
HIP 73123 |
3.84 |
| 2026-03-28 12:00 |
14:56:18.31 |
-35:14:10.3 |
HIP 73123 |
4.81 |
| 2026-03-29 00:00 |
14:56:13.52 |
-35:14:07.8 |
HIP 73123 |
5.78 |
| 2026-03-29 12:00 |
14:56:08.70 |
-35:14:04.8 |
HIP 73123 |
6.77 |
| 2026-03-30 00:00 |
14:56:03.83 |
-35:14:01.6 |
HIP 73123 |
7.77 |
| 2026-03-30 12:00 |
14:55:58.92 |
-35:13:57.9 |
HIP 73123 |
8.77 |
| 2026-03-31 00:00 |
14:55:53.97 |
-35:13:53.9 |
HIP 73123 |
9.78 |
| 2026-03-31 12:00 |
14:55:48.98 |
-35:13:49.6 |
HIP 73082 |
10.53 |
| 2026-04-01 00:00 |
14:55:43.95 |
-35:13:44.9 |
HIP 73082 |
11.10 |
| 2026-04-01 12:00 |
14:55:38.88 |
-35:13:39.9 |
HIP 73082 |
11.73 |
| 2026-04-02 00:00 |
14:55:33.78 |
-35:13:34.5 |
HIP 73082 |
12.43 |
| 2026-04-02 12:00 |
14:55:28.63 |
-35:13:28.7 |
HIP 73082 |
13.19 |
| 2026-04-03 00:00 |
14:55:23.45 |
-35:13:22.6 |
HIP 73082 |
13.99 |
| 2026-04-03 12:00 |
14:55:18.23 |
-35:13:16.1 |
HIP 73082 |
14.83 |
| 2026-04-04 00:00 |
14:55:12.98 |
-35:13:09.3 |
HIP 73082 |
15.72 |
| 2026-04-04 12:00 |
14:55:07.68 |
-35:13:02.1 |
HIP 73082 |
16.63 |
| 2026-04-05 00:00 |
14:55:02.36 |
-35:12:54.6 |
HIP 73082 |
17.58 |
| 2026-04-05 12:00 |
14:54:57.00 |
-35:12:46.7 |
HIP 72948 |
18.42 |
| 2026-04-06 00:00 |
14:54:51.60 |
-35:12:38.4 |
HIP 72948 |
17.99 |
| 2026-04-06 12:00 |
14:54:46.17 |
-35:12:29.8 |
HIP 72948 |
17.61 |
| 2026-04-07 00:00 |
14:54:40.70 |
-35:12:20.9 |
HIP 72948 |
17.29 |
| 2026-04-07 12:00 |
14:54:35.21 |
-35:12:11.6 |
HIP 72948 |
17.04 |
| 2026-04-08 00:00 |
14:54:29.68 |
-35:12:01.9 |
HIP 72948 |
16.85 |
| 2026-04-08 12:00 |
14:54:24.12 |
-35:11:51.9 |
HIP 72948 |
16.73 |
| 2026-04-09 00:00 |
14:54:18.52 |
-35:11:41.5 |
HIP 72948 |
16.69 |
| 2026-04-09 12:00 |
14:54:12.90 |
-35:11:30.8 |
HIP 72948 |
16.72 |
| 2026-04-10 00:00 |
14:54:07.24 |
-35:11:19.7 |
HIP 72948 |
16.83 |
| 2026-04-10 12:00 |
14:54:01.56 |
-35:11:08.3 |
HIP 72948 |
17.01 |
| 2026-04-11 00:00 |
14:53:55.84 |
-35:10:56.5 |
HIP 72948 |
17.27 |
| 2026-04-11 12:00 |
14:53:50.10 |
-35:10:44.4 |
HIP 72806 |
16.77 |
| 2026-04-12 00:00 |
14:53:44.33 |
-35:10:31.9 |
HIP 72806 |
16.14 |
| 2026-04-12 12:00 |
14:53:38.53 |
-35:10:19.0 |
HIP 72806 |
15.57 |
| 2026-04-13 00:00 |
14:53:32.71 |
-35:10:05.8 |
HIP 72806 |
15.08 |
| 2026-04-13 12:00 |
14:53:26.85 |
-35:09:52.3 |
HIP 72806 |
14.68 |
| 2026-04-14 00:00 |
14:53:20.98 |
-35:09:38.4 |
HIP 72806 |
14.37 |
| 2026-04-14 12:00 |
14:53:15.07 |
-35:09:24.1 |
HIP 72806 |
14.17 |
| 2026-04-15 00:00 |
14:53:09.15 |
-35:09:09.5 |
HIP 72806 |
14.07 |
| 2026-04-15 12:00 |
14:53:03.19 |
-35:08:54.6 |
HIP 72806 |
14.09 |
| 2026-04-16 00:00 |
14:52:57.22 |
-35:08:39.3 |
HIP 72806 |
14.22 |