C/2015 X4 (Elenin)
| 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) |
| 2026-02-03 00:00 |
14:59:36.83 |
-34:48:16.8 |
HIP 73319 |
8.31 |
| 2026-02-03 12:00 |
14:59:38.20 |
-34:48:44.9 |
HIP 73319 |
8.54 |
| 2026-02-04 00:00 |
14:59:39.51 |
-34:49:12.9 |
HIP 73319 |
8.78 |
| 2026-02-04 12:00 |
14:59:40.75 |
-34:49:40.7 |
HIP 73319 |
9.04 |
| 2026-02-05 00:00 |
14:59:41.93 |
-34:50:08.3 |
HIP 73319 |
9.30 |
| 2026-02-05 12:00 |
14:59:43.06 |
-34:50:35.8 |
HIP 73319 |
9.57 |
| 2026-02-06 00:00 |
14:59:44.12 |
-34:51:03.0 |
HIP 73319 |
9.85 |
| 2026-02-06 12:00 |
14:59:45.11 |
-34:51:30.0 |
HIP 73319 |
10.13 |
| 2026-02-07 00:00 |
14:59:46.05 |
-34:51:56.8 |
HIP 73319 |
10.42 |
| 2026-02-07 12:00 |
14:59:46.92 |
-34:52:23.5 |
HIP 73319 |
10.70 |
| 2026-02-08 00:00 |
14:59:47.73 |
-34:52:49.9 |
HIP 73319 |
10.99 |
| 2026-02-08 12:00 |
14:59:48.47 |
-34:53:16.1 |
HIP 73319 |
11.27 |
| 2026-02-09 00:00 |
14:59:49.16 |
-34:53:42.1 |
HIP 73319 |
11.56 |
| 2026-02-09 12:00 |
14:59:49.78 |
-34:54:07.9 |
HIP 73319 |
11.84 |
| 2026-02-10 00:00 |
14:59:50.34 |
-34:54:33.5 |
HIP 73319 |
12.12 |
| 2026-02-10 12:00 |
14:59:50.83 |
-34:54:58.9 |
HIP 73319 |
12.39 |
| 2026-02-11 00:00 |
14:59:51.26 |
-34:55:24.0 |
HIP 73319 |
12.66 |
| 2026-02-11 12:00 |
14:59:51.63 |
-34:55:49.0 |
HIP 73319 |
12.93 |
| 2026-02-12 00:00 |
14:59:51.93 |
-34:56:13.7 |
HIP 73319 |
13.19 |
| 2026-02-12 12:00 |
14:59:52.17 |
-34:56:38.2 |
HIP 73319 |
13.44 |
| 2026-02-13 00:00 |
14:59:52.35 |
-34:57:02.5 |
HIP 73319 |
13.69 |
| 2026-02-13 12:00 |
14:59:52.47 |
-34:57:26.5 |
HIP 73319 |
13.94 |
| 2026-02-14 00:00 |
14:59:52.52 |
-34:57:50.3 |
HIP 73319 |
14.18 |
| 2026-02-14 12:00 |
14:59:52.51 |
-34:58:13.9 |
HIP 73319 |
14.41 |
| 2026-02-15 00:00 |
14:59:52.43 |
-34:58:37.2 |
HIP 73319 |
14.64 |
| 2026-02-15 12:00 |
14:59:52.29 |
-34:59:00.3 |
HIP 73319 |
14.86 |
| 2026-02-16 00:00 |
14:59:52.09 |
-34:59:23.2 |
HIP 73319 |
15.07 |
| 2026-02-16 12:00 |
14:59:51.82 |
-34:59:45.8 |
HIP 73319 |
15.28 |
| 2026-02-17 00:00 |
14:59:51.49 |
-35:00:08.2 |
HIP 73319 |
15.49 |
| 2026-02-17 12:00 |
14:59:51.10 |
-35:00:30.3 |
HIP 73319 |
15.69 |
| 2026-02-18 00:00 |
14:59:50.64 |
-35:00:52.2 |
HIP 73319 |
15.88 |
| 2026-02-18 12:00 |
14:59:50.13 |
-35:01:13.8 |
HIP 73319 |
16.07 |
| 2026-02-19 00:00 |
14:59:49.54 |
-35:01:35.1 |
HIP 73319 |
16.25 |
| 2026-02-19 12:00 |
14:59:48.90 |
-35:01:56.3 |
HIP 73319 |
16.43 |
| 2026-02-20 00:00 |
14:59:48.19 |
-35:02:17.1 |
HIP 73319 |
16.60 |
| 2026-02-20 12:00 |
14:59:47.42 |
-35:02:37.7 |
HIP 73319 |
16.77 |
| 2026-02-21 00:00 |
14:59:46.58 |
-35:02:58.0 |
HIP 73319 |
16.93 |
| 2026-02-21 12:00 |
14:59:45.68 |
-35:03:18.1 |
HIP 73319 |
17.09 |
| 2026-02-22 00:00 |
14:59:44.72 |
-35:03:37.9 |
HIP 73319 |
17.25 |
| 2026-02-22 12:00 |
14:59:43.70 |
-35:03:57.5 |
HIP 73319 |
17.40 |
| 2026-02-23 00:00 |
14:59:42.61 |
-35:04:16.7 |
HIP 73319 |
17.54 |
| 2026-02-23 12:00 |
14:59:41.47 |
-35:04:35.7 |
HIP 73319 |
17.69 |
| 2026-02-24 00:00 |
14:59:40.26 |
-35:04:54.4 |
HIP 73319 |
17.83 |