| 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 |
0.807 |
| 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) |
| 2026-07-29 00:00 |
14:37:59.30 |
-33:10:50.1 |
HIP 71477 |
11.68 |
| 2026-07-29 12:00 |
14:37:59.59 |
-33:10:19.5 |
HIP 71477 |
11.75 |
| 2026-07-30 00:00 |
14:37:59.93 |
-33:09:49.1 |
HIP 71477 |
11.85 |
| 2026-07-30 12:00 |
14:38:00.33 |
-33:09:18.9 |
HIP 71477 |
11.99 |
| 2026-07-31 00:00 |
14:38:00.78 |
-33:08:48.9 |
HIP 71477 |
12.15 |
| 2026-07-31 12:00 |
14:38:01.29 |
-33:08:19.1 |
HIP 71477 |
12.35 |
| 2026-08-01 00:00 |
14:38:01.86 |
-33:07:49.6 |
HIP 71477 |
12.57 |
| 2026-08-01 12:00 |
14:38:02.48 |
-33:07:20.4 |
HIP 71477 |
12.82 |
| 2026-08-02 00:00 |
14:38:03.16 |
-33:06:51.3 |
HIP 71477 |
13.09 |
| 2026-08-02 12:00 |
14:38:03.90 |
-33:06:22.5 |
HIP 71477 |
13.39 |
| 2026-08-03 00:00 |
14:38:04.69 |
-33:05:53.9 |
HIP 71477 |
13.71 |
| 2026-08-03 12:00 |
14:38:05.54 |
-33:05:25.6 |
HIP 71477 |
14.05 |
| 2026-08-04 00:00 |
14:38:06.44 |
-33:04:57.5 |
HIP 71477 |
14.41 |
| 2026-08-04 12:00 |
14:38:07.40 |
-33:04:29.7 |
HIP 71477 |
14.78 |
| 2026-08-05 00:00 |
14:38:08.42 |
-33:04:02.1 |
HIP 71477 |
15.17 |
| 2026-08-05 12:00 |
14:38:09.49 |
-33:03:34.8 |
HIP 71477 |
15.58 |
| 2026-08-06 00:00 |
14:38:10.62 |
-33:03:07.7 |
HIP 71477 |
16.00 |
| 2026-08-06 12:00 |
14:38:11.80 |
-33:02:40.8 |
HIP 71477 |
16.44 |
| 2026-08-07 00:00 |
14:38:13.04 |
-33:02:14.2 |
HIP 71477 |
16.88 |
| 2026-08-07 12:00 |
14:38:14.33 |
-33:01:47.9 |
HIP 71477 |
17.34 |
| 2026-08-08 00:00 |
14:38:15.68 |
-33:01:21.8 |
HIP 71477 |
17.81 |
| 2026-08-08 12:00 |
14:38:17.09 |
-33:00:55.9 |
HIP 71477 |
18.29 |
| 2026-08-09 00:00 |
14:38:18.55 |
-33:00:30.4 |
HIP 71477 |
18.78 |
| 2026-08-09 12:00 |
14:38:20.07 |
-33:00:05.0 |
HIP 71477 |
19.28 |
| 2026-08-10 00:00 |
14:38:21.64 |
-32:59:40.0 |
HIP 71477 |
19.78 |
| 2026-08-10 12:00 |
14:38:23.27 |
-32:59:15.2 |
HIP 71477 |
20.30 |
| 2026-08-11 00:00 |
14:38:24.95 |
-32:58:50.7 |
HIP 71477 |
20.82 |
| 2026-08-11 12:00 |
14:38:26.69 |
-32:58:26.4 |
HIP 71477 |
21.35 |
| 2026-08-12 00:00 |
14:38:28.48 |
-32:58:02.4 |
HIP 71477 |
21.89 |
| 2026-08-12 12:00 |
14:38:30.33 |
-32:57:38.7 |
HIP 71477 |
22.44 |
| 2026-08-13 00:00 |
14:38:32.23 |
-32:57:15.2 |
HIP 71477 |
22.99 |
| 2026-08-13 12:00 |
14:38:34.19 |
-32:56:52.0 |
HIP 71477 |
23.55 |
| 2026-08-14 00:00 |
14:38:36.20 |
-32:56:29.1 |
HIP 71477 |
24.12 |
| 2026-08-14 12:00 |
14:38:38.26 |
-32:56:06.5 |
HIP 71477 |
24.69 |
| 2026-08-15 00:00 |
14:38:40.38 |
-32:55:44.1 |
HIP 71477 |
25.27 |
| 2026-08-15 12:00 |
14:38:42.56 |
-32:55:22.0 |
HIP 71477 |
25.85 |
| 2026-08-16 00:00 |
14:38:44.78 |
-32:55:00.2 |
HIP 71477 |
26.45 |
| 2026-08-16 12:00 |
14:38:47.06 |
-32:54:38.6 |
HIP 71477 |
27.04 |
| 2026-08-17 00:00 |
14:38:49.40 |
-32:54:17.4 |
HIP 71477 |
27.65 |
| 2026-08-17 12:00 |
14:38:51.78 |
-32:53:56.4 |
HIP 71477 |
28.26 |
| 2026-08-18 00:00 |
14:38:54.22 |
-32:53:35.7 |
HIP 71477 |
28.88 |
| 2026-08-18 12:00 |
14:38:56.71 |
-32:53:15.3 |
HIP 71477 |
29.50 |
| 2026-08-19 00:00 |
14:38:59.26 |
-32:52:55.1 |
HIP 71445 |
30.00 |