| Parameter |
Value |
| Designation |
C/2017 E4 (Lovejoy) |
| Type |
C |
| Perihelion (tp_cal, UTC) |
2017-04-23T07:32:57.215040Z |
| Orbit solution date (soln_date, UTC) |
2021-04-15T23:33:31Z |
| Obs used |
642 |
| NEO |
- |
| M1 |
15.600 |
| K1 |
29.750 |
| PC |
- |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
2017-03-31.0000000 |
| e |
0.99896241 |
| q (au) |
0.493573 |
| a (au) |
475.690786 |
| i (deg) |
88.186837 |
| Ω (om, deg) |
223.171811 |
| ω (w, deg) |
87.244054 |
| M (ma, deg) |
359.997785 |
Magnitude
Scatter + Global Linear
$$
M_a = (15.265 + 6.000\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
15.265 |
| n |
6.000 |
| gf |
1.000 |
| gb |
-0.500 |
| k |
1.000 |
| δ90 |
10.000 |
| 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 |
| 2017-03-09 |
2017-03-27 |
+15.0652 |
-0.620 |
| 2017-03-27 |
2017-04-23 |
-14.4941 |
-4.028 |
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 |
04:26:56.54 |
-49:18:47.2 |
HIP 20792 |
3.98 |
| 2026-03-26 12:00 |
04:27:00.07 |
-49:17:44.9 |
HIP 20792 |
3.22 |
| 2026-03-27 00:00 |
04:27:03.66 |
-49:16:42.8 |
HIP 20792 |
2.77 |
| 2026-03-27 12:00 |
04:27:07.30 |
-49:15:41.0 |
HIP 20792 |
2.79 |
| 2026-03-28 00:00 |
04:27:10.99 |
-49:14:39.5 |
HIP 20792 |
3.26 |
| 2026-03-28 12:00 |
04:27:14.74 |
-49:13:38.3 |
HIP 20792 |
4.03 |
| 2026-03-29 00:00 |
04:27:18.54 |
-49:12:37.3 |
HIP 20792 |
4.97 |
| 2026-03-29 12:00 |
04:27:22.39 |
-49:11:36.7 |
HIP 20792 |
5.99 |
| 2026-03-30 00:00 |
04:27:26.29 |
-49:10:36.3 |
HIP 20792 |
7.06 |
| 2026-03-30 12:00 |
04:27:30.24 |
-49:09:36.2 |
HIP 20792 |
8.16 |
| 2026-03-31 00:00 |
04:27:34.25 |
-49:08:36.5 |
HIP 20792 |
9.28 |
| 2026-03-31 12:00 |
04:27:38.31 |
-49:07:37.0 |
HIP 20792 |
10.42 |
| 2026-04-01 00:00 |
04:27:42.41 |
-49:06:37.8 |
HIP 20792 |
11.56 |
| 2026-04-01 12:00 |
04:27:46.57 |
-49:05:38.9 |
HIP 20792 |
12.71 |
| 2026-04-02 00:00 |
04:27:50.78 |
-49:04:40.4 |
HIP 20792 |
13.87 |
| 2026-04-02 12:00 |
04:27:55.03 |
-49:03:42.1 |
HIP 20792 |
15.03 |
| 2026-04-03 00:00 |
04:27:59.34 |
-49:02:44.2 |
HIP 20792 |
16.20 |
| 2026-04-03 12:00 |
04:28:03.69 |
-49:01:46.6 |
HIP 20792 |
17.36 |
| 2026-04-04 00:00 |
04:28:08.10 |
-49:00:49.3 |
HIP 20792 |
18.53 |
| 2026-04-04 12:00 |
04:28:12.55 |
-48:59:52.4 |
HIP 20792 |
19.70 |
| 2026-04-05 00:00 |
04:28:17.05 |
-48:58:55.7 |
HIP 20792 |
20.88 |
| 2026-04-05 12:00 |
04:28:21.59 |
-48:57:59.4 |
HIP 20792 |
22.05 |
| 2026-04-06 00:00 |
04:28:26.19 |
-48:57:03.5 |
HIP 20792 |
23.22 |
| 2026-04-06 12:00 |
04:28:30.83 |
-48:56:07.9 |
HIP 20792 |
24.40 |
| 2026-04-07 00:00 |
04:28:35.52 |
-48:55:12.6 |
HIP 20967 |
25.54 |
| 2026-04-07 12:00 |
04:28:40.25 |
-48:54:17.7 |
HIP 20967 |
24.37 |
| 2026-04-08 00:00 |
04:28:45.03 |
-48:53:23.1 |
HIP 20967 |
23.22 |
| 2026-04-08 12:00 |
04:28:49.85 |
-48:52:28.9 |
HIP 20967 |
22.07 |
| 2026-04-09 00:00 |
04:28:54.72 |
-48:51:35.1 |
HIP 20967 |
20.92 |
| 2026-04-09 12:00 |
04:28:59.64 |
-48:50:41.6 |
HIP 20967 |
19.79 |
| 2026-04-10 00:00 |
04:29:04.59 |
-48:49:48.5 |
HIP 20967 |
18.67 |
| 2026-04-10 12:00 |
04:29:09.60 |
-48:48:55.7 |
HIP 20967 |
17.57 |
| 2026-04-11 00:00 |
04:29:14.64 |
-48:48:03.3 |
HIP 20967 |
16.48 |
| 2026-04-11 12:00 |
04:29:19.73 |
-48:47:11.3 |
HIP 20967 |
15.42 |
| 2026-04-12 00:00 |
04:29:24.87 |
-48:46:19.7 |
HIP 20967 |
14.38 |
| 2026-04-12 12:00 |
04:29:30.04 |
-48:45:28.5 |
HIP 20967 |
13.37 |
| 2026-04-13 00:00 |
04:29:35.26 |
-48:44:37.6 |
HIP 20967 |
12.41 |
| 2026-04-13 12:00 |
04:29:40.52 |
-48:43:47.2 |
HIP 20967 |
11.50 |
| 2026-04-14 00:00 |
04:29:45.82 |
-48:42:57.1 |
HIP 20967 |
10.66 |
| 2026-04-14 12:00 |
04:29:51.16 |
-48:42:07.4 |
HIP 20967 |
9.90 |
| 2026-04-15 00:00 |
04:29:56.54 |
-48:41:18.2 |
HIP 20967 |
9.24 |
| 2026-04-15 12:00 |
04:30:01.96 |
-48:40:29.3 |
HIP 20967 |
8.71 |
| 2026-04-16 00:00 |
04:30:07.43 |
-48:39:40.8 |
HIP 20967 |
8.34 |