| 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) |
| 2026-07-29 00:00 |
04:52:48.51 |
-48:53:49.5 |
HIP 22572 |
32.68 |
| 2026-07-29 12:00 |
04:52:53.13 |
-48:54:44.7 |
HIP 22572 |
32.16 |
| 2026-07-30 00:00 |
04:52:57.71 |
-48:55:40.3 |
HIP 22572 |
31.66 |
| 2026-07-30 12:00 |
04:53:02.24 |
-48:56:36.3 |
HIP 22572 |
31.20 |
| 2026-07-31 00:00 |
04:53:06.72 |
-48:57:32.6 |
HIP 22572 |
30.76 |
| 2026-07-31 12:00 |
04:53:11.16 |
-48:58:29.3 |
HIP 22572 |
30.36 |
| 2026-08-01 00:00 |
04:53:15.55 |
-48:59:26.3 |
HIP 22572 |
29.98 |
| 2026-08-01 12:00 |
04:53:19.90 |
-49:00:23.7 |
HIP 22572 |
29.65 |
| 2026-08-02 00:00 |
04:53:24.20 |
-49:01:21.4 |
HIP 22572 |
29.34 |
| 2026-08-02 12:00 |
04:53:28.45 |
-49:02:19.5 |
HIP 22572 |
29.07 |
| 2026-08-03 00:00 |
04:53:32.65 |
-49:03:17.9 |
HIP 22572 |
28.84 |
| 2026-08-03 12:00 |
04:53:36.80 |
-49:04:16.7 |
HIP 22572 |
28.65 |
| 2026-08-04 00:00 |
04:53:40.91 |
-49:05:15.8 |
HIP 22572 |
28.49 |
| 2026-08-04 12:00 |
04:53:44.97 |
-49:06:15.2 |
HIP 22572 |
28.38 |
| 2026-08-05 00:00 |
04:53:48.98 |
-49:07:15.0 |
HIP 22572 |
28.30 |
| 2026-08-05 12:00 |
04:53:52.94 |
-49:08:15.0 |
HIP 22572 |
28.26 |
| 2026-08-06 00:00 |
04:53:56.85 |
-49:09:15.5 |
HIP 22572 |
28.27 |
| 2026-08-06 12:00 |
04:54:00.71 |
-49:10:16.2 |
HIP 22572 |
28.31 |
| 2026-08-07 00:00 |
04:54:04.52 |
-49:11:17.2 |
HIP 22572 |
28.39 |
| 2026-08-07 12:00 |
04:54:08.28 |
-49:12:18.6 |
HIP 22572 |
28.52 |
| 2026-08-08 00:00 |
04:54:11.98 |
-49:13:20.3 |
HIP 22572 |
28.68 |
| 2026-08-08 12:00 |
04:54:15.64 |
-49:14:22.3 |
HIP 22572 |
28.88 |
| 2026-08-09 00:00 |
04:54:19.24 |
-49:15:24.5 |
HIP 22572 |
29.12 |
| 2026-08-09 12:00 |
04:54:22.80 |
-49:16:27.1 |
HIP 22572 |
29.39 |
| 2026-08-10 00:00 |
04:54:26.30 |
-49:17:30.0 |
HIP 22572 |
29.70 |
| 2026-08-10 12:00 |
04:54:29.74 |
-49:18:33.2 |
HIP 22572 |
30.05 |
| 2026-08-11 00:00 |
04:54:33.14 |
-49:19:36.6 |
HIP 22572 |
30.42 |
| 2026-08-11 12:00 |
04:54:36.48 |
-49:20:40.4 |
HIP 22572 |
30.83 |
| 2026-08-12 00:00 |
04:54:39.77 |
-49:21:44.4 |
HIP 22572 |
31.28 |
| 2026-08-12 12:00 |
04:54:43.00 |
-49:22:48.7 |
HIP 22572 |
31.75 |
| 2026-08-13 00:00 |
04:54:46.18 |
-49:23:53.2 |
HIP 22572 |
32.24 |
| 2026-08-13 12:00 |
04:54:49.30 |
-49:24:58.0 |
HIP 22976 |
31.36 |
| 2026-08-14 00:00 |
04:54:52.37 |
-49:26:03.1 |
HIP 22976 |
30.19 |
| 2026-08-14 12:00 |
04:54:55.38 |
-49:27:08.5 |
HIP 22976 |
29.02 |
| 2026-08-15 00:00 |
04:54:58.34 |
-49:28:14.1 |
HIP 22976 |
27.85 |
| 2026-08-15 12:00 |
04:55:01.24 |
-49:29:19.9 |
HIP 22976 |
26.68 |
| 2026-08-16 00:00 |
04:55:04.09 |
-49:30:26.0 |
HIP 22976 |
25.52 |
| 2026-08-16 12:00 |
04:55:06.88 |
-49:31:32.3 |
HIP 22976 |
24.37 |
| 2026-08-17 00:00 |
04:55:09.61 |
-49:32:38.9 |
HIP 22976 |
23.22 |
| 2026-08-17 12:00 |
04:55:12.28 |
-49:33:45.7 |
HIP 22976 |
22.08 |
| 2026-08-18 00:00 |
04:55:14.90 |
-49:34:52.7 |
HIP 22976 |
20.96 |
| 2026-08-18 12:00 |
04:55:17.47 |
-49:35:59.9 |
HIP 22976 |
19.84 |
| 2026-08-19 00:00 |
04:55:19.97 |
-49:37:07.3 |
HIP 22976 |
18.74 |