C/2015 ER61 (PANSTARRS)
| Parameter |
Value |
| Designation |
C/2015 ER61 (PANSTARRS) |
| Type |
C |
| Perihelion (tp_cal, UTC) |
2017-05-09T22:39:09.815040Z |
| Orbit solution date (soln_date, UTC) |
2021-04-15T23:33:07Z |
| Obs used |
2826 |
| NEO |
- |
| M1 |
10.700 |
| K1 |
5.750 |
| PC |
- |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
2017-04-30.0000000 |
| e |
0.99727861 |
| q (au) |
1.042132 |
| a (au) |
382.940360 |
| i (deg) |
6.348649 |
| Ω (om, deg) |
235.221741 |
| ω (w, deg) |
68.192259 |
| M (ma, deg) |
359.998692 |
Magnitude
Scatter + Global Linear
$$
M_a = (6.320 + 4.711\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
6.320 |
| n |
4.711 |
| gf |
0.992 |
| gb |
-0.804 |
| k |
0.997 |
| δ90 |
9.979 |
| 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 |
| 2016-02-04 |
2017-05-08 |
-1.6782 |
-0.087 |
| 2017-05-13 |
2018-02-24 |
-0.6062 |
+0.657 |
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 |
06:31:07.59 |
+18:41:42.4 |
HIP 31258 |
32.19 |
| 2026-02-03 12:00 |
06:31:03.36 |
+18:41:49.1 |
HIP 31258 |
33.16 |
| 2026-02-04 00:00 |
06:30:59.16 |
+18:41:55.8 |
HIP 31258 |
34.13 |
| 2026-02-04 12:00 |
06:30:54.99 |
+18:42:02.6 |
HIP 31258 |
35.09 |
| 2026-02-05 00:00 |
06:30:50.86 |
+18:42:09.4 |
HIP 31014 |
35.36 |
| 2026-02-05 12:00 |
06:30:46.75 |
+18:42:16.1 |
HIP 31014 |
35.12 |
| 2026-02-06 00:00 |
06:30:42.69 |
+18:42:22.9 |
HIP 31014 |
34.91 |
| 2026-02-06 12:00 |
06:30:38.66 |
+18:42:29.7 |
HIP 31014 |
34.72 |
| 2026-02-07 00:00 |
06:30:34.66 |
+18:42:36.5 |
HIP 31014 |
34.55 |
| 2026-02-07 12:00 |
06:30:30.70 |
+18:42:43.3 |
HIP 31014 |
34.42 |
| 2026-02-08 00:00 |
06:30:26.77 |
+18:42:50.1 |
HIP 30801 |
33.91 |
| 2026-02-08 12:00 |
06:30:22.88 |
+18:42:56.9 |
HIP 30801 |
33.13 |
| 2026-02-09 00:00 |
06:30:19.03 |
+18:43:03.8 |
HIP 30801 |
32.37 |
| 2026-02-09 12:00 |
06:30:15.21 |
+18:43:10.6 |
HIP 30801 |
31.63 |
| 2026-02-10 00:00 |
06:30:11.43 |
+18:43:17.5 |
HIP 30801 |
30.90 |
| 2026-02-10 12:00 |
06:30:07.69 |
+18:43:24.3 |
HIP 30801 |
30.18 |
| 2026-02-11 00:00 |
06:30:03.99 |
+18:43:31.2 |
HIP 30801 |
29.49 |
| 2026-02-11 12:00 |
06:30:00.32 |
+18:43:38.0 |
HIP 30801 |
28.81 |
| 2026-02-12 00:00 |
06:29:56.69 |
+18:43:44.9 |
HIP 30801 |
28.16 |
| 2026-02-12 12:00 |
06:29:53.10 |
+18:43:51.7 |
HIP 30801 |
27.52 |
| 2026-02-13 00:00 |
06:29:49.55 |
+18:43:58.6 |
HIP 30773 |
26.72 |
| 2026-02-13 12:00 |
06:29:46.04 |
+18:44:05.5 |
HIP 30773 |
25.88 |
| 2026-02-14 00:00 |
06:29:42.56 |
+18:44:12.3 |
HIP 30773 |
25.05 |
| 2026-02-14 12:00 |
06:29:39.13 |
+18:44:19.2 |
HIP 30773 |
24.23 |
| 2026-02-15 00:00 |
06:29:35.74 |
+18:44:26.1 |
HIP 30773 |
23.42 |
| 2026-02-15 12:00 |
06:29:32.39 |
+18:44:33.0 |
HIP 30773 |
22.62 |
| 2026-02-16 00:00 |
06:29:29.07 |
+18:44:39.8 |
HIP 30773 |
21.83 |
| 2026-02-16 12:00 |
06:29:25.80 |
+18:44:46.7 |
HIP 30773 |
21.04 |
| 2026-02-17 00:00 |
06:29:22.57 |
+18:44:53.6 |
HIP 30773 |
20.27 |
| 2026-02-17 12:00 |
06:29:19.39 |
+18:45:00.5 |
HIP 30773 |
19.51 |
| 2026-02-18 00:00 |
06:29:16.24 |
+18:45:07.3 |
HIP 30773 |
18.76 |
| 2026-02-18 12:00 |
06:29:13.13 |
+18:45:14.2 |
HIP 30773 |
18.01 |
| 2026-02-19 00:00 |
06:29:10.07 |
+18:45:21.1 |
HIP 30773 |
17.28 |
| 2026-02-19 12:00 |
06:29:07.05 |
+18:45:27.9 |
HIP 30773 |
16.56 |
| 2026-02-20 00:00 |
06:29:04.07 |
+18:45:34.8 |
HIP 30773 |
15.84 |
| 2026-02-20 12:00 |
06:29:01.14 |
+18:45:41.6 |
HIP 30773 |
15.14 |
| 2026-02-21 00:00 |
06:28:58.25 |
+18:45:48.4 |
HIP 30773 |
14.45 |
| 2026-02-21 12:00 |
06:28:55.40 |
+18:45:55.3 |
HIP 30773 |
13.76 |
| 2026-02-22 00:00 |
06:28:52.59 |
+18:46:02.1 |
HIP 30773 |
13.09 |
| 2026-02-22 12:00 |
06:28:49.83 |
+18:46:08.9 |
HIP 30773 |
12.43 |
| 2026-02-23 00:00 |
06:28:47.11 |
+18:46:15.7 |
HIP 30773 |
11.78 |
| 2026-02-23 12:00 |
06:28:44.44 |
+18:46:22.5 |
HIP 30773 |
11.13 |
| 2026-02-24 00:00 |
06:28:41.81 |
+18:46:29.3 |
HIP 30773 |
10.50 |