| Parameter |
Value |
| Designation |
C/2015 XY1 (Lemmon) |
| Type |
C |
| Perihelion (tp_cal, UTC) |
2018-04-29T23:09:25.130880Z |
| Orbit solution date (soln_date, UTC) |
2022-07-31T01:42:27Z |
| Obs used |
741 |
| NEO |
- |
| M1 |
6.400 |
| K1 |
8.250 |
| PC |
0.030 |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
2018-03-20.0000000 |
| e |
1.00401907 |
| q (au) |
7.927954 |
| a (au) |
-1972.582314 |
| i (deg) |
148.846771 |
| Ω (om, deg) |
281.616004 |
| ω (w, deg) |
196.354336 |
| M (ma, deg) |
-0.000461 |
Magnitude
Scatter + Global Linear
$$
M_a = (-0.857 + 6.000\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
-0.857 |
| n |
6.000 |
| gf |
0.882 |
| gb |
-0.939 |
| k |
1.000 |
| δ90 |
3.911 |
| 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
Ephemeris
| Date/Time (UTC) |
RA (J2000) |
Dec (J2000) |
Nearest HIP |
Dist from HIP (arcmin) |
| 2026-03-26 00:00 |
23:59:35.16 |
-29:54:56.8 |
HIP 118241 |
7.80 |
| 2026-03-26 12:00 |
23:59:40.28 |
-29:54:33.5 |
HIP 118241 |
8.92 |
| 2026-03-27 00:00 |
23:59:45.39 |
-29:54:10.7 |
HIP 118241 |
10.05 |
| 2026-03-27 12:00 |
23:59:50.50 |
-29:53:48.3 |
HIP 118241 |
11.18 |
| 2026-03-28 00:00 |
23:59:55.60 |
-29:53:26.3 |
HIP 118241 |
12.32 |
| 2026-03-28 12:00 |
00:00:00.70 |
-29:53:04.7 |
HIP 118241 |
13.46 |
| 2026-03-29 00:00 |
00:00:05.78 |
-29:52:43.6 |
HIP 118241 |
14.61 |
| 2026-03-29 12:00 |
00:00:10.86 |
-29:52:22.9 |
HIP 77 |
14.98 |
| 2026-03-30 00:00 |
00:00:15.92 |
-29:52:02.6 |
HIP 77 |
14.57 |
| 2026-03-30 12:00 |
00:00:20.98 |
-29:51:42.8 |
HIP 77 |
14.24 |
| 2026-03-31 00:00 |
00:00:26.03 |
-29:51:23.4 |
HIP 77 |
13.98 |
| 2026-03-31 12:00 |
00:00:31.07 |
-29:51:04.4 |
HIP 77 |
13.81 |
| 2026-04-01 00:00 |
00:00:36.10 |
-29:50:45.9 |
HIP 77 |
13.73 |
| 2026-04-01 12:00 |
00:00:41.11 |
-29:50:27.8 |
HIP 77 |
13.74 |
| 2026-04-02 00:00 |
00:00:46.12 |
-29:50:10.2 |
HIP 77 |
13.83 |
| 2026-04-02 12:00 |
00:00:51.11 |
-29:49:53.0 |
HIP 77 |
14.00 |
| 2026-04-03 00:00 |
00:00:56.10 |
-29:49:36.2 |
HIP 77 |
14.25 |
| 2026-04-03 12:00 |
00:01:01.07 |
-29:49:19.9 |
HIP 77 |
14.57 |
| 2026-04-04 00:00 |
00:01:06.02 |
-29:49:04.1 |
HIP 77 |
14.96 |
| 2026-04-04 12:00 |
00:01:10.97 |
-29:48:48.6 |
HIP 77 |
15.42 |
| 2026-04-05 00:00 |
00:01:15.89 |
-29:48:33.7 |
HIP 183 |
14.88 |
| 2026-04-05 12:00 |
00:01:20.81 |
-29:48:19.2 |
HIP 183 |
13.80 |
| 2026-04-06 00:00 |
00:01:25.71 |
-29:48:05.1 |
HIP 183 |
12.73 |
| 2026-04-06 12:00 |
00:01:30.60 |
-29:47:51.5 |
HIP 183 |
11.66 |
| 2026-04-07 00:00 |
00:01:35.47 |
-29:47:38.3 |
HIP 183 |
10.61 |
| 2026-04-07 12:00 |
00:01:40.33 |
-29:47:25.7 |
HIP 183 |
9.56 |
| 2026-04-08 00:00 |
00:01:45.17 |
-29:47:13.4 |
HIP 183 |
8.54 |
| 2026-04-08 12:00 |
00:01:49.99 |
-29:47:01.6 |
HIP 183 |
7.53 |
| 2026-04-09 00:00 |
00:01:54.80 |
-29:46:50.3 |
HIP 183 |
6.54 |
| 2026-04-09 12:00 |
00:01:59.59 |
-29:46:39.5 |
HIP 183 |
5.59 |
| 2026-04-10 00:00 |
00:02:04.36 |
-29:46:29.1 |
HIP 183 |
4.69 |
| 2026-04-10 12:00 |
00:02:09.11 |
-29:46:19.2 |
HIP 183 |
3.88 |
| 2026-04-11 00:00 |
00:02:13.85 |
-29:46:09.7 |
HIP 183 |
3.22 |
| 2026-04-11 12:00 |
00:02:18.56 |
-29:46:00.7 |
HIP 183 |
2.80 |
| 2026-04-12 00:00 |
00:02:23.26 |
-29:45:52.2 |
HIP 183 |
2.74 |
| 2026-04-12 12:00 |
00:02:27.94 |
-29:45:44.2 |
HIP 183 |
3.05 |
| 2026-04-13 00:00 |
00:02:32.59 |
-29:45:36.6 |
HIP 183 |
3.64 |
| 2026-04-13 12:00 |
00:02:37.23 |
-29:45:29.5 |
HIP 183 |
4.39 |
| 2026-04-14 00:00 |
00:02:41.85 |
-29:45:22.9 |
HIP 183 |
5.23 |
| 2026-04-14 12:00 |
00:02:46.44 |
-29:45:16.7 |
HIP 183 |
6.11 |
| 2026-04-15 00:00 |
00:02:51.01 |
-29:45:11.1 |
HIP 183 |
7.03 |
| 2026-04-15 12:00 |
00:02:55.57 |
-29:45:05.9 |
HIP 183 |
7.96 |
| 2026-04-16 00:00 |
00:03:00.09 |
-29:45:01.2 |
HIP 183 |
8.90 |