| Parameter |
Value |
| Designation |
C/2025 A1 (Lemmon) |
| Type |
C |
| Perihelion (tp_cal, UTC) |
2027-03-12T16:07:18.552000Z |
| Orbit solution date (soln_date, UTC) |
2026-06-18T16:12:19Z |
| Obs used |
484 |
| NEO |
- |
| M1 |
5.500 |
| K1 |
12.000 |
| PC |
- |
| Discovery observation (MPC, UTC) |
2025-01-02T06:39:55.180800Z |
| Discovery magnitude (MPC) |
20.50 G |
| Discovery observatory (MPC) |
G96 · University of Arizona Mt. Lemmon Survey |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
2025-08-15.0000000 |
| e |
1.00250102 |
| q (au) |
5.345147 |
| a (au) |
-2137.190000 |
| i (deg) |
33.424560 |
| Ω (om, deg) |
101.331106 |
| ω (w, deg) |
68.048693 |
| M (ma, deg) |
-0.005733 |
Magnitude
Scatter + Global Linear
$$
M_a = (4.576 + 4.828\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
4.576 |
| n |
4.828 |
| gf |
0.912 |
| gb |
-1.000 |
| k |
1.000 |
| δ90 |
7.289 |
| 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 |
| 2021-11-11 |
2025-06-03 |
-4.6349 |
+4.324 |
| 2025-06-03 |
2026-06-09 |
+10.9163 |
-8.571 |
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 |
09:45:39.61 |
+33:33:06.6 |
HIP 47739 |
23.92 |
| 2026-07-29 12:00 |
09:46:11.25 |
+33:31:33.6 |
HIP 48003 |
25.10 |
| 2026-07-30 00:00 |
09:46:42.92 |
+33:30:00.7 |
HIP 48003 |
21.34 |
| 2026-07-30 12:00 |
09:47:14.63 |
+33:28:27.8 |
HIP 48106 |
19.01 |
| 2026-07-31 00:00 |
09:47:46.37 |
+33:26:54.8 |
HIP 48106 |
13.01 |
| 2026-07-31 12:00 |
09:48:18.14 |
+33:25:22.0 |
HIP 48106 |
8.32 |
| 2026-08-01 00:00 |
09:48:49.94 |
+33:23:49.1 |
HIP 48106 |
7.89 |
| 2026-08-01 12:00 |
09:49:21.77 |
+33:22:16.3 |
HIP 48106 |
12.18 |
| 2026-08-02 00:00 |
09:49:53.63 |
+33:20:43.4 |
HIP 48232 |
15.44 |
| 2026-08-02 12:00 |
09:50:25.52 |
+33:19:10.7 |
HIP 48232 |
17.70 |
| 2026-08-03 00:00 |
09:50:57.44 |
+33:17:38.0 |
HIP 48232 |
21.95 |
| 2026-08-03 12:00 |
09:51:29.39 |
+33:16:05.3 |
HIP 48232 |
27.27 |
| 2026-08-04 00:00 |
09:52:01.37 |
+33:14:32.6 |
HIP 48497 |
21.40 |
| 2026-08-04 12:00 |
09:52:33.37 |
+33:13:00.1 |
HIP 48497 |
15.30 |
| 2026-08-05 00:00 |
09:53:05.40 |
+33:11:27.5 |
HIP 48497 |
10.22 |
| 2026-08-05 12:00 |
09:53:37.46 |
+33:09:55.1 |
HIP 48497 |
8.34 |
| 2026-08-06 00:00 |
09:54:09.55 |
+33:08:22.7 |
HIP 48497 |
11.40 |
| 2026-08-06 12:00 |
09:54:41.66 |
+33:06:50.3 |
HIP 48497 |
16.90 |
| 2026-08-07 00:00 |
09:55:13.79 |
+33:05:18.0 |
HIP 48497 |
23.17 |
| 2026-08-07 12:00 |
09:55:45.95 |
+33:03:45.9 |
HIP 48798 |
18.28 |
| 2026-08-08 00:00 |
09:56:18.14 |
+33:02:13.7 |
HIP 48798 |
11.40 |
| 2026-08-08 12:00 |
09:56:50.34 |
+33:00:41.7 |
HIP 48798 |
4.66 |
| 2026-08-09 00:00 |
09:57:22.58 |
+32:59:09.8 |
HIP 48798 |
3.05 |
| 2026-08-09 12:00 |
09:57:54.83 |
+32:57:38.0 |
HIP 48798 |
9.65 |
| 2026-08-10 00:00 |
09:58:27.10 |
+32:56:06.2 |
HIP 48798 |
16.53 |
| 2026-08-10 12:00 |
09:58:59.40 |
+32:54:34.6 |
HIP 49000 |
15.01 |
| 2026-08-11 00:00 |
09:59:31.72 |
+32:53:03.1 |
HIP 49000 |
12.94 |
| 2026-08-11 12:00 |
10:00:04.06 |
+32:51:31.7 |
HIP 49000 |
14.36 |
| 2026-08-12 00:00 |
10:00:36.42 |
+32:50:00.4 |
HIP 49000 |
18.48 |
| 2026-08-12 12:00 |
10:01:08.79 |
+32:48:29.3 |
HIP 49170 |
18.17 |
| 2026-08-13 00:00 |
10:01:41.19 |
+32:46:58.3 |
HIP 49170 |
16.07 |
| 2026-08-13 12:00 |
10:02:13.60 |
+32:45:27.4 |
HIP 49170 |
16.83 |
| 2026-08-14 00:00 |
10:02:46.03 |
+32:43:56.6 |
HIP 49315 |
16.21 |
| 2026-08-14 12:00 |
10:03:18.47 |
+32:42:26.1 |
HIP 49315 |
9.29 |
| 2026-08-15 00:00 |
10:03:50.93 |
+32:40:55.6 |
HIP 49315 |
2.73 |
| 2026-08-15 12:00 |
10:04:23.41 |
+32:39:25.3 |
HIP 49315 |
5.15 |
| 2026-08-16 00:00 |
10:04:55.90 |
+32:37:55.2 |
HIP 49315 |
11.99 |
| 2026-08-16 12:00 |
10:05:28.41 |
+32:36:25.3 |
HIP 49334 |
17.84 |
| 2026-08-17 00:00 |
10:06:00.92 |
+32:34:55.5 |
HIP 49334 |
23.43 |
| 2026-08-17 12:00 |
10:06:33.45 |
+32:33:25.9 |
HIP 49334 |
29.63 |
| 2026-08-18 00:00 |
10:07:06.00 |
+32:31:56.5 |
HIP 49737 |
28.57 |
| 2026-08-18 12:00 |
10:07:38.55 |
+32:30:27.3 |
HIP 49737 |
21.64 |
| 2026-08-19 00:00 |
10:08:11.12 |
+32:28:58.2 |
HIP 49737 |
14.79 |