| Parameter |
Value |
| Designation |
C/2021 O1 (Nishimura) |
| Type |
C |
| Perihelion (tp_cal, UTC) |
2021-08-13T22:16:11.570880Z |
| Orbit solution date (soln_date, UTC) |
2023-04-24T19:06:44Z |
| Obs used |
59 |
| NEO |
- |
| M1 |
10.800 |
| K1 |
10.000 |
| PC |
- |
| Discovery observation (MPC, UTC) |
2021-07-21T18:47:36.384000Z |
| Discovery magnitude (MPC) |
10.70 T |
| Discovery observatory (MPC) |
247 · Roving Observer |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
2021-07-26.0000000 |
| e |
1.00305367 |
| q (au) |
0.787409 |
| a (au) |
-257.856271 |
| i (deg) |
27.567888 |
| Ω (om, deg) |
41.631614 |
| ω (w, deg) |
74.438198 |
| M (ma, deg) |
-0.004505 |
Magnitude
Scatter + Global Linear
$$
M_a = (9.855 + 3.673\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
9.855 |
| n |
3.673 |
| 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
Ephemeris
| Date/Time (UTC) |
RA (J2000) |
Dec (J2000) |
Nearest HIP |
Dist from HIP (arcmin) |
| 2026-05-12 00:00 |
17:51:32.48 |
-44:34:06.6 |
HIP 87412 |
14.32 |
| 2026-05-12 12:00 |
17:51:24.21 |
-44:34:34.5 |
HIP 87412 |
15.17 |
| 2026-05-13 00:00 |
17:51:15.87 |
-44:35:02.1 |
HIP 87412 |
16.12 |
| 2026-05-13 12:00 |
17:51:07.47 |
-44:35:29.3 |
HIP 87412 |
17.15 |
| 2026-05-14 00:00 |
17:50:59.01 |
-44:35:56.2 |
HIP 87412 |
18.27 |
| 2026-05-14 12:00 |
17:50:50.49 |
-44:36:22.8 |
HIP 87412 |
19.45 |
| 2026-05-15 00:00 |
17:50:41.91 |
-44:36:49.0 |
HIP 87412 |
20.68 |
| 2026-05-15 12:00 |
17:50:33.27 |
-44:37:14.8 |
HIP 87412 |
21.96 |
| 2026-05-16 00:00 |
17:50:24.57 |
-44:37:40.3 |
HIP 87412 |
23.29 |
| 2026-05-16 12:00 |
17:50:15.82 |
-44:38:05.4 |
HIP 87412 |
24.65 |
| 2026-05-17 00:00 |
17:50:07.01 |
-44:38:30.2 |
HIP 87104 |
24.82 |
| 2026-05-17 12:00 |
17:49:58.14 |
-44:38:54.5 |
HIP 87104 |
23.40 |
| 2026-05-18 00:00 |
17:49:49.22 |
-44:39:18.6 |
HIP 87104 |
21.99 |
| 2026-05-18 12:00 |
17:49:40.25 |
-44:39:42.2 |
HIP 87104 |
20.61 |
| 2026-05-19 00:00 |
17:49:31.22 |
-44:40:05.5 |
HIP 87104 |
19.25 |
| 2026-05-19 12:00 |
17:49:22.15 |
-44:40:28.4 |
HIP 87104 |
17.94 |
| 2026-05-20 00:00 |
17:49:13.02 |
-44:40:50.9 |
HIP 87104 |
16.67 |
| 2026-05-20 12:00 |
17:49:03.85 |
-44:41:13.1 |
HIP 87104 |
15.48 |
| 2026-05-21 00:00 |
17:48:54.62 |
-44:41:34.8 |
HIP 87104 |
14.36 |
| 2026-05-21 12:00 |
17:48:45.35 |
-44:41:56.2 |
HIP 87104 |
13.36 |
| 2026-05-22 00:00 |
17:48:36.03 |
-44:42:17.2 |
HIP 87104 |
12.50 |
| 2026-05-22 12:00 |
17:48:26.66 |
-44:42:37.8 |
HIP 87104 |
11.80 |
| 2026-05-23 00:00 |
17:48:17.25 |
-44:42:58.0 |
HIP 87104 |
11.32 |
| 2026-05-23 12:00 |
17:48:07.80 |
-44:43:17.8 |
HIP 87104 |
11.07 |
| 2026-05-24 00:00 |
17:47:58.30 |
-44:43:37.2 |
HIP 87104 |
11.07 |
| 2026-05-24 12:00 |
17:47:48.76 |
-44:43:56.2 |
HIP 87104 |
11.33 |
| 2026-05-25 00:00 |
17:47:39.18 |
-44:44:14.8 |
HIP 87104 |
11.84 |
| 2026-05-25 12:00 |
17:47:29.56 |
-44:44:33.0 |
HIP 87104 |
12.56 |
| 2026-05-26 00:00 |
17:47:19.90 |
-44:44:50.8 |
HIP 87104 |
13.47 |
| 2026-05-26 12:00 |
17:47:10.20 |
-44:45:08.2 |
HIP 86956 |
13.89 |
| 2026-05-27 00:00 |
17:47:00.46 |
-44:45:25.2 |
HIP 86956 |
12.77 |
| 2026-05-27 12:00 |
17:46:50.69 |
-44:45:41.8 |
HIP 86956 |
11.79 |
| 2026-05-28 00:00 |
17:46:40.88 |
-44:45:58.0 |
HIP 86956 |
11.01 |
| 2026-05-28 12:00 |
17:46:31.03 |
-44:46:13.8 |
HIP 86956 |
10.45 |
| 2026-05-29 00:00 |
17:46:21.16 |
-44:46:29.1 |
HIP 86956 |
10.17 |
| 2026-05-29 12:00 |
17:46:11.25 |
-44:46:44.1 |
HIP 86956 |
10.18 |
| 2026-05-30 00:00 |
17:46:01.30 |
-44:46:58.6 |
HIP 86956 |
10.50 |
| 2026-05-30 12:00 |
17:45:51.33 |
-44:47:12.7 |
HIP 86956 |
11.09 |
| 2026-05-31 00:00 |
17:45:41.32 |
-44:47:26.4 |
HIP 86956 |
11.92 |
| 2026-05-31 12:00 |
17:45:31.29 |
-44:47:39.6 |
HIP 86956 |
12.94 |
| 2026-06-01 00:00 |
17:45:21.23 |
-44:47:52.5 |
HIP 86956 |
14.12 |
| 2026-06-01 12:00 |
17:45:11.14 |
-44:48:04.9 |
HIP 86956 |
15.41 |
| 2026-06-02 00:00 |
17:45:01.02 |
-44:48:16.9 |
HIP 86788 |
14.55 |