| Parameter |
Value |
| Designation |
C/2021 Y1 (ATLAS) |
| Type |
C |
| Perihelion (tp_cal, UTC) |
2023-04-30T16:42:49.288320Z |
| Orbit solution date (soln_date, UTC) |
2024-04-13T16:42:29Z |
| Obs used |
1857 |
| NEO |
- |
| M1 |
12.000 |
| K1 |
4.500 |
| PC |
- |
| Discovery observation (MPC, UTC) |
2021-12-26T06:50:24.691200Z |
| Discovery magnitude (MPC) |
18.99 o |
| Discovery observatory (MPC) |
T08 · ATLAS-MLO, Mauna Loa |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
2022-10-17.0000000 |
| e |
1.00083371 |
| q (au) |
2.032510 |
| a (au) |
-2437.901109 |
| i (deg) |
77.187480 |
| Ω (om, deg) |
244.769593 |
| ω (w, deg) |
245.810207 |
| M (ma, deg) |
-0.001602 |
Magnitude
Scatter + Global Linear
$$
M_a = (11.482 + 2.000\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
11.482 |
| n |
2.000 |
| gf |
0.833 |
| gb |
-0.807 |
| k |
0.997 |
| δ90 |
1.000 |
| 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
Finding Chart
Ephemeris
| Date/Time (UTC) |
RA (J2000) |
Dec (J2000) |
Nearest HIP |
Dist from HIP (arcmin) |
| 2026-05-12 00:00 |
16:39:16.49 |
-08:29:09.4 |
HIP 81499 |
10.67 |
| 2026-05-12 12:00 |
16:39:05.37 |
-08:27:55.3 |
HIP 81499 |
10.18 |
| 2026-05-13 00:00 |
16:38:54.21 |
-08:26:41.4 |
HIP 81499 |
10.55 |
| 2026-05-13 12:00 |
16:38:43.02 |
-08:25:27.8 |
HIP 81499 |
11.71 |
| 2026-05-14 00:00 |
16:38:31.80 |
-08:24:14.4 |
HIP 81499 |
13.46 |
| 2026-05-14 12:00 |
16:38:20.55 |
-08:23:01.4 |
HIP 81499 |
15.61 |
| 2026-05-15 00:00 |
16:38:09.26 |
-08:21:48.7 |
HIP 81499 |
18.02 |
| 2026-05-15 12:00 |
16:37:57.95 |
-08:20:36.3 |
HIP 81499 |
20.59 |
| 2026-05-16 00:00 |
16:37:46.61 |
-08:19:24.1 |
HIP 81499 |
23.28 |
| 2026-05-16 12:00 |
16:37:35.25 |
-08:18:12.3 |
HIP 81499 |
26.05 |
| 2026-05-17 00:00 |
16:37:23.86 |
-08:17:00.8 |
HIP 81499 |
28.88 |
| 2026-05-17 12:00 |
16:37:12.45 |
-08:15:49.7 |
HIP 81355 |
30.53 |
| 2026-05-18 00:00 |
16:37:01.01 |
-08:14:38.8 |
HIP 81355 |
29.01 |
| 2026-05-18 12:00 |
16:36:49.55 |
-08:13:28.3 |
HIP 81355 |
27.75 |
| 2026-05-19 00:00 |
16:36:38.08 |
-08:12:18.1 |
HIP 81355 |
26.79 |
| 2026-05-19 12:00 |
16:36:26.58 |
-08:11:08.3 |
HIP 81355 |
26.16 |
| 2026-05-20 00:00 |
16:36:15.07 |
-08:09:58.8 |
HIP 81159 |
25.10 |
| 2026-05-20 12:00 |
16:36:03.54 |
-08:08:49.6 |
HIP 81159 |
22.23 |
| 2026-05-21 00:00 |
16:35:52.00 |
-08:07:40.8 |
HIP 81159 |
19.42 |
| 2026-05-21 12:00 |
16:35:40.44 |
-08:06:32.3 |
HIP 81159 |
16.69 |
| 2026-05-22 00:00 |
16:35:28.87 |
-08:05:24.2 |
HIP 81159 |
14.11 |
| 2026-05-22 12:00 |
16:35:17.29 |
-08:04:16.5 |
HIP 81159 |
11.76 |
| 2026-05-23 00:00 |
16:35:05.70 |
-08:03:09.1 |
HIP 81159 |
9.82 |
| 2026-05-23 12:00 |
16:34:54.10 |
-08:02:02.1 |
HIP 81159 |
8.57 |
| 2026-05-24 00:00 |
16:34:42.49 |
-08:00:55.4 |
HIP 81159 |
8.32 |
| 2026-05-24 12:00 |
16:34:30.88 |
-07:59:49.2 |
HIP 81159 |
9.17 |
| 2026-05-25 00:00 |
16:34:19.26 |
-07:58:43.2 |
HIP 81159 |
10.84 |
| 2026-05-25 12:00 |
16:34:07.64 |
-07:57:37.7 |
HIP 81159 |
13.04 |
| 2026-05-26 00:00 |
16:33:56.01 |
-07:56:32.6 |
HIP 81159 |
15.53 |
| 2026-05-26 12:00 |
16:33:44.38 |
-07:55:27.8 |
HIP 81159 |
18.20 |
| 2026-05-27 00:00 |
16:33:32.76 |
-07:54:23.4 |
HIP 81159 |
20.97 |
| 2026-05-27 12:00 |
16:33:21.13 |
-07:53:19.5 |
HIP 81159 |
23.82 |
| 2026-05-28 00:00 |
16:33:09.50 |
-07:52:15.9 |
HIP 81159 |
26.71 |
| 2026-05-28 12:00 |
16:32:57.88 |
-07:51:12.7 |
HIP 80904 |
25.01 |
| 2026-05-29 00:00 |
16:32:46.26 |
-07:50:09.9 |
HIP 80904 |
22.39 |
| 2026-05-29 12:00 |
16:32:34.64 |
-07:49:07.5 |
HIP 80904 |
19.89 |
| 2026-05-30 00:00 |
16:32:23.03 |
-07:48:05.5 |
HIP 80904 |
17.58 |
| 2026-05-30 12:00 |
16:32:11.43 |
-07:47:03.9 |
HIP 80904 |
15.51 |
| 2026-05-31 00:00 |
16:31:59.83 |
-07:46:02.7 |
HIP 80904 |
13.82 |
| 2026-05-31 12:00 |
16:31:48.25 |
-07:45:02.0 |
HIP 80904 |
12.64 |
| 2026-06-01 00:00 |
16:31:36.67 |
-07:44:01.7 |
HIP 80904 |
12.12 |
| 2026-06-01 12:00 |
16:31:25.11 |
-07:43:01.7 |
HIP 80891 |
11.64 |
| 2026-06-02 00:00 |
16:31:13.56 |
-07:42:02.2 |
HIP 80891 |
9.79 |