| 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) |
| 2026-09-20 00:00 |
16:15:24.47 |
-06:58:31.3 |
HIP 79545 |
22.83 |
| 2026-09-20 12:00 |
16:15:29.40 |
-06:58:50.7 |
HIP 79645 |
23.31 |
| 2026-09-21 00:00 |
16:15:34.41 |
-06:59:10.2 |
HIP 79645 |
23.28 |
| 2026-09-21 12:00 |
16:15:39.48 |
-06:59:29.7 |
HIP 79645 |
23.31 |
| 2026-09-22 00:00 |
16:15:44.63 |
-06:59:49.2 |
HIP 79645 |
23.43 |
| 2026-09-22 12:00 |
16:15:49.85 |
-07:00:08.8 |
HIP 79645 |
23.63 |
| 2026-09-23 00:00 |
16:15:55.13 |
-07:00:28.5 |
HIP 79645 |
23.90 |
| 2026-09-23 12:00 |
16:16:00.49 |
-07:00:48.1 |
HIP 79645 |
24.26 |
| 2026-09-24 00:00 |
16:16:05.92 |
-07:01:07.8 |
HIP 79645 |
24.70 |
| 2026-09-24 12:00 |
16:16:11.42 |
-07:01:27.5 |
HIP 79645 |
25.21 |
| 2026-09-25 00:00 |
16:16:16.98 |
-07:01:47.3 |
HIP 79645 |
25.81 |
| 2026-09-25 12:00 |
16:16:22.61 |
-07:02:07.0 |
HIP 79645 |
26.47 |
| 2026-09-26 00:00 |
16:16:28.31 |
-07:02:26.8 |
HIP 79821 |
26.14 |
| 2026-09-26 12:00 |
16:16:34.08 |
-07:02:46.6 |
HIP 79821 |
25.61 |
| 2026-09-27 00:00 |
16:16:39.92 |
-07:03:06.4 |
HIP 79821 |
25.14 |
| 2026-09-27 12:00 |
16:16:45.82 |
-07:03:26.2 |
HIP 79821 |
24.74 |
| 2026-09-28 00:00 |
16:16:51.78 |
-07:03:46.0 |
HIP 79821 |
24.42 |
| 2026-09-28 12:00 |
16:16:57.82 |
-07:04:05.8 |
HIP 79821 |
24.19 |
| 2026-09-29 00:00 |
16:17:03.91 |
-07:04:25.6 |
HIP 79821 |
24.05 |
| 2026-09-29 12:00 |
16:17:10.07 |
-07:04:45.4 |
HIP 79821 |
24.00 |
| 2026-09-30 00:00 |
16:17:16.30 |
-07:05:05.2 |
HIP 79821 |
24.06 |
| 2026-09-30 12:00 |
16:17:22.59 |
-07:05:24.9 |
HIP 79821 |
24.21 |
| 2026-10-01 00:00 |
16:17:28.95 |
-07:05:44.7 |
HIP 79821 |
24.47 |
| 2026-10-01 12:00 |
16:17:35.36 |
-07:06:04.4 |
HIP 79821 |
24.83 |
| 2026-10-02 00:00 |
16:17:41.84 |
-07:06:24.2 |
HIP 79942 |
24.48 |
| 2026-10-02 12:00 |
16:17:48.39 |
-07:06:43.9 |
HIP 79942 |
22.93 |
| 2026-10-03 00:00 |
16:17:54.99 |
-07:07:03.5 |
HIP 79942 |
21.38 |
| 2026-10-03 12:00 |
16:18:01.66 |
-07:07:23.2 |
HIP 79942 |
19.85 |
| 2026-10-04 00:00 |
16:18:08.38 |
-07:07:42.8 |
HIP 79942 |
18.32 |
| 2026-10-04 12:00 |
16:18:15.17 |
-07:08:02.3 |
HIP 79942 |
16.82 |
| 2026-10-05 00:00 |
16:18:22.02 |
-07:08:21.9 |
HIP 79942 |
15.36 |
| 2026-10-05 12:00 |
16:18:28.93 |
-07:08:41.4 |
HIP 79942 |
13.95 |
| 2026-10-06 00:00 |
16:18:35.89 |
-07:09:00.8 |
HIP 79942 |
12.61 |
| 2026-10-06 12:00 |
16:18:42.92 |
-07:09:20.2 |
HIP 79942 |
11.38 |
| 2026-10-07 00:00 |
16:18:50.00 |
-07:09:39.5 |
HIP 79942 |
10.30 |
| 2026-10-07 12:00 |
16:18:57.15 |
-07:09:58.8 |
HIP 79942 |
9.44 |
| 2026-10-08 00:00 |
16:19:04.35 |
-07:10:18.0 |
HIP 79942 |
8.87 |
| 2026-10-08 12:00 |
16:19:11.60 |
-07:10:37.2 |
HIP 79942 |
8.65 |
| 2026-10-09 00:00 |
16:19:18.92 |
-07:10:56.2 |
HIP 79942 |
8.82 |
| 2026-10-09 12:00 |
16:19:26.29 |
-07:11:15.3 |
HIP 79942 |
9.36 |
| 2026-10-10 00:00 |
16:19:33.71 |
-07:11:34.2 |
HIP 79942 |
10.23 |
| 2026-10-10 12:00 |
16:19:41.19 |
-07:11:53.1 |
HIP 79942 |
11.35 |
| 2026-10-11 00:00 |
16:19:48.72 |
-07:12:11.8 |
HIP 79942 |
12.66 |