C/2021 Y1 (ATLAS)
| 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) |
| 2026-02-03 00:00 |
16:49:09.51 |
-12:32:14.5 |
HIP 82388 |
16.31 |
| 2026-02-03 12:00 |
16:49:16.18 |
-12:31:21.1 |
HIP 82388 |
14.46 |
| 2026-02-04 00:00 |
16:49:22.77 |
-12:30:27.4 |
HIP 82388 |
12.63 |
| 2026-02-04 12:00 |
16:49:29.27 |
-12:29:33.4 |
HIP 82388 |
10.82 |
| 2026-02-05 00:00 |
16:49:35.68 |
-12:28:39.0 |
HIP 82388 |
9.02 |
| 2026-02-05 12:00 |
16:49:42.00 |
-12:27:44.3 |
HIP 82388 |
7.24 |
| 2026-02-06 00:00 |
16:49:48.23 |
-12:26:49.2 |
HIP 82388 |
5.48 |
| 2026-02-06 12:00 |
16:49:54.37 |
-12:25:53.7 |
HIP 82388 |
3.75 |
| 2026-02-07 00:00 |
16:50:00.42 |
-12:24:58.0 |
HIP 82388 |
2.09 |
| 2026-02-07 12:00 |
16:50:06.37 |
-12:24:01.8 |
HIP 82388 |
0.85 |
| 2026-02-08 00:00 |
16:50:12.23 |
-12:23:05.3 |
HIP 82388 |
1.72 |
| 2026-02-08 12:00 |
16:50:18.00 |
-12:22:08.5 |
HIP 82388 |
3.31 |
| 2026-02-09 00:00 |
16:50:23.68 |
-12:21:11.4 |
HIP 82388 |
4.95 |
| 2026-02-09 12:00 |
16:50:29.26 |
-12:20:13.8 |
HIP 82388 |
6.60 |
| 2026-02-10 00:00 |
16:50:34.75 |
-12:19:16.0 |
HIP 82388 |
8.23 |
| 2026-02-10 12:00 |
16:50:40.15 |
-12:18:17.8 |
HIP 82388 |
9.86 |
| 2026-02-11 00:00 |
16:50:45.44 |
-12:17:19.3 |
HIP 82388 |
11.47 |
| 2026-02-11 12:00 |
16:50:50.65 |
-12:16:20.4 |
HIP 82388 |
13.06 |
| 2026-02-12 00:00 |
16:50:55.75 |
-12:15:21.2 |
HIP 82388 |
14.65 |
| 2026-02-12 12:00 |
16:51:00.76 |
-12:14:21.6 |
HIP 82388 |
16.21 |
| 2026-02-13 00:00 |
16:51:05.67 |
-12:13:21.7 |
HIP 82388 |
17.76 |
| 2026-02-13 12:00 |
16:51:10.49 |
-12:12:21.5 |
HIP 82388 |
19.30 |
| 2026-02-14 00:00 |
16:51:15.20 |
-12:11:21.0 |
HIP 82388 |
20.82 |
| 2026-02-14 12:00 |
16:51:19.82 |
-12:10:20.1 |
HIP 82388 |
22.33 |
| 2026-02-15 00:00 |
16:51:24.34 |
-12:09:18.8 |
HIP 82388 |
23.82 |
| 2026-02-15 12:00 |
16:51:28.76 |
-12:08:17.3 |
HIP 82388 |
25.30 |
| 2026-02-16 00:00 |
16:51:33.08 |
-12:07:15.4 |
HIP 82388 |
26.76 |
| 2026-02-16 12:00 |
16:51:37.30 |
-12:06:13.2 |
HIP 82388 |
28.21 |
| 2026-02-17 00:00 |
16:51:41.42 |
-12:05:10.7 |
HIP 82388 |
29.64 |
| 2026-02-17 12:00 |
16:51:45.44 |
-12:04:07.8 |
HIP 82388 |
31.06 |
| 2026-02-18 00:00 |
16:51:49.35 |
-12:03:04.7 |
HIP 82602 |
30.20 |
| 2026-02-18 12:00 |
16:51:53.17 |
-12:02:01.2 |
HIP 82602 |
28.79 |
| 2026-02-19 00:00 |
16:51:56.88 |
-12:00:57.3 |
HIP 82602 |
27.39 |
| 2026-02-19 12:00 |
16:52:00.49 |
-11:59:53.2 |
HIP 82602 |
26.01 |
| 2026-02-20 00:00 |
16:52:04.00 |
-11:58:48.8 |
HIP 82602 |
24.63 |
| 2026-02-20 12:00 |
16:52:07.40 |
-11:57:44.0 |
HIP 82602 |
23.27 |
| 2026-02-21 00:00 |
16:52:10.70 |
-11:56:38.9 |
HIP 82602 |
21.93 |
| 2026-02-21 12:00 |
16:52:13.90 |
-11:55:33.6 |
HIP 82602 |
20.60 |
| 2026-02-22 00:00 |
16:52:16.99 |
-11:54:27.9 |
HIP 82602 |
19.28 |
| 2026-02-22 12:00 |
16:52:19.98 |
-11:53:21.9 |
HIP 82602 |
17.98 |
| 2026-02-23 00:00 |
16:52:22.87 |
-11:52:15.6 |
HIP 82602 |
16.69 |
| 2026-02-23 12:00 |
16:52:25.65 |
-11:51:09.0 |
HIP 82602 |
15.43 |
| 2026-02-24 00:00 |
16:52:28.32 |
-11:50:02.1 |
HIP 82602 |
14.18 |