メタデータ

項目	値
Designation	C/2020 Y2 (ATLAS)
Type	C
Perihelion (tp_cal, UTC)	2022-06-17T16:46:06.738240Z
Orbit solution date (soln_date, UTC)	2024-12-26T20:12:24Z
Obs used	1775
NEO	-
M1	10.500
K1	4.500
PC	-
Discovery observation (MPC, UTC)	2020-12-28T15:18:23.155200Z
Discovery magnitude (MPC)	18.30 o
Discovery observatory (MPC)	T08 · ATLAS-MLO, Mauna Loa

オスキュレーティング軌道要素

項目	値
Epoch (epoch_cal, TDB)	2022-09-03.0000000
e	0.99700512
q (au)	3.132490
a (au)	1045.948256
i (deg)	101.297766
Ω (om, deg)	26.515016
ω (w, deg)	266.105810
M (ma, deg)	0.002252

等級

散乱 + 全体線形

$$ M_a = (11.072 + 2.941\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta $$ $$ \theta = 180^\circ - \alpha $$ $$ \Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b) $$ $$ \Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1 $$

モデル定数

項目	値
H0	11.072
n	2.941
gf	1.000
gb	-0.718
k	0.800
δ90	10.000

パラメータ	記号	範囲	説明
太陽・地球距離が1 AUのときの絶対等級	H0	-5 to 20	彗星の固有の明るさ
測光スロープパラメータ	n	2 to 6	太陽距離に対する明るさ変化率
前方散乱非対称係数	gf	0.8 to 1	前方散乱の強さ
後方散乱非対称係数	gb	-1 to -0.5	後方散乱の強さ
分配係数	k	0.8 to 1	前方/後方散乱の寄与比
ダスト/ガス明るさ比	δ90	1 to 10	ダスト散乱とガス放射の相対寄与

参考: EPSC-DPS2025-160

残差 (区間線形)

$$\epsilon = a \log_{10} r_{\mathrm{au}} + b$$

開始日 (UTC)	終了日 (UTC)	a	b
2020-03-25	2021-01-29	+12.9145	-9.677
2021-01-29	2021-05-17	-5.4955	+4.015
2021-05-17	2022-06-01	-2.1125	+1.423
2022-06-19	2023-12-12	-1.0342	+0.680
2023-12-12	2024-10-29	+16.6054	-12.913

log10 r = log10(太陽距離/AU)、Δ = 地球距離(AU)

ファインディングチャート

天体暦

Date/Time (UTC)	RA (J2000)	Dec (J2000)	Nearest HIP	Dist from HIP (arcmin)
2026-03-26 00:00	00:41:11.49	+26:55:52.7	HIP 3275	17.01
2026-03-26 12:00	00:41:20.03	+26:57:06.0	HIP 3275	15.12
2026-03-27 00:00	00:41:28.57	+26:58:19.6	HIP 3275	13.35
2026-03-27 12:00	00:41:37.11	+26:59:33.8	HIP 3275	11.73
2026-03-28 00:00	00:41:45.66	+27:00:48.3	HIP 3275	10.36
2026-03-28 12:00	00:41:54.21	+27:02:03.2	HIP 3275	9.34
2026-03-29 00:00	00:42:02.77	+27:03:18.6	HIP 3275	8.80
2026-03-29 12:00	00:42:11.32	+27:04:34.4	HIP 3275	8.82
2026-03-30 00:00	00:42:19.87	+27:05:50.6	HIP 3275	9.41
2026-03-30 12:00	00:42:28.43	+27:07:07.1	HIP 3275	10.48
2026-03-31 00:00	00:42:36.98	+27:08:24.1	HIP 3275	11.89
2026-03-31 12:00	00:42:45.53	+27:09:41.5	HIP 3275	13.55
2026-04-01 00:00	00:42:54.09	+27:10:59.3	HIP 3275	15.37
2026-04-01 12:00	00:43:02.64	+27:12:17.5	HIP 3275	17.31
2026-04-02 00:00	00:43:11.18	+27:13:36.0	HIP 3275	19.32
2026-04-02 12:00	00:43:19.73	+27:14:55.0	HIP 3275	21.40
2026-04-03 00:00	00:43:28.27	+27:16:14.3	HIP 3275	23.51
2026-04-03 12:00	00:43:36.80	+27:17:34.0	HIP 3275	25.67
2026-04-04 00:00	00:43:45.33	+27:18:54.1	HIP 3331	25.96
2026-04-04 12:00	00:43:53.86	+27:20:14.5	HIP 3331	26.28
2026-04-05 00:00	00:44:02.38	+27:21:35.4	HIP 3331	26.79
2026-04-05 12:00	00:44:10.90	+27:22:56.6	HIP 3331	27.48
2026-04-06 00:00	00:44:19.40	+27:24:18.1	HIP 3331	28.34
2026-04-06 12:00	00:44:27.90	+27:25:40.1	HIP 3331	29.36
2026-04-07 00:00	00:44:36.40	+27:27:02.4	HIP 3331	30.51
2026-04-07 12:00	00:44:44.88	+27:28:25.0	HIP 3546	30.33
2026-04-08 00:00	00:44:53.36	+27:29:48.0	HIP 3546	28.56
2026-04-08 12:00	00:45:01.82	+27:31:11.4	HIP 3546	26.88
2026-04-09 00:00	00:45:10.28	+27:32:35.1	HIP 3546	25.30
2026-04-09 12:00	00:45:18.72	+27:33:59.1	HIP 3546	23.83
2026-04-10 00:00	00:45:27.16	+27:35:23.5	HIP 3546	22.50
2026-04-10 12:00	00:45:35.58	+27:36:48.3	HIP 3546	21.34
2026-04-11 00:00	00:45:43.99	+27:38:13.3	HIP 3546	20.38
2026-04-11 12:00	00:45:52.39	+27:39:38.7	HIP 3546	19.65
2026-04-12 00:00	00:46:00.77	+27:41:04.5	HIP 3546	19.16
2026-04-12 12:00	00:46:09.14	+27:42:30.5	HIP 3546	18.95
2026-04-13 00:00	00:46:17.50	+27:43:56.9	HIP 3546	19.02
2026-04-13 12:00	00:46:25.84	+27:45:23.6	HIP 3546	19.37
2026-04-14 00:00	00:46:34.16	+27:46:50.6	HIP 3546	19.99
2026-04-14 12:00	00:46:42.47	+27:48:18.0	HIP 3546	20.84
2026-04-15 00:00	00:46:50.77	+27:49:45.6	HIP 3546	21.90
2026-04-15 12:00	00:46:59.04	+27:51:13.6	HIP 3546	23.15
2026-04-16 00:00	00:47:07.30	+27:52:41.8	HIP 3546	24.56