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)
2026-05-12 00:00	00:53:37.93	+29:14:42.5	HIP 4196	9.90
2026-05-12 12:00	00:53:44.46	+29:16:21.9	HIP 4196	11.70
2026-05-13 00:00	00:53:50.93	+29:18:01.5	HIP 4197	11.74
2026-05-13 12:00	00:53:57.36	+29:19:41.1	HIP 4197	10.65
2026-05-14 00:00	00:54:03.75	+29:21:20.9	HIP 4197	9.91
2026-05-14 12:00	00:54:10.08	+29:23:00.8	HIP 4197	9.61
2026-05-15 00:00	00:54:16.36	+29:24:40.8	HIP 4197	9.77
2026-05-15 12:00	00:54:22.60	+29:26:20.9	HIP 4197	10.38
2026-05-16 00:00	00:54:28.78	+29:28:01.1	HIP 4197	11.36
2026-05-16 12:00	00:54:34.92	+29:29:41.4	HIP 4197	12.61
2026-05-17 00:00	00:54:41.00	+29:31:21.8	HIP 4197	14.07
2026-05-17 12:00	00:54:47.03	+29:33:02.2	HIP 4197	15.68
2026-05-18 00:00	00:54:53.01	+29:34:42.8	HIP 4197	17.38
2026-05-18 12:00	00:54:58.94	+29:36:23.4	HIP 4378	17.73
2026-05-19 00:00	00:55:04.81	+29:38:04.1	HIP 4378	15.72
2026-05-19 12:00	00:55:10.63	+29:39:44.9	HIP 4378	13.75
2026-05-20 00:00	00:55:16.40	+29:41:25.7	HIP 4378	11.84
2026-05-20 12:00	00:55:22.11	+29:43:06.6	HIP 4378	10.02
2026-05-21 00:00	00:55:27.76	+29:44:47.5	HIP 4378	8.33
2026-05-21 12:00	00:55:33.36	+29:46:28.5	HIP 4378	6.87
2026-05-22 00:00	00:55:38.91	+29:48:09.6	HIP 4378	5.82
2026-05-22 12:00	00:55:44.39	+29:49:50.7	HIP 4378	5.40
2026-05-23 00:00	00:55:49.82	+29:51:31.8	HIP 4378	5.75
2026-05-23 12:00	00:55:55.19	+29:53:13.0	HIP 4378	6.75
2026-05-24 00:00	00:56:00.51	+29:54:54.2	HIP 4378	8.15
2026-05-24 12:00	00:56:05.76	+29:56:35.5	HIP 4378	9.78
2026-05-25 00:00	00:56:10.96	+29:58:16.8	HIP 4378	11.54
2026-05-25 12:00	00:56:16.10	+29:59:58.1	HIP 4378	13.38
2026-05-26 00:00	00:56:21.17	+30:01:39.4	HIP 4402	14.34
2026-05-26 12:00	00:56:26.19	+30:03:20.7	HIP 4402	12.59
2026-05-27 00:00	00:56:31.15	+30:05:02.1	HIP 4402	10.93
2026-05-27 12:00	00:56:36.04	+30:06:43.4	HIP 4402	9.41
2026-05-28 00:00	00:56:40.88	+30:08:24.8	HIP 4402	8.08
2026-05-28 12:00	00:56:45.65	+30:10:06.2	HIP 4402	7.06
2026-05-29 00:00	00:56:50.36	+30:11:47.5	HIP 4402	6.49
2026-05-29 12:00	00:56:55.00	+30:13:28.9	HIP 4402	6.48
2026-05-30 00:00	00:56:59.59	+30:15:10.3	HIP 4402	7.03
2026-05-30 12:00	00:57:04.11	+30:16:51.6	HIP 4402	8.02
2026-05-31 00:00	00:57:08.56	+30:18:33.0	HIP 4402	9.30
2026-05-31 12:00	00:57:12.95	+30:20:14.3	HIP 4531	10.54
2026-06-01 00:00	00:57:17.28	+30:21:55.6	HIP 4531	10.00
2026-06-01 12:00	00:57:21.54	+30:23:36.8	HIP 4531	9.82
2026-06-02 00:00	00:57:25.74	+30:25:18.1	HIP 4531	10.03