メタデータ
| 項目 |
値 |
| Designation |
C/2021 A2 (NEOWISE) |
| Type |
C |
| Perihelion (tp_cal, UTC) |
2021-01-22T15:13:06.119040Z |
| Orbit solution date (soln_date, UTC) |
2025-01-02T20:12:26Z |
| Obs used |
980 |
| NEO |
- |
| M1 |
15.000 |
| K1 |
4.500 |
| PC |
- |
| Discovery observation (MPC, UTC) |
2021-01-03T00:31:00.192000Z |
| Discovery magnitude (MPC) |
15.00 R |
| Discovery observatory (MPC) |
C51 · WISE |
オスキュレーティング軌道要素
| 項目 |
値 |
| Epoch (epoch_cal, TDB) |
2021-02-20.0000000 |
| e |
0.99451672 |
| q (au) |
1.412974 |
| a (au) |
257.687917 |
| i (deg) |
106.978275 |
| Ω (om, deg) |
125.238283 |
| ω (w, deg) |
338.849015 |
| M (ma, deg) |
0.006759 |
等級
散乱 + 全体線形
$$
M_a = (14.158 + 2.000\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
モデル定数
| 項目 |
値 |
| H0 |
14.158 |
| n |
2.000 |
| gf |
1.000 |
| gb |
-1.000 |
| k |
0.991 |
| 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 |
| 2021-01-23 |
2021-05-09 |
+4.2062 |
-1.270 |
log10 r = log10(太陽距離/AU)、Δ = 地球距離(AU)
天体暦
| Date/Time (UTC) |
RA (J2000) |
Dec (J2000) |
Nearest HIP |
Dist from HIP (arcmin) |
| 2026-09-25 00:00 |
20:27:58.52 |
+36:54:42.3 |
HIP 101118 |
22.21 |
| 2026-09-25 12:00 |
20:27:53.91 |
+36:53:04.3 |
HIP 100826 |
23.37 |
| 2026-09-26 00:00 |
20:27:49.37 |
+36:51:26.0 |
HIP 100826 |
21.54 |
| 2026-09-26 12:00 |
20:27:44.89 |
+36:49:47.5 |
HIP 100826 |
19.72 |
| 2026-09-27 00:00 |
20:27:40.50 |
+36:48:08.7 |
HIP 100826 |
17.92 |
| 2026-09-27 12:00 |
20:27:36.17 |
+36:46:29.8 |
HIP 100826 |
16.14 |
| 2026-09-28 00:00 |
20:27:31.91 |
+36:44:50.5 |
HIP 100826 |
14.39 |
| 2026-09-28 12:00 |
20:27:27.73 |
+36:43:11.1 |
HIP 100826 |
12.68 |
| 2026-09-29 00:00 |
20:27:23.62 |
+36:41:31.5 |
HIP 100826 |
11.03 |
| 2026-09-29 12:00 |
20:27:19.58 |
+36:39:51.6 |
HIP 100826 |
9.47 |
| 2026-09-30 00:00 |
20:27:15.62 |
+36:38:11.6 |
HIP 100826 |
8.03 |
| 2026-09-30 12:00 |
20:27:11.73 |
+36:36:31.4 |
HIP 100826 |
6.82 |
| 2026-10-01 00:00 |
20:27:07.91 |
+36:34:51.0 |
HIP 100826 |
5.96 |
| 2026-10-01 12:00 |
20:27:04.16 |
+36:33:10.4 |
HIP 100826 |
5.60 |
| 2026-10-02 00:00 |
20:27:00.49 |
+36:31:29.7 |
HIP 100826 |
5.84 |
| 2026-10-02 12:00 |
20:26:56.90 |
+36:29:48.8 |
HIP 100826 |
6.61 |
| 2026-10-03 00:00 |
20:26:53.38 |
+36:28:07.7 |
HIP 100826 |
7.76 |
| 2026-10-03 12:00 |
20:26:49.93 |
+36:26:26.5 |
HIP 100826 |
9.13 |
| 2026-10-04 00:00 |
20:26:46.55 |
+36:24:45.2 |
HIP 100826 |
10.65 |
| 2026-10-04 12:00 |
20:26:43.26 |
+36:23:03.7 |
HIP 100826 |
12.25 |
| 2026-10-05 00:00 |
20:26:40.03 |
+36:21:22.1 |
HIP 100826 |
13.91 |
| 2026-10-05 12:00 |
20:26:36.89 |
+36:19:40.4 |
HIP 100826 |
15.60 |
| 2026-10-06 00:00 |
20:26:33.81 |
+36:17:58.7 |
HIP 100826 |
17.32 |
| 2026-10-06 12:00 |
20:26:30.82 |
+36:16:16.8 |
HIP 100826 |
19.05 |
| 2026-10-07 00:00 |
20:26:27.89 |
+36:14:34.8 |
HIP 100826 |
20.80 |
| 2026-10-07 12:00 |
20:26:25.05 |
+36:12:52.7 |
HIP 100826 |
22.55 |
| 2026-10-08 00:00 |
20:26:22.28 |
+36:11:10.6 |
HIP 100777 |
22.91 |
| 2026-10-08 12:00 |
20:26:19.59 |
+36:09:28.4 |
HIP 100777 |
21.14 |
| 2026-10-09 00:00 |
20:26:16.97 |
+36:07:46.1 |
HIP 100777 |
19.37 |
| 2026-10-09 12:00 |
20:26:14.43 |
+36:06:03.8 |
HIP 100777 |
17.60 |
| 2026-10-10 00:00 |
20:26:11.96 |
+36:04:21.4 |
HIP 100777 |
15.84 |
| 2026-10-10 12:00 |
20:26:09.58 |
+36:02:39.1 |
HIP 100777 |
14.08 |
| 2026-10-11 00:00 |
20:26:07.26 |
+36:00:56.6 |
HIP 100777 |
12.34 |
| 2026-10-11 12:00 |
20:26:05.03 |
+35:59:14.2 |
HIP 100777 |
10.59 |
| 2026-10-12 00:00 |
20:26:02.87 |
+35:57:31.8 |
HIP 100777 |
8.86 |
| 2026-10-12 12:00 |
20:26:00.79 |
+35:55:49.3 |
HIP 100777 |
7.15 |
| 2026-10-13 00:00 |
20:25:58.79 |
+35:54:06.9 |
HIP 100777 |
5.46 |
| 2026-10-13 12:00 |
20:25:56.86 |
+35:52:24.5 |
HIP 100777 |
3.82 |
| 2026-10-14 00:00 |
20:25:55.01 |
+35:50:42.1 |
HIP 100777 |
2.36 |
| 2026-10-14 12:00 |
20:25:53.23 |
+35:48:59.8 |
HIP 100777 |
1.60 |
| 2026-10-15 00:00 |
20:25:51.53 |
+35:47:17.4 |
HIP 100777 |
2.36 |
| 2026-10-15 12:00 |
20:25:49.91 |
+35:45:35.2 |
HIP 100777 |
3.82 |
| 2026-10-16 00:00 |
20:25:48.37 |
+35:43:52.9 |
HIP 100777 |
5.43 |