C/2021 A2 (NEOWISE)
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) |
| 2026-02-03 00:00 |
20:44:07.33 |
+34:19:47.8 |
HIP 102319 |
15.86 |
| 2026-02-03 12:00 |
20:44:16.14 |
+34:20:03.2 |
HIP 102319 |
16.56 |
| 2026-02-04 00:00 |
20:44:24.94 |
+34:20:19.3 |
HIP 102319 |
17.44 |
| 2026-02-04 12:00 |
20:44:33.72 |
+34:20:36.1 |
HIP 102319 |
18.46 |
| 2026-02-05 00:00 |
20:44:42.50 |
+34:20:53.7 |
HIP 102319 |
19.62 |
| 2026-02-05 12:00 |
20:44:51.26 |
+34:21:11.9 |
HIP 102319 |
20.88 |
| 2026-02-06 00:00 |
20:45:00.01 |
+34:21:30.9 |
HIP 102319 |
22.23 |
| 2026-02-06 12:00 |
20:45:08.74 |
+34:21:50.6 |
HIP 102549 |
22.97 |
| 2026-02-07 00:00 |
20:45:17.46 |
+34:22:11.0 |
HIP 102549 |
21.18 |
| 2026-02-07 12:00 |
20:45:26.17 |
+34:22:32.1 |
HIP 102549 |
19.39 |
| 2026-02-08 00:00 |
20:45:34.86 |
+34:22:53.9 |
HIP 102549 |
17.61 |
| 2026-02-08 12:00 |
20:45:43.53 |
+34:23:16.4 |
HIP 102549 |
15.84 |
| 2026-02-09 00:00 |
20:45:52.19 |
+34:23:39.6 |
HIP 102549 |
14.08 |
| 2026-02-09 12:00 |
20:46:00.83 |
+34:24:03.5 |
HIP 102549 |
12.34 |
| 2026-02-10 00:00 |
20:46:09.45 |
+34:24:28.1 |
HIP 102549 |
10.63 |
| 2026-02-10 12:00 |
20:46:18.05 |
+34:24:53.4 |
HIP 102549 |
8.95 |
| 2026-02-11 00:00 |
20:46:26.64 |
+34:25:19.4 |
HIP 102549 |
7.33 |
| 2026-02-11 12:00 |
20:46:35.21 |
+34:25:46.0 |
HIP 102549 |
5.84 |
| 2026-02-12 00:00 |
20:46:43.75 |
+34:26:13.4 |
HIP 102549 |
4.57 |
| 2026-02-12 12:00 |
20:46:52.28 |
+34:26:41.4 |
HIP 102549 |
3.78 |
| 2026-02-13 00:00 |
20:47:00.78 |
+34:27:10.1 |
HIP 102549 |
3.76 |
| 2026-02-13 12:00 |
20:47:09.27 |
+34:27:39.5 |
HIP 102549 |
4.53 |
| 2026-02-14 00:00 |
20:47:17.73 |
+34:28:09.5 |
HIP 102549 |
5.78 |
| 2026-02-14 12:00 |
20:47:26.17 |
+34:28:40.2 |
HIP 102571 |
6.99 |
| 2026-02-15 00:00 |
20:47:34.59 |
+34:29:11.6 |
HIP 102571 |
8.35 |
| 2026-02-15 12:00 |
20:47:42.98 |
+34:29:43.6 |
HIP 102571 |
9.86 |
| 2026-02-16 00:00 |
20:47:51.35 |
+34:30:16.3 |
HIP 102571 |
11.46 |
| 2026-02-16 12:00 |
20:47:59.70 |
+34:30:49.7 |
HIP 102560 |
12.89 |
| 2026-02-17 00:00 |
20:48:08.01 |
+34:31:23.7 |
HIP 102560 |
14.31 |
| 2026-02-17 12:00 |
20:48:16.31 |
+34:31:58.3 |
HIP 102560 |
15.80 |
| 2026-02-18 00:00 |
20:48:24.58 |
+34:32:33.6 |
HIP 102560 |
17.35 |
| 2026-02-18 12:00 |
20:48:32.82 |
+34:33:09.6 |
HIP 102560 |
18.93 |
| 2026-02-19 00:00 |
20:48:41.03 |
+34:33:46.2 |
HIP 102560 |
20.54 |
| 2026-02-19 12:00 |
20:48:49.21 |
+34:34:23.4 |
HIP 102560 |
22.17 |
| 2026-02-20 00:00 |
20:48:57.37 |
+34:35:01.2 |
HIP 102560 |
23.82 |
| 2026-02-20 12:00 |
20:49:05.50 |
+34:35:39.7 |
HIP 102910 |
24.65 |
| 2026-02-21 00:00 |
20:49:13.60 |
+34:36:18.8 |
HIP 102910 |
22.86 |
| 2026-02-21 12:00 |
20:49:21.67 |
+34:36:58.5 |
HIP 102910 |
21.08 |
| 2026-02-22 00:00 |
20:49:29.70 |
+34:37:38.8 |
HIP 102910 |
19.29 |
| 2026-02-22 12:00 |
20:49:37.71 |
+34:38:19.7 |
HIP 102910 |
17.51 |
| 2026-02-23 00:00 |
20:49:45.68 |
+34:39:01.2 |
HIP 102910 |
15.73 |
| 2026-02-23 12:00 |
20:49:53.63 |
+34:39:43.3 |
HIP 102910 |
13.95 |
| 2026-02-24 00:00 |
20:50:01.54 |
+34:40:26.0 |
HIP 102910 |
12.18 |