メタデータ
| 項目 |
値 |
| Designation |
C/1991 A2 (Arai) |
| Type |
C |
| Perihelion (tp_cal, UTC) |
1990-12-10T21:20:14.118720Z |
| Orbit solution date (soln_date, UTC) |
2021-04-15T23:29:38Z |
| Obs used |
110 |
| NEO |
- |
| M1 |
6.400 |
| K1 |
32.000 |
| PC |
- |
オスキュレーティング軌道要素
| 項目 |
値 |
| Epoch (epoch_cal, TDB) |
1991-01-21.0000000 |
| e |
0.99066384 |
| q (au) |
1.434192 |
| a (au) |
153.616954 |
| i (deg) |
70.980280 |
| Ω (om, deg) |
115.522769 |
| ω (w, deg) |
337.640099 |
| M (ma, deg) |
0.021282 |
等級
散乱 + 全体線形
$$
M_a = (8.566 + 5.072\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
モデル定数
| 項目 |
値 |
| H0 |
8.566 |
| n |
5.072 |
| gf |
1.000 |
| gb |
-0.993 |
| k |
1.000 |
| 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
天体暦
| Date/Time (UTC) |
RA (J2000) |
Dec (J2000) |
Nearest HIP |
Dist from HIP (arcmin) |
| 2026-09-20 00:00 |
18:31:50.15 |
+13:16:13.7 |
HIP 90777 |
10.49 |
| 2026-09-20 12:00 |
18:31:49.83 |
+13:15:54.4 |
HIP 90777 |
10.27 |
| 2026-09-21 00:00 |
18:31:49.54 |
+13:15:35.0 |
HIP 90777 |
10.05 |
| 2026-09-21 12:00 |
18:31:49.26 |
+13:15:15.7 |
HIP 90777 |
9.84 |
| 2026-09-22 00:00 |
18:31:49.00 |
+13:14:56.3 |
HIP 90777 |
9.65 |
| 2026-09-22 12:00 |
18:31:48.76 |
+13:14:37.0 |
HIP 90777 |
9.46 |
| 2026-09-23 00:00 |
18:31:48.54 |
+13:14:17.6 |
HIP 90777 |
9.29 |
| 2026-09-23 12:00 |
18:31:48.33 |
+13:13:58.2 |
HIP 90777 |
9.13 |
| 2026-09-24 00:00 |
18:31:48.15 |
+13:13:38.8 |
HIP 90777 |
8.99 |
| 2026-09-24 12:00 |
18:31:47.98 |
+13:13:19.5 |
HIP 90777 |
8.86 |
| 2026-09-25 00:00 |
18:31:47.83 |
+13:13:00.1 |
HIP 90777 |
8.74 |
| 2026-09-25 12:00 |
18:31:47.69 |
+13:12:40.7 |
HIP 90778 |
8.63 |
| 2026-09-26 00:00 |
18:31:47.58 |
+13:12:21.4 |
HIP 90778 |
8.54 |
| 2026-09-26 12:00 |
18:31:47.48 |
+13:12:02.0 |
HIP 90778 |
8.45 |
| 2026-09-27 00:00 |
18:31:47.41 |
+13:11:42.7 |
HIP 90778 |
8.39 |
| 2026-09-27 12:00 |
18:31:47.35 |
+13:11:23.3 |
HIP 90778 |
8.34 |
| 2026-09-28 00:00 |
18:31:47.30 |
+13:11:04.0 |
HIP 90778 |
8.31 |
| 2026-09-28 12:00 |
18:31:47.28 |
+13:10:44.6 |
HIP 90778 |
8.29 |
| 2026-09-29 00:00 |
18:31:47.27 |
+13:10:25.3 |
HIP 90778 |
8.29 |
| 2026-09-29 12:00 |
18:31:47.29 |
+13:10:06.0 |
HIP 90778 |
8.31 |
| 2026-09-30 00:00 |
18:31:47.32 |
+13:09:46.7 |
HIP 90778 |
8.35 |
| 2026-09-30 12:00 |
18:31:47.37 |
+13:09:27.4 |
HIP 90778 |
8.40 |
| 2026-10-01 00:00 |
18:31:47.43 |
+13:09:08.2 |
HIP 90778 |
8.47 |
| 2026-10-01 12:00 |
18:31:47.52 |
+13:08:48.9 |
HIP 90778 |
8.55 |
| 2026-10-02 00:00 |
18:31:47.62 |
+13:08:29.7 |
HIP 90778 |
8.65 |
| 2026-10-02 12:00 |
18:31:47.75 |
+13:08:10.5 |
HIP 90778 |
8.76 |
| 2026-10-03 00:00 |
18:31:47.89 |
+13:07:51.3 |
HIP 90778 |
8.89 |
| 2026-10-03 12:00 |
18:31:48.04 |
+13:07:32.1 |
HIP 90778 |
9.03 |
| 2026-10-04 00:00 |
18:31:48.22 |
+13:07:13.0 |
HIP 90778 |
9.19 |
| 2026-10-04 12:00 |
18:31:48.42 |
+13:06:53.9 |
HIP 90778 |
9.36 |
| 2026-10-05 00:00 |
18:31:48.63 |
+13:06:34.8 |
HIP 90778 |
9.53 |
| 2026-10-05 12:00 |
18:31:48.86 |
+13:06:15.7 |
HIP 90778 |
9.73 |
| 2026-10-06 00:00 |
18:31:49.11 |
+13:05:56.7 |
HIP 90778 |
9.93 |
| 2026-10-06 12:00 |
18:31:49.38 |
+13:05:37.7 |
HIP 90778 |
10.14 |
| 2026-10-07 00:00 |
18:31:49.66 |
+13:05:18.7 |
HIP 90778 |
10.36 |
| 2026-10-07 12:00 |
18:31:49.97 |
+13:04:59.7 |
HIP 90778 |
10.59 |
| 2026-10-08 00:00 |
18:31:50.29 |
+13:04:40.8 |
HIP 90778 |
10.82 |
| 2026-10-08 12:00 |
18:31:50.63 |
+13:04:22.0 |
HIP 90778 |
11.07 |
| 2026-10-09 00:00 |
18:31:50.99 |
+13:04:03.1 |
HIP 90778 |
11.32 |
| 2026-10-09 12:00 |
18:31:51.37 |
+13:03:44.4 |
HIP 90778 |
11.58 |
| 2026-10-10 00:00 |
18:31:51.76 |
+13:03:25.6 |
HIP 90778 |
11.84 |
| 2026-10-10 12:00 |
18:31:52.17 |
+13:03:06.9 |
HIP 90778 |
12.12 |
| 2026-10-11 00:00 |
18:31:52.61 |
+13:02:48.2 |
HIP 90778 |
12.39 |