彗星の異常な窒素同位体比は彗星に存在する
Claude Arpigny1, Emmanuël Jehin, Jean Manfroid
1Institut d'Astrophysique et de Géophysique, Sart-Tilman, Bâtiment B5c, B-4000 Liège, Belgium. Claude.Arpigny@ulg.ac.be
まとめ
高解像度スペクトルを用いて測定した彗星の窒素同位体比は,地球の比より低い. これは,彗星にはHCN以外にも他の窒素源,おそらく有機化合物が含まれていることを示唆しています.
科学分野:
- 天文学と天体物理学について
- 惑星科学 惑星科学
- スペクトロスコーピーは,スペクトロスコーピーを用います.
背景:
- 彗星の構成は,初期の太陽系についての洞察を提供します.
- 彗星の同位体比は,彗星の起源と化学的進化を明らかにすることができます.
- CN分子は,彗星昏睡における一般的なトレーサーである.
研究 の 目的:
- 彗星C/1995 O1 (ヘイル・ボップ) とC/2000 WM1 (LINEAR) の炭素 (12C/13C) と窒素 (14N/15N) の同位体比を決定する.
- 彗星の同位体組成の潜在的な異常を,地上の値と比較して調査する.
- 彗星におけるCN根の潜在的な親分子を特定するために.
主な方法:
- 390 nmのCN B2+-X2+ (0,0) バンドの高解像度スペクトルスコピー.
- 12C/13Cと14N/15Nの同位体比を導き出すために,スペクトルデータを分析する.
- 彗星の同位体比を地上の基準と比較し,他の彗星測定結果.
主要な成果:
- ヘイル・ボップとLINEARの測定された12C/13C比は,それぞれ165 +/- 40と115 +/- 20でした.
- ヘイル・ボップとLINEARで測定された14N/15N比率は,それぞれ140 +/- 35と140 +/- 30でした.
- 測定された14N/15N比率は,HCNからのヘイルボップの地上値 (272) および以前に報告された比率より大幅に低い.
結論:
- 異常な窒素同位体比は,これらの彗星のCNは,HCN以外の親分子から由来することを示唆しています.
- 14N/15N比率がさらに低い親分子の存在が示されています.
- 惑星間塵の粒子で見つかったものと同様の有機化合物は,これらの代替のCN親種のための妥当な候補である.
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