恒星間氷に凍結した分子水素のスペクトル顕微鏡検出

S A Sandford¹, L J Allamandola, T R Geballe

¹NASA/Ames Research Center, Moffett Field, CA 94035, USA.

Science (New York, N.Y.)

|October 15, 1993

まとめ

凍った分子水素とメタノールは,赤外線源 WL5.5 方向の氷に検出されました. この発見は,恒星間氷の組成と恒星形成領域の化学の洞察を提供します.

科学分野:

* アストロケミストリー
* 星間媒体の構成
* 赤外線スペクトロスコピーは,赤外線スペクトロスコピーを用います.

背景:

* rho Ophiuchus雲複合体は,恒星形成が活発な近くの地域である.
* 恒星間氷の組成を理解することは,宇宙における化学的進化を追跡する上で極めて重要です.
*赤外線スペクトロスコピーは,塵の粒子の氷のマントルの分子識別のための強力なツールです.

研究の目的:

* 赤外線源 WL5.5 方向の氷の分子種を特定し,特徴づけること.
* この視線に沿って凍った分子水素とメタノールの豊富さを決定します.
* 凍った分子水素と凍った一酸化炭素の濃度を比較する.

主な方法:

* WL5.5のスペクトルを観測するために,高解像度の赤外線スペクトロスコーピーを使用しました.
*スペクトルの吸収特性の分析により,分子種を特定することができました.
*検出された分子のコラム密度は,それらの吸収特性の強さから計算されました.

主要な成果:

* 凍った分子水素 (H2) に起因する 4141 cm−1 (2.415 μm) の弱い赤外線吸収特性が検出されました.
* 4125 cm−1 (2.424 μm) でより広範な吸収は,氷の中のメタノール (CH3OH) に起因する可能性がある.
*推論された列密度は,H2について約2.5 x 1018 cm−2で,CH3OHについて約3.0 x 1019 cm−2である.
*大量に冷凍された分子水素が発見され,冷凍された一酸化炭素の約3倍でした.

結論:

* 放射線で形成され,in situで凍結された分子水素は,WL5.5の方向に水分豊富な氷に存在します.
*メタノールもこれらの恒星間氷に含まれています.
* 凍ったH2がCOに比べて豊富に存在するため,原星の環境で氷の形成と処理に制約が生じます.

キーワード:

NASA Center ARCは,NASAセンターのARCとして運営されています.NASAの規律エキゾバイオロジー NASAの規範52-10号について

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