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最後のシグマ・オリニス星団の恒星群の中で,若い,孤立した惑星質量天体の発見
M R Zapatero Osorio1, V J Béjar, E L Martín
1Instituto de Astrofísica de Canarias, E-38200 La Laguna, Tenerife, Spain.
まとめ
天文学者は,若いシグマ・オリニス星団で孤立した巨大惑星を発見した. 木星の質量に似ているこれらの自由浮遊天体は,惑星形成に関する現在の理論に挑戦しています.
科学分野:
- 天文学と天体物理学について
- エクソプラネット研究
- 恒星の進化について
背景:
- シグマ・オリニス星団は,近くの (352パーセック),若い (1〜5百万年) 恒星団である.
- その低い内部絶滅は,星下物体の明確な視点を提供します.
- 群集は複数の巨大な恒星を宿し,その環境に影響を与えています.
研究 の 目的:
- シグマ・オリオニス星団内の極低光度で孤立した天体を発見し,特徴づけること.
- ジュピター質量の数個まで星下領域を調査する.
- 惑星質量の天体の形成過程を調査する.
主な方法:
- 光学および近赤外線画像は,孤立した赤色の物体を特定するために使用されます.
- 低解像度のスペクトロスコーピーは,スペクトルエネルギー分布と大気温を測定します.
- 質量の推定は,スペクトル特性とクラスターメンバーシップに基づいています.
主要な成果:
- 極度に赤く,低明るさの孤立したオブジェクトの集団の発見.
- 非常に冷たい大気効果温度 (1700~2200 K) のスペクトル検査による確認.
- 3つのオブジェクトの推定質量は,木星の質量5〜15の範囲です.
結論:
- これらの天体は,孤立した巨大惑星の新種を代表し,どの恒星にも縛られていません.
- 数百万年以内に形成されたと思われる惑星は,既存の惑星形成モデルに異議を唱える.
- この発見は,惑星質量の物体が恒星群の中でどのように形成されるかを再評価することを必要としています.
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