|
NGC 2023 (also known as LBN 954) is a reflection nebula located in the constellation of Orion (The Hunter). Regarding infrared wavelengths, it is a heavy source of fluorescent molecular hydrogen emission,〔http://adsabs.harvard.edu/full/1998PASA...15..194B〕 and at 4 light-years wide, it is one of the largest reflection nebulae in the sky. It is powered by an extremely hot B-type star (B1.5), called HD 37903, the most luminous member of a cluster of young Herbig–Haro objects that illuminate the outermost material in the Lynds 1630 molecular cloud (Barnard 33) in Orion B. NGC 2023 forms a cavity in the surface of the cloud, some 450 parsecs from Earth. It produces a bright visual reflection nebula and an ultraviolet-excited photodissociation region. It is about a third of a degree from the Horsehead Nebula 〔http://www.fromquarkstoquasars.com/apotd-ngc-2023/〕 and is often included (but not labeled) in images of that object. Additionally, one of the defining features of NGC 2023 — the overtly bright streak often seen in the upper-left hand corner — is not a true feature. Instead, the flare is an artifact generated by Hubble’s optics.〔http://www.spacetelescope.org/images/potw1130a/〕 ==Gallery== File:NGC 2023 Hubble WikiSky.jpg|South part of NGC 2023 by HST, 3′ view 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「NGC 2023」の詳細全文を読む スポンサード リンク
|