“umbra”的概念、定义、翻译、参考文献-科学参考

umbra

Physics

See shadow.

Astronomy

1. The conical inner region of shadow cast by a planet or satellite, from within which the Sun’s disk is completely obscured. Passage of a body through this shadow results in its eclipse as, for example, when the Moon traverses Earth’s umbra. The dark umbra is surrounded by a broader penumbra (1) in which the Sun’s disk is only partially obscured.

2. The central, darkest part of a sunspot. It is also the coolest part, with a temperature of about 4200 K, and an intense magnetic field (about 0.4 tesla). Umbrae are not uniformly dark but contain light umbral dots and light bridges. The dots are smaller versions of photospheric granules, only about 300 km across, and last somewhat longer than granules, up to 25 min. They seem to be penumbral grains that have just entered the umbra. The umbra accounts for about 30% of a spot’s surface area.

Space Exploration

The central region of a shadow that is totally dark because no light reaches it, and from which no part of the light source can be seen (compare penumbra). In astronomy, it is a region of the Earth from which a complete eclipse of the Sun can be seen.

单词	umbra
释义	umbra Physics See shadow. Astronomy 1. The conical inner region of shadow cast by a planet or satellite, from within which the Sun’s disk is completely obscured. Passage of a body through this shadow results in its eclipse as, for example, when the Moon traverses Earth’s umbra. The dark umbra is surrounded by a broader penumbra (1) in which the Sun’s disk is only partially obscured. 2. The central, darkest part of a sunspot. It is also the coolest part, with a temperature of about 4200 K, and an intense magnetic field (about 0.4 tesla). Umbrae are not uniformly dark but contain light umbral dots and light bridges. The dots are smaller versions of photospheric granules, only about 300 km across, and last somewhat longer than granules, up to 25 min. They seem to be penumbral grains that have just entered the umbra. The umbra accounts for about 30% of a spot’s surface area. Space Exploration The central region of a shadow that is totally dark because no light reaches it, and from which no part of the light source can be seen (compare penumbra). In astronomy, it is a region of the Earth from which a complete eclipse of the Sun can be seen.
随便看	k‐simplex K–Ar method K–T boundary L L2TP label labelling labelling algorithm labes labia labile labium laboratory Labor Party((Australia)) labour labour-augmenting technical progress labour economics Labourers, Statute of (1351) labour force Labour Force Survey labour, geographies of labour hoarding labour intensity labour market Labour Party((Britain))