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Glossary term: 光谱类型

Description: 恒星根据其光谱中的特征被划分为不同的光谱类型。

对于大多数恒星来说,光谱类型主要基于恒星表面的温度,按照温度从高到低的顺序依次为:O、B、A、F、G、K 和 M。这个序列最近扩展到了更冷的类型L、T和Y。这三种类型主要代表褐矮星,但一些光谱类型为 L 的天体是恒星,而不是褐矮星。

还有一些字母也被用来划分特殊类型的恒星。碳星是光谱中具有强烈含碳分子特征的恒星。它们被称为C型。S型恒星介于K或M型和C型之间,其表面氧和碳的丰度几乎相等。白矮星根据其光谱特征分为一系列不同类型;所有这些类型都以字母 D 开头(DA、DB 等)。具有宽发射线的大质量高温恒星被分为一系列以 W 开头的类型(WN、WC、WO)。

目前的命名法源于哈佛大学天文台的第一次现代分类尝试。最初的类别按字母顺序标记为 A-Q,后来按温度序列重新排序,形成了今天仍在使用的主要类型。主要的光谱类别又被进一步细分,由从 0 到 9 的数字表示。太阳的光谱类型为 G2。附加字母被用于表示特殊特征(如 e 表示具有明亮发射线的恒星),光度等级也可以用罗马数字表示。

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Term and definition status: The original definition of this term in English have been approved by a research astronomer and a teacher
The translation of this term and its definition is still awaiting approval

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Related Diagrams


Seven lines. The peak of each line moves from short wavelengths for the top line to longer wavelengths for the bottom line.

Stellar spectral types

Caption: The spectra of seven stars ordered by spectral type ranging from the hottest (O-type) at the top to the coolest (M-type at the bottom). The x-axis shows the wavelength of light and the y-axis is a measure of the flux of light received at that wavelength. Each spectrum is normalized (the flux at each wavelength is divided by the maximum flux in that spectrum) and the spectra are then offset from each other along the y-axis to make the plot easier to view. The colour of the lines between 400 nm and 700 nm roughly corresponds to the colour the human eye would see light of that wavelength. Below 400 nm and above 700 nm, where the human eye can see little to no light, the lines are coloured blue and red respectively. The hotter stars have more of their flux at the bluer end of the spectrum and the cooler stars have more of their flux at the redder end. However the total amount of flux a star emits depends on its size and temperature. Due to this, a hot star will emit more red light than a cool star of the same size even if the cool star emits almost all its light in red light but this is not visible in this plot due to the normalization mentioned above. The sharp, narrow drops in the spectra are absorption lines caused by atoms and ions in the stars’ atmospheres. The strength of a spectral line depends on the temperature of a star’s atmosphere. Take the hydrogen line at 656.5 nm as an example. All of the stars in this plot are primarily made of hydrogen, but the 656.5 nm hydrogen line is weak for the hottest and coolest stars but strongest for spectral types A and F. This is because hydrogen absorbs more light at 656.5 nm at the temperatures of A and F stars’ atmospheres than in hotter or cooler stars. The coolest star here, the M-type star, has wide absorption bands in its spectra. This is because this star is cool enough to have compounds such as titanium oxide in its atmosphere. These compounds, often called molecules in astronomy, produce wider spectral absorption features than atoms or ions.
Credit: IAU OAE/SDSS/Niall Deacon

License: CC-BY-4.0 Creative Commons 署名 4.0 国际 (CC BY 4.0) icons


Seven bands with bright and dark patches. The brightest part of the band moves from blue in the top band to red at the bottom

Stellar spectral types - bands

Caption: The spectra of seven stars ordered by spectral type ranging from the hottest (O-type) at the top to the coolest (M-type at the bottom). The x-axis shows the wavelength of light while the brightness or darkness at each wavelength corresponds to the flux of light received from the star at that wavelength with darker patches having less flux and brighter patches more. Each spectrum is normalized (the flux at each wavelength is divided by the maximum flux for that spectrum) so that the maximum flux should appear with the same brightness for all the spectra. The colour plotted between 400 nm and 700 nm roughly corresponds to the color the human eye would see light of that wavelength. Below 400 nm and above 700 nm, where the human eye can see little to no light, the lines are coloured blue and red respectively. The hotter stars have more of their flux at the bluer end of the spectrum and the cooler stars have more of their flux at the redder end. However the total amount of flux a star emits depends on its size and temperature. Due to this, a hot star will emit more red light than a cool star of the same size even if the cool star emits almost all its light in red light but this is not visible in this plot due to the normalization mentioned above. The dark, narrow patches in the spectra are absorption lines caused by atoms and ions in the stars’ atmospheres. The strength of a spectral line depends on the temperature of a star’s atmosphere. Take the hydrogen line at 656.5 nm as an example. All of the stars in this plot are primarily made of hydrogen, but the 656.5 nm hydrogen line is weak for the hottest and coolest stars but strongest for spectral types A and F. This is because hydrogen absorbs more light at 656.5 nm at the temperatures of A and F stars’ atmospheres than in hotter or cooler stars. The coolest star here, the M-type star, has wide absorption bands in its spectra. This is because this star is cool enough to have compounds such as titanium oxide in its atmosphere. These compounds, often called molecules in astronomy, produce wider spectral absorption features than atoms or ions.
Credit: IAU OAE/SDSS/Niall Deacon

License: CC-BY-4.0 Creative Commons 署名 4.0 国际 (CC BY 4.0) icons