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Glossary term: 光譜類型

Description: 恆星根據其光譜中的特徵被劃分為不同的光譜類型。

對於大多數恆星來說,光譜類型主要基於恆星表面的溫度,按照溫度從高到低的順序依次為:O、B、A、F、G、K 和 M。這個序列最近擴展到了更冷的類型L、T和Y。這三種類型主要代表褐矮星,但一些光譜類型為 L 的天體是恆星,而不是褐矮星。

還有一些字母也被用來劃分特殊類型的恆星。碳星是光譜中具有強烈含碳分子特徵的恆星。它們被稱為C型。S型恆星介於K或M型和C型之間,其表面氧和碳的丰度幾乎相等。白矮星根據其光譜特徵分為一系列不同類型;所有這些類型都以字母 D 開頭(DA、DB 等)。具有寬發射線的大質量高溫恆星被分為一系列以 W 開頭的類型(WN、WC、WO)。

目前的命名法源於哈佛大學天文臺的第一次現代分類嘗試。最初的類別按字母順序標記為 A-Q,後來按溫度序列重新排序,形成了今天仍在使用的主要類型。主要的光譜類別又被進一步細分,由從 0 到 9 的數字表示。太陽的光譜類型為 G2。附加字母被用於表示特殊特徵(如 e 表示具有明亮發射線的恆星),光度等級也可以用羅馬數字表示。

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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

This is an automated transliteration of the simplified Chinese translation of this term

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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 姓名標示 4.0 國際 (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 姓名標示 4.0 國際 (CC BY 4.0) icons