Spectral classification of stars
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This document discusses how the spectral classification of stars can reveal information about their composition and temperature. It explains that stars are classified into seven main categories (O, B, A, F, G, K, M) based on their absorption spectra, with O being the hottest and M being the coolest. Each class is associated with a range of surface temperatures and colors. By analyzing a star's spectrum, astronomers can determine what chemical elements are present in its atmosphere and measure its temperature, allowing insights into its composition and properties.
Spectral classification of stars
- 1. SHOBANA.N.S QUEEN MARY’SCOLLEGE FOR WOMEN1
- 2. What is a spectra? What is an absorption spectrum ? Can we see what stars are made up of ? Can we measure how hot they are ? 2
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- 5. For the other two questions the answer is : Yes we can !!! Using spectral classification of the stars. 5
- 6. Surface temperature of the star is associated with specific spectral classification. The spectral classification includes 7 main types: O, B, A, F, G, K, M. 6
- 7. This is called “Morgan-Keenan spectral classification” The classes, listed from hottest to coldest Class Temperature Star Color O 30,000 – 60,000 °K Blue B 10,000 – 30,000 °K Blue A 7,500 - 10,000 °K White F 6,000 - 7,500 °K White (yellowish) G 5,000 - 6,000 °K Yellow (like the Sun) K 3,500 - 5,000 °K Orange M 2,000 - 3,500 °K Red 7
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- 9. Notice that hottest stars are blue, while coldest stars are red. 9
- 10. Naos (in the constellation Puppis) These have prominent ionized and neutral helium lines and only weak hydrogen lines. Class O stars emit most of their radiation in ultra-violet. 10
- 11. Class B stars are again very luminous Rigel (in the great constellation Orion) is a prominent B class blue supergiant. Their spectra have neutral helium and moderate hydrogen lines. 11
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- 13. Class A stars are amongst the more common naked eye stars. Deneb in Cygnus is another very powerful star. Sirius, that appears the brightest star as seen from Earth, is also an A class star. As with all class A stars, they are white. Many white dwarfs are also A.They have strong hydrogen lines and also ionized metals. 13
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- 16. Class F stars are still quite powerful.. Fomalhaut in Pisces Australis. Their spectra is characterized by the weaker hydrogen lines and ionized metals, their color is white with a slight tinge of yellow. 16
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- 18. Class G stars are probably the most well known for the reason that our Sun is of this class. They have even weaker hydrogen lines than F and have neutral helium lines but along with the ionized metals, they have neutral metals. 18
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- 20. Class K are orange stars which are slightly cooler than our Sun. Some K stars are giants and supergiants, such as Arcturus, while others like Alpha Centauri B are smaller. They have extremely weak hydrogen lines, if they are present at all, and mostly neutral metals. 20
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- 22. Class M is the most common class by the number of stars. All red dwarfs, such Proxima Centauri, the closest star to our Solar System The spectrum of an M star shows lines belonging to molecules and neutral metals but hydrogen is usually absent. Titanium oxide can be strong in M stars. 22
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- 24. M stars may be dwarf stars or supergiant stars, and A stars can be white dwarfs or white giants as well. This can be understood through the Hertzsprung-Russell diagram, that is very important in astrophysics and relates temperature and spectral classification of stars with their luminosity and size. A number of other spectral types have been taken into use for rare types of stars: these areW, L,T, S, and C (that includes R and N). 24
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