According to Wikipedia, (sample shown below), the lower the number, the hotter and more massive the star, but absorption lines are not included. The calibration of the colour index scale means that a star of spectral class A0 and luminosity class V (ie a main sequence star) has a colour index of 0.0. Its not the closest star, but is one of the closest. I Star Radius & Mass from Spectral Class, B-V, Luminosity. (b) radius. spectral type or spectral class. The spectral class of a star is related to its: (a) luminosity. Then looking at the second image, we can see that different spectral types have different absorption lines. This brightness, or flux is related to the amount of light emitted by the source, the true luminosity, by flux or brightness = f = L / (4 π D 2) where D in this equation is the distance to the object. The seven main types are M, K, G, F, A, B and O. M stars are the coldest stars and O stars are the hottest. Eugene R. Zizka. When you observe a star with a telescope, you are actually measuring its brightness, not its luminosity. 8 - An 08 V star has an apparent magnitude of +1. On it, astronomers plot stars' color, temperature, luminosity, spectral type, and evolutionary stage. The word 'luminosity' is used because the more luminous a star is, the larger its size has to be. d. distance. radius d . An A-type main-sequence star (A V) or A dwarf star is a main-sequence (hydrogen-burning) star of spectral type A and luminosity class V. These stars have spectra which are defined by strong hydrogen Balmer absorption lines. The star's luminosity depends on: Definition. the star's mass, the star's temperature, the star's color, and the star's radius: Term . For instance, the hottest stars in class A are A0, and then A1, A2, etc all the way to A9, the coolest A type star. Stars hotter than Vega will have a negative colour index and appear more bluish. Sirius A is the brightest star in the sky after our sun. Figure 1 illustrates the approximate position of stars of various luminosity classes on the H–R diagram. From the vertical axis at the right, we get the intrinsic brightness (luminosity) of the star when compared to the Sun. The hotter a star, the brighter its surface. Stars are also grouped into spectral types or classes by color. where d is the distance to the star. Astronomers use the patterns of lines observed in stellar spectra to sort stars into a spectral class. e. None of these . Because a star’s temperature determines which absorption lines are present in its spectrum, these spectral classes are a measure of its surface temperature. Based on the position of a star on the H-R diagram, we can find out its luminosity, color, and spectral class. Question Get Answer. Related to spectral types: HR diagram. 8 - To which spectral classes do the stars in Problem... Ch. (c) temperature. (a) air resistance (b) electromagnetic (c) friction (d) gravity 5. A diagram of spectral types with information on temperature, color and what elements and compounds show up in each spectral class. Spectral Energy Distribution of T Tauri stars. The spectral type of stars has an OBAFGKM class, along with a number, from 0 to 9. 13.6 - Understand how a star’s colour and spectral type are related to its surface temperature. The Hertzsprung-Russell diagram uniquely describes: Definition. Last Post; Apr 28, 2016; Replies 4 Views 2K. There is a fair amount of scatter around the main sequence so it is likely that some stars a few spectral subtypes away may have absolute magnitudes near zero. 8 - If a star has an apparent magnitude equal to its... Ch. The temperature of each spectral class is then further subdivided from hot to cool by the simple addition of a number, where 0 is the hottest and 9 the coolest. What force holds planets in their orbits? Select one: a. temperature. Magnitude. A G2V Main Sequence Star. The luminosity class of the star pins down the vertical position of the star on the HR Diagram. c. mass. Astrophysicists classify stars according to 7 main spectral classes (0 - blue, B - bluish-white, A - white, F - white-yellow, G - yellow, K - orange, M - red). 8 - If a main-sequence star has a luminosity of 400... Ch. Each class is subdivided into 10 subclasses, numbered from 0 to 9 (our Sun is a G2 star with characteristics part-way between G and F). Add a few letters and numbers like " G 2V" or " B 5IV-Vshnne" and the star suddenly gains personality and character. Also, the color of the star is directly related to its surface temperature, beginning from red, to orange, to yellow, to yellow-white, to white, to blue-white, and then to blue. Last Post; Apr 9, … To discriminate between a giant and a dwarf star of the same spectral class astronomers use: Definition. Note that the table there only covers the main sequence, it does not cover other luminosity classes that may also fall into this range, e.g. There are seven standard spectral classes. Spectral class is used as a method of categorizing stars. By analysing their spectral lines, we can understand what they are made of and their temperature. Use... Ch. (c) star B (d) not enough information 24. The average density of a star is its mass divided by volume. The dashed portions of the lines represent regions with very few or no stars. Last Post; Jan 24, 2010; Replies 8 Views 2K. Uploaded by: cpulley. But when a star starts to die, its spectral class and luminosity changes. The full spectral specification of a star includes its luminosity class. Classification of stars by spectral lines Spectral differences mostly due to Temperature, ... received. The most important classification (Harvard classification) has a series of classes O, B, A, F, G, K, M, the series also being a scale of diminishing surface temperature. 8 - terrnine the temperatures of the following stars... Ch. Ch. The Hertzsprung -Russell (H-R) Diagram is a graph that plots stars color (spectral type or surface temperature) vs. its luminosity (intrinsic brightness or absolute magnitude). The actual mass of a star and its age can play a huge difference in the surface temperature of a star, but the spectral type and color of a star are dependent solely on its surface temperature. Previous question Next question Get more help from Chegg. Temperature B. Radius C. Mass D. Distance E. None Of These . The temperature of the stars decreases from blue (very hot) to red (less hot). Since more massive stars use their fusion fuel more quickly than smaller ones, Vega's main-sequence lifetime is roughly one billion years, a tenth of the Sun's. Without its spectral type a star is a meaningless dot. 22. The spectral class of a star is related to its : luminosity b . (a) star A (b) The two stars are the same distance. The star’s spectral type, A0mA1 Va, indicates that Sirius A would have the classification A1 based on its hydrogen and helium lines, but it would belong to the spectral class A0 based on the absorption lines of metals. The Sun is a class G star; these are yellow, with surface temperatures of 5,000–6,000 K. Class K stars are yellow to orange, at about 3,500–5,000 K, and M stars are red, at about 3,000 K, with titanium oxide prominent in their spectra. It’s important to specify the luminosity class and the spectral class for a star, as a K5 star could be a main sequence, gaint, or super giant. 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