Main sequence - Wikipedia
Make sure to label the axes, the main sequence, white dwarves, giants, and super Describe stars A, B, C, and D in terms of their brightness and temperature. Why was it so hard to prove that black holes exist? You can't see color, temperature, size, composition, and brightness . What kind of star is our sun? What do you need to know to classify a star as a main sequence star? What is the relationship between brightness and temperature shown within the main sequence?. The existence of a Main Sequence in an H-R Diagram indicates that for most stars, Recall that for a blackbody, the total intensity and temperature are related as follows: What if there exist stars whose sizes are three times larger than that of the Sun? What kind of temperature-luminosity relation might those stars have?.
In the Sun, a one solar-mass star, only 1. Stellar structure This diagram shows a cross-section of a Sun-like star, showing the internal structure. Because there is a temperature difference between the core and the surface, or photosphereenergy is transported outward. The two modes for transporting this energy are radiation and convection. A radiation zonewhere energy is transported by radiation, is stable against convection and there is very little mixing of the plasma.
By contrast, in a convection zone the energy is transported by bulk movement of plasma, with hotter material rising and cooler material descending. Convection is a more efficient mode for carrying energy than radiation, but it will only occur under conditions that create a steep temperature gradient.
Consequently, there is a high temperature gradient in the core region, which results in a convection zone for more efficient energy transport. The outer regions of a massive star transport energy by radiation, with little or no convection. This results in a steady buildup of a helium-rich core, surrounded by a hydrogen-rich outer region. By contrast, cool, very low-mass stars below 0.
Since it is the outflow of fusion-supplied energy that supports the higher layers of the star, the core is compressed, producing higher temperatures and pressures. Both factors increase the rate of fusion thus moving the equilibrium towards a smaller, denser, hotter core producing more energy whose increased outflow pushes the higher layers further out. Thus there is a steady increase in the luminosity and radius of the star over time. While this is probably a good starting point, since the Sun is the only stellar object for which we can measure a size, there's no reason all stars have to have the same size as the Sun.
What if there exist stars whose sizes are three times larger than that of the Sun? What kind of temperature-luminosity relation might those stars have?
Main Sequence Stars
Well, for a given temperature, a larger star will have a larger luminosity. Because while the temperature determines the intensity of the surface of the star, the larger star will have more surface area and therefore will radiate more luminosity, even if the temperatures and therefore the intensities of the two stars are the same you had a question on this in Problem Set 2 ; now you know why.
So we might expect that the blackbody model for larger stars might appear higher on the H-R Diagram than the line for Sun-sized stars. Likewise, the blackbody model for stars smaller than the Sun would appear lower on the H-R Diagram, since smaller stars have less surface area for radiating. And that's exactly what you get: All three model curves have the same slope, and this slope is not the slope of the Main Sequence, so individually, none of these models is going to fit the Main Sequence.
This says that stars on the Main Sequence aren't all of the same size, which when you think about it is just fine. After all, why should all stars be the same size anyway? Although these models individually don't match the Main Sequence, together they span much of the Main Sequence.
Stars and the Hertzsprung-Russell Diagram Teacher Sheet - Science NetLinks
That is, as long as you don't mind using different star sizes for different parts of the Main Sequence, we can explain all of the stars with a blackbody model where the temperature and star size increase together.
Low temperature Main Sequence stars can be best explained by our blackbody model if their sizes are also smaller than the Sun, and high temperature Main Sequence stars can be best explained if their sizes are also larger than the Sun.
Thus we can explain the apparent correlation between temperature and luminosity in the HR Diagram in terms of a blackbody model and another correlation -- the correlation between temperature and size -- for Main Sequence stars. In addition, we can also see that position on the H-R Diagram can tell us the size of the star; stars in the upper right are much larger than the Sun, and stars in the lower left are much smaller than the Sun. What star serves as a standard of comparison against which the luminosity of other stars is measured?
Sketch and label the HR Diagram. Make sure to label the axes, the main sequence, white dwarves, giants, and super giants. Students should sketch the HR Diagram, from the website: The class of star that corresponds to the color we observe from earth.
What are the four important things to note about the HR Diagram? Are blue stars hotter or cooler than red stars? If a star has a luminosity of ten thousand 10,how many times brighter is it than the sun?
How does the brightness of white dwarfs relate to that of the sun? White dwarfs are less bright than the sun. Part Two Describe the general trend between temperature and luminosity that the Main Sequence shows.