E.5 Fusion and stars Flashcards
What is the equilibrium that allows stars to maintain their stability?
Stars maintain stability through the equilibrium between gravitational forces pulling inwards and radiation pressure pushing outwards. This balance prevents the star from collapsing.
What is nuclear fusion in stars?
Nuclear fusion in stars is a process where two or more atomic nuclei combine to form a new, heavier nucleus, releasing a significant amount of energy. This process powers stars and produces the elements.
What are the main nuclear fusion processes in the Sun?
The main fusion processes in the Sun include the fusion of hydrogen nuclei, hydrogen with deuterium, and helium-3 with hydrogen, leading to the production of helium-4 and releasing energy.
What is the mass defect, and why is it important in nuclear fusion?
The mass defect refers to the difference in mass between the reactants and the products in a nuclear reaction. It’s crucial because the mass that “disappears” is converted into energy, as described by Einstein’s equation E=mc^2, and this energy is what powers the star.
What conditions are necessary for nuclear fusion to occur in stars?
For nuclear fusion to occur in stars, extremely high temperatures and pressures are necessary. These conditions bring nuclei close enough to overcome their electrostatic repulsion, allowing the strong nuclear force to bind them together.
What is the HR Diagram?
The Hertzsprung-Russell (HR) Diagram is a graphical tool that plots stars according to their luminosity (brightness) and temperature (color). It reveals patterns that help astronomers understand the life cycle and classification of stars.
What does the x-axis represent in the HR Diagram?
The x-axis of the HR Diagram represents the temperature of stars, organized from cooler (right) to hotter (left) temperatures, following a logarithmic scale.
How is luminosity plotted in the HR Diagram?
Luminosity in the HR Diagram is plotted on the y-axis, indicating the brightness of stars relative to the Sun, on a logarithmic scale. It shows how much energy a star emits compared to the Sun.
What are the main regions of the HR Diagram?
The main regions of the HR Diagram include the main sequence, where most stars, including the Sun, are found; the red giants and supergiants; and the white dwarfs.
How does the HR Diagram explain star evolution?
The HR Diagram helps astronomers understand star evolution by showing the transition of stars from one stage to another, such as from main sequence stars to red giants or white dwarfs, depending on their mass.
What equation is used to calculate the luminosity of a star based on its radius and temperature?
The Stefan-Boltzmann law is used to calculate the luminosity (L) of a star, where r is the radius, T is the temperature, and σ is the Stefan-Boltzmann constant
How can we determine the radius of a star using the HR diagram?
The HR diagram can determine a star’s radius by using its luminosity and temperature plotted on the diagram, with lines of constant radius helping to estimate the star’s size.
What does the Stefan-Boltzmann law relate to in terms of a star’s physical properties?
The Stefan-Boltzmann law relates a star’s luminosity to its surface area and temperature, indicating how the emitted energy (luminosity) is dependent on its radius and temperature.
What is the significance of the area formula A=4πr^2 in the context of stars?
This formula is significant as it represents the surface area through which a star emits its energy, directly influencing its luminosity and temperature in calculations.
What is the practical application of the Stefan-Boltzmann law in astrophysics?
It allows astronomers to calculate the radius of a star by knowing its luminosity and temperature, providing insight into the star’s size and the energy it emits.
How is the distance to a star calculated using parallax?
The distance to a star can be calculated using this formula, where d is the distance in parsecs and p is the parallax angle in arcseconds.
