45 Questions
What is the minimum core mass required to form a neutron star?
1.44M☉
What is the significance of a star's position on the Hertzsprung-Russell diagram?
It can be used to determine the star's spectral class
What is the energy released when an electron moves from a higher energy state to a lower energy state?
A photon with a specific wavelength
What is the minimum core mass required to form a black hole?
3M☉
What is the characteristic of energy levels of electrons in an atom?
Discrete and negative
What is required for an electron to move from a lower energy state to a higher energy state?
External energy input, e.g. heat or absorption of a photon
What is the significance of the negative sign in the energy of an electron in an atom?
The negative sign represents the energy required to remove the electron from the atom.
What is the characteristic of an emission line spectrum that makes it unique to each element?
Each element produces a unique emission line spectrum due to the unique set of energy levels associated with its electrons.
What is the difference between emission and absorption line spectra?
Emission line spectra appear as a series of coloured lines, while absorption line spectra appear as a series of dark lines against a continuous spectrum.
What is the formula that relates the energy of a photon to its wavelength, and what do the variables represent?
The formula is E = hc/λ, where E is the energy, h is the Planck constant, c is the speed of light, and λ is the wavelength of the photon.
What is the relationship between the energy levels of an electron and the wavelength of the photon it releases when de-excited?
The energy released is the difference between the initial energy level of the electron and the final energy level of the photon, and this energy corresponds to a specific wavelength.
What is the significance of the energy levels of an electron in producing different wavelengths of light?
Transitions between different energy levels produce photons with different wavelengths.
What is the relationship between the peak wavelength of a black body radiator and its temperature, according to Wien's law?
The peak wavelength is inversely proportional to the temperature of the object.
What is the formula for Wien's law, relating the peak wavelength of a black body radiator to its temperature?
λmax ∝ 1 / T, or λmax T = 2.9 x 10^(-3) mK
What is the relationship between the luminosity of a star and its temperature, according to Stefan's law?
The luminosity is proportional to the fourth power of its absolute temperature.
What is the formula for Stefan's law, relating the luminosity of a star to its temperature and radius?
L ∝ 4πr^2 T^4, or L = 4πr^2 T^4 σ (where σ is Stefan's constant, 5.67 x 10^(-8) Wm^-2 K^-4)
What is the importance of using absolute temperatures in Kelvin when applying Wien's law and Stefan's law?
It is essential to use absolute temperatures in Kelvin to avoid errors in the calculations, as the temperatures are often given in Centigrade.
What information can be determined about a star if its color and luminosity are known?
The absolute temperature and radius of the star can be determined using Wien's law and Stefan's law.
What is the significance of the Doppler Effect in the context of star light?
The Doppler Effect shifts the position of spectral lines, allowing us to determine the relative speed of a star using the shift in wavelength from a hydrogen emission spectrum.
How does the Doppler equation relate to the velocity of a star?
The Doppler equation (∆𝜆 𝑣 = 𝜆 𝑐) is used to determine the relative speed of a star using the shift in wavelength from a hydrogen emission spectrum.
What is the relationship between the recessional velocity of a galaxy and its distance from Earth according to Hubble's law?
The recessional velocity of a galaxy is proportional to its distance from Earth, as described by the equation 𝑉 = 𝐻+ 𝑑.
What is the implication of the redshift of light from distant galaxies?
The redshift of light from distant galaxies suggests that the galaxies are moving away from Earth, providing evidence for the expanding universe model.
What is the role of the Hubble constant in understanding the expansion of the universe?
The Hubble constant (67.8 kms-1Mpc-1) is a key factor in the equation 𝑉 = 𝐻+ 𝑑, describing the relationship between the recessional velocity of a galaxy and its distance from Earth.
What is the general implication of the expanding universe model?
The expanding universe model suggests that the fabric of space and time is expanding, and any point in the universe is moving away from any other point.
What is the relationship between the distance of a galaxy from Earth and its speed, according to Hubble's law?
The distance of a galaxy from Earth is directly proportional to its speed.
What is the approximate age of the universe, as estimated using Hubble's law?
14 billion years
What is the Big Bang theory, and what was the initial state of the universe according to this theory?
The Big Bang theory is an attempt to describe the origins and development of the early universe. According to this theory, all objects were initially contained in a singularity, which suddenly expanded outwards.
What are the two key pieces of evidence that support the Big Bang theory?
Hubble's Law, which shows the universe is expanding, and the microwave background radiation
Why is the Big Bang theory not considered a reliable scientific theory, despite the evidence that supports it?
The Big Bang theory is not considered a reliable scientific theory because there is no experimental evidence to support it - we cannot recreate the initial conditions of the Big Bang.
What is the significance of the microwave background radiation in the context of the Big Bang theory?
The microwave background radiation is thought to be a remnant of the initial high-energy gamma photons, which were stretched into the microwave region as the universe expanded.
What is the main component of a nebula?
Gigantic clouds of dust and gas
What is the characteristic shape of a planet?
Spherical
What is the typical orbit of a comet around the sun?
Eccentric elliptical
What is the approximate number of stars in a typical galaxy?
100 billion
What is the result of the gravitational collapse of dust and gas particles in a nebula?
A protostar
What happens when the remaining core mass of a star is greater than 1.44M☉?
Protons and electrons combine to form neutrons, producing a dense neutron star.
What is the significance of the Hertzsprung-Russell diagram in understanding stars?
It shows the stellar luminosity of a star against its temperature, allowing us to determine the star's spectral class.
What happens when an electron moves from a lower energy state to a higher energy state in an atom?
It becomes 'excited' and requires the input of external energy, such as heat or absorption of a photon.
What is the characteristic of energy levels of electrons in an atom?
They are discrete and negative, with the ground state being the most negative.
What happens when an electron is de-excited in an atom?
It releases energy in the form of a photon with a specific wavelength.
What is the process that occurs when hydrogen gas nuclei in a protostar overcome the electrostatic forces of repulsion?
Nuclear fusion
What is the main phase of a star, and what maintains its stability during this phase?
The main phase is when a star remains in stable equilibrium, maintained by the balance between gravitational forces and radiation pressure from photons and gas pressure from nuclei in the core.
What determines the length of a star's main phase?
The mass of the star, with larger stars being hotter and undergoing fusion faster, resulting in a shorter main phase.
What happens to a low-mass star once its hydrogen supplies are low?
The star begins to collapse inwards and evolves into a red giant.
What is the mass range of a low-mass star's core?
Between 0.5M and 10M, where M is the solar mass (1.99 x 10^30 kg).
Explore the final stages of a star's life, including the formation of neutron stars and black holes, and understand how the Hertzsprung-Russell diagram relates to a star's luminosity and temperature. Test your knowledge of stellar evolution and its remnants.
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