Star Evolution and Life Cycle

What is the term for the phase of a star's life where it fuses hydrogen into helium?

main phase

Why do larger stars have a shorter main phase than smaller stars?

because they undergo fusion faster, using up available hydrogen nuclei more quickly

What happens to a low-mass star once its hydrogen supplies are low?

it begins to collapse inwards and evolves into a red giant

What is the process that prevents a white dwarf star from collapsing further?

electron degeneracy pressure Signup and view all the answers

What is the maximum mass of a white dwarf star that is stable?

1.44M☉ (Chandrasekhar limit) Signup and view all the answers

What is the final stage of evolution for a low-mass star?

a white dwarf Signup and view all the answers

What is the process by which a red giant loses its outer layers, forming a planetary nebula?

the outer shells begin to drift off into space Signup and view all the answers

What is the temperature of a white dwarf star?

around 3000K Signup and view all the answers

How does the evolution of a massive star differ from that of a low-mass star?

it forms a red supergiant and fuses helium into heavier elements Signup and view all the answers

What is the significance of the negative sign in the energy level of an electron?

The negative sign represents the energy required to be inputted to remove the electron from the atom. Signup and view all the answers

What is the characteristic feature of an emission line spectrum?

A series of coloured lines on a black background. Signup and view all the answers

What is the formula that relates the energy of a photon to its wavelength?

E = hc/λ Signup and view all the answers

What is the primary difference between the energy levels of electrons in different elements?

The unique set of discrete energy levels. Signup and view all the answers

What is the purpose of spectroscopy?

To identify elements based on the wavelengths of light emitted when atoms in a gas are exited. Signup and view all the answers

What is the appearance of an absorption line spectrum?

A series of dark spectral lines against the background of the continuous spectrum. Signup and view all the answers

What is the role of diffraction gratings in spectroscopy?

They can diffract light, allowing us to study the spectra of light. Signup and view all the answers

What is the relationship between the energy released by an electron and the energy levels of the electron?

The energy released is the difference between the initial energy level of the electron and the final energy level of the photon. Signup and view all the answers

Why do different elements produce different wavelengths of light when their atoms are de-excited?

Because each element has a unique set of discrete energy levels, producing photons with different wavelengths. Signup and view all the answers

What assumption was made about the velocity of an object moving away from the centre of a galaxy?

That it would decrease due to a lower gravitational field. Signup and view all the answers

What was the implication of observations suggesting that mass is not concentrated in the centre of a galaxy?

That there must be another type of matter that we can't see, called 'Dark Matter'. Signup and view all the answers

Why can't Dark Matter be seen through telescopes?

Because it doesn't interact with light. Signup and view all the answers

What are some suggested particles that could make up Dark Matter?

Gravitinos and axions. Signup and view all the answers

What is the average distance from the Earth to the Sun, and what unit is it measured in?

1.5 x 10^11m, Astronomical Unit (AU) Signup and view all the answers

What determines the outcome of the expansion of the universe?

The density of the universe. Signup and view all the answers

What is a light year, and how is it calculated?

A light year is the distance light travels in one year, calculated by multiplying the speed of light by the time of one year in seconds. Signup and view all the answers

What is the 'open' outcome of the universe?

That the universe will continue expanding for all of time. Signup and view all the answers

What is the relationship between arcminutes and arcseconds?

There are 60 arcminutes in one degree, and 3600 arcseconds in one degree. Signup and view all the answers

How is a Parsec (pc) defined, and what is its equivalent in meters?

A Parsec is defined as the distance at which a radius of 1 AU subtends an angle of 1 arcsecond, equivalent to 3.1x10^16m. Signup and view all the answers

What is the 'closed' outcome of the universe?

That the universe will stop expanding, contract, and collapse on itself. Signup and view all the answers

What is the 'flat' outcome of the universe?

That the universe will reach a fixed size and stop expanding. Signup and view all the answers

What is stellar parallax, and what is its limitation in measuring distances?

Stellar parallax is the apparent shift in position of an object against a backdrop of distant objects, limited to distances of up to 100pc due to the small angles involved. Signup and view all the answers

What is the formula to calculate distance using stellar parallax, and what are the units of the variables?

The formula is d = 1/p, where d is the distance in parsecs and p is the parallax angle in arcseconds. Signup and view all the answers

What is currently unknown about the universe's fate?

What will happen in our universe. Signup and view all the answers

What is the significance of 1 AU in astronomical distance measurements?

1 AU is the average distance from the Earth to the Sun, used as a standard unit of measurement in astronomy. Signup and view all the answers

What is the key evidence provided by Hubble's law that supports the model of an expanding universe?

Almost all light from distant galaxies is red shifted, showing that the galaxies are moving away from Earth. Signup and view all the answers

How does the unit of light year relate to astronomical distances?

A light year is a unit of distance used to express the vast distances to stars and other galaxies. Signup and view all the answers

How does the distance of a galaxy from Earth and its speed relate to the time taken for the galaxy to reach this distance away from Earth?

The time is given by d/v, which is equal to 1/H0, with the Hubble constant measured in seconds. Signup and view all the answers

What is the relationship between the angle of an object and its distance from the observer?

The smaller the angle, the greater the distance from the observer. Signup and view all the answers

What is the approximate age of the universe estimated using Hubble's law?

14 billion years Signup and view all the answers

What is the Big Bang theory attempting to describe?

The origins and development of the early universe. Signup and view all the answers

What are the two key pieces of evidence that support the Big Bang theory?

Hubble's Law showing the universe is expanding, and microwave background radiation. Signup and view all the answers

What is the origin of the microwave background radiation?

High energy gamma photons that were stretched into the microwave region as the universe expanded. Signup and view all the answers

What is the limitation of the Big Bang theory?

There is no experimental evidence – we can’t recreate the initial conditions of the Big Bang. Signup and view all the answers

What is the significance of the redshift of light from distant galaxies?

It shows that the galaxies are moving away from Earth. Signup and view all the answers

What is the relationship between the fabric of space and time in the expanding universe?

The fabric of space and time is expanding, and any point in the universe is moving away from any other point. Signup and view all the answers