6.2 Stars and the universe checklist

Core

Know that the Sun is a star of medium size, consisting mostly of hydrogen and helium, and that it radiates most of its energy in the infrared, visible light and ultraviolet regions of the electromagnetic spectrum.
State that:a)galaxies are each made up of many billions of starsb)the Sun is a star in the galaxy known as the Milky Wayc)other stars that make up the Milky Way are much further away from the Earth than the Sun is from the Earthd)astronomical distances can be measured in light-years, where one light-year is the distance travelled in (the vacuum of) space by light in one year
Know that the Milky Way is one of many billions of galaxies making up the Universe and that the diameter of the Milky Way is approximately 100 000 light-years.
Describe redshift as an increase in the observed wavelength of electromagnetic radiation emitted from receding stars and galaxies.
Know that the light emitted from distant galaxies appears redshifted in comparison with light emitted on the Earth.
Know that redshift in the light from distant galaxies is evidence that the Universe is expanding and supports the Big Bang Theory.

Extended

Know that one light-year is equal to 9.5 × 10¹⁵ m.
Describe the life cycle of a star:a)a star is formed from interstellar clouds of gas and dust that contain hydrogenb)a protostar is an interstellar cloud collapsing and increasing in temperature as a result of its internal gravitational attractionc)a protostar becomes a stable star when the inward force of gravitational attraction is balanced by an outward force due to the high temperature in the centre of the stard)all stars eventually run out of hydrogen as fuel for the nuclear reactione)most stars expand to form red giants and more massive stars expand to form red supergiants when most of the hydrogen in the centre of the star has been converted to heliumf)a red giant from a less massive star forms a planetary nebula with a white dwarf star at its centreg)a red supergiant explodes as a supernova, forming a nebula containing hydrogen and new heavier elements, leaving behind a neutron star or a black hole at its centreh)the nebula from a supernova may form new stars with orbiting planets.
Know that microwave radiation of a specific frequency is observed at all points in space around us and is known as cosmic microwave background radiation (CMBR).
Explain that the CMBR was produced shortly after the Universe was formed and that this radiation has been expanded into the microwave region of the electromagnetic spectrum as the Universe expanded.
Know that the speed v at which a galaxy is moving away from the Earth can be found from the change in wavelength of the galaxy's starlight due to redshift.
Know that the distance d of a far galaxy can be determined using the brightness of a supernova in that galaxy.
Define the Hubble constant H₀ as the ratio of the speed at which the galaxy is moving away from the Earth to its distance from the Earth; recall and use the equation H₀ = v/d
Know that the current estimate for H₀ is 2.2 × 10⁻¹⁸ per second.
Know that the equation 1/H₀ = d/v represents an estimate for the age of the Universe and that this is evidence for the idea that all the matter in the Universe was present at a single point.

6.2Stars and the universe

-- Core --

-- Extended --

Core

Extended