Worksheet: Using Supernovae to Measure Distances to other Galaxies

In this worksheet, we will practice using the peak absolute magnitude of type 1a supernovas to determine how far away they are.

Q1:

Which of the following statements correctly describes what causes a type 1a supernova?

  • AWhen a white dwarf star in a binary system accretes mass from the companion star, the matter in the accretion disc may become sufficiently hot and dense to initiate hydrogen fusion. This causes a sudden increase in the luminosity of the accretion disc.
  • BWhen the core of a very massive star no longer produces enough energy through fusion, the core will collapse under its own gravity. The outer layers of the star will be expelled and the core will become either a neutron star or a black hole.
  • CWhen a white dwarf star in a binary system accretes mass from the companion star, it may be pushed past the upper mass limit for white dwarf stars, of approximately 1.44 solar masses. Above this mass, the pressure and temperature in the core of the white dwarf will be high enough for carbon fusion. Within a few seconds of carbon fusion beginning, a substantial fraction of the matter in the white dwarf undergoes a runaway reaction, releasing a vast quantity of energy.
  • DWhen a neutron star in a binary system accretes mass from the companion star, it may be pushed past the upper mass limit for neutron stars, of approximately 1.44 solar masses. Above this mass, the pressure and temperature in the core of the neutron star will be high enough for carbon fusion. Within a few seconds of carbon fusion beginning, a substantial fraction of the matter in the neutron star undergoes a runaway reaction, releasing a vast quantity of energy.

Q2:

Which of the following binary star systems could eventually lead to a type 1a supernova?

  • AA red giant star and a black hole
  • BTwo O-type main sequence stars
  • CA red giant star and a neutron star
  • DTwo black holes
  • EA red giant star and a white dwarf star

Q3:

IK Pegasi is the nearest star to Earth that is a candidate for a type 1a supernova. The star is 46 pc away. If the star were to become a supernova next week, what would its peak apparent magnitude be on Earth? Give your answer to 2 significant figures.

Q4:

There are an estimated 2 × 1 0 galaxies in the observable universe. If supernovas occur on average at a rate of 3 per century per galaxy, how many supernovas occur in the observable universe each second? Give your answer to 3 significant figures.

Q5:

The Milky Way has on average 3 supernovas per century. Assuming that this rate is the same for all galaxies, how many galaxies would you have to observe to see supernovas at a rate of 1 per day? Use a value of 365.25 for the number of days in a year.

Q6:

The graph shows the absolute magnitude over time of five different supernova events. Which light curve has been produced by a type 1a supernova?

  • AThe orange line
  • BThe green line
  • CThe red line
  • DThe purple line
  • EThe blue line

Q7:

The graph shows the absolute magnitude over time of five different supernova events. Which light curve has been produced by a type 1a supernova?

  • AThe green line
  • BThe purple line
  • CThe orange line
  • DThe red line
  • EThe blue line

Q8:

In 1006 CE, a type 1a supernova was observed in the constellation Lupus. It was the brightest stellar event in recorded history, with a peak apparent magnitude of 7 . 5 . How far away from Earth has the supernova occurred? Give your answer to 2 significant figures.

Q9:

A type 1a supernova occurs in a nearby galaxy with a peak apparent magnitude of 4.78. How far away is the galaxy? Give your answer to 3 significant figures.

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