The Sun
This is the envelope around the Sun that is visible during a total solar eclipse
What is the Corona?
This is the diagram used to classify stars by temperature and luminosity
What is the Hertzsprung-Russell diagram?
This is the evolution of the Sun after it spends its hydrogen fuel
What is a Red Giant then a white dwarf with a surrounding planetary nebula?
These are the types of nebulae within galaxies
What are dark, reflection, and emission nebulae?
This law describes how the velocity of a galaxy changes depending on its distance from us
What is the Hubble-Lemaitre law?
Major types of these ejections can be damaging to us on Earth as they can disrupt power grids with their high energy charged particles
What are solar flares?
This method of measuring distance is good for stars nearby to us (give the formula as well)
What is parallax? Formula is d (pc) = 1/p (arcseconds)
This is the fate of stars larger than about 10 solar masses, of which we learned much about from Supernova 1987A
What is a Type 2 supernova? (Be sure to study what made 1987A special!)
These variable stars were/are used to calibrate distances and are often referred to as standard candles
What are Cepheids?
This is the cause of the observed velocity of galaxies away from us
What is the expansion of space?
This is the primary source of energy for the Sun on the main sequence
What is nuclear fusion of hydrogen to helium?
List the order of stellar classification by surface temperature starting from the hottest type to the coolest
OBAFGKM
These compact objects are the remnants of the death of a massive star, and can sometimes be seen as these other objects
What are neutron stars and pulsars?
These observations of galaxies are a key reason why we believe dark matter exists in the universe
What are the flat rotation curves of the galaxies?
These objects are the current theory for the cause of high energy quasars through this process
What are supermassive black holes accreting matter?
The Sun can be approximated as one of these objects in thermodynamics
What is a blackbody?
Explain what determines the lifetimes of MS stars
Their initial mass determines the length of the lifetime. The more massive the star, the faster the hydrogen fuel is consumed (due to high efficiency) which reduces their lifetime.
Black holes are little understood but dangerous objects. This phenomenon is a reason why less-massive black holes are arguably more dangerous to be near than massive ones
What are tidal forces?
This effect is seen when light from a distant galaxy/object is bent and magnified by the mass of a foreground galaxy/object
What is gravitational lensing?
How might we guess there is a black hole in the center of our galaxy without being able to see it physically? (Not in the form of a question but whatever)
We can observe the orbits of stars that we can see around the center and deduce from Newtonian/Keplerian mechanics that there is a massive object affecting their orbits
The surface temperature of the Sun is about 6000K. The surface temperature of Earth we will approximate to be 300K. This is the ratio of the peak wavelength of the Sun to Earth
What is 1/20? (Using Wien's Law)
For a given cluster of stars, explain how the age of the cluster can be determined by its HR diagram
Since stars live different lifetimes depending on age, then on an HR diagram, you would see a turnoff point where the massive stars start to move off the MS line. Since we know approximately how long a star of a given mass can live, then the cluster is at least as old as the last MS star to move off.
This prediction of general relativity has been detected by massive binary objects merging together
What are gravitational waves? (Neutron star mergers are especially interesting!)
Suppose there are 2 galaxies (A and B) that are observed. measurements show that they have the same luminosity but the flux from A is 1.6 x 10(3) and the flux from B is 2 x 10(2). This is the ratio of the distance of galaxy A to B
What is 1/squareroot(8)? Use F = L/(4pi d^2) using a ratio; F_a/F_b = 8 = (d_b/d_a)^2 so d_a/d_b = 1/sqrt(8)
Explain why we know that the Milky Way is not the center of the Universe even though all galaxies appear to be moving away from us (this is a near future topic but can be explained using a relative perspective and Hubble's law)
Imagine we were in a different galaxy than the Milky Way. From this location, everything will still appear to move away from us (we think ourselves stationary) including the Milky Way. Since Hubble's law is applicable to outside the Milky Way, then we would see galaxies moving away from us just the same, so there is no unique center of the Universe