Exam tips Flashcards
What relates parsecs and arcseconds?
1/1”=1pc
What is the flux proportionate to?
The collecting power
f is proportional to d^2
How can we estimate the fraction of dark matter in our galaxy?
Use rotation curves of stars and gas within the galaxy compared with the expected amount of rotation considering the luminosity profile
Observe the redshift in different portions to find rotation curve
What is the definition of an AU?
The orbital radius of a body orbiting one solar mass with a period of one year
What is the separation between two stars?
The sum of their orbital radii
When can two objects not be resolved from the ground?
When their separation is too low
Due to turbulence in the atmosphere blurring the two objects together
e.g <180”
What relates parsecs and arcseconds and AU?
1AU/1”=1pc
What are the advantages of studying star clusters for stellar evolution?
The stars share common characteristics such as distance, age and chemical composition
For what range are neutron stars formed?
7-9 solar masses and 30-40 solar masses
Why is there a mass limit for neutron stars?
The degeneracy pressure balances the gravitational force
With too much mass, the pressure cannot keep up and the star collapses into a black hole
Why do gas giants not form very close to the host star?
Close to the star there is a lack of ices which can prevent formations of large solid cores
Instead formed in the middle zone where water ices were found
What is the progenitor of a type Ia supernovae?
A white dwarf
What is the typical resolution limit due to Earth’s atmosphere?
1”
What star will have a higher temperature?
The most blue star
How do absolute magnitude and luminosity relate?
A small absolute magnitude means a higher luminosity
What is the source of luminosity for a quasar?
Powered by accretion on to a supermassive black hole in the centre of a galaxy
Why are quasars not found in the nearby Universe?
They are very rare and the nearby universe does not have enough volume
Most galaxies have finished accretion on to the central black hole by this current era
What is the RA and dec at the North pole?
RA=N/A
Dec=90
What makes up the density of the universe?
5% physical matter
25% dark matter seen by gravitational effect on universe
70% dark energy seen by acceleration of expanding universe
What is the duration of a transit?
T_dur=pα/2π
