Space Flashcards
What is parallax?
The apparent change of a position of a star due to the earths orbit
what is an astronomical unit (AU)?
The average distance between the centre of the earth and the centre of sun.
What is a parsec?
The distance of which the angle of parallax is 1 arcsecond (1/3600 th of a degree)
What some trends in Hertzsprung Russell diagram?
In the main sequence, there is roughly a negative correlation between luminosity (L) and temperature (T).
Supergiants have high L and high T.
Giants have lower L but still high T.
Dwarfs have low L and low T.
Why is the method of trigonal parallax limited to near stars?
As the distance increases, the angle decreases until it becomes immeasurably small.
What is the Trigonometric parallax method of measuring the distance of stars?
As the Earth orbits the sun our position in space changes.
We take a reading at our current position and measure the angle to the star. After 6 months, when we are the furthest point from where we were, we take another reading and see how it changes.
Then using d=r/θ you can find the distance.
What is the standard candle method of measuring the distance of stars?
This is where we know the L of a certain object.
Using d^2=L/4πI. We can determine the distance of the star.
How can the HR diagram be linked to the life cycle of stars?
Clumps of clouds contract under the force of gravity. When dense enough it becomes a protostar.
The protostar which gradually heats up, until it can fuse hydrogen to helium in its core. The star moves to the left of the diagram and it becomes a main sequence (MS) star.
The fusion stops the contracting of gravity.
The outward pressure which stopped this stops with the hydrogen fusion, the helium core beings to contract and heat up.
This is when it becomes a red giant or supergiant and it moves to the top right of the HR diagram.
The He fusion stops the force of gravity and pushes the outer layers outward due to the energy produced.
Once the He fusion halts, the star collapses in on itself until stopped by the electrons in the core, this is where it becomes a hotter and dimmer white dwarf.
What is the doppler effect?
This is when the waves of a moving object are compressed or spread out. An object emitting or reflecting waves while moving, has the waves in front of it compress and the waves behind it spread out.
What does Hubble’s law state?
It states that the further a galaxy from earth the higher the recession velocity, therefore making them proportional. v=Hd, where H is Hubble’s constant (around 70 km s^-1 Mpc^-1)
How does the expanding of the universe lead to the possible existence of dark matter?
Centripetal force is inversely proportional to the distance from the centre.
Using this you would assume that the stars on the outer orbits of the galaxy would move slower.
This is not the case. All stars move at the same speed, suggesting there is an unaccounted for mass, this is assumed to be dark matter.
How can you use Hubble’s law to find the age of the universe?
Hubble’s law states, v=Hd, v/H=d , therefore, 1/H=d/v, t=d/v therefore, t=1/H. Using hubble’s constant you can find t= age of the universe.
Why can using Hubble’s law to find the age of the universe be inaccurate?
The methods of finding H differ and as time goes on experimental methods become better, therefore the value of H varies, meaning the value for the age of the universe majorly varies. This leads to us not knowing the true value for the age of the universe.
What is redshift?
The doppler effect causes the line spectra to shift depending on whether it is moving towards (blue shift) or away (red shift) from the earth.
How can we use redshift to assume the universe it expanding?
The greater the redshift, the further away from the earth the object is.
