Test 2 Short Answers Flashcards
Why can’t we use Infrared Telescopes?
Because Earth is too hot.
How do X-Ray Telescopes Work?
Scim photons off metal surfaces.
Why Build Larger Telescopes?
Larger areas capture more light - 2x radius = 4 x area.
Why Improve the Resolution of Telescopes?
Enables us to differentiate between close objects.
What is Interferometry?
Connecting telescopes together to make sharper images than a single large telescope.
Why are Telescopes Built High Up?
Atmosphere absorbs light - on mountains there is less atmosphere so less distortion.
What is Twinkle?
Refracts starlight in random directions very quickly.
What is Wien’s Law?
A star’s temperature is related to its colour.
How are Hydrogen Lines Effected by Temperature?
Hotter = less hydrogen lines.
What is the Use of Standard Candles?
If we know the type of star (and also brightness), we can compare this value with how bright it appears to get a distance.
How do we know the Type of Star?
Obtain a spectrum and compare it with other stars with similar spectra whose distances and brightness we know.
What is the Inverse Square Law?
Light spreads out with the square of the distance - with a sphere 2x as large, energy covers 4x area.
How does Magnitude Relate to Brightness?
Increased magnitude, decreased brightness.
What does m Stand for?
m - Apparent magnitude.
What does p Stand for?
p - Parallax.
How do we get the Radius?
A small hot star can have the same luminosity as a large, cool object.
What are Spectroscopic Binaries?
Systems in which stars are so close together that they appear as a single star even in a telescope.
What are Apparent Binaries?
Stars seem close together but are not physically connected.
What are Visual Binaries?
Stars seem close together and are physically connected.
What are the 3 Things Determined by Mass?
Luminosity, radius, temperature.
Why does Increased Mass = Increased Luminosity?
More massive stars have greater gravity compression. They need higher core temperatures to be stable and have very many more nuclear reactions.
Why do More Massive Stars Live for Less Time?
Because luminosity increases faster than fuel.
Why does High Temperature = Nuclear Fusion?
Nuclei can get close enough to fuse.
Why does Low Temperature = No Nuclear Fusion?
Electrical repulsion prevents fusion.
What Size are Solar Type Stars?
Less than 8 solar masses, greater than 0.8.
What is the S-Process?
Adding protons to make things heavier and heavier.
What Size are Low Mass Stars?
Less than 0.8 solar masses.
What Percentage of Stars are Binaries?
75%.
Why can’t Binaries Become Red Giants?
H envelope will be lost, secondary star may accrete some mass.
What is Unique about Degenerate Stars?
More mass = smaller size.
What are White Dwarfs?
What remains of the core of low mass stars that have undergone evolution.
Why do Neutron Stars Spin so Fast?
Because angular momentum is conserved.
Where do New Stars Form?
Interstellar gas.
Where are Stars Arranged in terms of Age?
New stars in the disk, old stars in the halo.
What are the 5 Characteristics of Population 1 Stars?
Ordered motion, circular orbits in disk, plane, younger, more metal rich.
What are the 4 Characteristics of Population 2 Stars?
Random motion, eccentric orbits passing through disk plane, older, more metal-poor.
What are the 3 Main Types of Galaxy?
Spiral, elliptical, irregular.
How Old is the Universe?
13.8 billion years old.
How Old is the Sun?
4.6 billion years old.
How can we Identify the Shape of the Milky Way?
Lots of stars visible in the disk, not many visible in other directions.
Which Stars Move Fastest in terms of Proximity?
Closer stars appear to move quicker than distant stars.
How Big is the Milky Way?
100,000 light years in diameter.
What is Harlow Shapley Responsible for?
Mapping distribution of globular clusters.
What are Oort and Lindblad Responsible for?
Concluding that the galaxy rotates, structure of the Milky Way.
Where are Blue Stars Located?
In disks and spiral arms.
Where are Red Stars Located?
In central bulge and halo.
What are Population 1 Stars?
1 million to 1 billion years old, high metal concentration.
What are Population 2 Stars?
10 billion years old, low metal concentration.
When was Radio Astronomy Invented?
1930.
How Often would the Sun Rise and Set Without Earth’s Spin?
Once a year.
What is the Orion Nebula?
Star forming region.
What did Harlow Shapley Argue about Nebulae?
They are ‘local’.
What did Heber Curtis Argue about Nebulae?
They are galaxies.
How are Telescopes Measured?
According to diameter.
What are Cepheid Variables?
Big pulsating stars - population 1 and population 2.
What is One Piece of Evidence of an Expanding Universe?
Distant galaxies move faster than nearby ones.
What did Einstein Believe about the Universe?
It is static.
What does Einstein’s Cosmological Principle Assume?
The universe is isotropic and homogeneous.
What does Isotropic Mean?
Same in every direction.
What does Homogeneous Mean?
Same in every place.
How did Einstein Explain the Expanding Universe?
Increase in space, nothing moves.
How did Newton Explain the Expanding Universe?
Space stays the same, but everything moves outwards.
How can we Identify the Type of Universe we Live in?
Critical density - above means closed (recollapse), below means open (expand forever), equal to means flat (expand forever).
What is the Size of the Universe?
40 light years across.
How does Gravity Work in White Dwarfs?
Electrons run out of room to move around, preventing further collapse.
How does Gravity Work in Neutron Stars?
Neutrons run out of run to move around, preventing further collapse - smaller than white dwarfs.
How does Gravity Work in Black Holes?
Gravity wins and nothing prevents collapse.
