astrophysics ughhh

What is the life cycle of a star?

1. Nebula attracted to each other due to their gravitational force (protostar)

2. Cloud becomes hotter and more dense until fusion occurs and becomes a main sequence star

3. Main sequence star is stable as long as outward pressure from fusion is balanced with inward gravitational force

4. Star dies and outward pressure increases, causing it to expand and turn into a red giant (similar size to the sun) or a super red giant (when star is larger than our sun)

5. Red giant will collapse into a white dwarf when fuel for fusion has run out. It becomes a black dwarf once cooled

6. A super red giant will explode into a supernova, producing heavy elements and new nebula. It leaves a dense neutron star at the middle, and a black hole. Nebula formed as nuclei fuse together due to immense energy from a Supernova

Whay is luminosity?

Total radiative power output of a star, given by stefan’s law luminosity = stefan constant x surface area (4 pi r 2) x surface temp in K ^4

How do we model stars?

As black bodies (emitting and absorbing all wave lengths)

What is wein’s law?

The wavelength as which the most energy is emitted is called wavelength peak or max. The hotter the star, the shorter this wavelength

Wavelength peak T = 0.0029

Hertz spring Russel diagram

What is a parsec?

The distance at which 1 AU subtends an angle of 1 at second

What is an astronomical unit?

The mean radius of the earth’s orbit / distance to the sun

What is a light year?

The distance light travels in a year

What is red shift?

Wavelengths of radiation from other galaxies are red shifted because they’re moving away from us. More distance galaxies appear more red shifted. This is evidence that they all originated from the same point in space, and is therefore evidence for the Big Bang theory

Evidence for the Big Bang theory

• red theory

• Cosmic microwave background radiation (CMBRh

What is Doppler shift equation?

Z = V / c = change in wavelength / wavelength = change in frequency / frequency

What is a binary star system?

two stars orbiting each other. Causes spectral lines to split and recombine periodically due to their changing recessional velocity

What is hubble graph?

The recessional velocity of galaxies and its distance from our galaxy. Gradient is Hubble constant. V = h0 d. The reciprocal theoretically gives you the age of the universe. Hubble constant is in seconds ^ -1

How do things orbit?

Centripetal motion, velocity always perpendicular to force

What is a UV catastrophe?

Theoretical is assuming black body