Space

What are the spectral classes in order? What is the mnemonic to remember them?

O be a fat guy kill me

O B A F G K M

What can Stefan’s law equation be used to find?

The luminosity/power given off by a star

The heat loss/gain in insulating or cooling systems

What do all the symbols represent in Stefan’s law? And their units

P=\sigma AT^4

What is the equation to find the surface area of a sphere/star?

4\pi r²

When using Stefan’s law to calculate the luminosity of a star what assumptions are you making? (4 marks)

The surface temperature is the same across the whole area of the star

The intensity is the same across the whole area of the star

The star is a perfect black body

The star is perfectly spherical

Suggest why can the spectrum of a star is useful?

The wavelengths of EM waves they release

Their velocity

Their Elemental composition

Their age

Their Surface area

Their Volume

Their Luminosity

What light is emitted when the temperature of a star is above the absolute temperature of -237K

Infrared light

State Wiens law

the peak wavelength of a star is inversely proportional to its absolute temperature.

The surface temperature of the sun is 5500K. Calculate its peak wavelength in nanometers

527nm

Define absorption (with the idea of atoms)

When atoms absorb photons to give them the energy to move to higher energy levels.

Define excitation

When an electron gains enough energy to move to higher energy levels and can leave if the energy is above the work function

Define ionization

When electrons are added or removed from atoms to produce ions

Explain the presence of black lines in a star spectrum

some photons from the light source is absorbed by electrons in a gas cloud before they’re not detected, so black lines appear

What elements would be expected to be found in the hottest stars?

Explain why

Iron cores

Heavier elements

Because elements have time to collide, So there is higher rate of fusion. More nuclei are fused together to form heavier elements

What would we expect to see in the absorption spectra of Hotter stars?

More black absorption lines

What elements would be expected to be found in cooler stars?

Lighter elements

What are nebula?

Collapsing clouds of gas and dust

Define what a nebula is

It is a collapsing cloud of gas and dust

Describe the life cycle of a low mass star

Nebula are giant clouds of gas and dust, which overtime collapse due to the attractive forces of gravity, this causes the dust particles to heat up from friction. Creating light.

Becoming a proto star, when temperature and pressure is high enough, nuclear fusion occurs in its core, causing lighter elements to form heavier elements,while release energy

Overtime it will grow in size and become a main sequence star

Gravity and radiation pressure is equal

When hydrogen runs out, nuclear fusion cannot occur and the forces of gravity become greater. And decreases in size

This allows the temperature to increase in the core, now helium can fuse together.

Star expands and becomes a red giant

Describe the lifecycle of a high mass star

Nebula are giant clouds of gas and dust, which overtime collapse due to the attractive forces of gravity, this causes the dust particles to heat up from friction. Creating light.

Becoming a proto star, when temperature and pressure is high enough, nuclear fusion occurs in its core, causing lighter elements to form heavier elements,while release energy

Overtime it will grow in size and become a main sequence star

Gravity and radiation pressure is equal

When hydrogen runs out, nuclear fusion cannot occur and the forces of gravity become greater. And decreases in size

This allows the temperature to increase in the core, now helium can fuse together.

Star expands and becomes a red super giant

What is the most stable type of star?

Main sequence star

Why is it that iron is only present in the star’s core?

iron is the most stable element, so fusion no longer happens

What happens after a red super giant?

The temperature decreases and fusion stops so the star collapses rapidly, and all the matter rebounds off the iron core.

Core becomes very dense and electrons become neutrons.

If it was a large mass star, it would become a black hole

If it was a lesser mass star it would become a neutron star

Define a black hole

When all the stars mass condenses to a singularity

What causes the radiation pressure in stars?

Nuclear Fusion

Explain why the binding energy per nucleon for fission has a steeper gradient, then for fission

Cause more energy is produced from fusion than fission

Define a light year

The distance light travels in one year

What is the distance for one light year in meters?

365×24×60×60= 31536000

\left(3\times10^8\right)\times31536000=9.46\times10^{15}

What is the standard unit for the measurement of distance in space?

Astronomical unit (Au or au)

What Does one astronomical unit represent?

The main radius of the Earth orbit around the sun, which is 1.5\times10^{11}m

How many Au is voyager which is 2.6\times10^{13}m away from earth?

\frac{2.6\times10^{13}}{1.5\times10^{11}}=173 Au

What is the unit for a parallax angle?

Arc seconds

What is one arc second worth?

\frac{1\degree}{3600}

If the parallax angle is 1 arc second the d is…

1 parsec

The parallax angle does Alpha Centuri found the angle measures after six months was 1.5 to Arc seconds1.52 different from that measured at first how far is Alpha Centuri from earth in parsec?

Describe the controls used in the method to test the inverse square law for intensity

1. Keep the 2 objects at the same height to the oil drop

2. Keep the surrounding dark

3. Measure from the centers of the object when measuring the distance

What is the formula used in the method for testing the inverse square law for intensity of an object

If the distance are doubled, What would happen to the brightness of the image?

It would quartered

Explain how we can use the parallax method to determine the distance between the probes and the angles to the vertical to find the distance of a star to the Earth, using trigonometry

1. observe the start over six months period

2. Measure the angle of the star against the background of stars

3. Use trigonometry to find the distance between a star and the sun

Define standard candles

They are a class of stellar objects which have a known luminosity,

and whose distance can be determined by measuring the radiant flux density

What is one example of standard candles?

Cepheid variables

What are Cepheid variables?

Stars that vary that luminosity from a maximum to a minimum in a regular time. Because they’re radius varies, which causes it’s temperature to also vary

What is the formula to work out the luminosity of a Cepheid variable star? And what are the units for each symbol?

Red shift