2.1 Stars Colour and Magnitude Flashcards
Learn STars (9 cards)
Define and calculate light years
How astronomers measure interstellar distances.
1 light year = 9.5x10 power of 12
Define and explain how gravity drives the motion of the planets
The gravitational force from the Sun acts as an inward (centripetal) force on a planet, causing the planet to accelerate towards the Sun. Without this force, a planet would move in a straight line due to inertia. However, because of gravity, the planet’s path continuously curves towards the Sun, resulting in an orbit.
Identify and explain the two opposing forces that determines the structure of a star
The outwards force of Radiation pressure (heat radiated by nuclear fusion in core) and the inward force of gravity. Must be balanced to keep star stable and burning.
Explain what galaxies are and identify the three different shapes:
A galaxy is a huge collection of dust, stars and their solar systems all held together by gravity.
1. Elliptical - Oval shape (Andromeda Galaxy)
2. Spiral - spiral arms (whirlpool galaxy)
3. Barred Spiral - A linear bar shaped band of stars in centre (milky way Galaxy)
Define nuclear fusion
Process by which two hydrogen atoms fuse together to form 1 heavier helium atom which produces heat and light due to gravity.
Define plasma and explain how it relates to nuclear fusion
Plasma is a state of matter consisting of a soup of positively charged ions and free electrons among the nuclei of atoms. Plasma is the medium in which fusion occurs.
Describe the three nuclear fusion reactions
- Proton + Proton -> Deuterium + positron+neutrino+energy
- Proton +Deuterium->helium-3+energy
- Helium-3+Helium-3->Helium-4+proton+proton+energy
one of the protons is converted into a neutron and two tiny particles positron
(positively charged particle) and neutrino (neutral particle) are released.
The positron (antimatter particle) collides with an electron and the two particles
destroy each other and become two high-energy gamma rays.
The new nucleus formed consists of a proton and a neutron (deuterium: isotope
of hydrogen)
Describe eth HR
The H-R diagram shows that
there is a relationship between
the absolute magnitude
(brightness) and temperature of
stars.
Most stars fall on a broad line running from the top left-hand
corner (larger/older) to the bottom right-hand
(smaller/younger) corner of the H-R diagram known as the
main sequence.
Gravitational Force = Radiation Pressure (Equilibrium)
There is a simple relationship between the mass of the star
and its temperature and brightness – the heavier the star, the
hotter and brighter it will be.
More mass = greater gravitational force = more hotter and
brighter
The core is more tightly packed and causes the core to be
more compressed and nuclear fusion occurs more rapidly.
More heat and light is produced!
What are red giants
When a medium star runs out of hydrogen, fusion stops and outward radiation pressure stops. Gravity causes star to collapse inwards and outwards layers of star begin to fuse. Heat from fusion produces radiation pressure which causes outer layers of the star to expand and cool. Forms red giant
