67
Unit 16: Astronomy and space science Learning aim A – Understand the fundamental aspects of the solar system
Unit 16: Astronomy and space science
Learning aim A – Understand the fundamental aspects of the solar
system
Contents page
Note: anywhere you see a capital D means you MUST draw a diagram.
Core Convectivezone
CoronaRadiative
zone
Chromosphere Photosphere
You need a copy of
this in your notes
Page 6.
Hydrostatic equilibrium
Hydrostatic equilibrium occurs when the force
due to gas pressure exactly balances out
the force due to gravity.
Sun’s magnetic field
Sunspots
Life cycle of a star (D)
Hertz sprung-Russel diagramStars DO
NOT progress
along their stage!
What do you notice about this axis?
The Sun has a surface temperature of about 5,300 K.
Spectral classes
Spectral Class Intrinsic Color Temperature (K)
O Blue Over 25,000
B Blue 11,000 – 25,000
A Blue-white 7,500 – 11,000
F White 6000 - 7,500
G Yellow-white 5,000 - 6,000
K Orange 3,500 - 5,000
M Red Under 3,500
TYPE Star
IaVery luminous
supergiants
IbLess luminous
supergiants
II Luminous giants
III Giants
IV Subgiants
VMain sequence stars
(dwarf stars)
VI Subdwarf
Inner core
Mantle
Outer core
Crust
Anatomy of the Earth
Composition of Earth’s Atmosphere
What can you
remember?
Earth’s tilted axis
The Earth’s axis is tilted
by 23.5°.
Day and night
Solar and
Sidereal days
Orbits
These orbits are NOT circular:
Kepler’s Laws 1. All planets move in elliptical orbits with the Sun at the centre.
2. A line that connects a planet to the Sun sweeps out equal areas in equal times.
3. The square of the period of any planet is proportional to the cube of the semi-major axis of its orbit.
Eclipses
Moon phases
What is this?
Have you even see this before?
You only ever see one side of the Moon, why?
The Moon is tidally locked.
It’s orbital rotation is the same as the time it takes
to orbit Earth.
Centripetal force
The planets are accelerating just fast enough to remain in their
orbits.
Centrifugal force
Van Allen Radiation Belts
Formation of the Aurora Borealis
The Aurora
Borealis or “Northern lights” as viewed
from space.
The aurora seen on Earth
Forces involved in the Solar System
The 3 mains ones:
• Gravitational forces
• Centrifugal forces
• Centripetal forces
• The centripetal force arises from the gravitational pull on a planet from the Sun.
(E.g. water in a bucket, if you swing a bucket full with water fast enough, the water will remain in the bucket and the string attached to the bucket will remain taut - this is because of the centripetal force.)
• The centrifugal force arises from the planet orbiting the Sun at a great speed.
(E.g. a mixture put into a centrifuge, the mixture separated out depending on the density of the substances initially mixed together.)
Inner and outer planets
Can you remember the planets in order?
You will need to find a diagram of each planet for your assignment.
Planetary ring systems
Features and characteristics of other Solar System objects
• Asteroids
• Meteors
• Comets
• Kuiper belt
• Oort cloud
Measuring astronomical distances
There are a few methods you need to write about:
• Trigonometric Parallax
• Cepheid variables as standard candles
• Eclipsing binaries
Trigonometric parallax
Limitations?Inaccurate for distances greater than 65 light years.
Units
Cepheid variables
Brighter stars have longer periods
We can use an equation and the inverse square law to calculate the distance:
Cepheid variables can be used to measure distances of
20 million light years.
http://hyperphysics.phy-astr.gsu.edu/hbase/Astro/cepheid.html
Eclipsing binaries
Evidence for an expanding Universe?
Redshift and blue shift
Hubble’s Law
Hubble’s Law
The further away a galaxy is from
another point in space, the faster it
appears to recede, and therefore, the
Universe is expanding.
Determining the age of the Universe:
𝐴𝑔𝑒 𝑜𝑓 𝑈𝑛𝑖𝑣𝑒𝑟𝑠𝑒 =1
𝐻0
Possible fate of the Universe based on density:
https://futurism.com/four-ways-the-universe-could-end/
Cosmological theories of the present day
• Big Bang theory.
• Olbers’ paradox.
• Steady state.
Big Bang Theory
Olbers’ Paradox
Is the night sky infinitely bright?
Reasons why the night sky is not infinitely bright:
1. There is too much dust to see the distant stars.2. The Universe only has a finite (opposite of infinite) number of stars.3. The position of stars in not even – stars could hind behind one another.4. The Universe is expanding.5. The Universe is young meaning distant light has not reached us yet.
Steady state theory
https://universeandphysics.wordpress.com/2017/05/08/steady-state-theory-rejected/
Note
Anything with a name must have a capital letter:
• Sun
• Moon (if you are talking about ours)
• Earth
• Solar System
