Space Physics

• The Earth rotates around its axis at a rate of

  about 1,600 kilometers (1,000 miles) an hour.
• Earth revolves in orbit around the sun in 365 days, 6 hours, 9 minutes with reference to the stars, at a speed ranging from 29.29 to 30.29 km/s. The 6 hours, 9 minutes adds up to about an extra day every fourth year, which is designated a leap year, with the extra day added as February 29th.
• Rotation of moon produce 8 phases : new

  Moon, waxing crescent, first quarter, waxing

  gibbous, full Moon, waning gibbous, last

  quarter and waning crescent. The cycle repeats

  once a month (every 29.5 days).
• By assuming that the distance from centers are constant:

  v= distance/time =circumference/period = 2.Π.r f= 1/T

  Where v= speed of rotation (m/s) f=frequency(Hz)

  r= distance of two massive objects from centers:

  T= period= time to make one rotation
• Our solar system is made up of a star—the Sun—eight

  planets, 146 moons, a bunch of comets, asteroids and

  space rocks, ice, and several dwarf planets, such as Pluto.

  The eight planets are Mercury, Venus, Earth, Mars,

  Jupiter, Saturn, Uranus, and Neptune.
• Jupiter has the most named moons—50. Mercury and

  Venus don't have any moons.
• The first four, Mercury through Mars are "terrestrial" planets (rocky). The outer four, Jupiter through Neptune are "Jovian" planets (gaseous) It is because of gravity from the sun towards all the material.
• The gravitational field strength of each planet is directly

  proportional to the Mass and inversely proportional to the

  size of the planet (the radius). Jupiter has the biggest

  gravity (2.4g) since it is the most massive although it is

  big.
• All are circling the sun in elliptical orbit

  .Sun consists of hydrogen atoms that react in fusion to

  produce helium and huge energy

  All planets revolve around since it has the most mass in

  which creates the biggest gravitational field strength (gravity)

  
  

  The energy is conserved so the further the distance (bigger

  potential energy) means smaller speed (smaller kinetic

  energy).
• Stars: spherical masses of hot gases that produce heat and light

  energy. Most of its energy is in infrared, visible and ultraviolet of

  the electromagnetic spectrum.

  Measured in light years because they are so far away.

  Light year (9.5x1015 m): the distance light travels in a

  year.
• It is powered by fusion reaction of hydrogens to helium in nucleus

  How bright a star appears depends upon:

  1. Distance from Earth: The closer it is, the brighter it will appear.
  2. Size: The bigger it is, the brighter it will appear.
  3. Temperature: The hotter it is, the brighter it will appear - The objective measurement
• Most stars appear white to the naked eye, but stars come in different colors.

  E.g. the sun is yellow.

  The hottest stars are the blue coloured stars while the coolest

  stars are the red coloured stars.

  When our Sun runs out of Hydrogen, it will lose its mass and

  become a white dwarf.
• Facts about life cycle of Stars:

  This means they change over time.

  A stars complete life cycle can take many millions of years.

  When a star’s mass is used up, the star dies.
• • Gravitational strength and Temperature increases.
  • a protostar becomes a stable star when the inward force of gravitational attraction is balanced by an outward force due to the high temperature in the centre of the star
  • a red supergiant explodes as a supernova, which can cause huge gamma rays and heat emissions that can kill a lot of life.
  • Black hole is a dead star that absorb anything around it including light.
• Galaxies: Large groupings of millions or billions of stars and other

  forms of masses held together by gravity.

  Some examples: Milky Way , Andromeda, Canis Major dwarf

  Segue 1, Sag DEG, Large Magellanic Cloud.

  Our solar system is in the Milky Way galaxy which has diameter of

  100,000 light years (9.5 x 1017 km).
• The light that we received from galaxies are red shifted so the

  colour and the position are not exact. (means the color is towards red

  than it actually is). Red shifted means the frequency is getting lower.

  This only happens when the galaxies are moving away from us

  (Doppler’s theory).
• This suggest that a long time ago (13.8 billion years ago) the

  universe must be compiled in a small area (hot and dense small

  region) that has expanded with acceleration outwards (BIG BANG

  theory).

  This theory also backed by the discovery of cosmic microwave

  background radiation (CMBR) which is the remains of the energy

  from the Big Bang, spread thinly across the whole Universe in

  microwave.

  The distance of galaxy can be found from the brightness of a

  supernova in the galaxy. The speed of the movement can be found

  from the red shift frequency.
• Big Bang theory : all galaxies are moving away from each

  other with different velocities. The universe is pulsating

  (expansion and contraction).

  If galaxies are moving away, they must have been

  close to one point together millions of years ago.
• If Hubble’s graph is used,

  the origin of this movement = approx. 10 biliion years old.

  Hubble’s data is plotted into graph.

  The gradient of Hubble’s graph= Ho
• Age of universe = 1/H0 Right now around 10 billion years old

  The derivation: according to Hubble’s law:

  v= Ho. r

  v= speed of movement of object

  r = distance from solar system.
• The universe is pulsating (pulsating universe theory) between expansion and

  contraction.

  The universe will end either:

  1. Continue to expand forever---Hubble’s law, it means that the sun will befurther from the earth.Return in on itself back to its origin (Big Crunch) IF the gravity overpowers
  2. Return in on itself back to its origin (Big Crunch) IF the gravity overpowers expansion.