Space Physics

What is a day?

The time it takes for the earth to complete one rotation about its axis

What is a month?

The time it takes for the moon to complete one orbit around Earth

What is a year?

The time it takes for the earth to complete one orbit around the sun

What is the shape of a planet’r orbit around the sun?

Elliptical with the sun at one focus of the ellipse

What are the order of the planets from the sun?

Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune

What is a light year?

The distance travelled by light in one year

What is the energy source of the sun?

Nuclear fusion of hydrogen to helium

What are the main parts of the electromagnetic spectrum that the sun emits?

Infrared, U.V and Visible light

What is a galaxy?

A collection of millions of stars

What is the diameter of the Milky Way?

100,000 light years

What is the life cycle of a sun-sized star?

Nebula (a cloud of interstellar dust) to a protostar to a stable star to a red giant to a white dwarf and planetary nebula

What is the life cycle of a large star?

Nebula to a protostar to a stable star to a red supergiant to a supernova to a black whole or neutron star

What is redshift?

An increase in the observed wavelength of the electromagnetic radiation emitted from stars and galaxies that are receding from an observer on Earth

What is cosmic microwave background radiation?

CMBR is microwave radiation of a specific frequency which is observed at all points in space around us produced shortly after the universe was created. This radiation has increased in wavelength and decreased in frequency and expanded into the microwave region as the universe expanded

How can the speed of a distant galaxy be determined?

The speed depends on the amount of redshift in the light from that galaxy

How can the distance of a distant galaxy be determined?

Using the brightness of a supernova

What is Hubble’s constant?

The ratio of the speed that a galaxy is receding from Earth to its distance from Earth

What is the estimated value of Hubble’s Constant?

2.2 × 10^-18

How can the age of the universe be determined?

All matter in the universe was present at a single point due to the Big Bang theory, and so the distance of a galaxy from Earth is the total distance it has travelled since the Big Bang. If we assume the galaxies have been travelling at a constant speed, we can do T=D/v=1/Hubble Constant