Space Physics

Question 1

Formation explained by accretion model

Answer 1

• Gravity attracts particles in interstellar gas and dust clouds.
• Clouds contain varied elements, with heavier ones closer to the center.
• Material rotation forms accretion disc around central protostar.

Question 2

Elliptical Orbits and Conservation of Energy

Answer 2

• Objects in elliptical orbits around the Sun travel faster when closer to it.
• This is explained by the conservation of energy principle.
• As objects move closer to the Sun, their gravitational potential energy decreases, leading to an increase in kinetic energy and velocity.
• Conversely, as objects move farther from the Sun, their gravitational potential energy increases, causing a decrease in kinetic energy and velocity.
• This phenomenon demonstrates the balance between potential and kinetic energy to maintain a constant total energy in orbits.

Question 3

Characteristics of Galaxies and Astronomical Distances

Answer 3

• Galaxies comprise many billions of stars.
• The Sun, our star, resides in the Milky Way galaxy.
• Other stars within the Milky Way are much farther away from Earth than the Sun.
• Astronomical distances are often measured in light-years, where one light-year represents the distance light travels in one year in the vacuum of space.

Question 4

Definition:
Redshift

Answer 4

Redshift is the observed increase in the wavelength of electromagnetic radiation emitted from receding stars and galaxies.

Question 4

Life Cycle of a Star

Answer 4

• Stars form from interstellar clouds of gas and dust containing hydrogen.
• A protostar forms when an interstellar cloud collapses, increasing in temperature due to gravitational attraction.
• A protostar becomes a stable star when gravitational attraction balances the outward force from high internal temperature.
• Stars eventually exhaust hydrogen fuel for nuclear reactions.
• Most stars expand into red giants, while more massive stars become red supergiants after converting most hydrogen to helium.
• Less massive stars form planetary nebulae with a white dwarf at their center after becoming red giants.
• Red supergiants explode as supernovae, leaving behind nebulae containing hydrogen and new heavy elements, with a neutron star or black hole at the center.

Question 5

Definition:
Cosmic Microwave Background Radiation (CMBR):

Answer 5

Microwave radiation of a specific frequency observed throughout space is known as cosmic microwave background radiation (CMBR).

Question 6

Determining Galaxy Velocity (v):

Answer 6

The speed at which a galaxy moves away from Earth can be found from the change in wavelength of the galaxy’s starlight due to redshift.

Question 7

Define:
Hubble Constant (H₀):

Answer 7

is defined as the ratio of the speed at which a galaxy is moving away from the Earth to its distance from the Earth.

Question 7

Calculating Galaxy Distance (d)

Answer 7

The distance of a far galaxy can be determined using the brightness of a supernova in that galaxy.

Question 8

Current Estimate for H₀:

Answer 8

• The current estimate for H₀ is approximately 2.2 × 10^(-18) per second.

Question 9

Equation:
Age of the Universe

Answer 9

d / v = 1 / H₀