Astronomy Quiz

What is the closest star to Earth?

• Sirius

• The Sun

• Proxima Centauri

• Alpha Centauri

Answer explanation

The closest star to Earth is The Sun, as it is the central star of our solar system. Proxima Centauri is the closest star outside our solar system, but The Sun is the nearest overall.

Which of the following is NOT true about Newton's laws of motion?

• A force is required to change the direction of a moving object.

• The gravitational force between two bodies is proportional to their masses.

• The Moon is constantly falling towards Earth but does not hit it.

• Objects at rest require force to remain at rest.

Answer explanation

The statement about the Moon is misleading; it implies a misunderstanding of gravity. The Moon is in orbit due to its velocity, which balances the gravitational pull, preventing it from falling directly to Earth.

Arrange the parts of the electromagnetic spectrum in order of increasing energy.

• Infrared, visible light, X-rays, gamma rays

• Radio waves, visible light, ultraviolet, gamma rays

• Microwaves, infrared, visible, gamma rays

• Radio waves, X-rays, ultraviolet, infrared

Answer explanation

The correct order of increasing energy in the electromagnetic spectrum is: Radio waves, visible light, ultraviolet, and gamma rays. This reflects the increasing frequency and decreasing wavelength, leading to higher energy.

Which planet has the thickest atmosphere that traps heat effectively?

• Mercury

• Mars

• Venus

• Jupiter

Answer explanation

Venus has the thickest atmosphere of all the planets, composed mainly of carbon dioxide, which creates a strong greenhouse effect, trapping heat effectively and leading to extremely high surface temperatures.

If the Schwarzschild radius of a black hole is proportional to its mass, what happens if the mass increases by a factor of 10?

• The radius decreases by 10 times

• The radius doubles

• The radius increases by a factor of 10

• The radius increases by a factor of 100

Answer explanation

The Schwarzschild radius (R) is directly proportional to mass (M), expressed as R = 2GM/c^2. If mass increases by a factor of 10, the radius also increases by a factor of 10, confirming the correct choice.

During a star’s main-sequence stage, energy is produced through:

• Gravitational contraction

• Fusion of hydrogen into helium

• Fusion of carbon into iron

• Electron degeneracy pressure

Answer explanation

During a star's main-sequence stage, energy is primarily produced through the fusion of hydrogen into helium in the core, which releases a significant amount of energy, unlike the other processes listed.

What happens when a star exhausts hydrogen in its core?

• It collapses into a neutron star immediately

• The core contracts and heats, igniting helium fusion

• It undergoes immediate fusion of iron

• It becomes a black hole instantly

Answer explanation

When a star exhausts hydrogen in its core, the core contracts and heats up, leading to the ignition of helium fusion. This process allows the star to continue its life cycle, rather than collapsing immediately.

White dwarfs are supported against collapse by electron degeneracy pressure.

• True

• False

Answer explanation

True. White dwarfs are indeed supported against gravitational collapse by electron degeneracy pressure, which arises from the Pauli exclusion principle preventing electrons from occupying the same quantum state.

Which of the following is FALSE about supernovae?

• Type II supernovae occur in massive stars

• Type Ia supernovae result from white dwarf explosions

• Supernovae produce all the elements heavier than iron

• Supernovae occur only in binary systems

Answer explanation

The statement 'Supernovae produce all the elements heavier than iron' is false. While supernovae do create many heavy elements, not all elements heavier than iron are produced in supernovae; some are formed in other processes like neutron star mergers.

What is the Chandrasekhar limit for white dwarfs?

• 0.8 solar masses

• 1.4 solar masses

• 3 solar masses

• 5 solar masses

Answer explanation

The Chandrasekhar limit is the maximum mass of a white dwarf, which is approximately 1.4 solar masses. Beyond this limit, a white dwarf cannot support itself against gravitational collapse.