Physics · Science General

Astronomy and Cosmology

4,450 Questions

This topic provides questions on astronomy, cosmology, and the physical universe. It covers subjects like the Hubble sequence, constellations, dark matter, and stellar evolution. These questions help build a strong foundation for general science exam sections.

Galaxies and clustersConstellations and starsStellar evolutionSpace observatories

Astronomy and Cosmology Questions

Multiple choice

How many galaxies is the known universe made of?

  1. 5

  2. 5 billion

  3. 5 million

  4. 50 billion
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Current estimates from deep-field observations, such as those from the Hubble Space Telescope, suggest that the observable universe contains at least 50 billion to 2 trillion galaxies.

Multiple choice physics in the world of stars evolution and end stages of stars life cycle of stars stars

What do astronomers mean when they say that we are all "star stuff"? 

  1. that life would be impossible without energy from the Sun

  2. that life would be possible without energy from the Sun

  3. that the carbon, oxygen, and many elements essential to life were created by nucleosynthesis in stellar cores

  4. None of these
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The phrase star stuff refers to the fact that the heavy elements (like carbon, oxygen, and iron) that make up our bodies and the Earth were synthesized through nuclear fusion in the cores of stars and later dispersed into space.

Multiple choice physics in the world of stars evolution and end stages of stars life cycle of stars stars

The brightness of a star which can be seen from earth is called

  1. absolute magnitude

  2. apparent magnitude

  3. light year

  4. parallax
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Apparent magnitude measures the brightness of a star as observed from Earth. Absolute magnitude measures intrinsic luminosity at a standard distance, while light year is a unit of distance.

Multiple choice physics in the world of stars evolution and end stages of stars life cycle of stars stars

What is the first stage of a stars life.

  1. Nebula collapsing under itself

  2. Supernova of old star

  3. Planets collapsing

  4. Fusion of atoms
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

A star is a luminous globe of gas producing its own heat and light by nuclear reactions (nuclear fusion). They are born from the nebula and consist mostly of hydrogen and helium gas. Surface temperatures range from 2000 C to above 30,000 C, and the corresponding colors from red to blue-white. 

Multiple choice physics in the world of stars evolution and end stages of stars life cycle of stars stars

What happens during the Main Sequence phase of a star?

  1. Hydrogen atoms are fused into helium atoms

  2. The star explodes and releases energy

  3. Helium atoms are fused into heavy elements

  4. The star is born out of dust and gas
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Main sequence stars fuse hydrogen atoms to form helium atoms in their cores. About 90 percent of the stars in the universe, including the sun, are main sequence stars. 

Multiple choice physics in the world of stars evolution and end stages of stars life cycle of stars stars

A main sequence star is 

  1. A star that shines steadily due to nuclear fusion

  2. Several stars close together

  3. A star with planets orbiting it

  4. A Nebula that skips a protostar and is instantly turns into a star.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Main sequence stars are in the longest stage of their life cycle, where they fuse hydrogen into helium in their cores. This process releases the energy that makes them shine steadily.

Multiple choice physics in the world of stars evolution and end stages of stars life cycle of stars stars

What is a Star?

  1. A cloud of particles held together loosely by their own collective gravity

  2. A very big collection of matter, mostly gas compressed to incredible pressure and heat by gravity.

  3. A nuclear explosion caused by a growth of hydrogen onto the surface of a white dwarf star

  4. A ball of gas.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

A star is a massive, luminous sphere of plasma held together by its own gravity. The intense pressure and heat at the core are necessary to sustain nuclear fusion.

Multiple choice physics in the world of stars evolution and end stages of stars life cycle of stars stars

A star in the main sequence will maintain a constant size

  1. as long as its helium supply holds out.

  2. because its tendency to contract is opposed by the pressure of the hot interior.

  3. until it is devoured by black holes.

  4. provided that gravitational collapse does not overwhelm its photosphere.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

All main sequence stars (including the Sun) are in hydrostatic equilibrium. That is, the inward force of gravity, which tends to compress the star, is balanced by the outward force due to the pressure.

Multiple choice physics in the world of stars evolution and end stages of stars life cycle of stars stars

Stars are believed to originate

  1. in clouds composed largely of hydrogen gas.

  2. when black holes eject excess matter and energy.

  3. when a supernova explode.

  4. when a cloud of helium starts to collapse and breaks into constituent protons (hydrogen atoms).
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Stars form within giant molecular clouds, which are composed primarily of hydrogen gas. Gravity causes these clouds to collapse, eventually leading to the formation of protostars.

Multiple choice physics in the world of stars evolution and end stages of stars life cycle of stars stars

A protostar is a developing star not yet hot enough to engage in the process of:

  1. nuclear fusion

  2. nuclear fission

  3. atomic transmission

  4. atomic emission
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

An object is considered a protostar for as long as material is still falling inward. For our Sun, and stars of the same mass, the protostar phase would have ended after approximately 100,000 years. After this, the protostar stops growing and the disk of material surrounding it is destroyed by radiation.


If the protostar was unsuccessful in acquiring enough mass, a brown dwarf will come into shape. These substellar objects that are unable to sustain hydrogen fusion reactions in their cores, due to their insufficient mass

Multiple choice physics in the world of stars evolution and end stages of stars life cycle of stars stars

The gaseous body that continues to form, now appears as a large red object called a:

  1. protostar

  2. red dwarf

  3. red star port

  4. red giant
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

A protostar is an early stage in stellar evolution where a cloud of gas and dust is collapsing under gravity. It is often associated with a glowing, dense, and relatively cool appearance before reaching the main sequence.