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This astronomy and astrophysics quiz has 140 free questions with answers and starts in the Solar System and ends at the event horizon. The astronomy half covers the planets and their moons, Halley's Comet, the Kuiper belt and Oort cloud, Betelgeuse and Sirius, Copernicus, Kepler, Tycho Brahe and Herschel, Voyager 1, the Hubble telescope, exoplanets and the transit method. The astrophysics half asks about the physics behind it all: white dwarfs and the Chandrasekhar limit, neutron stars and pulsars, black holes, Hawking radiation and the Schwarzschild radius, the cosmic microwave background and its 2.7-kelvin glow, Hubble and Lemaitre's expanding universe, dark matter and dark energy, Type Ia supernovae as standard candles, stellar nucleosynthesis and the B2FH paper, the Hertzsprung-Russell diagram, Cecilia Payne's hydrogen thesis, LIGO's first gravitational-wave detection and the Event Horizon Telescope's image of M87. Easy questions ask which planet is largest and who walked on the Moon first. Medium ones cover stellar evolution and famous discoveries. Hard ones want the share of the universe that is dark energy, the Sun's Schwarzschild radius, the masses of the first merging black holes detected and the physicist who founded astrophysics with a spectroscope in 1860. Every answer has been checked against a reference encyclopaedia, and each question shows its explanation and citation once you have answered.
30 of 140 questions with answers and explanations. Play the quiz
Q 01Which planet is the largest in our solar system?
Jupiter
Jupiter is the largest planet in our solar system by both volume and mass. It is a gas giant made primarily of hydrogen and helium.
Q 02Our Sun is classified as which type of star?
Yellow Dwarf
Yellow Dwarf is a misnomer: the Sun is actually white, and only looks yellow through Earth's atmosphere.
Q 03What type of galaxy is the Milky Way?
Barred Spiral
The Milky Way is classified as a barred spiral galaxy, characterized by its pinwheel-like shape with a central bar structure.
Q 04Halley's Comet returns to the inner Solar System roughly every how many years?
76
Edmond Halley never saw his prediction confirmed; he died in 1742 and the comet duly reappeared in 1758. Its next visit is due in 2061.
Q 05In astronomy, what kind of quantity does a 'light-year' measure?
Distance
Despite the name it is a length, about 9.46 trillion kilometres, defined using the 365.25-day Julian year rather than the calendar year.
Q 06Which Bell Labs radio astronomers accidentally found the cosmic microwave background in 1964?
Penzias and Wilson
They first blamed the persistent hiss in their horn antenna on pigeon droppings. The signal was the afterglow of the Big Bang, and it won them the 1978 Nobel Prize in Physics.
Q 07What is a nebula in astronomy?
A giant cloud of dust and gas in space
A nebula is an interstellar cloud of dust, hydrogen, helium, and other ionized gases. They are often star-forming regions or remnants of dying stars.
Q 08Which of these best describes 'dark matter'?
Invisible mass detected only through its gravity
About five-sixths of the universe's mass appears to be this stuff, inferred from galaxy rotation curves and gravitational lensing. Nobody has yet caught a particle of it in a detector.
Q 09What is the primary process that defines a 'main sequence star'?
Fusing hydrogen into helium in its core
A main sequence star is defined by the nuclear fusion of hydrogen into helium in its core, a process that generates the energy it radiates and represents the longest phase of a star's life.
Q 10What is a quasar?
An extremely luminous active galactic nucleus powered by a supermassive black hole
A quasar is an extremely luminous and distant active galactic nucleus (AGN), thought to be powered by accretion onto a supermassive black hole at the center of a galaxy.
Q 11What is a solar flare?
An intense burst of radiation from the Sun's atmosphere
A solar flare is a sudden, intense burst of electromagnetic radiation from the Sun's atmosphere, caused by the release of magnetic energy.
Q 12Which volcano is the tallest planetary mountain in the Solar System?
Olympus Mons
It is so wide and gently sloped that someone standing on its flank would not be able to tell they were on a mountain at all; the summit rises about 22 km above the surrounding plains.
Q 13Whose 1543 book placed the Sun, not the Earth, at the centre of the solar system?
Nicolaus Copernicus
Q 21What type of nebula is formed from the expanding shell of gas ejected by an aging, dying star?
Planetary nebula
Planetary nebulae are beautiful, often colorful, shells of ionized gas expelled by low- to intermediate-mass stars during the final stages of their lives, before they become white dwarfs.
Q 22Which body was demoted to 'dwarf planet' by the IAU in 2006 because it has not cleared its orbit of other debris?
Pluto
Pluto was reclassified in 2006; Ceres, Haumea, Makemake and Eris share the dwarf-planet label.
Q 23What phenomenon provides the primary observational evidence that the universe is expanding?
Redshift of distant galaxies
Nicolaus Copernicus's De revolutionibus revived the Sun-centred model — Aristarchus of Samos had proposed one some 1,800 years earlier — and challenged the prevailing geocentric view.
Q 14Which spacecraft became the first to enter interstellar space, in August 2012?
Voyager 1
Voyager 1's radio signals now take more than 22 hours to reach Earth; its twin Voyager 2 crossed the heliopause in 2018.
Q 15What is the final evolutionary stage for a low-mass star like our Sun?
White dwarf
After exhausting its nuclear fuel, a low-mass star like the Sun will shed its outer layers to form a planetary nebula, leaving behind a dense core known as a white dwarf.
Q 16Which constellation is home to the bright red supergiant star Betelgeuse?
Orion
Betelgeuse is a prominent red supergiant star located in the constellation Orion, marking the hunter's eastern shoulder.
Q 17Which famous space telescope, launched in 1990, has provided iconic images of the universe?
Hubble Space Telescope
The Hubble Space Telescope was launched in 1990 and has since become one of the most important tools in astronomical research, capturing breathtaking images and data.
Q 18What is the name of the boundary around a black hole beyond which nothing, not even light, can escape?
Event horizon
The event horizon is the point of no return around a black hole, marking the boundary where the escape velocity exceeds the speed of light.
Q 19Which disc of icy bodies extends from about 30 to 50 AU from the Sun, just beyond the outermost planet?
Kuiper belt
Neptune's moon Triton and Saturn's moon Phoebe may both have been born there before being captured by their planets.
Q 20What unit of distance is defined as the average distance between the Earth and the Sun?
Astronomical Unit
An Astronomical Unit (AU) is a standard unit of distance in astronomy, representing the average distance from the Earth to the Sun, approximately 150 million kilometers (93 million miles).
The redshift of light from distant galaxies indicates that they are moving away from us, providing crucial evidence for the expansion of the universe as described by Hubble's Law.
Q 24Who was the first human to walk on the Moon?
Neil Armstrong
Neil Armstrong made history on July 20, 1969, as the first person to step onto the lunar surface during NASA's Apollo 11 mission.
Q 25Which color of star indicates the highest surface temperature?
Blue
A star's color is directly related to its surface temperature; blue stars are the hottest, while red stars are the coolest.
Q 26Which of these planets is classified as a terrestrial planet?
Mars
Terrestrial planets are rocky planets with solid surfaces. In our solar system, they include Mercury, Venus, Earth, and Mars.
Q 27Comets are often described as 'dirty snowballs' and are primarily composed of what materials?
Frozen gases, dust, and rock
Comets are essentially cosmic 'dirty snowballs' made up of a mixture of ice (frozen water, carbon dioxide, methane, etc.), dust, and small rocky particles.
Q 28Which of Kepler's laws says the line from a planet to the Sun sweeps out equal areas in equal times?
Second Law
Second Law, really a speed rule: a planet hurries near the Sun and dawdles far from it; the first is ellipses, the third links period to distance.
Q 29What exoplanet detection method watches a star dim as a planet passes in front of it?
Transit method
The transit method is a highly successful technique for finding exoplanets, where astronomers detect a periodic dip in a star's brightness caused by a planet crossing its face.
Q 30Which gas giant is famous for its 'Great Red Spot,' a persistent storm larger than Earth?
Jupiter
Jupiter, the largest planet, is home to the iconic Great Red Spot, an anticyclonic storm that has been observed for centuries and is larger than our home planet.