Astronomy
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8correct to beat the crowd
This astronomy and astrophysics quiz has 190 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 190 questions with answers and explanations. Play the quiz
Q 01What is the name of the Sun's visible surface layer?
Photosphere
The photosphere is about 5,500°C, yet the corona above it reaches millions of degrees, and why the corona is so much hotter is still unsolved.
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 a barred spiral, and the Sun takes more than 200 million years to complete one orbit around its centre.
Q 04Which American author said he came in with Halley's Comet and expected to go out with it?
Twain
Mark Twain was born two weeks after the comet's 1835 approach, and he died in 1910, one day after it next swung closest to the Sun.
Q 05In astronomy, what kind of quantity does a 'light-year' measure?
Distance
Despite the name, a light-year is a distance: how far light travels in one Julian year of 365.25 days.
Q 06Which Bell Labs radio astronomers accidentally found the cosmic microwave background in 1964?
Penzias and Wilson
Penzias and Wilson even scraped pigeon droppings out of their horn antenna to kill the hiss, which turned out to be the afterglow of the Big Bang and won them a Nobel Prize.
Q 07What is a nebula in astronomy?
A giant cloud of dust and gas in space
A nebula is a giant cloud of dust and gas in space, and many are 'star nurseries' where new stars are beginning to form.
Q 08Which of these best describes 'dark matter'?
Invisible mass detected only through its gravity
Dark matter is invisible mass detected only through its gravity; it seems to outweigh ordinary matter more than five to one, yet no experiment has detected it directly.
Q 09The Sun is in which long, stable phase where most stars spend most of their lives?
Main sequence
The Sun has spent about 4.5 billion years on the main sequence, a little under halfway through, before it will swell into a red giant.
Q 10What is a quasar?
A galaxy's core lit by a feeding black hole
A quasar is a galaxy's core lit by a feeding black hole, and the most powerful shine thousands of times brighter than the entire Milky Way.
Q 11What is a solar flare?
An intense burst of radiation from the Sun's atmosphere
A solar flare is an intense burst of radiation from the Sun's atmosphere; the first ever recorded was seen in 1859 by two English astronomers working independently.
Q 12Which volcano is the tallest planetary mountain in the Solar System?
Olympus Mons
Olympus Mons rises over 21 km, well over twice Mount Everest's height above sea level.
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
A planetary nebula has nothing to do with planets: early astronomers named these glowing shells for their round, planet-like look through small telescopes.
Q 22What is the leading explanation for how Earth's Moon formed?
A Mars-sized body smashing into Earth
A Mars-sized body smashing into Earth most likely made the Moon, and Moon rocks brought back by astronauts share Earth's isotopic fingerprint.
Q 23What phenomenon provides the primary observational evidence that the universe is expanding?
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 crossed into interstellar space 35 years after launch, and its radio signals now take more than 22 hours to reach Earth.
Q 15What is the final evolutionary stage for a low-mass star like our Sun?
White dwarf
A white dwarf packs about half the Sun's mass or more into a ball only about the size of Earth.
Q 16Which constellation, home to the bright supergiant Rigel, has a famous belt of stars?
Orion
Orion is named after a hunter in Greek myth, and the fuzzy middle 'star' of his sword is really the Orion Nebula, where new stars are forming.
Q 17Which famous space telescope, launched in 1990, has provided iconic images of the universe?
Hubble Space Telescope
The Hubble Space Telescope launched with a mirror ground too flat at its edge, so its images were blurry until astronauts fitted corrective optics in 1993.
Q 18What is the name of the boundary around a black hole beyond which nothing, not even light, can escape?
Event horizon
An event horizon isn't a solid surface: someone falling through the event horizon of a giant black hole would notice nothing special as they crossed.
Q 19Which region of icy bodies lies beyond the outermost planet, 30 to 50 times as far from the Sun as Earth?
Kuiper belt
The Kuiper belt is named after Gerard Kuiper, yet he believed such icy bodies would have been swept clear long ago, leaving few or none there today.
Q 20What name is given to the average distance between Earth and the Sun?
Astronomical Unit
Sunlight takes a little over 8 minutes to cross one Astronomical Unit, so we always see the Sun as it was about 8 minutes earlier.
Redshift of distant galaxies
The redshift of distant galaxies grows the farther away they are: a galaxy twice as far is receding about twice as fast, as an expanding universe predicts.
Q 24Who was the first human to walk on the Moon?
Neil Armstrong
Neil Armstrong's first steps were broadcast live to hundreds of millions of viewers, among the most-watched television events in history.
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 NASA rover landed in Mars's Gale Crater in August 2012?
Curiosity
Curiosity was lowered onto Mars on cables from a hovering rocket-powered 'sky crane', which then flew off and crash-landed hundreds of metres away.
Q 27What are comets mainly made of?
Frozen gases, dust, and rock
Comets are frozen gases, dust, and rock, and when one nears the Sun, sunlight and the solar wind push its glowing tail to point away from the Sun.
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 can also sniff out a planet's air: some starlight passes through its atmosphere during the crossing, revealing what that atmosphere contains.
Q 30What gives Mars its reddish colour?
Rusty minerals in its soil
Rusty minerals in its soil make Mars red, and strong winds can whip up storms that cover the entire planet.